Aerial drone for acquiring atmospheric samples, a payload arrangement for mounting to a drone, and methods of sample collection from an atmosphere

Abstract

A payload arrangement for aerial copter drone mounting to an aerial copter drone for collection of atmospheric eDNA / eRNA samples, comprising a sample collection system to collect the samples, the sample collection system having an inlet opening to admit samples, the arrangement being so configured that when mounted to a corresponding aerial copter drone the inlet opening is located to receive downwash from a rotor so that particulates in the atmosphere are propelled into the sample collection system via the inlet opening. A funnel may be provided to receive downwash and feed it into the inlet opening. Also provided is an aerial copter drone having motor-driven rotors to provide propulsion, including a sample collection system to collect eDNA / eRNA samples from an atmosphere, the sample collection system having an inlet opening to admit samples, the inlet opening being located so as to receive, in use, downwash from a rotor of the aerial copter drone so that particulates in the atmosphere are propelled into the sample collection system via the inlet opening.

Description

Technical field The present disclosure relates to an aerial copter-type drone for collecting samples from an atmosphere through which the drone is flown or hovering, a payload arrangement for mounting to a drone, and methods of collecting samples using such a drone, and in particular to aerial copter drones configured to collect environmental DNA or RNA, related payload arrangements, and to methods of collecting environmental DNA or RNA. Background It is now accepted that biodiversity is declining faster than at any previous time in human history. The International Union for Conservation of Nature (IUCN) reports that globally 42,100 species (almost a third of all assessed species) are threatened with extinction. The problem affects both the developed world and the developing world. It is reported that in the UK there has been on average a 70% decline in the populations of mammals, birds, fish, reptiles, and amphibians since 1970, while the UK’s flying insect population has declined by as much as 60% in the last 20 years. It is reported that as many as 40% of the world’s insect species, including bees, ants, and butterflies, could become extinct. Such an extreme loss of pollinators is likely to result in insect-pollinated crop plants becoming significantly less productive - further straining already strained global food supplies. The 2022 UN Biodiversity Conference agreed on an historic package of measures to address dangerous loss of biodiversity and restoring natural ecosystems. The package, known as the Kunming-Montreal Global Biodiversity Framework” (GBF) includes 4 goals and 23 targets for achievement by 2030. The first of the goals states: “The integrity, connectivity and resilience of all ecosystems are maintained, enhanced, or restored, substantially increasing the area of natural ecosystems by 2050; Human induced extinction of known threatened species is halted, and, by 2050, extinction rate and risk of all species are reduced tenfold, and the abundance of native wild species is increased to healthy and resilient levels; The genetic diversity within populations of wild and domesticated species, is maintained, safeguarding their adaptive potential.”. While the following are among the 23 targets: i) Effective conservation and management of at least 30% of the world’s lands, inland waters, coastal areas, and oceans, with emphasis on areas of particular importance for biodiversity and ecosystem functioning and services. The GBF prioritizes ecologically-representative, well-connected and equitably governed systems of protected areas and other effective area-based conservation, recognizing indigenous and traditional territories and practices. Currently 17% and 10% of the world’s terrestrial and marine areas respectively are under protection. ii) Have restoration completed or underway on at least 30% of degraded terrestrial, inland waters, and coastal and marine ecosystems; iii) Reduce to near zero the loss of areas of high biodiversity importance, including ecosystems of high ecological integrity; iv) Prevent the introduction of priority invasive alien species, and reduce by at least half the introduction and establishment of other known or potential invasive alien species, and eradicate or control invasive alien species on islands and other priority sites; and v) Require large and transnational companies and financial institutions to monitor, assess, and transparently disclose their risks, dependencies, and impacts on biodiversity through their operations, supply and value chains and portfolios. It can be seen therefore that governments and commercial companies will require biodiversity data to monitor progress, and to take the right decisions to mitigate decline and risk. Currently many governments already have surveying programs in place to monitor general wildlife stocks, protected species, invasive species, agricultural pests, and disease vectors. Many of these survey programs focus on a single species or target group and are designed to manage a particular risk or performance indicator, consequently they do not provide a clear picture of overall biodiversity. Environmental DNA (eDNA) is a very promising technique to deliver biodiversity data in a cost-effective way. eDNA is genetic material that animals release to the environment. The fragments of DNA or RNA from, for instance, skin cells, scales, and faeces can be sequenced and compared to reference databases to get a taxonomic (species) identification. Samples of eDNA can come from anywhere and are relatively easy to acquire. Unlike current ecological monitoring techniques, that rely for a large part on visual identification of species and, in general, require field surveys and trapping, the eDNA technique is non-invasive and often a lot more sensitive to detect rare and evasive species as well as those organisms that are very small or difficult to identify visually. Currently eDNA is mostly used in (fresh water) aquatic environments. This is largely driven by the fact that aquatic environments are challenging to survey through conventional methods, but also because fish and amphibians excrete significant amounts of eDNA which is subsequently distributed throughout the water body. Within this context eDNA is often used in ponds or lakes to provide a local but very detailed snapshot. Also, in flowing streams and the ocean where eDNA is used it is assumed the eDNA has its provenance further upstream or is 3 influenced by currents. There are autosampler devices being used to alleviate sampling effort but in many case eDNA collection still requires physical human presence to take a sample. This hampers uptake and deployment at larger regional scales or over significant time periods. In the paper “Measuring biodiversity from DNA in the air”, Current Biology 32, 693700, February 7, 2022, Clare et al report on a project to filter air samples at a zoological park to collect DNA which was then used to identify species and their ecological interactions. The air samples were found to contain DNA from 25 species of mammals and birds, including 17 known terrestrial resident zoo species. Also identified were food items from air sampled in animal enclosures, and taxa native to the local area - including the endangered Eurasian hedgehog. In a similar study “Airborne environmental DNA for terrestrial vertebrate community monitoring”, Current Biology 32, 701-707, February 7, 2022, Lynggard et al report on eDNA obtained by filtering air samples at the Copenhagen Zoo. Filtering air at three locations (a stable, outside between outdoor animal enclosures, and in the Rainforest House) allowed the capture of eDNA from which were detected 49 vertebrate species spanning 26 orders and 37 families: 30 mammal, 13 bird, 4 fish, 1 amphibian, and 1 reptile species. These species spanned animals kept at the zoo, species occurring in the zoo surroundings, and species used as feed in the zoo. The detected species comprise a range of taxonomic orders and families, sizes, behaviours, and abundances. Although these two studies showed that air filtering could be used to isolate eDNA, the approaches taken required frequent site visits to change and collect the filter elements on which the eDNA is collected, presenting logistical challenges to widescale deployment. There therefore exists a need for alternative solutions to the problem of gathering biological material, such as eDNA, from terrestrial animals and other organisms, for use in focused surveys as well as to support investigations into biodiversity. Unmanned aerial vehicles (UAVs), also known as aerial drones (frequently referred to simply as “drones”, although this term more correctly applies to all vehicles that can be operated without a pilot or driver inside, whether airborne, terrestrial, or aquatic), are now commonly used in many industrial, commercial, and even military contexts. Typically equipped with one or more cameras to capture real time video which is transmitted back to the drone’s operator, optionally with both optical and thermal imaging capabilities, drones enable inspection and monitoring of equipment and installations at great heights and / or in inaccessible rugged terrain, such as pylonmounted electrical transmission lines, wind turbines, oil pipelines, etc. Drones have also been proposed as tools to enable the collection of biological material in inhospitable, inaccessible, or difficult to traverse terrain such as rain forests and mangrove swamps. This disclosure proposes an aerial copter drone configured to collect samples from an atmosphere through which the drone is flown, methods of collecting samples using such a drone. Such drones may be useful not only to collect samples of airborne DNA and or RNA, but also to collect other airborne material such as particulate matter such as air pollution, agrochemicals, etc. Such drones may be configured to also obtain other samples, such as samples of or from water (and of material present in the water, such as algae, plankton, etc.) from marine and other aquatic environments, from seas, lakes, rivers, canals, and other bodies of water, for example by collecting samples of water or filtering water to collect material from the water, and / or to collect vegetable samples such as foliage, fruit, seeds, and / or other plant tissue (including of fungi, lichen, etc.) during a flight in which the atmosphere is also sampled. Under certain circumstances such a drone may be controlled to obtain a sample from a body of water, or a sample of vegetable / fungal material, while simultaneously acquiring a sample from the atmosphere through which the drone is being flown. A suitably configured drone may therefore be able to obtain, for example during a single flight, samples of airborne material, water and water-borne material from a body of water, and plant tissue from one or more plants, fungi or lichen. Drones according to aspects of the invention may also find application in helping to reduce use of pesticides and fungicides -for example the drones could be used to capture insect signatures (e.g. eDNA or eRNA for insects of concern), and / or fungal spores. Analysis of the captured samples could then be used to determine whether and when an intervention (with the relevant pesticide or fungicide) is required, and may also help to demonstrate a significant presence of beneficial insects (for example) which would make insecticidal intervention unwise. Summary According to a first aspect there is provided an aerial copter drone having one or more motor-driven rotors to provide propulsion to the drone, the drone including a sample collection system to collect samples from an atmosphere through which the drone is flown, the sample collection system having an inlet opening to admit samples, the inlet opening being located so as to receive, in use, downwash / downdraft from a rotor of the drone so that suspended particulates in the atmosphere are propelled / or driven / or directed into the inlet opening and hence into the sample collection system. The samples may be eDNA or eRNA samples from an atmosphere through which the drone is flown. According to a second aspect there is provided an aerial copter drone having one or more motor-driven rotors to provide propulsion to the drone, the drone including a sample collection system to collect samples of eDNA and / or eRNA from an atmosphere through which the drone is flown, a rotor of the drone defining, in use, a swept volume having an outer periphery, an inlet opening of the collection arrangement being located behind the swept volume and within an area 5 defined by projection of the area defined by the periphery, the area defined by the projection being centred on the rotor’s axis of rotation, the sample collection system optionally including a medium, e.g. a nucleic acid friendly medium, to retain the samples at least for the duration of a flight, e.g. until they can be removed for analysis. The nucleic acid friendly medium may be a medium capable of retaining or absorbing free or particle-enclosed nucleic acids. The medium may be added, i.e. be additional to the structure of a collection chamber of the collection arrangement. By using rotor downwash to drive samples into the collection system, rather than using suction, it is possible to take advantage of pressure differentials much greater than are achievable using suction (where the maximum pressure differential will be less than 1 atmosphere). This may permit sampling extremely large air volumes per unit time, increasing sampling efficiency. Additionally, commercially available air sampling equipment capable of achieving the high suction pressures or high air flow rates required for effective sampling, has energy requirements, dimensions and weights that are not compatible with the restrictions for equipment mounting of most commonly used survey drones, making it extremely challenging to adapt such equipment for drone-based sampling. Due to the sheer size and weight of most high capacity air sampling equipment, the category of drones possible to be fitted with such devices is consequently more limited, with greater dimensions, higher cost (both per acquisition and per flight) higher level requirements for pilot training and increased legal flight operation restrictions. Therefore, this combination implies a significant practical limitation on the areas where this sampling procedures can be applied, simultaneously increasing the overall cost of the operations and the associated logistical hurdles. It will be appreciated that the approach to sampling represented by the first and second aspects may use one (or more) of the rotors that is used to provide propulsion to the drone, but it would also be possible to add one or more rotors (optionally activatable and controllable remotely, e.g. via the controller used to control the drone and its payload, and optionally powered by the drone’s own batteries) dedicated to sample collection, so that the downwash that is used for sample collection comes from such dedicated rotors rather than from a rotor used primarily for propulsion and this disclosure should be understood against that background - thus the invention in its various aspects is not restricted to drones that capture aerial samples using downwash from a rotor primarily devoted to providing lift or propulsion. Using such a dedicated rotor it would theoretically be possible to direct all or virtually all of that rotor’s downwash into the relevant sample collection system (e.g., the sample collection system may have an inlet or inlets that represent 100% or more of the rotor’s swept area). In an aerial drone according to any variant of the first or second aspects, the rotor from which the inlet opening receives downwash may define, in use, a swept area having an outer periphery, the inlet opening being located behind (often below) the swept area and at least partially within an area defined by the projection of the swept area, the projected area being centred on the rotor’s axis of rotation. The swept area may at least partially overlap the inlet opening. Thus, the inlet of a sample collection system may be located at least partially behind (and be at least partially overlapped by) a respective rotor, or it may lie wholly outside the area overlapped by the respective rotor but close enough to receive rotor downwash. In an aerial drone according to any variant of the first or second aspects, the or each sample collection system may include a cyclonic separation arrangement, optionally in the form of a cyclonic separator array, and optionally the or each cyclonic separation arrangement comprises a vortex separator. An aerial drone according to any variant of the first or second aspects may have a reservoir for liquid, and one or more nozzles connected to the reservoir, the drone being operable to dispense liquid from the reservoir via the one or more nozzles during flight into a region behind a rotor and the arrangement being such that at least some of the liquid dispensed from the nozzle(s) during flight will be propelled into an inlet of the collection system under the action of downwash from the rotor behind which the liquid was dispensed, optionally by wake reingestion (or based on so-called circular flow or circular airflow) and optionally the collection system may include a vortex separator and at least one of the one or more nozzles may be so located as to receive, in use, an exhaust flow from an outlet of the vortex separator. The inlet opening may be wholly within the projected area, partially within the projected area, or wholly outside the projected area. The inlet opening may have a cross sectional area whose size is between one half and one quarter of the size of the area swept by the rotor. The inlet opening is preferably within 150mm of the rearmost extremity of the swept volume (which may also be considered to be the rotor plane), more preferably within 100mm, for example no more that 75, 60, 55, 50, 45, 40, 35, 30, 25 or 20mm, optionally within 18 to 36 mm, 20 to 35mm, 20 to 30mm or 25 to 30 mm. The airborne eDNA and / or eRNA is likely to exist in the form of cells, pollen, spores, viral particles or biological 'particles', and possibly some free floating DNA / RNA. These particle may exist in aerosols or within floating liquid phases. In an aerial drone according to any variant of the first or second aspects, the or each sample collection system may include a medium to retain the samples until the samples can be removed for analysis. In an aerial drone according to any variant of the first or second aspects the or each sample collection system may include a sampling liquid arrangement (e.g. a filtering arrangement) in which rotor downwash is passed through or along a liquid medium to capture particles carried by the downwash, and optionally the liquid medium comprises PBS and / or nuclease-free water. An aerial drone according to any variant of the first or second aspects may have multiple rotors, and a plurality of the multiple rotors may each be provided with such a sample collection system, and optionally the plurality is half, a majority, or all of the multiple rotors. In an aerial drone according to any variant of the first or second aspects the inlet opening of the or each sample collection system: may be wholly within the projected area of its respective rotor; and / or may have a cross sectional area size that is within 10% to 50%, optionally 20 to 40%, optionally 25 to 35% of the size of the area swept by the respective rotor; and / or that is within 150 mm of the rearmost extremity of the swept volume of the respective rotor, optionally within 100 mm, 90 mm, 80 mm, 70, 60, 50, 40, 30 or 20 mm; and / or that is no closer than 10 mm from the rearmost extremity of the swept volume of the respective rotor. An aerial copter drone having multiple rotors may be configured so that either or both of the following conditions are met: (i) the inlet openings of the multiple sample collection systems are so sized and so located with respect to a longitudinal axis of the drone so as to balance laterally the loss of lift occasioned by the presence of the multiple sample collection systems; (ii) the inlet openings of at least some of the multiple sample collection systems are disposed either side of the longitudinal axis of the drone in an arrangement that is symmetrical about the longitudinal axis. In an aerial drone according to any variant of the first or second aspects that has multiple inlet openings the multiple openings may be arranged to supply a common collection chamber that is shared between multiple sampling systems. In an aerial drone according to any variant of the first or second aspects the or each sample collection system may be provided with a mechanism operable to selectively open an inlet and / or an outlet of a sample collection chamber of the sample collection system during flight of the drone, and optionally the mechanism may be operable to activate a valve configured to close the inlet to the sample collection chamber. In an aerial drone according to any variant of the first or second aspects the or each sample collection system may be provided with a plurality of sample collection chambers, and a mechanism may be provided to expose different sample collection chambers of the plurality 8 sequentially one after the other so that separate samples may be obtained by an individual sample collection system at different times during a flight, and optionally each plurality of sample collection chambers may be provided as a cartridge which may be inserted into, and removed from the relevant sample collection system as a unit. In an aerial drone according to any variant of the first or second aspects the or each sample collection system may include a sample collection chamber optionally provided with a removable sample collection vessel. In an aerial drone according to any variant of the first or second aspects the or each sample collection system may comprise one or more exhaust ports, for the escape of air in a direction transverse to, or in line with or generally parallel to, the direction in which air is received through the inlet of the respective sample collection system. According to a third aspect, there is provided an eDNA / eRNA sampling method performed using a drone according to any variant of the first or second aspects, the method comprising: performing a flight with the drone through an atmosphere containing material that includes eDNA and / or eRNA; using downwash from one or more rotors of the drone to propel the material into a sample collection system of the drone; retaining sampled material within the sample collection system for the duration of the flight; and subjecting the sampled material to molecular analysis to generate data on sources of the eDNA and / or eRNA. According to a fourth aspect, there is provided an eDNA / eRNA sampling method performed using a drone according to any variant of the first or second aspects, the method optionally according to the third aspect and comprising: performing a flight with the drone, the flight involving flying the drone in proximity to a substrate, the substrate being the ground, a body of water, a tree canopy, vegetation, or a man-made structure; using downwash from one or more rotors of the drone to render airborne material from the substrate, the material containing eDNA and / or eRNA; pulling the airborne material down between blades of