METHOD FOR SOIL POLLUTION ANALYSIS

Abstract

The invention presents a method for analyzing soil contamination by pollutants, particularly organic pollutants, by hyperspectral analysis of reflection and / or photoluminescence, characterized in that said analysis is carried out with a first piece of equipment by illuminating a sample with a light source and with at least one spectral sensor sensitive to a spectrum ranging from thermal infrared to ultraviolet. Abstract figure: 2

Description

Title of the invention: METHOD FOR SOIL POLLUTION ANALYSIS

[0001] The present invention relates to the field of soil contamination analysis by organic pollutants.

[0002] Sources of soil contamination are varied: the use of fertilizers, pesticides, discharges from an industrial site, proximity to an incinerator, a waste storage site, discharges of drug residues from livestock manure, hydrocarbons... Soil, land, garden or playground pollution can come from chemical agents: dioxins, PCBs or extremely dangerous toxic metals.

[0003] The origin of these pollutions can be accidental (spills or occasional deposits of pollutants due to negligence, malfunction of an industrial installation, accident of an installation or of a vehicle for transporting polluting materials), with a large quantity of pollutant spilled, or chronic (continuous supply of contaminants by leakage or leaching, the cumulative effects of which can be more significant and more insidious than those of an accidental pollution).

[0004] Polluted soil can cause poisoning when fruits and vegetables from the garden are consumed. The bioaccumulation of pollutants in soils by plants and animals makes them among the most dangerous pollutants for human and animal health. They have the particularity of contaminating the food chain (dioxins, PCBs, radioactivity, etc.). Soil pollutants can also cause skin and respiratory irritation. They are also responsible for cardiac and neurological disorders, loss of fertility, developmental problems in the fetus, and are a cause of certain cancers.

[0005] To assess the presence of contamination and to characterize and quantify the nature of the pollutants, it is common practice to take samples, for example by coring, and to submit these samples to a physicochemical analysis laboratory. The "Methodological Guide for the Analysis of Polluted Soils," published in February 2000 under reference BRGM / RP-50128-FR, presents in detail the techniques for the analysis of polluted soils.

[0006] Since these analyses require high-level scientific resources and skills, it has also been proposed to automate all or part of these analyses.

[0007] For a given site, the standard soil analysis steps involve: 1. Bring in a polling company to carry out the core sampling; 2. Send samples to analytical laboratories; 3. Wait for the results of the analyses to come back; 4. Interpret these analyses in the form of maps; 5. Write a recommendation report.

[0008] The minimum duration of such an analysis is 6 to 8 weeks. Following these analyses, the report often shows significant uncertainties due to heterogeneity in the soil studied, thus recommending a new sampling campaign. Indeed, the initial sampling is often insufficient because the distances between sampling points are too great (cost considerations). It is then necessary to repeat the process described in the previous problem statement, one or more times. The delay due to this problem is at least one month.

[0009] Finally, during the remediation process, the site is excavated by the remediation company, and unforeseen pollution may be detected. This results in a work stoppage, and the process resumes with re-sampling and analysis as described above. During this time, the excavated material is temporarily stored on-site until the nature of the pollution is determined and it is sent to the appropriate treatment facilities. In this case, an additional delay of at least 15 days is observed, along with significant additional costs related to the downtime of workers and machinery, as well as the reprocessing of the initially undiagnosed contaminated soil. State of the art

[0010] In the prior art, various equipment solutions are known that allow for on-site analysis of the presence of contaminants and provide a partial improvement to these difficulties.

[0011] US patent 5128882 relates to a method and apparatus for the real-time on-site detection and analysis of soil contaminants by continuously measuring the specific spectral properties of potentially contaminated soil along a profile using a soil penetration probe. The probe is equipped with a light-transparent window and a light source disposed inside the probe. Light from inside the probe passes through the window and is reflected through the soil window as the probe penetrates the soil. The light reflected from the soil through the window is collected by a fiber optic link inside the probe. The collected light is then transmitted via the fiber optic link to the surface for the measurement and recording of the spectral distribution and intensity.The type and quantity of contaminant can be determined by comparing the soil's spectral signature to standards prepared by adding known concentrations of a specific contaminant to soil similar to that found at the test site. This prior art apparatus thus allows for rapid on-site determination of the location, depth, and quantity of contaminant in soils, and in particular... soils at waste disposal sites.

[0012] The device proposed in this document comprises: - a probe to penetrate the ground; - means of driving the probe into the ground; - a window formed in the probe to allow the transmission of light between the outside and inside of the probe; - means of light arranged inside the probe to produce light ranging from visible to ultraviolet which passes through the window to irradiate the ground adjacent to the window when the probe passes through the ground; - means for collecting and transmitting light arranged inside the probe to collect reflected light or fluorescence returning through the window from the ground; and, - means of analysis receiving light or reflected fluorescence means of collecting and transmitting light to analyze said light or reflected fluorescence in order to produce a spectral signature for each locus of the soil through which the probe passes, said spectral signatures containing information on the contaminants present in the soil.

[0013] European patent EP0885386 describes another example of a portable, battery-operated device for detecting contamination of a solid substance, such as soil. The device measures fluorescence and is adapted to be positioned on the surface of the solid substance during measurement. The device excites the fluorescent emission of contaminants in a specific area of ​​the surface by transmitting a pulsed beam of electromagnetic energy to the surface, one axis of the beam being substantially perpendicular to the surface, and detects the amount of fluorescent emission excited by the surface through the beam pulses. Furthermore, the device calculates a measurement value corresponding to the concentration of contaminant present in the specific area of ​​the surface based on the detected quantities.