a rotor of the drone, or otherwise combining the airborne material with downwash from one or more rotors so that the airborne material is propelled into a sample collection system of the drone; retaining sampled material within the sample collection system for the duration of the flight; subjecting the sampled material to molecular analysis to generate data on sources of the eDNA and / or eRNA. In a method according to the third or fourth aspects the sample collection system may include a medium to retain the sampled material until the samples can be removed for analysis. According to a fifth aspect there is provided a payload arrangement for mounting to a drone to enable the collection of eDNA and / or eRNA samples from an atmosphere through which the drone is flown, the arrangement comprising a sample collection system to collect the eDNA and / or eRNA samples, the sample collection system having an inlet opening to admit samples, the payload arrangement being so configured that when mounted to a corresponding drone the inlet opening is located so as to receive, in use, downwash from a rotor of the drone so that suspended particulates in the atmosphere are propelled into the inlet opening and hence into the sample collection system, and optionally the payload arrangement includes a funnel arranged to receive the rotor downwash and to feed the downwash into the inlet opening. A payload arrangement according to a fifth aspect may comprise a plurality of sample collection systems mounted to a support structure, and the sample collection systems may be so located that, once the payload arrangement is mounted to a corresponding drone, each of the sample collection systems is positioned so as to receive downwash from a respective rotor of the drone. In a payload arrangement according to any variant of the fifth aspect the or each sample collection system may be provided with a plurality of sample collection chambers, and a mechanism may be provided to expose different sample collection chambers of the plurality sequentially one after the other so that separate samples may be obtained at different times by an individual sample collection system, and optionally each plurality of sample collection chambers may be provided as a cartridge which may be inserted into, and removed from the relevant sample collection system as a unit. In a payload arrangement according to any variant of the fifth aspect the arrangement may include a reservoir for liquid, and one or more nozzles connected to the reservoir, the payload arrangement may be operable to dispense liquid from the reservoir via the one or more nozzles during flight into a region behind a rotor and the arrangement may be such that at least some of the liquid dispensed from the nozzle(s) will be propelled into an inlet of the collection system under the action of downwash from the rotor behind which the liquid was dispensed, optionally by wake reingestion, and optionally wherein at least one sample collection system of the payload arrangement includes a vortex separator and at least one of the one or more nozzles may be so located as to receive, in use, an exhaust flow from an outlet of the vortex separator. In general, we prefer to avoid the use of membrane type filters for sample capture, as these are prone to blockage reducing both efficiency and capacity. Under some circumstances drones according to aspects of the invention may use one or glass fibre depth filters (which have the benefits of strength and the fact that the non-uniformly defined pore sizes trap particles at multiple levels and thus do not clog that quickly). But in general drones according to aspects of the invention will include at least some (and possible all) sample capture arrangements that do not rely on physical filters and which are thus less prone to rapid blockage with consequent reductions in efficiency. Brief description of Figures Embodiments of the invention will now be described, by way of example only, with reference to the accompanying figures, in which: Figure lisa schematic showing, in end elevation, part of an aerial drone according to an aspect of the invention; Figure 2A is a schematic plan view of a drone from above, illustrating placement of inlets of several sample collection systems in relation to areas swept by respective rotors of a drone according to an aspect of the invention; Figure 2B is an alternative schematic plan view of another drone from above, illustrating placement of inlets of several sample collection systems in relation to areas swept by respective rotors of a drone according to an aspect of the invention; Figure 3 is a schematic showing, in end elevation, an arrangement of a pair of sample collection systems in relation to respective rotors of a drone according to an aspect of the invention; Figure 4 shows details of a sample collection system including a funnel arrangement according to an aspect of the invention; Figures 5A and 5B illustrate sampling methods according to aspects of the invention; Figure 6A and 6B is a schematic plane view of a magazine arrangement to permit sequential gathering of discrete samples in segregated sampling compartments; Figure 7 is a schematic showing a potential arrangement for obtaining samples of water and water-borne material from a body of water; Figure 8 is a schematic showing a potential arrangement for obtaining samples of plant material Figure 9A shows a vortex tube sampling device suitable for use in a sample collection drone according to aspects of the invention; Figure 9B is a schematic showing another vortex tube sampling device suitable for use in a sample collection drone according to aspects of the invention; Figures 9C and 9D are schematic plan views of sample collection systems including one or more cyclonic separator arrays and / or a plurality of cyclonic separators; Figure 10 is a schematic showing a tornado sampling device suitable for use in a sample collection drone according to aspects of the invention; Figure 11 is a schematic showing a positive pressure cyclone sampling device suitable for use in a sample collection drone according to aspects of the invention; Figure 12 is a schematic showing use of a vortex sampling arrangement in conjunction with one or more nozzles that are arranged to deliver water, an aqueous solution, or some other liquid, in order to improve collection of airborne material; Figure 13 is a flow chart representing elements of possible approaches to methods of processing biological material collected from the air, for example using a drone according to aspects of the invention, including various optional elements; Figure 14 illustrates schematically an alternative approach to sample collection in which downwash is passed through a liquid collecting medium; and Figures 15A and 15B are plots illustrating species recovery, under different flight conditions, using two different collection media. Specific description Figure 1 shows schematically, in end elevation, part of an aerial copter drone 100 according to an aspect of the invention. The drone 100 comprises a body 102, extending from which is an arm 104. A drive arrangement 106 (typically including at least one drive motor) is provided at the remote end of the arm 104, and coupled to the drive arrangement 106 is a rotor 108. The drive arrangement 106 rotates the rotor 108 to pull the atmosphere from in front of the rotor 108 (the “intake side”), at 109, and expel it behind the rotor 108 as downwash 118 to provide lift to the drone 100. Throughout this specification references to “behind” a rotor are used to refer to things that are on the downwash side of the rotor which will often be below the rotor. For ease of explanation, figure 1 only shows one of each of the arm 104, drive arrangement 106, and rotor 108, but it will be appreciated that in practice, the drone 100 is likely to be provided with multiple rotors, optionally each driven by a respective drive arrangement and each at the end of a respective arm. The drone 100 may, as shown, be provided with undercarriage 110 to permit the drone to land on a suitable landing surface without causing damage to the rotors, optional camera equipment (which may be carried beneath the drone body 102), or any other part of the drone. Thus far, the drone as described is conventional. The illustrated arrangement differs from conventional drones in that it also includes a sample collection system 112. In the illustrated example the sample collection system is coupled to the body 102 by means of a support 114 which is carried by the undercarriage (aka “landing gear”) 110, although other arrangements in which the sample collection system 112 is coupled to the body other than via undercarriage are also possible, for example by means of an optional payload supporting arrangement or via a cage (e g. about one or more of the rotors) that is attached to the arm 104 or to the body 102. If coupled to the undercarriage 110 the arm 104 may extend from a point part way down a leg or strut of the undercarriage, as shown, or may extend at an end of an element of the undercarriage (e g. a leg, strut, or frame member). The sample collection system 112 is arranged to collect samples from an atmosphere through which the drone is flown or is hovering and includes an inlet 116 to admit samples. The inlet is so located as to receive, in use, downwash 118 from a rotor 108 of the drone so that in use particulates in the atmosphere are propelled / driven / directed into the inlet and hence into the sample collection system. The sample collection system 112 is also provided with one or more outlets (or exhaust ports) 120 through which the captured atmosphere leaves the sample collection system 112. Various configurations of sample collection system will be described later, but in the example illustrated on Figure 1 a plurality of exhaust ports 120 are provided around the periphery of the collection system. In the arrangement shown, air that has passed through the sample collection system 112 exits the system in a direction substantially orthogonal to the direction in which air enters the inlet 116. In other arrangements, the exhaust ports 120 may direct the exiting air more nearly rearwards, in a direction(s) that is closer to parallel to the direction in which air enters through the inlet 116, and such arrangements may be designed to benefit from the presence of areas of reduced pressure to reduce back pressure experienced by air within the collection system. While the drone is perhaps most likely to be flown through air, it will be appreciated that there may be occasions where sampling is desirable or necessary within locations (e.g. enclosures) having an atmosphere that is something other than air, for example an inert atmosphere (of nitrogen, carbon dioxide, or some other gas or gas mixture lacking a significant oxygen component) may be maintained for storage of fruit, vegetables, grain, other foodstuffs, or other e g. plant materials. Similarly it may be necessary to take samples from within the atmosphere of a reactor or containment vessel. For simplicity and convenience we will hereafter refer to the atmosphere as “air”, but it should be understood that no limitation is intended to the scope of application of drones according to aspects of the invention by such references, unless the context clearly requires the more limited meaning. In figure 1 the rotor 108, which is shown schematically, defines, in use, a swept volume (which in side elevation is also represented schematically by figure element 108) having (when viewed in plan) a generally circular area with an outer periphery which extends between boundary lines 122 and 122’. The boundary lines 122 and 122’ are here parallel to the rotor’s axis of rotation 124. Projection of the area of the swept volume rearwardly from the rotor (that is, in the downwash direction, being the direction in which the rotor directs air when rotating in normal (lift-giving) flight defines an area within which the inlet 116 of the sample collection system 112 is located. That is, an inlet opening of the collection arrangement is located behind the swept volume and within an area defined by proj ection of the area defined by the periphery (the area defined by the projection being centred on the rotor’s axis of rotation). In other words, 13 when viewed in plan from above the rotor (i.e. in front of the rotor), the rotor will be seen to overlap, at least in part, the inlet 116. Although in Figure 1 an intake opening 116 is shown as being wholly within the area defined by boundary lines 122 and 122’, it should be understood that the sample collection system 112 may have an opening that extends beyond one or other boundary line 122, 122’. The sample collection system 112 may have more than one opening, with at least one opening located in the space defined by the boundary lines 122 and 122’ and optionally at least one opening outside the space defined by the boundary lines 122 and 122’. In practice, the downwash from the rotor is likely to extend beyond the space defined by the boundary lines 122 and 122’, for example extending at an angle so as to form a generally conical shape whose width increases in a direction away from the rotor, so that an opening or opening portion outside the space defined by the boundary lines 122 and 122’ may still be exposed to downwash and result in the sample collection system 112 receiving more entrained substances (particles, droplets, etc.). The drone of Figure 1 is shown as incorporating an integral camera / vision system 130, and also an camera / imaging arrangement 132 carried as payload beneath the body 102 of the drone. It will be appreciated that the sample collection system, which may be provided in the form of a detachable payload arrangement, may co-exist with such a payload camera 132 or may take its place. Figure 2A is a schematic plan view of a drone 100 from above, illustrating placement of inlets 116 of several sample collection systems 112 in relation to areas 200 swept by respective rotors 108 of a drone according to an aspect of the invention. In this schematic the inlets 116 are represented as being smaller than the outline of the sample collection systems 112, but as will be seen by reference to Figures 3 and 4, a funnel arrangement may be used to gather air from an area of downwash that is larger, and optionally much larger, than the area represented by the outline of a sample collection system 112. Where no funnel is used, the inlet to a sample collection system 112 will necessarily be no larger than the outline of the sample collection system. Where a funnel is used, the funnel inlet will in effect serve as the inlet to the sample collection system 112, and references to sample collection system inlet throughout the rest of the specification should be construed accordingly. Figure 2B is an alternative schematic plan view of another drone 220 from above, illustrating placement of inlets 116 of several sample collection systems 112 in relation to areas 200 swept by respective rotors 108 of a drone 220 according to an aspect of the invention. In this case each inlet 116 extends beyond the outline of the area 200 swept by the respective rotor 108. In some embodiments the inlets may lie wholly beyond the outline of the area 200 swept by the respective rotor 108, not overlapping with the area swept by the respective rotor. Each sample 14 collection system may therefore consist of an annular body, having a generally central bore through which downwash from the rotor passes to provide lift to the drone. The annular body may have an inner side wall which overlaps with the area swept by its associated rotor, and an outer side wall which does not overlap with the area swept by its associated rotor. Thus, in such an arrangement a rotor does not overlap the inlet of its associated sample collection system (in contrast with the arrangement shown in and described with reference to Figure 1). Figure 3 shows, in end elevation, a drone 350 (which may correspond to the drone 100, as previously described, but which may also differ in certain particulars) according to an aspect of the invention, with a pair of sample collection systems 112 and their relationship to respective rotors 108. The drone may have, for example, 4,6 or more rotors, and one, two, more, or all of these rotors may each have an associated sample collection system 112. Those parts common to the drone of Figures 1 and / or 2A / 2B bear the same reference numbers. This figure provides more detail of possible configurations of sample collection systems 112. In this example the figure shows two sample collection systems 112, each of which is shown with a structure 300 in the form of a “bell mouth” or funnel from the open end of which the structure tapers inwardly towards an outlet of significantly smaller cross sectional area which feeds a collection chamber of the sample collection system 112. Air that enters the collection chamber via the structure 300 exits the collection chamber via outlets 120. Here the outlets are shown as being formed in the side wall of the collection chamber, the side wall optionally being cylindrical with a long axis generally parallel to the rotational axis of the associated rotor 108. It should be appreciated that it is not essential for the collection chamber to have a cylindrical form, nor for a longitudinal axis of the collection chamber to be arranged generally parallel to the rotational axis of the rotor - acceptable collection performance can still be achieved with the collection chamber substantially offset with respect to the rotational axis of the rotor. Also, the collection chamber outlets 120 could also be designed and positioned in such a way that they take advantage of the velocity of the airflow from the rotors that doesn’t enter the funnel, resulting in a lower pressure outside the holes, thereby enhancing airflow through the chamber and potentially reducing the reduction in the overall lift capacity of the drone. The object of providing the structure 300 is to provide an increased capture area for a given collection chamber footprint, the tapering shape of the funnel concentrating the air flow. This helps to increase the amount of airflow into the sample collection system 112 per unit time (i.e. the rate of airflow), which can help improve sample capture. A side effect is that the velocity of air flow increases as the cross sectional area of the structure reduces. The outlet end of the structure 300 opens into the collection chamber. Particles, droplets, and other material carried by the air entering the structures 300 will tend to be deposited within the collection chamber, due to inertia forces that cause particles and aerosols to exit the airflow as it is deflected, hence causing these particles to remain in the collection chamber. Possible configurations of the sample collection systems 112, their internal arrangement, and the possible use of sampling cups, etc., will be described later. The interior of the collection chamber may be provided with an added sample retention medium, for example in the form of a tacky surface, a special fluid (e.g. such as phenol buffered saline PBS, or one of the other fluids mentioned in the discussion of Figure 14, or one of the other options mentioned in the discussion of Figure 4), or for example an FDA card optionally treated with one of the fluids mentioned in the discussion of Figure 14. The sample collection media are described as “added” because they will in most if not all cases be additions to the structure of the collection chamber, typically being replaced after every sample collection event. The interior of the collection chamber may additionally or alternatively be designed to deflect air to follow a rotational cyclonal path resulting in forcing particles outwards from the cyclonal path causing them to exit the airstream due to centrifugal forces and therefore be deposited within the chamber(s). In the arrangement shown in Figure 3 the sample collection systems 112 are mounted to a base 302 that is itself coupled to legs of the undercarriage 110. For reasons of structural stability a single common base 302 may be used to couple the two sample collection systems 112, as shown in the figure. Similarly, if there are more than two sample collection systems, for example one for each of the drone’s rotors, a single common base 302 may be used to couple these systems together. Provided the drone has a sufficiently powerful drive system, and a suitably advanced flight control system, the provision of such a base is unlikely to impair the drone’s flight characteristics. Alternatively, each sample collection system may be mounted to the undercarriage, or to a suitable payload carrying support, individually, as a payload arrangement that may include all or multiple of the sample collection systems to be used, or integrated into a drone that is specifically designed or configured for atmospheric sampling of this kind. That is, the use of a common support, frame, or structure to carry one or more sample collection systems, which may form what may be termed a payload arrangement is one of several alternatives to solving the problem of incorporating atmospheric sampling for biological material such as eDNA and / or eRNA; an another alternative is to mount multiple sample collection systems to a drone without the use of a common support system (at least without one that is additional to existing components of the drone); while a further option is to integrate one or more suitable sample collection systems into the design of a drone so that the or each sample collection system forms an integral part of a drone, rather than being an “add on”. The base and / or individual supports (which may be used in combination) may be made of any material that is suitably light and strong, such as polycarbonate, FRP (e.g. carbon fibre reinforced plastic), titanium, or an aluminium alloy. It will be appreciated that the base is an example of a support arrangement that may be used to provide a payload arrangement for a drone, the payload arrangement being mountable to and demountable from a corresponding drone, the payload arrangement including the one or more sample collection systems each suitable located so that, when mounted to the corresponding drone, the inlet of the or each sample collection system is so located with respect to a respective rotor of the drone that it will, in use, be exposed to that rotor’s downwash to enable collection of the desired particulates (e.g. eDNA or eRNA). In this example we have referred to a base, but it should be understood that a payload arrangement may equally well be designed to use a framework or other structure that supports the or some of the sample collection systems from above or from the side, rather than from below. By “corresponding drone” means a drone type for which the payload arrangement is an appropriate fitment to ensure that the sample collection system(s) is / are suitably located with respect to a respective rotor of the drone for the sampling system(s) to perform as intended. For example, multiple different payload arrangements may be built each to work with a different model of drone such as the different DJI models M300, M3 50 and M600 - and equally one might build different payload arrangements for one or more different models available commercially from other manufacturers. And of course, one might build such a removable payload arrangement for use on a bespoke “work horse” drone which may not be available commercially but which is variously repurposed for different flight tasks. Although, as already indicated, aspects of the invention extend both to drones provided with such a removable payload arrangement and to the alternative solution in which the sample collection system(s) is / are integrated into the drone build / construction. As with the drone described with reference to figure 1, here the drone 350 is shown as including a payload camera / vision system 332 in addition to an integrated camera / vision system 330, but the sample collecting systems or a sample collection payload arrangement may take the place of the payload camera 332. Each of the sample collection systems may be carried by a “cage” provided around the respective rotor - e.g. where cages are provided to shield the rotors and hence reduce the likelihood of the rotors becoming damaged by striking external objects. The or each cage may be coupled to a respective arm 104 of the drone or a single cage may enclose all of the rotors of the drone. Such a single cage could be configured as a payload arrangement, as just described, facilitating the switching of different payload arrangements to enable a single drone to perform different tasks, or could be an integral feature of the drone design / build. Whether a base 302 or individual supports are used to support the sample collection systems 112, provision may be made to adjust the position of a sample collection system with respect to the respective rotor 108. That is, the lateral offset of the sample collection system with respect to the respective rotor may be adjustable, for example by providing a slidable attachment which may permit continuous adjustment. Alternatively, a mounting arrangement that provides stepped adjustment may be used. As previously noted, a sample collection system may be so located that its inlet is wholly between the boundary lines 322 that define the outer edges of a rotor’s swept volume, or so located that the inlet lies partly outside. A mechanism to permit inflight adjustment of the positioning of the sample collection system(s) and / or of their inlets with respect to the relevant rotor may be provided, and be controllable using a suitable remote control optionally integrated into the drone control system. The benefit of allowing the collection device to be moved beyond the boundary lines 322 is that this may increase drone lift capacity and save battery power when flying towards the sampling area or will allow for larger payloads to be used in addition to the sampling device. Optionally, the base may be coupled to, or be formed integrally with, an upstanding support portion 304 that may, as shown extend between legs of the undercarriage. The upstanding support portion may provide strength and structural stability to the base 302. It may also serve as a support for electronics associated with the sample collection system. For example, a sample collection system could be provided with a mechanism that optionally can be remotely activated to open an inlet (and / or the air outlets 120) of the sample collection system in flight to begin a sampling event (and optionally operable thereafter to reclose the inlet and / or outlets to end a sampling event) so that localised sampling can be undertaken. Such a mechanism could be controlled by electronics mounted on the base 302 and / or on the upstanding support portion 304, or even directly to the drone body 102. Such a mechanism, however controlled, could also be used to activate different sample collection systems at different times (at the same or different geographical locations, at the same or different heights). One suitable control mechanism would involve providing a valve (for example in the form of a throttle plate or disc akin to that used in some carburettor designs) in the inlet path (for example at the smallest throat of the funnel) which could be closed until such time as sampling was to begin. Such a valve could be solenoid controlled, so that it can be opened and closed remotely, or could be biased into the fully open position and held shut until being released when sampling is to begin. Any such mechanism could be coupled to electronics remotely controllable by a drone operator (or drone operating system). But it is also possible for any such mechanism to be controlled by an on-board controller, for example programmed to control a sampling event based on preset instructions (e g. based on GNSS data, time, altitude, temperature, atmospheric pressure, etc.), so that a sampling event begins (and optionally ends) according to preset instructions / conditions. Such autonomous sampling may be particularly useful for repeated monitoring of a sampling zone. The inlets to the structures 300 are, in this embodiment, directly below the rotors (propellors) although this is not essential. Preferably the inlets of the structures are close to the rotors, optionally as close as possible, but it is prudent to allow 2 centimetres or more of clearance to allow for potential movement of the collection system (e.g. as the result of deflection of the system’s support, or possible deflection of the mounting arm 104 perhaps during a hard landing). Typically the inlets (here represented by the funnel inlets) will be less than 10 cm from the closest part of the rotor, for example no more than 5cm away, and optionally about 3cm away. This is very close to the actual ‘power’ and directly in the air stream. Basically the entire lift generated for the diameter of the funnel is captured and concentrated into the collection chamber (optionally within a sampling cup within the chamber). A further consideration about positioning of the sample collection system is the desirability of ensuring that the system and its supports do not get in the way during landing -we want the drone to be able to land safely and stably, so we do not want the sample collection systems or their mounting arrangements to risk destabilising the drone during landing, so we don’t want to impair the proper functioning of the undercarriage. While we could extend the undercarriage of a drone, with new leg bases that extend further down, a stable lift-off and landing base is essential. It is likely that the landing sensor / calibration would then have to be redesigned / reconfigured as the drone is likely to know the distance to the earth based on the standard leg base. We therefore prefer to work within the constraints set by the configuration of the undercarriage provided and the respective positions of the rotors and the undercarriage. Figure 3 shows the funnels 300 with diameters approximately half the diameter of the associated rotors, but funnel size can vary over a wide range in drones according to aspects of the invention. One consideration is the amount of excess lift provided by the drone’s rotors. Large, powerful drones such as the DJI models M300, M350 and M600 (a 6-rotor design, which could be provided with up to six rotor-specific sample collection systems) are designed to be able to carry heavy payloads, and these and like models from other manufacturers are likely to be able to generate so much lift that “losing” one quarter of the lift from each of several rotors as the result of using funnels / collection arrangements half the diameter of the associated rotor may still allow sufficient lift to support essentially normal flight (indeed one could possibly get away with losing 1 / 3 the lift for powerful drones and still be able to fly successfully). Depending upon the sophistication of the flight control systems, it may be necessary to take care to balance the amount of lift sacrificed front to back and side to side - for example by adjusting the offset of the funnels with respect to their respective rotors, and balancing (optionally equalising) the amount 19 of lift from each rotor sacrificed to sample collecting (which may make it desirable to use the same or similar sized funnels or more generally inlet size) for different sampling collection systems. Our experience is that, at least below a certain size of funnel inlet for a given rotor / prop size, more powerful drones tend to fly as well and be as easily controlled as their un-adapted selves. For example, with the DJI M300, which is a 4-rotor device which uses propellers 21 inches in diameter (approximately 53 cm), adding 4 sample collection systems with funnels with inlets 7.5 cm in diameter had no discernible effect on the drone’s flight behaviour. In general we favour using funnels with the largest possible inlets that still permit stable and controllable flight at the elevations, and in the wind / climatic conditions, at which it is intended to sample. There is however a trade off in the size and design of the sample collection chamber - as using a larger funnel inlet means that more air will flow through the chamber, and the increased velocities of air movement may prove to be a limiting factor, especially if samples are to be collected by use of a liquid collection medium. When the areas of the sampling system inlets are only a very small fraction of the swept area of their associated rotors it is likely that flight control electronics will readily compensate for even very unbalanced placements of different sampling system inlets with respect to their associated rotors, but if systems have inlet areas that are about a quarter or more of the area of the associated rotor swept area it may be advantageous to mirror inlet placement to reduce asymmetry between inlet placement with respect to the longitudinal axis of the drone. It may also be helpful, in terms of maintaining predictable and stable flight, to consider balancing the amount of thrust given over to sample collection not only side to side, but also front to back. Hence, inlet area and placement may be chosen to be symmetrical with respect to the longitudinal axis of the drone. Additionally or alternatively, inlet area and placement may be chosen to be symmetrical front to back (i.e. with respect to a median transverse axis). An alternative way of considering the issue of flight balance is to consider the amount of thrust effectively “lost” from a rotor to sample collection, and to attempt to provide a symmetrical loss of effective thrust side to side, and optionally additionally or alternatively front to back. For most drone systems such compensation occurs automatically based on internal sensory systems. It would be possible to have multiple sample collection systems that share a common sample collection chamber, but in general we favour providing each collection system with its own localised chamber - not least because this would likely increase the friction (and hence back pressure) seen by the sampling air, and also would involve needing to clean or replace the ducting or pipework connecting the sampling inlets to the common collector. Whether or not the sample collection system(s) include(s) funnels or the like, the entirety of the or each collection system (including funnels, if used) may be configured to be readily removable from the drone, to permit their wholesale replacement between sampling sessions to reduce contamination between sampling events. It will be appreciated that some, typically large, drones may be provided with retractable undercarriage, which may retract automatically upon take-off (the DJI 600 is one such drone). While it should generally be possible to modify the behaviour of such a drone to prevent automatic retraction of the undercarriage, it may be possible to suitably locate a sample collection system with respect to a respective rotor such that there is no interference between the collection system and its mount (if any) and the undercarriage in its movement from deployed to retracted (and back). This may involve modification of the undercarriage, and / or the use of a suitable payload system (e.g. coupled to the body 102). Air flow calculations Based on the paper by McKinney et al paper “A sampler for atmospheric volatile organic compounds by copter unmanned aerial vehicles, Atmos. Meas. Tech. 12, 3123-3135, 2019 velocity of 12m / s is calculated for the airflow just below the propellers of a drone. Notably this velocity is also very consistently distributed right below the propellors and does not disperse a lot and maintains a rather stable downward airstream. Calculating displacement for the DJI M300. A DJI M300 drone weighs 6.3kg with batteries and can carry a max payload of 2.7kg, so total maximum weight is 9kg at which it can still propel itself upward with significant speed. The propellor diameter is approximately 53cm, and it has 4 propellors. This equates to a total swept area of 71 *0.2652*4=0.883m2. During hovering ((i.e. flight at stable altitude, which is often the mode at which samples are taken) and with a full payload 9kg worth of airmass is being displaced to compensate for the weight of the drone in an area of 0.883m2 with a full payload (or in force: 9kg * 9.81N / kg = 88.29N). Air has a density of approximately 1.225kg / m3 at sea level. And this thus means 9x1.225=11.025m3 air is displaced within the total aggregated swept area to counterbalance this gravitational force and this amounts to ~12.5m / s and thus aligns well with the 12m / s airflow velocity calculated by McKinney et al (2019). With a lighter payload this may be less and for a DJI M300 drone without payload this may be roughly 8.5m / s2 when the drone is hovering. As the drone can safely carry 2.7 kg on top of its 6.3 base weight, we assume we can either add 40% more weight or remove 40% of the lift capacity by impeding the free airflow. In essence this would mean we could capture and divert the air from almost 40% of the swept area 200. However, as we are also adding weight and assume the funnels (if used) cause interference we would only recommend to scale up to 25%. Although this should be calculated, modelled and evaluated for each drone and sampler design; also incorporating any interference plus any residual lift of the air exiting the sampling chambers. If we assume 20% of the swept area 200 can be covered by an inlet this means we capture the moving air over an area of 0.17m2 (i.e. 4 circular inlets each of approximately 23cm in diameter for a DJI M300). At air flow speeds between 8.5 to 12.5m / s this means we potentially sample between 1445 to 2125 L / s. The drone will re-adjust the propellor speed to counterbalance the lost lift capacity due to the funnel, so the low end of 8.5m / s is likely never achieved and this value should be higher. Each minute this device can thus sample up to 127,500 L. This is roughly 70 times higher than the l,800L / min achieved with one of the highest power stationary suction samplers which is a 220V powered vacuum cleaner using a water reservoir. In tests using funnels having a diameter of 7.5cm, each thus having an area of 0.0044m2 giving a total area of 0.0177m2. This yields an air sampling volume of 220L / s or 13,253L / min. This is roughly 7 times higher than the 220V powered vacuum cleaner using a water reservoir (1800L / min). Figure 4 shows an example of a sample collection system including a funnel arrangement. In Figure 4A the system is assembled, as it was in the example shown in Figure 3. A sample collection chamber 400 may be provided with a removable end cap 402. The end cap 402 may be attached to the base 302 so that it remains in place when the sample collection is decoupled from the end cap 402. Conveniently the chamber and the cap are provided with cooperating thread formations to allow them to be releasably secured together. The cap and / or a mating surface of the chamber may be provided with one or more sealing elements so that when secured together a waterproof seal is provided between the chamber and the cap. A removable sample collection vessel 404 is provided within the chamber, for example resting on, or attaching to, the inner surface of the cap, the vessel 404 receiving the lower end of the funnel 300. Air is free to flow from the lower end of the funnel into and then out of the collection vessel, to exit the chamber 400 via outlets 120. That is, the collection vessel does not sealingly engage with the funnel (such an arrangement would be possible if the collection vessel were ventilated, but such an approach is less favoured albeit remaining an option). Figure 4B shows the base or end cap 402 removed, and a sample collection vessel 404 removed from within the chamber 400. To maintain sterile sampling conditions it is possible the entire chamber 400 and funnel structure 300 are replaced for each sampling run, while the base 302 and base cap 402 remains attached to the drone. Alternatively it is cleaned in between sampling flights using for example a bleach solution at 5% after which the equipment is washed off with sterile water and dried. The collection vessel may be pre-charged (for example to a depth of 1 or 2 cm) with a buffer solution suitable for harvesting environmental DNA or RNA - for example freshly prepared phosphate buffered saline (PBS). A suitable composition of PBS may be prepared by adding to 1 litre of distilled water 8 g of sodium chloride; 0.2 g of potassium chloride; 1.44 g of sodium phosphate dibasic and 0.245 g of potassium phosphate monobasic, the pH of the solution being adjusted to pH = 7.4. Other liquids which may be used to pre-charge the collection vessel are listed in the section discussing Figure 14, and these may each be used in this application. As an alternative to providing a tall sample collection vessel 404 of the general form shown in Figure 4, a shallow collection vessel may be used - for example such a shallow collection vessel may take the form of a Petri dish. Shallow collection vessels may for example be used to hold collection gels, porous substrates or FDA cards wetted with one of the previously referenced sampling liquids (such as nuclease-free water, PBS, etc.). The sampling collection vessels, and their variants, whatever their form, may also be provided instead with other sampling materials, all of which represent nucleic acid friendly media which may be used to retain the samples until (for example the end of a flight) or until they can be removed for analysis or until further processing, such as one or more of the following: 1) Silica matrices, including silica beads, silica particles, hydrated silica matrix and silica gels; Based on the high affinity of the negatively charged DNA backbone towards the positively charged silica particles; 2) Glass particles, powder or beads, including silicate glass, flint glass, and borosilicate glass (e g. in the form of one or more glass fibre depth filters (as distinct from the more common membrane filters) such as those manufactured and marketed by SKC Limited of Blandford Forum, Dorset, England. As SKC’s marketing material explains “depth filters of this kind do not have a uniformly defined pore structure, but rather fibres or sintered particles that intertwine to create a tortuous path of openings that allow air to pass through, but trap particles throughout the depth of the filter”.); 3) Mixtures of silica gel and glass particles, as these may be highly effective; 4) Magnetic beads specific for nucleic acid purification, as well as zirconia beads, can be envisaged to be used. A binding buffer is used to activate the magnetic particles ability to bind DNA and then a salt solution is used to release the DNA for processing. Magnetic beads could also easily be fixed to the cup either using adhesive or by providing a ferromagnetic part (and / or one or more permanent magnets, which could optionally be embedded or otherwise integrated into the structure of the sampling cup). For the avoidance of doubt, these largely solid state sampling media may also be used in conjunction with the cyclonic separation approaches described for example with reference to figures 9 to 12. Turning once again to figure 3, the arrangement shown could be applied to a drone such as DJI’s M300 device. This has 4 rotors with propellers having a diameter of 21 inches (approximately 53cm). A sample collection system may be provided for each rotor. Each collection system may be secured in place with its inlet wholly behind its respective rotor - that is with the inlet opening located within a projection of the periphery of the area swept by the tips of the rotor, the projection being the same size as the swept area and centred on the axis of rotation of the rotor. Each collection system may be provided with a funnel whose inlet diameter is between 5 and 25 cm, for example 7.5cm, 10cm, 12.5cm, 15cm, 17.5cm or 20cm. Each funnel inlet may be separated from its respective rotor by a distance of between 1 and 10 cm, for example 2, 3, 4, 5, 6, 7, 8, or 9cm. It will be appreciated that a funnel arrangement generally as described and shown with reference to Figure 4 may equally well be applied to collections systems according to both Figures 2A and 2B. Figure 5A illustrates a sampling method according to an aspect of the invention. Here a drone 100, which may be of the described with reference to any of Figures 1 to 4, is being flown in relatively close proximity to the ground, typically at a height of less than 3 metres, and generally at a height of 1.75 or 1.5 metres or less from the ground, so that downwash 502 from the drone’s rotors disturb material, such as organic material in the form of microorganisms growing or feeding on leaf litter, eDNA or eRNA shed by (or coming from the remains of) animals that live in or have visited the sample site or that has settled from the air. If the drone is flown sufficiently close to a substrate such as the ground, a body of water, a man made structure such as a solar panel array, a building, vegetation, or a foliage canopy, disturbed material may be thrown upwards sufficiently far that at least some of it is then sucked into the drone’s rotors from where it is driven down into the inlet(s) of the drone’s sample collection system(s). That is, downwash may circulate to provide a kind of recirculating air flow (sometimes referred to as “circular flow” or “circular air flow”). This effect, or something similar, may also be referred to as wake reingestion, based on the phenomenon of that name observed with helicopters. It will be appreciated that the ease with which material on the ground is disturbed, and hence the ease with which this ground material may be sampled by the drone 100 depends upon the inherent nature of the material and its size and weight. More generally, animal scales, hairs, and excrement, insects, fungal spores, and plant material may be expected to be collectable. The other main controlling factor is the moisture content of the material - where a fully saturated substrate / floor may reduce the ease with which material can be blown upwards by downwash, whereas a dry substrate / floor or merely moistened substrate / floor may facilitate sample collection. The extent to which material on the ground experiences downwash from the drone depends not only upon the power supplied to the drone’s rotors, their size and number, but also on the separation between the material and the drone’s rotors. Flying the drone closer to the ground is likely to throw up more material, so that by controlling the height at which the drone is flown (and optionally the amount of power fed to the rotors, and / or the rotor speed) it may be possible to control a sampling event so that an acceptable level of the right kind(s) of material can be harvested from the ground. It will be appreciated that a certain amount of trial and error is likely to be required in order to optimise sample collection. Some results of the described sampling method, performed at a range of heights, are shown in figure 15, which is also described later in this application. It will also be appreciated that this sampling method, which may require a drone to be flown at heights at which collision with people walking on or otherwise present on the ground is a significant possibility. In most jurisdictions there are restrictions on flying drones at such low heights in urban and other inhabited places. To this end, the method is particularly suited to wilderness areas (wetlands, marsh areas, savannah, tundra, mangrove swamps, rainforests,), and agricultural areas (especially arable terrain) where the farmer / landowner can restrict human and animal access to the terrain, and / or where the substrate is inaccessible due to height or other restrictions. The technique is also highly applicable to the collection of samples from bodies of water (seas, lakes, rivers, etc.). An alternative to the collection method described with reference to Figure 5A is illustrated in Figure 5B. Here, a drone 500 according to any of the aspects of this invention is arranged to drip or spray a liquid (such as nuclease-free water, distilled water, PBS, or a suitable isotonic solution, or one or more of the liquids mentioned in the discussion of figure 14 ) onto a rotor or into a zone in front or behind the rotor, so that the liquid forms small droplets in the downwash, the droplets acting to capture (optionally bind to) material of interest (such as dust particles, pollen, insects, fungal spores, animal matter, excreta, etc.) which may then be caught up in air circulating around the rotor - so that sample-rich droplets arrive at the inlet of a sample collection system of the drone. Depending upon whether cell-integrity is important, the liquid may include a soap, a detergent, or other surfactant so that the liquid serves facilitates the release of DNA-containing particles from surfaces, such as tree leaves. In Figure 5B the drone 500 is shown as having 3 nozzles 502, 504, and 506, the first 502 arranged to dispense, drip or spray liquid in a generally downward direction 507, the second 504 arranged to spray liquid laterally 508, and the third 506 arranged to spray liquid generally upwards 509. It will be noted that nozzle 502 is located to the rear of both rotor 510 and rotor 511, and is positioned so that the area swept by rotor 510 overlaps the nozzle 502. Similarly, nozzle 504 is located to the rear of both rotor 510 and rotor 511, proximate to the area swept by rotor 510. In this way the nozzles 502 and 504 both dispense liquid into regions behind at least one rotor, yet the liquid so dispensed may be caught up in an airstream that caused the liquid to enter an inlet of a sample collection system either having passed through the swept volume of the relevant rotor or having otherwise becoming caught up in downwash so that the downwash pushes the liquid (and any entrained particles or other biological material) into a collection system inlet. It will also be noted that in figure 5B the sideways directed nozzle 504 is shown as being positioned to be more or less aligned with the outer edge of the closest rotor’s swept area, as this may enable spray from the nozzle to jet sideways without too much disturbance by rotor downwash. On occasion it may be beneficial to locate the nozzle 504 more outwardly from the drone, beyond the (projection of the) outer edge of the closest rotor’s swept area, to reduce disruption to spray emerging from the nozzle 504, while at other times there may be a benefit to locating the nozzle 504 further in, so that its spray is more directly influenced by the rotor’s downwash. To some extent, optimal positioning will depend upon the results to be achieved and the nature of the liquid being sprayed, the velocity and volume of downwash, and the nature of the substrate being sprayed. Likewise, the extent to which spray from downward facing nozzle 502 and upward facing nozzle 506 is sucked into a rotor, or pulled into a downwash flow is likely to depend on the positioning of the relevant nozzle: e.g. for nozzle 502, directly under the respective rotor, at the edge of the projection of the rotor’s swept area, or beyond the projection of that area; and for nozzle 506 the height of the nozzle above the rotor(s) and the amount of offset with respect to the closest rotor. The sample-rich droplets and other material disturbed by the downwash and / or the liquid release may enter an inlet 516 of a sample collection system 512 with or without having passed through the swept area of a rotor, since such droplets / material may be picked up by downwash and thereby propelled into an inlet 516. In practice such a drone may have only one of these nozzle arrangements, two of them, or all three nozzle arrangements, depending upon the area, surface, or region being targeted and the planned sampling objective. Additionally, the nozzles may rotate on an axis to allow the spraying direction to be changing continuously, or in a step-wise manner, covering the downward, later and upwards regions sequentially. The or each nozzle may also be adjustable to control the lateral spread and the degree to which the liquid flow is broken up into small droplets (at one extreme) or a stream of liquid (at the other extreme) may also be adjustable before (manually or under electrical control) or during a flight. When the drone is hovering, or indeed in flight generally, there is a tendency (at least under some flight conditions) for air to circulate, as shown schematically by looped arrows indicated as 514, so that air (and particles) in downwash loops back upwards to be sucked into rotors again. In the arrangement shown we take advantage of this drift tendency (or recirculation) to improve the harvesting of material from the environment through which the drone is flown by spraying a liquid, such as PBS, or (a particularly favoured solution) a DNA extraction buffer that is based on a mix of Tris-EDTA with SDS, a detergent, which may dislodge, disturb, or dissolve organic material which is then entrained in the swirling airflow 514 and hence forming part of the downwash which can then be captured by the sampling systems 520. Nozzles spraying a liquid, such as those mentioned in the discussion of figure 14 , would lead to disturbance of surfaces possibly more effectively liberating eDNA / eRNA (if jetted with force); possibly washing eDNA / eRNA from surfaces; and possibly aerosolizing eDNA / eRNA particles by encapsulating them into droplets allowing for better capture. Another example of such an arrangement, this time using a vortex separation device, is illustrated in Figure 12. Figure 6A is a schematic plane view of a magazine arrangement to permit sequential gathering of discrete samples in segregated sampling compartments. Figure 6B shows the same arrangement in side elevation. In the figures the swept volume of a drone rotor is shown as 108. Beneath this swept volume, a funnel 300 feeds an inlet of a sample collection system. In this example a magazine 600 is provided to house a plurality of removable sample collection vessel 602, each received in a respective chamber 604. In the arrangement shown it is assumed that the magazine is formed of a flexible material so that it can follow an elliptical path, thereby potentially reducing undesirable obstruction of rotor downwash and hence reducing loss of lift. Suitable materials include durable rubbers, including potentially silicone rubbers, optionally with an aramid or polyamide core (or cores). The magazine 600 may include or be coupled to a toothed arrangement by means of which a pinion of a drive motor 606 may be used to rotate the magazine with respect to the inlet of the sample collection system. The drive motor 606 is operatively coupled to a controller 608, by means of which the motor may be controlled to rotate the magazine step wise so that for each new sampling event (as controlled by a human flight controller and / or according to a pre-programmed schedule (e g. based on detected location, time, height, atmospheric pressure, temperature, and / or other sensor values) a fresh sample collection vessel is provided to collect output from the funnel 300. It will be appreciated that in alternative arrangements a magazine may be provided which moves through a circular rather than an elliptical path - thereby enabling the use of a rigid or substantially rigid magazine (although of course a resilient magazine could still be used). Such a circular magazine could be rotated about its axis using a direct drive system or a belt drive system, for example In order to maintain the integrity of the individual samples, the magazine arrangement may be provided with a cover 616. The magazine arrangement may be configured as a cassette to be loaded to and unloaded from the drone to permit rapid exchange of a fresh magazine for one containing samples. Preferably, the relevant sampling system (not all of which on a given drone may necessarily use a magazine system) is arranged to permit the rapid replacement of the inlet funnel (if used) - funnels being provided with a quick release coupling arrangement, e.g. a quarter turn to release or lock to a cooperating mount. Optionally the funnel is so arranged that samples do not come into contact with any mount to which the funnel couples, for example the mount being annular and the funnel extending fully through the annular mount. In an alternative arrangement each of the collection chambers may be provided with its own dedicated funnel, the cover 616 being arranged to cover the funnels, so that only the funnel of the collection chamber currently in use is exposed. Such an arrangement is likely to reduce the risk of contamination between different sampling events. Although, for the sake of simplicity, Figures 6A and 6B do not show the presence of air outlets for the sampling chamber positioned at the base of the funnel, it will be understood that such ventilation is provided to permit the escape of air after it has passed through the sampling chamber. Thus, the magazine preferably includes outlet ports for each chamber 604, at least on the outer periphery and optionally both on the outer and inner peripheries. The magazine, or a cassette including the magazine, may include one or more walls or other structures to block these outlet ports for all but the chamber positioned to receive air from the funnel 300, to reduce the risk of undesirable contamination before or after sample collection. Figure 6C is a schematic plan view of the aerial copter drone 100, with an alternative example of a magazine 600 to permit sequential gathering of discrete samples in segregated sample collection chambers 604. Figure 6C illustrates the placement of the inlets 116 of the sample collection system 112 in relation to areas 200 swept by the respective rotors 108 of the aerial copter drone. The magazine 600 comprises a plurality of sampling positions 622 arranged to receive air from the inlets 116 of the sample collection system 112. The magazine 600 may comprise one respective sampling position 622 for each respective inlet 116. The magazine 600 comprises a plurality of sample collection chambers 604. The plurality of sample collection chambers 604 of the magazine 600 are arranged such that they may be positioned at one of the plurality of sampling positions 622. When positioned at one of the sampling positions 622, the respective sample collection chamber 604 overlaps with the respective inlet 116 of said sampling position 622. The plurality of sampling positions 622 are arranged such that when a sample collection chamber 604 of the plurality of sample collection chambers 604 is positioned at one of the plurality of sampling positions 622, the sample collection chamber 604 may receive air from 28 the respective inlet 116. A respective funnel 300 (not shown) may be arranged to feed air to each respective inlet 116. The magazine 600 according to the embodiment of Figure 6C may include or be coupled to a drive motor 606 (not shown) which may be used to move the plurality of sample collection chambers 604 of the magazine 600 with respect to the plurality of sampling positions 622. By such movement, the plurality of sample collection chambers 604 may be sequentially one after the other exposed to air from the inlets 116. In Figure 6C the magazine 600 is illustrated as overlayed on the aerial copter drone for ease of understanding, however it is to be understood that the magazine 600 is arranged beneath the swept volume of the rotors 108 of the aerial copter drone such that the air from the inlets 116 is received by the magazine 600. An advantage of the magazine 600 according to the embodiment of Figure 6C is that it comprises a plurality of sampling positions but only requires a single drive motor 606, thus requiring fewer electronic components and resulting a lower weight as compared to having a plurality of separate magazines arranged under different respective rotors 108 of the aerial copter drone. Although, for the sake of simplicity, Figure 6C does not show the presence of air outlets for the sample collection chambers 604, it will be understood that such ventilation is provided to permit the escape of air after it has passed through each respective sample collection chamber 604. Thus, the arrangement 620 preferably includes outlet ports for each chamber 604, at least on the outer periphery and optionally both on the outer and inner peripheries. The arrangement may include one or more walls or other structures to block these outlet ports for all but the sample collection chambers 604 positioned to receive air from the funnel 300, to reduce the risk of undesirable contamination before or after sample collection. The aerial copter drone 100 may comprise any number of rotors 108, for example one, two, three, four, five, six, seven, or eight rotors 108. The aerial copter drone 100 may comprise any number of funnels 300, for example one, two, three, four, five, six, seven, or eight funnels. The aerial copter drone 100 may comprise one funnel for each respective rotor 108. Each inlet 116 may have a corresponding funnel 300, or one funnel 300 may be connected to a plurality of inlets 116. Each inlet 116 may have one corresponding sample collection system 100. Alternatively, more than one of the inlets 116 is connected to one sample collection system. The sampling chambers of the previously described arrangements, and their variants, may contain a sampling liquid, such as nuclease-free water, PBS, or any of the other options referred to later in the discussion of Figure 14. They may also be provided instead with other sampling materials such as one or more of the following: 1) Silica matrices, including silica beads, silica particles, hydrated silica matrix and silica gels; Based on the high affinity of the negatively charged DNA backbone towards the positively charged silica particles; 2) Glass particles, powder or beads, including silicate glass, flint glass, and borosilicate glass (e g. in the form of a glass fibre depth filter of the kind previously mentioned); 3) Mixtures of silica gel and glass particles, as these may be highly effective; 4) Magnetic beads specific for nucleic acid purification, as well as zirconia beads, can be envisaged to be used. A binding buffer is used to activate the magnetic particles ability to bind DNA and then a salt solution is used to release the DNA for processing. Magnetic beads could also easily be fixed to the cup either using adhesive or by providing a ferromagnetic part (and / or one or more permanent magnets, which could optionally be embedded or otherwise integrated into the structure of the sampling cup). In variants of one or more of the previously described sampling arrangements the or each sample collection system may include a cyclone arrangement, downstream of any funnel, to spin captures particles to provide some degree of particle separation based on the well-known principles of cyclonic separation. Suitable such arrangements are described with reference to Figures 9 to 12. In variants of one or more of the previously described sampling arrangements the or each sample collection system may be configured to capture sampled material of interest using one or more of adhesion (e.g. to a tacky or sticky surface), adsorption, absorption, electrostatic attraction, or chemical bonding. In variants of one or more of the previously described sampling arrangements the or each sample collection system may be configured to capture sampled material of interest using a filter or matrix through which air may pass to leave behind particulate material. Figure 7 is a schematic showing a potential arrangement for obtaining samples of water and water-borne material from a body of water (which may find application when the method illustrated in Figure 5 is not possible for example). A sampling drone, for example as described with reference to any one figures 1 to 4, 700 is provided with a water sampling rig 702 that is carried beneath the drone 700. In the example shown the water sampling rig 702 rather than being close coupled to the body of the drone 700 is suspended on flexible cables 704 to hang, typically a metre or more, below the underside of the body of the drone 700. In an alternative configuration the water sampling rig may be close coupled to the drone, rather than being suspended by cables, although the decoupling of the rig with respect to the drone that comes with the use of a flexible suspension arrangement means that sampling from rough or choppy water is much easier - since the drone can be flown or hovered at a fixed height with the sampling rig floating on the surface of the water despite any choppiness or swell. The water sampling rig 702 here comprises a buoyant body 706, here in the form of a ring (for example made of closed cell polymeric foam) which is shown in vertical cross section. Coupled to the buoyant body 706 is a support 708, such as a platform, that carries a water pump 710, that in turn is coupled to a controller 712. A power supply, no shown, provides electrical power to the pump 710 and controller 712 (although these may instead contain their own power supplies). The controller 712, which may control operation of the pump 710, may be in wired or wireless communication with a controller of the drone. The pump 710 is coupled to a feed pipe 714 which protrudes beneath the lower edge of the buoyant body, so that when the buoyant body is at rest on the surface of a body of water the pipe 714 extends into the water with the open end of the pipe beneath the surface of the water. The water sampling rig 702 may be provided with an indicator 716 in the form of a float which protrudes beneath the support 708 so that when the rig floats on the surface of a body of water an indicator or indicator portion of the float becomes visible (or becomes fully visible) to signal that the rig is resting on the surface of a body of water - and hence that the water may be sampled. The rig may include a video camera to capture the behaviour of the indicator 716 (although a camera 718 of the drone may be able to capture any necessary images to perform this function). Additionally or alternatively an electronic sensing arrangement may be provided in order to signal that the water sampling rig 702 is in position for sampling to take place. The pump 710 may be arranged to pump sampled water through one or more filter in order to capture material from the sampled body of water (e g. eDNA, eRNA, microcellular organisms, etc.). Additionally or alternatively the pump may be arranged to collect one or more water samples that are then stored in an appropriate container(s) 720 on the water sampling rig 702 for subsequent analysis. The water sampling rig 702 may be arranged to be lowered from the drone during flight, to permit sampling to take place, e.g. under the control of a human or automated external flight controller, or according to instructions stored on the drone 700. The water sampling rig 702 may then be pulled back up towards the drone prior to landing. Alternatively, the position of the water sampling rig 702 with respect to the drone 700 may not be adjustable, a suitable landing station perhaps being provided to facilitate controlled landing and take-off without risk of the drone becoming unstable during landing, thereby reducing the risk of damage to the drone and its rotors. Figure 8 is a schematic showing a potential arrangement for obtaining samples of plant material. A sampling drone, for example as described with reference to any one figures 1 to 4, 800 is provided with a plant sampling rig 802 that is carried beneath the drone 800. In the example shown the plant sampling rig 802 rather than being close coupled to the body of the drone 800 is suspended on flexible cables 804 to hang, typically a metre or more, below the underside of the body of the drone 800. In an alternative configuration the plant sampling rig may be close coupled to the drone, rather than being suspended by cables, although depending upon the nature of the foliage being sampled The plant sampling rig 802 here comprises a platform or body 806, here in the form of a rigid beam. Coupled to the platform 806 are a mechanised clasping arrangement 808, and a mechanised cutting arrangement 810, both controllable by a human or automated controller. The mechanised clasping arrangement 808 and the mechanised cutting arrangement 810 may be coupled to a local controller 812 mounted on the platform 806, or they may be coupled (in a wired or wireless manner) to a controller of the drone 800 (and in either event controllable to grasp and cut on demand). The mechanised cutting arrangement 810 may conveniently be in the form of electric secateurs (for example of the kind available from Bahco and other suppliers). The platform 806 may also carry a local video camera 814 to provide close up views showing the position and state of the clasping and cutting arrangements 808 and 810, for example whether or not a suitable sample is available for capture. Alternatively, a camera of the drone 800 may be used to provide this information. In either case, the relevant images may be streamed to the drone’s remote pilot. The plant sampling rig 802 may be used to collect samples, such a leaves, twigs, and or branches, and this may provide not only information about the plant from which this material comes, but also information about fungi, insects, animals, etc. that have deposited organic material on the relevant substrate. To collect a sample the drone is flown into position and the sampling rig deployed (if not already deployed). The drone is then manoeuvred so that a suitable plant sample is in position to be grasped by mechanised clasping arrangement 808. By actuating the latter, the sample, e.g. a branch, is secured so that the branch also passes through the cutting arrangement (e.g. between a pair of blades of the mechanised cutting arrangement 810. The mechanised cutting arrangement 810 is then activated to sever the branch, freeing it to be carried away by the drone. The plant sampling rig 802 may be arranged to be lowered from the drone during flight, to permit sampling to take place, e.g. under the control of a human or automated external flight controller, or according to instructions stored on the drone 800. The plant sampling rig 802 may then be pulled back up towards the drone prior to landing. Alternatively, the position of the plant sampling rig 802 with respect to the drone 800 may not be adjustable, a suitable landing station perhaps being provided to facilitate controlled landing and take-off without risk of the drone 32 becoming unstable during landing, thereby reducing the risk of damage to the drone and its rotors. In an alternative arrangement, the plant sampling rig may use adhesive surface and or swabs that are brought into contact with a surface to be sampled. In this way, eDNA or eRNA and other biological materials may be gathered from elevated surfaces such as tree canopies, cliffs, and man-made structures such as pylons, chimneys, and wind turbines. We will now describe various potential approaches that may be used in sample collection systems to collect samples from an atmosphere through which the drone is flown. These include various particle filtering approaches based on the use of Coriolis or cyclonic separators, either individual cyclones or multicyclones comprising multiple cyclones. In a cyclonic separator, a gas stream is caused to rotate so that particles within the stream are subject to centrifugal acceleration. Commonly, a gas stream in a cyclonic separator is caused to rotate either by being introduced tangentially into a generally cylindrical (possibly also conical) void (in a tangential inlet device), or (in an axial feed device) by passing the gas stream through a “swirler” which gives rise to swirling motion. A suitable swirler may comprise a set of blades that define a helical path upstream of the generally cylindrical (possibly also conical) void. A further characteristic of cyclonic separators, of both inlet types, depends upon whether flow through the device reverses (i.e. the direction of flow changes by 180 degrees) so that cleaned gas and separated particles leave the device at opposite ends, or whether there is no reversal of flow so that the cleaned gas and the separated particles pass through the device to exit at the same end of the device: the two classes of device are referred to as “reverse flow ” and “through flow” respectively. Through flow devices may also be referred to as vortex tube separators. In attempting to extract particles from rotor downwash, as we are in aspects of the present invention, we could use reverse flow cyclonic separators (and their use is contemplated in the context of this invention), but it will generally be more efficient in terms of sacrificed lift to have the filtered air exit the cyclonic separator or cyclonic separator array at or towards the rear of the separator or separator array, air having entered at the opposite (upstream) end, so through flow devices are likely to be more interesting. In particular it can be beneficial to use a vortex tube separator with the filtered air output arranged to contribute lift to the drone (thus mitigating to some extent lift lost through the addition of a sampling arrangement in the downwash of a rotor. There are many variables that affect the efficiency of cyclonic separators, and these may usefully be optimised to improve the separation efficiency for particles (paying attention to the size, mass, etc. of the particles it is intended to collect) and to reduce the pressure drop through the cyclonic separator and thereby potentially to minimise the loss of lift for a given size of capture device. Many of these issues are discussed, in the context of improving filtration efficiency in cyclone assisted air filtering arrangements for internal combustion engines, in the paper “Experimental investigation of possibilities to improve filtration efficiency of tangential inlet return cyclones by modification of their design”, by Tadeusz Dziubak, published in Energies, 2022, 15, 3871. Despite the paper focusing on tangential inlet return (reverse flow) cyclones rather than on axial flow devices, there is much useful discussion of design considerations that may affect both axial and reverse flow devices whether or not they have tangential inlets. It should also be appreciated that because Dziubak was concerned with air filtration for the air intake of an IC engine the cyclonic separators were required to filter the intake air with a pressure differential of less than one atmosphere, whereas in our application the cyclonic separators will typically be exposed to inlet pressures leading to pressure differentials much greater than one atmosphere - as we have shown elsewhere in this application. Whereas in general the smaller the diameter of a cyclonic separator the smaller / lighter the particles that it can capture, by increasing the inlet pressure we may increase the flow velocities in the separator and hence enable smaller / lighter particles to be collected even with larger diameters, allowing more volume to be processed. With a significant increase in inlet pressure there will generally also be a significant increase in flow velocities and this may be expected (at least with suitable design of the separators) to increase the efficiency of filtration and permit the capture of lighter / smaller particles for a separator of a given size. The use of vortex based particle separation, using vortex tube separation, for example as described in US patent 4,985,058 (an example of many such designs which may be applicable to the present application) will be described with reference to Figure 9. Another type of cyclonic separation, here referred to as tornado sampling will be described with reference to Figure 10. An example of positive pressure cyclone sampling will be described with reference to Figure 11. Figure 9A is largely based upon Figure 1 of US4,985,058, with some additions. The following description of the figure is based upon that of the earlier patent. A vortex tube gas cleaning device is generally indicated by reference numeral 900. The device 900 has an outer tube 912 of round cylindrical shape with an inlet 914 at one end, the inlet end being the upstream end in use. Closely spaced downstream of the inlet 914, is a vortex generator generally indicated by reference numeral 916 positioned in a vortex generating region 918. Downstream of the vortex generating region 918, is a separation region 920. In use, flow through the device 900 is divided in the separation region 920 into a peripherally outward scavenge flow stream 922 and a central or main flow stream 926. Downstream of the separation region 920, there is defined a peripherally outward scavenge region 924 into which the scavenge flow stream 922 is directed. The scavenge flow stream is contracted toward an annular scavenge orifice 929. Concentrically inward of the scavenge region 924, a central or main outlet region 928 is provided, into which the main flow stream 926 is directed in use. The scavenge region 924 and the central outlet region 928 are separated by an inner extraction tube 930 which has an inlet defined by a leading edge 942 of a central orifice 940 at the downstream end of the separation region 920. The extraction tube 930 diverges generally outwardly to meet the outer tube 912 and is mounted to the outer tube 912 at a predetermined mounting position generally indicated by reference numeral 932. At the position 932, the inner tube 930 defines a concentric spigot formation 934 which may be slightly taper if desired. Further at the position 932, the inner periphery toward the downstream end of the outer tube 912 forms a concentric socket 936. The spigot formation 934 preferably seats snugly and concentrically in the socket 936. A shoulder 938 on a peripheral flange on the extraction tube 930 immediately downstream of the spigot formation 934, and a downstream end face 939 of the outer tube immediately downstream of the socket 936, form checking formations which inter-abut to locate the inner tube axially in relation to the outer tube. Thus, by means of the connecting formations 934 and 936, the inner tube 930 is stabilized relative to and concentrically positioned or centred relative to the outer tube 912, cantilever fashion. Thus, the inlet to the peripheral outlet region 924 is defined concentrically about the leading end of the inner tube 930. The inlet forms part of a continuous annular flow passage. Downstream of said inlet, a peripheral ring 927 having an oblique leading face 925 protrudes into the annular flow passage. The crown of the ring and the inner periphery of the outer tube 912 form the annular scavenge orifice 929. The ring 927 is integral with the inner tube 930 and extends from an outer periphery thereof. The oblique face 925 guides the scavenge flow stream 922 in contracting fashion into the scavenge orifice 929. Downstream of the scavenge orifice 929 there is defined an annular scavenge chamber 946 within the annular scavenge region 924. Circumferentially spaced ports 948 provided through the wall of the outer tube 912, lead from the scavenge chamber 946 and form circumferential outlet means for the scavenge flow 922. Upstream extremities 950 of the ports 948 are axially spaced a predetermined distance downstream of the scavenge orifice which is at least 25% of the internal diameter of the outer tube. In a preferred embodiment, the spacing is about 30% of said internal diameter. In use, a particle containing gas flow stream enters the device 900 at the inlet 914. Rotating flow is generated in the vortex region 918 which induces the particles, which will be of higher specific gravity than the gas, to move outwardly on account of the rotating flow. Thus, the 35 scavenge flow stream 922 will be enriched in respect of the particles and the main flow stream 926 will be depleted in respect of the particles. Expressed in other words, the gas is cleaned of particles, hence the term gas cleaning device. The scavenge flow stream 922 enters the peripheral outlet region 924, is contracted as it flows into the scavenge orifice 929, and then enters the extraction chamber 946 from where it is exhausted via the ports 948. The particle depleted or cleaned main flow stream 926 enters the central outlet region 928 and is exhausted from there. It will be appreciated that such a vortex device may be used to extract biological or other particles from an atmosphere by locating the vortex device in the downwash of a rotor of a drone in accordance with the approaches described with reference to Figures 1 to 6. The extracted particles may be collected by providing a collection surface or chamber 992 (shown in broken lines) around the ports 948 preferably provided with a lid or cover 993, the lid being spaced from the chamber to allow the escape of air. The chamber 992 may optionally contain a suitable film membrane or gel, a liquid (for example as mentioned in the discussion of Figure 14), a largely solid state sampling medium (e.g., as previously described), or an FDA card or the like, optionally wetted with PBS (or one of the other solutions mentioned elsewhere in the specification) or providing. The main flow stream 926, exiting via the central outlet region 928, leaves the vortex device at outlet 990, may contribute to the lift provided by the relevant rotor - so that the loss of lift due to the presence of the particle collection arrangement may be less than would be the case with a collection arrangement such as those shown in Figures 1 to 4 of comparable size. As with the collection arrangements illustrated in Figures 1 to 4, a vortex sampling arrangement may be provided with a funnel arrangement 995 at the inlet, as shown by the broken lines, to increase the percentage of the downwash from a rotor that is sampled. Indeed, using a sampling arrangement comprising an array of vortex samplers it may be possible to direct all or substantially all of the downwash from a rotor into the sampling arrangement and yet still obtain significant lift from that rotor, thanks to the volume of filtered air leaving the sampling arrangement in a direction suitable for providing lift or propulsion. Figure 9B is a schematic showing another vortex sampling arrangement in which a vortex generator 956, which may be of generally helical form, receives downwash 958 from a rotor 960, the output of the vortex generator feeding a body 962 having a generally conical inner chamber 964. A tubular exhaust section 966 is provided at the lower extremity of the chamber 964, and extends both upwards into the chamber 964 and out from the chamber 964. The tubular exhaust section 966 may, as shown be aligned with the longitudinal axis of the chamber, so that the 36 chamber and the exhaust section are co-axial. Most of the downwash 958 that enters the sampling arrangement exits via the exhaust section 966. The lower end of the chamber 964 has ports 967 that open into a collection arrangement 968 to allow separated particles to pass into the chamber 964. The collection arrangement 968 is arranged about the lower extremity of the body 962 and the exhaust 966 comprises two-parts, a lower part 970 and an upper part 972. The lower part 970 of the collection arrangement has a base 974 and an upstanding sidewall 976 around the periphery of the base which together a kind of open topped vessel. The upper surface of the base provides a collection surface for particles separated out from the downwash. The upper part 972 of the collection arrangement 968 provides what is in effect a lid or cover for the open topped vessel provided by the lower part 970. Thus the upper part has a top part 978, which may be in the form of a disc, and which extends around and seals to the body 962. An annular skirt or flange 980 extends downwardly from the periphery of the top part 978, enclosing and extending past the upper edge of the sidewall 976 of the base 974. The upper part 972 of the collection arrangement is larger (e.g. has a larger diameter) than the lower part 970, so that the skirt 980 and the sidewall 976 are spaced apart with a gap 982 between them. Also, the top part 978 is spaced from the upper edge of the sidewall 976, so that air that air that emerges from the lower end of the body 962 is able to pass through the collection arrangement and out through the gap 982 between its upper and lower parts. The lower part 970 of the collection arrangement may include a sampling liquid, for example as described with reference to figure 14, or a largely solid state sampling medium as previously described. In use, rotor downwash 958 enters the separator carrying particulates such as airborne e-DNA in the form of cells, pollen, spores, viral particles or biological “particles”, and possibly some free floating DNA / RNA, possibly in the form of aerosols or within floating liquid phases. The downwash is caused to spin by the vortex generator 956, and as the resulting vortex passes down the chamber 964 its rotational velocity increases, increasing the centrifugal force acting on particles carried by the vortex. Depending on the mass and air resistance, many of these particles will come into contact with the inner sidewall of the chamber 964 where they will decelerate and be carried down the sidewall to the open lower end 967 by the combined effects of the vortex and gravity. Air depleted of at least some of the originally carried particles emerges from the separator via the exhaust 966. A relatively small amount of air also exits the chamber 964 via the open lower end 967, carrying with it the particles that have separated out from the vortex. The separated particles tend to remain in the collection arrangement 968, while the air that carried them out of the chamber 964 escapes through the gap 982 between the upper and lower parts of the collection arrangement. Figures 9C and 9D show schematically how multiple cyclonic separators, for example as generally described with reference to Figure 9A or 9B, or a cyclonic separator array, may be used in a sample collection system (e.g. to collect eDNA or eRNA samples) that has a funnel which collects rotor downwash and feeds it to the multiplicity of cyclonic separators or the array(s). In other words, each sample collection chamber of the plurality of sample collection chambers may comprise multiple cyclonic separators. In figure 9C a sample collection system 1900 is shown schematically in plan view from above (for example as though looking down from an overlying rotor). A funnel has an open upper end defined by an outer periphery 1902. A tapering skirt 1904 feeds a nozzle section 1906. The nozzle section 1906 in turn feeds the inlets 1914 of multiple cyclonic separators 1916 that may be individual units or in the form of an integrated array. In this example the nozzle or throat of the funnel (which corresponds generally with funnel 995 of Figure 9A) is generally circular in section, although other shapes, such as hexagonal, octagonal, or square section shapes may equally well be used and may facilitate close packing of the cyclonic separators with less wasted space. But even a circular or other rounded shaped funnel throat may permit close packing with little wasted space. The cyclonic separators may all have the same inner diameter, or two or more different sized separators (i.e. having different internal diameters) may be used potentially to improve capture of samples of different sizes, weights, densities, etc. Figure 9D is a similar schematic plan view from above of another sample collection system 1950 (for example as though looking down from an overlying rotor). A funnel has an open upper end defined by an outer periphery 1952. A tapering skirt 1954 feeds a nozzle section 1956. The nozzle section 1956 in turn feeds the inlets 1964 of multiple cyclonic separators 1966 that may be individual units or in the form of an integrated array. In this example the nozzle or throat of the funnel (which corresponds generally with funnel 995 of Figure 9A) has the general form of a quadrilateral. Again, the cyclonic separators may all be the same size (e.g. have the same inner diameter), or two or more different sizes may be used to target different sample materials. The separators may conveniently be arranged in a closely packed formation. Another kind of cyclonic separation, here referred to as tornado sampling will now be described with reference to Figure 10. In this arrangement 1000, downwash 1002 from a rotor 1004 is directed into a funnel 1006 (at least the lower end of) which is positioned generally substantially centrally (i.e. on axis) on a conical collection cup 1008. The collection cup has a larger open top perimeter 1010 and smaller closed bottom 1012. The attachment of the funnel 1006 to the cup may be achieved by means of low profile connectors, such as wires or rods (illustrated generally as 1014, but the precise arrangement is a matter of design preference), that leave open most of the top of the collection cup (i.e. the open upper end is preferably substantially unobstructed by the coupling arrangement), while provide structural integrity to the funnel and collection cup apparatus. The funnel 1006 includes an upper flared skirt, that narrows from top to bottom, that communicates with a straight-sided or tapered tubular nozzle 1016. The nozzle 1016 directs and guides the air downwash towards the bottom of the collection cup, but may as shown terminate some distance above the bottom of the collection cup. The guided downwash directly impacts a swirl inducer 1018 which may be in the form of a generally conical shaped protuberance located or formed at the bottom of the collection cup. The swirl inducer 1018 may be formed with channels that spiral (e.g. helically) around the swirl inducer in order to induce the formation of a tornado-like body of swirling air. In the collection cup 1008 protruding ridges or other formations 1020 may further enhance swirl. The induced “tornado” (illustrated by solid arrows 1021) causes particles, droplets, and other material in the air to experience centrifugal force that urges at least some of the particles etc. outwards and into contact with the inner wall of the cup (and in particular against the lower end of the cup where the width of the tornado is smallest) causing them to decelerate and either fall to the bottom of the cup or to adhere to the surface provided at the cup inner wall. To further reduce the escape of particles with the exiting airstream inward positioned baffles 1022 may be used. The scavenged particles can be collected by covering the inner wall of the collection chamber with an FTA card, optionally wetted with PBS (or the like) or a suitable film membrane or gel. The particle-depleted air will be deflected and exit the collection cup by the top openings. Another example of a positive pressure cyclone sampling arrangement 1100 will now be described with reference to Figure 11. In this example of tornado sampling separation, the downwash 1102 from a rotor 1104 is channelled into an conical collection cup 1108 through a funnel 1106 having a nozzle 1116 which is offset from the longitudinal axis 1109 of the collection cup 1108. This funnel arrangement 1106 directs the downwash air through the angled nozzle 1116 directing the downwash against the sidewall of the collection cup chamber (rather than down the axis or substantially down the axis of the cup as in the arrangement shown in figure 10), inducing the formation of a vortex flow towards the bottom of the collection chamber. At the bottom of the collection cup, a swirl inducer 1118 such as a conical protuberance formed with swirled channels, induces an opposite twist to the air flow, leading to the reversal of the air flow direction and the ejection of particles, droplets and other materials (e.g. eDNA and eRNA, etc.) from the air flow. The particles are deposited in the lower bottom and lower interior walls of the collection cup which can for example be covered with FDA paper, potentially soaked with PBS, or some other suitable film membrane or gel. The particle-depleted air will subsequently exit the collection cup through the top, by an exit conduit 1122 which may be in the centre of a cover chamber 1123 and plate 1124. The cover chamber 1123 attaches to the top of the 39 collection cup 1108, the plate 1124 closing the upper end of the cup apart from the bore of the exit conduit. The cover chamber 1123 is open around its lower periphery to allow the escape of air 1125 that has entered the chamber 1123 via the conduit 1122. It will be appreciated that an individual sampling drone according to aspects of the invention may conveniently be provided with different air sampling arrangements for different of its rotors. For example, some of the rotors of a drone may be provided with cyclonic sampling arrangements, optionally with different rotors being provided with cyclonic samplers each configured for optimum sampling of a different particle size (and / or mass) or particle size (e.g. mass) range. Likewise, a given rotor may be provided with switchable / selectable cyclonic sampling arrangements so that different sample types (e.g. sizes, masses, materials) may be obtained from downwash of that rotor according to time, location, altitude and / or simply on command - for example by using a mechanised arrangement to revolve or translate a magazine or cartridge arrangement. Similarly, one or more of the rotors of a drone may be provided with a sampling arrangement based on passing downwash through PBS phosphate buffered saline, while one or more other rotors may be provided with a cyclonic sampling arrangement - for example a vortex sampling arrangement, while one or more other rotors may be provided with a sampling arrangement that uses an FDA card (optionally moistened with PBS or some alternative). In this way a single drone may be equipped to sample for numerous different sample types in a single flight or sequence of flights. A vortex sampling arrangement, such as that shown in Figure 9A or 9B, may also be used in conjunction with one or more nozzles that are arranged to deliver water, an aqueous solution, or some other liquid (e.g. as discussed with reference to figure 14), in order to improve collection of airborne material, as illustrated generally in Figure 12. Here we see that the nozzle 1200 is shown as being located directly beneath the vortex sampling arrangement 1202 (that in this example is of the type described with reference to figure 9B, albeit provided with an optional funnel 1203) that is in turn located directly beneath a respective rotor 1204. At the lower end of the vortex sampling arrangement there is provided a collection arrangement 1220 corresponding generally with the set ups 992 / 970 described with reference to figures 9A and 9B, and like those may include a sampling liquid, for example as described with reference to figure 14, or a largely solid state sampling medium as previously described. As previously noted, the positioning of collection sampling arrangements with respect to the relevant rotor is not restricted to being directly behind or below the rotor: it may be offset to the edge of a projection of the rotor’s swept volume, optionally extending part in and part out of the projection, or even beyond the projection However there are likely to be benefits to locating a vortex sampling arrangement directly behind the relevant rotor, as shown here. Likewise, when 40 using one or more nozzles to spray liquid, as previously described with reference to figure 5B, while it is not essential to locate one of the nozzles directly behind a collection / sampling arrangement there may be benefits to so doing when the relevant collection / sampling arrangement is a vortex sampling arrangement. In the figure, a nozzle support is indicated at 1206, and this may be part of or coupled to the drone body, to the vortex sampling arrangement, or to a cage surrounding the relevant rotor (or the whole drone). 1208 indicates, schematically, jet sprayed from nozzle 1200 although it will be appreciated that in reality spray from a nozzle will likely extend a considerable distance from the nozzle and may or may not fan out more or less than shown here. The drift action or “circular” (air) flow that may be observed as a result of interaction between rotor-induced air flow and spray from a nozzle carried by the drone is indicated at 1210. Figure 13 is a flow chart representing elements of possible approaches to methods of processing biological material collected from the air, for example using a drone according to aspects of the invention, including various optional elements. The first stage 1300 concerns collection of biological material (here, for brevity generally referred to as eDNA) from the air (although it also generally applies to eDNA collected via water sampling and by foliage / surface sampling, as previously described). Actual collection may be performed at step 1308 by moving a drone along a transect through a sample space to enable eDNA collection in a sampling chamber (or sampling surface) carried by the drone. Generally, the collection of eDNA is preceded by a sequence of planning steps in which a survey protocol is designed 1302 taking account of the extent and delimitation of the area or zone to be surveyed, and also of the survey’s objective in terms of the details of what (in a biological sense) is being looked for. For example, whether one or more identified species or taxa are being sought (either to confirm presence or absence), or whether a more general biodiversity survey is to be performed. At step 1304 consideration is given to the accessibility of the area to be surveyed. As we are using drones for sample collection we are freed from many constraints that apply to the use of terrestrial vehicles, but there may be other constraints such as restricted flight zones, or exclusion zones, for example. At step 1306 account is taken of temporal considerations - potentially both with regard to the nature of the target biology (e.g. whether the target biology is a nocturnal or diurnal species -which is likely to be more relevant for insects such as moths than to large mammal species such as badgers, and seasonal behaviours such as hibernation and reproduction). Account may need to be taken of time of year (summer or winter), public holidays, days of the week, school term 41 times, etc., since these may affect human activity in the proposed sample area with consequent effects on biological populations. The second stage 1310 biological material is sampled after having been collected by the drone. Collection or harvesting 1312 may be performed for example by swabbing (e.g. using a roller, swab, sponge, wipe, typically pre-treated with a suitable collecting fluid 1314) or rinsing the collection vessel or chamber with a suitable collecting fluid 1314, or by first removing the collection vessel / chamber from the drone and then processing, e.g. washing the chamber or sampling vessel with a suitable collecting fluid 1314. The harvested biological material, possibly while still attached to a collection surface removed from the drone, or on a roller, swab, sponge, wipe, or filter, may then need to be preserved 916 in order to maintain the integrity of the biological material (e.g. DNA, RNA or protein) for example by placing the material in a temperature controlled environment (e.g. in a refrigerated environment) and / or by adding a preservation buffer which may allow samples to be stored and transported at ambient temperatures without degradation. Subsequently, and typically within a suitable laboratory having a controlled environment to reduce the risk of cross-contamination, the samples are subjected to molecular analysis 920. The samples are initially processed 1321 and prepared for purification of DNA, RNA, and / or proteins or other biological substances. Typically, this will involve washing out sampling matrices (rollers, swabs, filters, sponges) or washing demounted collection surfaces with a buffer such as a phosphate buffer (or other suitable liquid) to collect the acquired biological and cellular material. Biological and cellular material may then be concentrated from the liquid (buffer) suspension by centrifugation. RNA 1323, DNA 1324, or proteins 1325, for example, may then be purified 922 from concentrated pellets using commercially available reagents and methodologies. Extracted DNA may be subject to population genetic studies 1326. Extracted DNA and / or RNA may be subject to qPCR analysis 1327, metabarcoding 1328, and / or untargeted sequencing 1329. Typically, we are not interested in collecting or analysing human DNA: the focus is upon the extraction of non-human DNA / RNA / proteins from the biological material that is collected. In particular, we are not generally interested in processing to isolate markers characteristic of individual humans. Nevertheless, there may be situations where it is useful to collect human DNA for analysis, and it may on occasion even be chosen to isolate markers characteristic of individual humans. It will also be appreciated that we may be interested not only in identifying animals but also in identifying plants and / or fungi - for example we may be interested in identifying the presence of invasive or problematic plant species, such as Japanese knotweed. Bioinformatics processing is then applied 1330 to the results obtained at the molecular analysis stage 1320 optionally to determine aspects such as genetic variability, derive all identified species, determine relative species abundance, or characterize the genomes and / or derive an organism’s (potential) activity. The use of RNA or DNA to identify functional or active genes, independent of the organism’s taxonomic identification, can tell us various things about the environment. Especially for bacteria this can help us tell if there are more genes detected to, for instance, facilitate nitrogen cycling in one area versus another area. Quality filtering 1332 is typically applied followed by denoising and assigning reads to taxa. The fifth step 1340 involves data delivery, the first step 1342 of which is the determination of temporal and spatial probabilities of taxa presence. Thereafter, summary indexes and visualisations may then be prepared at 1344. For the metabarcoding lab analysis the bioinformatics process is done following the best practices from the literature and delivers a set of quality-controlled (QC) reads - the output of the sequencing machine, consisting of nucleotide strings and associated quality scores; they are not necessarily unique in a sample, an inference of the unique DNA or RNA sequences present in the collected sample that are amplified by the used primer pair and, as the final output, a table with the taxa counts (number of reads assigned to each taxonomic group), and a measure of the signal intensity for each taxa in each sample. The specific methods to achieve each of these incremental results are not necessarily dependent on each other and can be substituted later. If the laboratory procedure used is shotgun (also called whole genome) metagenomics, then the bioinformatic analysis needs to be adjusted accordingly following best practices from literature to include: visualization and trimming of reads based on their quality scores; assignment of reads to genomes; identification of predicted gene sequences; and mapping of predicted gene sequences into detected protein domains. If the laboratory procedure used is population genetic analysis, then the bioinformatic analysis needs to be adjusted accordingly following best practices from literature to include: identification of molecular markers from raw sequencing reads; and estimation of number of individuals from the genetic diversity observed in the molecular markers. It will be appreciated that the described approach to the collection of biological material from the environment is applicable not only to an assessment of biodiversity but also to survey programs focused on a single species or target group, whether the species or group is monitored for reasons of conservation or because the species or group is considered a risk. That is, the techniques described may usefully be applied to detecting the presence of known rogue / non- 43 native species, known pests or animal / plant vectors, as well as at-risk, endangered or vulnerable species, etc. Sample collection using a fluid reservoir As previously mentioned, a sample collection chamber may be provided with an impact surface, which may be flat, onto which particles are thrown by the downwash, inertial forces expelling particles from the airflow. An FDA card, optionally wetted with PBS, may be used as the impact surface, but a suitable film membrane or gel may be used in addition or alternatively, and as also noted above, an individual drone may usefully be flown with multiple different collection arrangements optionally including one or more of these different impact surfaces. Figure 14 illustrates schematically an alternative approach to sample collection in which downwash from a rotor is directed into a container 1400 of liquid, the air from the downwash bubbling through the liquid before exiting the reservoir. Here we rely on inertial forces, agitation of the liquid causing more contact between air and the liquid, and the fact that particles become wetted and thus heavier. Downwash 1402 from a rotor of a drone is received at an inlet conduit 1404, here provided with a funnel 1406. The inlet conduit 1404 passes through a wall of the container 1400, optionally through a lid 1408 or cover of the container (dotted line 1410 indicates a possible demarcation between the lid 1408 and the main body of the container 1400). The open end 1412 of the conduit 1404 is, in use, submerged beneath the surface 1414 of the liquid 1416 contained within the container 1400. A baffle or shroud 1418 may be provided about the conduit to encourage greater mixing between the received downwash and the liquid, optionally set at a level beneath the initial fill level of the liquid in the container. The downwash, which has effectively been filtered by the liquid through which it passes, exits the container at 1420. A second baffle 1422 may be provided at the exhaust port 1424 of the container to reduce the risk of significant leakage of liquid at that point. One or more further baffles 1426 may also be provided within the container to reduce any tendency for the liquid to splash onto the exhaust port 1424 or baffle 1422. The liquid may be chosen based on the nature of the material to be sampled, for example PBS or distilled water. In an alternative arrangement the open end of the inlet conduit may be above or at the level 1414 of the liquid 1416, rather than submerged beneath the surface - in this way particles carried in the downwash impact on the surface of the liquid but don’t generally bubble through it. Such an arrangement may in practice be preferable in view of the gas flow rates likely to be involved. Having air hit the water surface with force and causing disturbance may provide the benefit that there is better capture of airborne eDNA as the inertial forces move entrained particles into the water where they immediately become heavier and stay in the water, some 44 water may also form droplets above the water level and these may also further capture airborne eDNA as it drips via the sides of the container back into the captive fluid. In either case the captured material is held in the liquid 1416 for subsequent analysis. The liquid used in the container / reservoir 1400 may be selected from among the following possible reagents, all of which represent nucleic acid friendly media capable of retaining or absorb free or particle-enclosed nucleic acids and which may be used in sample collection systems to retain the samples until they can be removed for analysis (e.g. until at least the end of a flight) or until further processing. A. Nuclease-free water, which is the general category of types of waters commonly used for nucleic acid isolation and analysis. It can include: 1) DEPC-treated water (nuclease-free water that has been autoclaved, membrane-filtered and contains diethyl pyrocarbonate (DEPC) to inhibit RNases; 2) Non-DEPC treated water (nuclease-free water that has been autoclaved, membrane-filtered specifically for elimination of RNases and DNases); 3) RT-PCR-grade water (nuclease-free water that has been autoclaved, membrane-filtered, certified nuclease-free, and free of any nucleic acid contamination, such as genomic DNA, that can lead to false positives; 4) Distilled water, for example UltraPure distilled water which is autoclaved and 0.1 -pm membrane-filtered to be certified RNase-, DNase- and also protease-free, although “ordinary” distilled water may generally be suitable; B. A solution for nuclease (DNA, RNA) preservation, such as: 1) PBS (Phosphate-buffered saline); 2) Tris buffer (has NaCl and Tris-HCL to narrow the pH range); 3) Tris-EDTA (Tris buffer to which is added EDTA to create Mg2+, preventing DNAse activity); 4) Tissue Lysis buffers, such as ATL, which has SDS and EDTA, or AL buffer that has guanidine hydrochloride and malic acid to denature proteins: there are many proprietary commercially available formulations; 5) DNA extraction buffer can also be used that is based on a mix of Tris-EDTA with SDS, a detergent; 6) Longmire's solution is the most common eDNA preservation solution (100 mM Tris, 100 mM EDTA, 10 mMNaCl, 0.5 % SDS, 0.2 % sodium azide); 9) BAC solution (benzalkonium chloride), which has also been shown to be good for preserving eDNA; and 10) RNAlater, which is a commercial formulation of an aqueous solution designed specifically to maintain DNA and RNA integrity during storage of fresh tissue and cell samples. C. Pure ethanol, which is very efficient in preserving eDNA and a very good candidate for this sampling liquid. These liquids can also each be used within the sampling arrangements described with reference to Figures 1 to 5A, and 6 to 11, for example to moisturise an FDA card(s), as media that are added to the structure of a sample collection system to retain biological samples until the samples can be removed for analysis (e.g. until at least the end of a flight) or until further processing of the sample(s). The non-toxic formulations may also be used with the approaches illustrated in Figures 5B and 12. Experimental Pilot Data results In our pilot we flew at 3 different heights and used two different collection media (wetted FDA cards - wetted with PBS in this case; and a thin layer of PBS fluid) and processed the collected DNA using 3 different primers. The results are illustrated by the bar graphs of Figures 15A (using PBS fluid) and 15B (using wetted FDA cards). In these pilot flights high altitude was about 20 to 30 meters, "mixed” altitude was about 5 to 15 meters, while low altitude was between 1.5 and 5 meters - as generally described with reference to figure 5A. Key observations are: • Wetted FDA cards perform better overall compared to PBS cups. • At lower altitudes the sampling method using a thin layer of PBS fluid collected eDNA from more different species. This is more apparent for insects enhancing primers than it is for vertebrates. • This difference is not very apparent for the FDA cards although the low altitude flight does detect more species with the insect primers (although many detections can be attributed to earth worms see below). • Both in the PBS and the FDA cards the low altitude flight has more detections (~11 species per sampling container) of earth worms (clitellata), indicating that DNA from soil based organisms is liberated and brought into the air by the downwash of the drone rotors. There was no real difference in total species detected when comparing FDA and PBS. Based on above we conclude that: The downwash of the rotor does suspend eDNA from soil-based organisms and enhances insect detection (but also vertebrates). This effect is more apparent with the PBS (water) based sampling which we attribute to the liquid being able to collect a wider range of particles (from small leaf fragments, to visible dust and microscopic particles which we observed while 46 obtaining the samples). The FDA card method may be using the impact collection mechanism which is a bit more prone to collect only a certain particle size based on the inertial forces exerted. Overall, the FDA method performed better in these tests, but benefits less from aerosolizing larger fragments. It is also suspected that different collection mechanisms and / or combinations of flight strategies can enhance species detection significantly. Drones according to certain aspects of the invention may be used to collect biological material (e.g. containing DNA and or RNA) from an atmosphere, and as we have seen by flying the drone in proximity to a substrate it may be possible to use rotor downwash to lift material present on the substrate up into the atmosphere from where it may be drawn into the low pressure area ahead of a rotor hence becoming part of that rotor’s downwash from where it may be captured using one of the sample collection systems described in this patent application. Such a process may, as we have also seen, involve dispensing a liquid from the drone to facilitate pick up and / or sample capture. This same approach may also be used when the liquid is dispensed from the drone for another (perhaps primary) purpose - for example when using water, a detergent solution (DNA friendly) or another cleaning solution (also DNA friendly) to clean solar cells (possible of a solar cell array mounted on an elevated structure, or in a solar farm) or glass such as windows and roof lights, it may be possible using a drone as described to acquire biological (e.g. containing eDNA or eRNA) or other material present on the surface of the relevant substrate. This approach may also be used when a drone is being used to distribute herbicides, insecticides or other agrochemicals. A further possibility is to use a drone according to any of the aspects of the invention to harvest particles from an atmosphere, the particles having been introduced into the atmosphere from a substrate as the result of another interaction with the substrate or with the material of which the particles are formed - for example a drone may be arranged to direct a stream of air (or another gas) at the substrate - for example from a nozzle connected to a pump or container of compressed gas, for the purpose of disturbing the substrate or material on the substrate. It would also be possible to configure the drone to drop (small) explosive charges which are arranged to explode on or in proximity to the substrate again for the purpose of disturbing the substrate or material on the substrate. As briefly discussed in the context of figure 3, one or more sample collection systems may be mounted to, or integrated with, a common support to provide a payload arrangement for a suitable drone, which may be useful if a particular drone has to perform multiple roles - and for example where alternative payloads are so configured (or their needs are such) that it is not possible to have them mounted to a given drone at the same time, or it may be that their combined weight either exceeds the drone’s payload limit or would severely impact the drone’s flight performance. To this end according to a further aspect of the invention there is provided a payload arrangement for mounting to a drone to enable the collection of eDNA and / or eRNA samples from an atmosphere through which the drone is flown, the arrangement comprising a sample collection system to collect the eDNA and / or eRNA samples, the sample collection system having an inlet opening to admit samples, the payload arrangement being so configured that when mounted to a corresponding drone the inlet opening is located so as to receive, in use, downwash from a rotor of the drone so that suspended particulates in the atmosphere are propelled into the inlet opening and hence into the sample collection system. Such a payload arrangement may comprise a plurality of sample collection systems mounted to a support structure, the sample collection systems being so located that, once the payload arrangement is mounted to a corresponding drone, each of the sample collection systems is positioned so as to receive downwash from a respective rotor of the drone. The payload arrangement may include, for the or each sample collection system, a funnel arranged to receive the rotor downwash and to feed the downwash into the inlet opening of the respective sampling system. The or each sample collection system of the payload arrangement may be provided with a plurality of sample collection chambers, and a mechanism is provided to expose different sample collection chambers of the plurality sequentially one after the other so that separate samples may be obtained at different times by an individual sample collection system. The plurality of sample collection chambers may be provided as elements of a magazine arrangement, for example as described with reference to figures 6A and 6B. Any such magazine arrangement may be configured as a cassette to be loaded to and unloaded from the drone to permit rapid exchange of a fresh magazine for one containing samples. Preferably, the relevant sampling system (not all of which on a drone may necessarily use a magazine system) is arranged to permit the rapid replacement of the inlet funnel (if used) - funnels being provided with a quick release coupling arrangement, e.g. a quarter turn to release or lock to a cooperating mount. Optionally the funnel is so arranged that samples do not come into contact with any mount to which the funnel couples, for example the mount being annular and the funnel extending fully through the annular mount. In an alternative arrangement each of the collection chambers may be provided with its own dedicated funnel, the cover 616 being arranged to cover the funnels, so that only the funnel of the collection chamber currently in use is exposed. Such an arrangement is likely to reduce the risk of contamination between different sampling events. A payload arrangement according to any variant of this aspect may also include a water sampling arrangement, for example as described with reference to figure 7, or a vegetation sampling arrangement, for example as described with reference to figure 8. A payload arrangement according to any variant of this aspect may include an electrical interface to couple to a power supply and / or control electronics of the drone, for example to enable mechanisms that form part of the payload arrangement to be controlled by a remote controller used to control operation of the drone. Drones and payload arrangements, and methods, according to aspects of the invention may find application in any or all of the following scenarios, and it is explicitly intended that the following scenarios may each be performed using any of the aspects of this invention, and that any such combination may later be claimed. Some examples may comprise the aerial copter drone 100 according to above, comprising a single funnel 300 to feed air into one inlet 116 of one sample collection system 116. The single funnel 300 may be arranged beneath the swept volume of some or all of the rotors 108 of the aerial copter drone 100. In other words, the single funnel 300 is large enough to capture air swept by some or all of the rotors and feed it into the inlet 116. The aerial copter drone according to such example may have any of the effects and benefits of the embodiments described above, and has a simple construction with a centered payload for the aerial copter drone. 1.1 EXAMPLE 1 - ECOLOGICAL METRICS 1.1.1 EXAMPLE - BIODIVERSITY REPORTING REQUIREMENT S A business may need to provide metrics around biodiversity impact in relation to its assets. This is linked to regulatory reporting requirements in various countries, including the EU. Such a company will have to list biodiversity metrics in and around a site, more specifically presence of endangered species. The approach to biological harvesting and the provision of biodiversity metrics described in this patent application may be applied by harvesting biological material from drone traversing transects around the site but beyond its perimeter, as well as from drones traversing transects on the site itself. Depending upon the scale and geography of the site this may require the use of drones or other aerial vehicles. A data platform that is based on the data collected using a technique according to an aspect of the invention could also provide this information through ‘data as a service’. The ever greater onus on businesses to take responsibility for the impact on biodiversity means that there should be a ready market for reliable data on biodiversity, such as that acquired using a method according to an aspect of the present invention. By conducting sufficiently frequent geographically extensive and thorough reviews of biodiversity based on methods according to aspects of this invention it would be possible to establish a reliable database of the biodiversity “status quo”- tailored if necessary for locally endangered or rare species. Such a database could provide the foundation for a site-specific biodiversity report that could be “topped up” with on-site surveys using the drone-based biological harvesting technique according to aspects of the invention. Such a database is likely to be of particular value in areas containing industrial plant and sites, and of great interest to local or regional councils / government. Drones, payload arrangements, and methods according to aspects of the invention may also be used in monitoring the biodiversity of an “offset” plot that is used to compensate for the loss of biodiversity that may be caused by activities at a “work site” (which might be an area of land that is being developed with a resultant loss of natural habitat, or a site where the nature of activities at the site affect biodiversity on the site or in the vicinity of the site - for example due to noise, artificial light, chemical or particulate pollution, etc.). A service could be offered in which a “polluter”, whose activities may result in a negative impact in biodiversity, pays for the establishment or management of an area whose biodiversity is increased or maintained, to offset or even over compensate for the loss: drones, payload systems, and methods according to aspects of the invention could be used by an independent entity (possibly the entity providing the service) to monitor the offset plot and to prove / demonstrate that the required improvement / maintenance of biodiversity is achieved and supported over the period required. The provision of such offset sites, and their continued monitoring, could also be offered as a service to others who want to do something positive for the environment - e.g. governments, businesses, concerned citizens, frequent flyers, etc.: the drones, payload arrangements and methods of aspects of the invention are particularly suited to such an application. The provision of such services, using any of these aspects of the invention, are also considered to be within the scope of this invention. 1.1.2 EXAMPLE - ENVIRONMENTAL IMPACT ASSESSMENT For the construction of a large infrastructure project an environmental assessment has to be made. Ecological consultants typically conduct a desktop screening prior to visiting the site. The desktop screening could be based on a database established as just described based on biological samples collected using a method according to an aspect of this invention. 1.1.3 EXAMPLE - ENVIRONMENTAL MONITORING OF GOVERNMENTAL POLICY For policies at regional level, like limitations on pesticides, reduced nitrogen run-off from agricultural land, restrictions in the use or discharge of toxic substances, etc. the ecological impact may have to be monitored to showcase the positive impact (for example in terms of increased biodiversity or the maintenance of endangered species) to various stakeholders. A data 50 platform of the type previously described could also usefully the basis for such comparative examination of biodiversity and biodiversity trends. 1.1.4 EXAMPLE - REGIONAL BIODIVERSITY TREND DATA Various countries have to report on national or regional biodiversity trends either as part of international agreements or due to their own laws and obligations. The collection of trend data on a large number of species and sampled in a consistent way, achieved through aspects of this invention, can provide this information to governments as well as potentially supporting NGOs and international bodies in their monitoring roles. 1.1.5 EXAMPLE - SCIENTIFIC STUDY DATA Scientific ecological studies often rely on other reports or (public) data sources to i) design the study or survey and ii) draw the final conclusions. By making the biodiversity data acquired using methods according to aspects of the invention available to researchers, NGOs, scientific institutes, or other non-profit organisation they can gain a stronger understanding of ecological networks, derive empirical relationships, advance science and better understand biodiversity changes and impacts. 1.2 EXAMPLE 2 - INVASIVE, ALIEN, HARMFUL & ILLEGAL SPECIES 1.2.1 EXAMPLE - INVASIVE SPECIES MONITORING FOR GOVERNMENTS Invasive species are one of the key threats to biodiversity and for that reason many governments have policies in place to monitor, locate and control or eradicate these invasive species. The lists of such species are constantly evolving as new information becomes available and known invasive species still spread into new areas. By using the drone-based harvesting techniques described in the context of aspects of this invention it becomes possible to carry out what are in effect routine large scale (geographically extensive and frequent) watches for such species, providing basis to determine trends and to spot new occurrences Moreover, in the event that a new species is added to the list of alien of harmful species it is possible for biological material previously harvested using methods according to aspects of the invention to be reexamined to check for presence of the new species. 1.2.2 EXAMPLE - CROP PLAGUE TRENDS DETECTION FOR FARMERS There are many known plant pests that occur in and around farmland. Currently such pests are often eradicated through preventative use of pesticides which causes damage to other species and may not be necessary at all or applied at a high dose due to lack of detailed information on the threat. In various countries pesticide usage is being lowered through regulation as it is very damaging to biodiversity and also to human health. With spatial and temporal data regarding the presence of pest (largely invertebrate, but occasionally also vertebrate) and plague (generally microbial) provided by methods according to aspects of the invention, farmers can better develop pesticide strategies (i.e., Integrated Pest Management; IPM) and tailor their usage allowing minimal damage while ensuring food security. 1.2.3 EXAMPLE - QUARANTINE SPECIES DETECTION FOR GOVERNMENTS Apart from commonly occurring pests there are also various species listed as quarantine species. These species are not prevalent in an area and if they were to be introduced, they could seriously damage crops. For that reason, governments maintain lists of quarantine species that are to be checked upon import of goods (phytosanitary control) or have regulation regarding quarantine times for plant-based material. Regardless of these checks the quarantine species still make their way into new areas and if left unchecked are very difficult to eradicate. Aspects of the present invention provide effective and low cost techniques to support an early monitoring network that would allow actions to be taken more rapidly, potentially reducing the risk of significant financial damage to the agricultural sector. 1.2.4 EXAMPLE - ANIMAL DISEASE (VECTOR, VIRAL, BACTERIAL, FUNGAL) MONITORING Partly due to intensive animal farming there has been a rise in cases of large outbreaks of viral, bacterial, or fungal diseases. In some cases, the spread is clearly airborne, in other cases it occurs through direct contact or via vectors (mostly insects, but also other species). Methods according to aspects of the invention can be used to support regional monitoring covering insects, bacteria, fungi, and viruses so that hotspots and spreading patterns may be identified. This can help animal welfare & health authorities and farmers to better manage such risk and control further spread. 1.3   EXAMPLE 3 - HEALTH MONITORING 1.3 1 EXAMPLE - HUMAN DISEASE VECTOR MONITORING FOR HEALTH AUTHORITIES A prime example of a human disease vector are the mosquitoes that spread Malaria and Dengue. The tiger mosquito is of especial concern to northern countries as this vector seems to be spreading, partly due to climate change. In some countries eradication and control measures are in place but practically these need to be focused, and currently such focusing relies on communal sightings or other localized surveys, seriously limiting the chance of detection. Using drones and methods according to aspects of the invention could provide an improved alternative to current sighting and survey techniques, offering a greater chance of containment and potentially eradication. Applying the drones and methods according to aspects of the invention to regional monitoring covering insects, hotspots and spreading patterns of such human / animal disease vectors can be identified allowing surveys and eradication to be more focussed. 1.3.2 EXAMPLE - VIRAL EPIDEMIOLOGY FOR HEALTH AUTHORITIES The recent COVID-19 epidemic has stressed the importance of early viral outbreak detection. During COVID many governments adopted a wastewater surveillance system that preceded detection of many of the clinical cases. Potentially by also monitoring airborne viral presence using the methods outlined in this patent a more extensive regional monitoring method can be deployed. For certain viruses such a method could even provide an earlier metric of infection rates, prevalence and / or infection risk with a larger spatial coverage. Adopting an untargeted detection and screening for viruses not yet present in an area could also provide a very early detection method potentially allowing mitigation of further spread. The WHO, Governments and Health authorities could benefit significantly from such data. A likely constraint here is the viability of viruses and viral particles in the air and once they have attached to the impact surface. Depending upon the nature of the impact surface, UV light levels, and temperature, there may be only a relatively brief window in which to harvest and process samples in order to be able to reveal the presence a virus. But if these factors are taken into account, and sampling and processing are done expeditiously it may be possible to use the techniques described in this patent application in monitoring for viral presence. 1.3.3 EXAMPLE - PATHOGEN PREVALENCE FOR INSURERS It is known that in certain regions or areas of cities there are higher occurrences of certain illnesses. In some cases, this has demographic causality, but it may also be due to other environmental factors or the presence of pathogens. One of the oldest examples was the analysis performed by John Snow in 1854 which revealed that an outbreak of cholera was linked to one specific water pump. More recently, Legionella has been linked to public fountains, but only after deducting a commonly visited location by all people falling ill. Through the methods outlined in this patent health authorities can take more focused actions to prevent new outbreaks or more easily understand and determine sources of clinical cases. 1.4 FURTHER ENUMERATED EXAMPLES EE 1. An aerial copter drone having one or more motor-driven rotors to provide propulsion to the drone, the drone including a sample collection system to collect eDNA or eRNA samples from an atmosphere through which the drone is flown, the sample collection system having an inlet opening to admit samples, the inlet opening being located so as to receive, in use, downwash from a rotor of the drone so that suspended particulates in the atmosphere are propelled into the inlet opening and hence into the sample collection system, the sample collection system optionally including a medium to retain the samples until the samples can be removed for analysis. EEII. An aerial copter drone according to EE / , wherein the rotor from which the inlet opening receives downwash defines, in use, a swept area, the inlet opening being located behind the swept area, and the swept area at least partially overlapping the inlet opening. EE III. An aerial copter drone according to EE I or II, wherein the or each sample collection system includes a cyclonic separation arrangement, optionally in the form of a cyclonic separator array, and optionally the or each cyclonic separation arrangement comprises a vortex separator. EE IV. An aerial copter drone according to any one of the preceding EE’s, wherein the drone has a reservoir for liquid, and one or more nozzles connected to the reservoir, the drone being operable to dispense liquid from the reservoir via the one or more nozzles into a region behind a rotor during flight and the arrangement being such that at least some of the liquid dispensed from the nozzle(s) during flight will be propelled into an inlet of the collection system under the action of downwash from the rotor behind which the liquid was dispensed, optionally by wake reingestion or circular flow, and optionally the collection system includes a vortex separator and at least one of the one or more nozzles is so located as to receive, in use, an exhaust flow from an outlet of the vortex separator. EE V. An aerial copter drone according to any one of the preceding EE’s, wherein the or each sample collection system includes a sampling liquid arrangement in which rotor downwash is passed through or along a liquid medium to capture particles carried by the downwash, and optionally the liquid medium comprises PBS and / or nuclease-free water. EE VI. An aerial copter drone according to any one of the preceding EE’s, wherein the drone has multiple rotors, and a plurality of the multiple rotors are each provided with such a sample collection system, and optionally the plurality is half, a majority, or all of the multiple rotors. EE VII. An aerial copter drone according to any one of the preceding EE’s, wherein the inlet opening of the or each sample collection system: is wholly within the projected area of its respective rotor; and / or has a cross sectional area size that is within 10% to 50%, optionally 20 to 40%, optionally 25 to 35% of the size of the area swept by the respective rotor; and / or is within 150 mm of the rearmost extremity of the swept volume of the respective rotor, optionally within 100 mm, 90 mm, 80 mm, 70, 60, 50, 40, 30 or 20 mm; and / or is no closer than 10 mm from the rearmost extremity of the swept volume of the respective rotor. EE VIII. An aerial copter drone according to EE VI, or EE VII as dependent on EE VI, wherein either or both of the following conditions are met: (i) the inlet openings of the multiple sample collection systems are so sized and so located with respect to a longitudinal axis of the drone so as to balance laterally the loss of lift occasioned by the presence of the multiple sample collection systems; (ii) the inlet openings of at least some of the multiple sample collection systems are disposed either side of the longitudinal axis of the drone in an arrangement that is symmetrical about the longitudinal axis. EE IX. An aerial copter drone according to any one of the preceding EE’s, wherein the or each sample collection system is provided with a mechanism operable to selectively open an inlet and / or an outlet of a sample collection chamber of the sample collection system during flight of the drone, and optionally the mechanism is operable to activate a valve configured to close the inlet to the sample collection chamber. EE X. An aerial copter drone according to any one of the preceding EE’s, wherein the or each sample collection system is provided with a plurality of sample collection chambers, and a mechanism is provided to expose different sample collection chambers of the plurality sequentially one after the other so that separate samples may be obtained by an individual sample collection system at different times during a flight, and optionally each plurality of sample collection chambers is provided as a cartridge which may be inserted into, and removed from the relevant sample collection system as a unit. EE XI. An aerial copter drone according to any one of the preceding EE’s, wherein the or each sample collection system comprises one or more exhaust ports, for the escape of air in a direction transverse to, or in line with or generally parallel to, the direction in which air is received through the inlet of the respective sample collection system. EE XII. An aerial copter drone according to EE VI or either of EE VII or EE VIII as dependent on EE VI, wherein multiple inlet openings are arranged to supply a common collection chamber that is shared between multiple sampling systems. EE XIII. An eDNA / eRNA sampling method performed using a drone according to any one of the preceding EE’s, the method comprising: performing a flight with the drone through an atmosphere containing material that includes eDNA and / or eRNA; using downwash from one or more rotors of the drone to propel the material into a sample collection system of the drone; retaining sampled material within the sample collection system for the duration of the flight; and subjecting the sampled material to molecular analysis to generate data on sources of the eDNA and / or eRNA. EE XIV.     An eDNA / eRNA sampling method performed using a drone as according to any one of EE I to XII, the method optionally according to EE XIII and comprising: performing a flight with the drone, the flight involving flying the drone in proximity to a substrate, the substrate being the ground, a body of water, a tree canopy, vegetation, or a manmade structure; using downwash from one or more rotors of the drone to render airborne material from the substrate, the material containing eDNA and / or eRNA; pulling the airborne material down between blades of a rotor of the drone, or otherwise combining the airborne material with downwash from one or more rotors so that the airborne material is propelled into a sample collection system of the drone; retaining sampled material within the sample collection system for the duration of the flight; subjecting the sampled material to molecular analysis to generate data on sources of the eDNA and / or eRNA. EEXV.X method according to EE XIII or EE XIV, wherein the sample collection system includes a medium to retain the sampled material until the samples can be removed for analysis. EEXVI.      A payload arrangement for mounting to a drone to enable the collection of eDNA and / or eRNA samples from an atmosphere through which the drone is flown, the arrangement comprising a sample collection system to collect the eDNA and / or eRNA samples, the sample collection system having an inlet opening to admit samples, the payload arrangement being so configured that when mounted to a corresponding drone the inlet opening is located so as to receive, in use, downwash from a rotor of the drone so that suspended particulates in the atmosphere are propelled into the inlet opening and hence into the sample collection system, and optionally the payload arrangement includes a funnel arranged to receive the rotor downwash and to feed the downwash into the inlet opening. EEXVII.     A payload arrangement as claimed in EE XVI, comprising a plurality of sample collection systems mounted to a support structure, the sample collection systems being so located that, once the payload arrangement is mounted to a corresponding drone, each of the sample collection systems is positioned so as to receive downwash from a respective rotor of the drone. EEXVIII. A payload arrangement according to EE XVI or XVII, wherein the or each sample collection system is provided with a plurality of sample collection chambers, and a mechanism is provided to expose different sample collection chambers of the plurality sequentially one after the other so that separate samples may be obtained at different times by an individual sample collection system, and optionally each plurality of sample collection chambers is provided as a cartridge which may be inserted into, and removed from the relevant sample collection system as a unit. EE XIX. A payload arrangement according to any one of EE’s XVI to XVIII, wherein the arrangement includes a reservoir for liquid, and one or more nozzles connected to the reservoir, the payload arrangement being operable to dispense liquid from the reservoir during flight via the one or more nozzles into a region behind a rotor and the arrangement being such that at least some of the liquid dispensed from the nozzle(s) will be propelled into an inlet of the collection system under the action of downwash from the rotor behind which the liquid was dispensed, optionally by wake reingestion, and optionally wherein at least one sample collection system of the payload arrangement includes a vortex separator and at least one of the one or more nozzles is so located as to receive, in use, an exhaust flow from an outlet of the vortex separator.

Claims

1. An aerial copter drone having one or more motor-driven rotors to provide propulsion to the aerial copter drone, the aerial copter drone including a sample collection system to collect eDNA or eRNA samples from an atmosphere through which the aerial copter drone is flown, the sample collection system having an inlet opening to admit the eDNA and / or eRNA samples, the inlet opening being located so as to receive, in use, downwash from the one or more motor-driven rotors of the aerial copter drone so that suspended particulates in the atmosphere are propelled into the inlet opening and hence into the sample collection system,wherein the sample collection system is provided with a plurality of sample collection chambers, and a mechanism is provided to expose different sample collection chambers of the plurality of sample collection chambers sequentially one after the other so that separate eDNA and / or eRNA samples may be obtained by the sample collection system at different times during a flight.

2. An aerial copter drone according to claim 1, wherein the one or more motor-driven rotors from which the inlet opening receives the downwash defines, in use, a swept area, the inlet opening being located behind the swept area, and the swept area at least partially overlapping the inlet opening.

3. An aerial copter drone according to claim 1 or claim 2, wherein the sample collection system includes a cyclonic separation arrangement.

4. An aerial copter drone according to any one of the preceding claims, wherein the aerial copter drone has a reservoir for liquid, and one or more nozzles connected to the reservoir, the aerial copter drone being operable to dispense liquid from the reservoir via the one or more nozzles into a region behind the one or more motor-driven rotors during flight and the arrangement being such that at least some of the liquid dispensed from the nozzle(s) during flight will be propelled into inlet opening of the sample collection system under the action of the downwash from the one or more motor-driven rotors behind which the liquid was dispensed.

5. An aerial copter drone according to any one of the preceding claims, wherein the sample collection system includes a sampling liquid arrangement in which the downwash is passed through or along a liquid medium to capture particles carried by the downwash.

6. An aerial copter drone according to any one of the preceding claims, wherein the aerial copter drone has multiple motor-driven rotors, and a plurality of the multiple motor-driven rotors are each provided with such a sample collection system, such that the aerial copter drone comprises multiple sample collection systems.

7. An aerial copter drone according to any one of the preceding claims, wherein the inlet opening of the sample collection system:is wholly within a projected area of its respective motor-driven rotor; and / orhas a cross sectional area size that is within 10% to 50% of the size of the area swept by the respective motor-driven rotor; and / oris within 150 mm of the rearmost extremity of the swept volume of the respective motor-driven rotor; and / oris no closer than 10 mm from the rearmost extremity of the swept volume of the respective motor-driven rotor.

8. An aerial copter drone according to claim 6, or claim 7 as dependent on claim 6, wherein either or both of the following conditions are met:(i) the inlet openings of the multiple sample collection systems are so sized and so located with respect to a longitudinal axis of the aerial copter drone so as to balance laterally the loss of lift occasioned by the presence of the multiple sample collection systems;(ii) the inlet openings of at least some of the multiple sample collection systems are disposed either side of the longitudinal axis of the aerial copter drone in an arrangement that is symmetrical about the longitudinal axis.

9. An aerial copter drone according to any one of the preceding claims, wherein the sample collection system is provided with a mechanism operable to selectively open the inlet opening and / or an outlet of a sample collection chamber of the sample collection system during flight of the aerial copter drone.

10. An aerial copter drone according to any one of the preceding claims, wherein the sample collection system comprises one or more exhaust ports, for the escape of air in a direction transverse to, or in line with or generally parallel to, the direction in which air is received through the inlet opening of the respective sample collection system.

11. An aerial copter drone according to any of the preceding claims, wherein each sample collection chamber of the plurality of sample collection chambers comprises multiple cyclonic separators.

12. An eDNA / eRNA sampling method performed using an aerial copter drone as claimed in any one of the preceding claims, the eDNA / eRNA sampling method comprising: performing a flight with the aerial copter drone through an atmosphere containing material that includes eDNA and / or eRNA;using the downwash from one or more motor-driven rotors of the aerial copter drone to propel the material into a sample collection system of the aerial copter drone;retaining sampled material within the sample collection system for the duration of the flight; and subjecting the sampled material to molecular analysis to generate data on sources of the eDNA and / or eRNA.

13. An eDNA / eRNA sampling method according to claim 12 further comprising: performing a flight with the aerial copter drone, the flight involving flying the aerial copter drone in proximity to a substrate, the substrate being the ground, a body of water, a tree canopy, vegetation, or a man-made structure;using the downwash from the one or more motor-driven rotors of the aerial copter drone to render airborne material from the substrate, the airborne material containing eDNA and / or eRNA;pulling the airborne material down between blades of the one or more motor-driven rotors of the aerial copter drone, or otherwise combining the airborne material with the downwash from the one or more motor-driven rotors so that the airborne material is propelled into a sample collection system of the aerial copter drone;retaining sampled material within the sample collection system for the duration of the flight; subjecting the sampled material to molecular analysis to generate data on sources of the eDNA and / or eRNA.

14. An eDNA / eRNA sampling method as claimed in claim 12 or claim 13, wherein the sample collection system includes a medium to retain the sampled material until the samples can be removed for analysis.

15. A payload arrangement for mounting to an aerial copter drone to enable the collection of eDNA and / or eRNA samples from an atmosphere through which the aerial copter drone is flown,the arrangement comprising a sample collection system to collect the eDNA and / or eRNA samples, the sample collection system having an inlet opening to admit the eDNA and / or eRNA samples, the payload arrangement being so configured that when mounted to a corresponding aerial copter drone the inlet opening is located so as to receive, in use, the downwash from one or more motor-driven rotors of the aerial copter drone so that suspended particulates in the atmosphere are propelled into the inlet opening and hence into the sample collection system, wherein the sample collection system is provided with a plurality of sample collection chambers, and a mechanism is provided to expose different sample collection chambers of the plurality of sample collection chambers sequentially one after the other so that separate eDNA and / or eRNA samples may be obtained by the sample collection system at different times during a flight, and each of the plurality of sample collection chambers are provided as a cartridge which may be inserted into, and removed from the sample collection system as a unit.

16. A payload arrangement as claimed in claim 15, comprising a plurality of sample collection systems mounted to a support structure, the sample collection systems being so located that, once the payload arrangement is mounted to a corresponding aerial copter drone, each of the sample collection systems is positioned so as to receive the downwash from a respective one of the one or more motor-driven rotors of the aerial copter drone.

17. A payload arrangement as claimed in any one of claim 15 to 16, wherein the arrangement includes a reservoir for liquid, and one or more nozzles connected to the reservoir, the payload arrangement being operable to dispense liquid from the reservoir during flight via the one or more nozzles into a region behind the one or more motor-driven rotors and the arrangement being such that at least some of the liquid dispensed from the nozzle(s) will be propelled into an inlet opening of the sample collection system under the action of the downwash from the one or more motor-driven rotors behind which the liquid was dispensed.

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