[0014] US patent 9995678B2 describes another example of a method for the quantitative assessment of organic pollutant contamination in soil using near-infrared reflection spectroscopy with modeling by neural networks, fuzzy logic, partial least squares, or supervised learning. The wavelength band studied covers the near- and far-infrared VNIR-SWIR (400-2500 nm).

[0015] French patent FR3074296 describes another example of a soil analysis and treatment process characterized in that it implements an analysis and treatment system, comprising at least one analysis unit including a spectrometer, a spectrum analyzer, a logic unit integrating a predictive model and a database, the process comprising at least the following steps: A. Provision of a sample of excavated soil, the sample taken being characterized by the date of sampling and / or by geolocation data of the tunnel boring machine, B. Determination of the soil type from which the sample was taken: the determination is carried out by the logical unit incorporating a predictive model. The logical unit performs a mapping from discrete and point data from the literature or preliminary analyses carried out by coring by a project owner. The logical unit compares the mapping with the sampling date and / or geolocation data of the tunnel boring machine from which the sample was taken to determine and predict the soil type being analyzed. C. Determination of the most relevant reference sample for the soil type determined in step B), by the logical unit which performs at least the following operations: a. Comparison of the soil type determined in step B with reference samples from a database integrated into the logical unit, the database including at least the soil type and pollutant content for a plurality of analyzed reference soil samples, b. Selection of the most relevant reference sample based on step C(a), D. Analysis of the sample by spectrometry and obtaining an energy spectrum of the excavated soil sample, E. Determination of the pollution level of the sample at least by comparing data derived from the energy spectrum obtained in step D with the pollutant content of the reference sample determined in step C, the pollutant content of the most relevant reference sample being entered in the database

[0016] The international application describes a method for analyzing soil located in an underground area. The optical probe comprises: • a head that can be introduced into the underground zone, the probe head comprising inside a transparent wall defining a hollow chamber; • a light source mounted in the hollow chamber, designed to generate a beam of light towards the ground, the beam of light passing through the transparent wall to irradiate the ground, thus producing afterlight emanating from the ground, part of the afterlight returning to the probe head and being guided into the transparent wall by total internal reflection along the optical path; • a detector designed to receive the afterglow portion of the light and deliver an output signal representative of one or more characteristics of the ground; • and an optical element guiding the part of the following light from the transparent wall to the detector.

[0017] Finally, patent application WO2019106179 describes a method for a sample (E), using a set of spectral images of the sample to be characterized previously acquired, in particular by infrared thermography or spectral imaging, and at least one neural network (RNCNN), the method comprising the steps of: - generating at least a volume of values ​​(D(Nx, Ny, Ne)) of a parameter observed from said spectral images, for a plurality of coordinates (x, y) of the pixels (N) of the images and a plurality of acquisitions (Ne), - extract at least one set (Jx) of input data (D'x,y(Ne)) from said data volume (D(Nx, Ny, Ne)), this input data corresponding to the values ​​of the observed parameter, for a pixel of the same coordinates according to different acquisitions (Ne), values ​​to which at least one transformation function has been applied, - train said at least one neural network (RNCNN) using the input data (Jx) to extract at least one feature of the sample (E) to be characterized, and - use said at least one feature extracted by the neural network (RNCNN) to perform a classification of the input data according to a plurality of classes, each class being representative of at least one feature of the sample (E) to be characterized. This process is intended to exploit data acquired by a drone and does not allow for in-depth analysis of contaminated soil. Disadvantages of prior art

[0018] Prior art solutions do not allow a sufficient level of precision and reliability to be achieved when the analysis is carried out directly on site by a spectrometric method and in particular by hyperspectral imaging.

[0019] Furthermore, to meet field needs, it is important to be able to provide qualified information on the content of pollutants as a function of depth, in order to optimize field treatment, and solutions based on the analysis of images taken remotely are poorly suited. Solution provided by the invention

[0020] To overcome these drawbacks, the invention, in its most general sense, relates to a system for analyzing soil contamination by pollutants, particularly organic pollutants, comprising a reflection spectroscopy device characterized in that said device is a portable device comprising a source luminous, including a Xenon or halogen source and at least one spectral sensor. It also relates to a method for analyzing soil contamination by pollutants, particularly organic pollutants, by hyperspectral analysis of reflection and / or photoluminescence characterized in that said analysis is carried out with a first piece of equipment by illuminating a sample with a light source and by at least one spectral sensor sensitive over a spectrum ranging from the near infrared NIR to the ultraviolet UV. The term "near-infrared (NIR)" refers to the wavelength range of 0.78 to 2.5 pm. Advantageously, the spectral sensor has a broader sensitivity range, including the mid-infrared (MWIR) and / or far-infrared (LWIR) as well as the short-wave infrared (SWIR). The method according to the invention comprises: - a learning sequence consisting of analyzing a plurality of reference samples and recording them in a training database • a) of the spectral reflection signature acquired by spectral analysis • b) known values ​​of the variables representing the contaminants present in each of said reference samples • c) known values ​​of the variables representing the substrates of each of said reference samples - a calibration sequence of field analysis equipment relative to said first equipment, said field equipment comprising a light source and a spectral sensor, - analysis sequences of a soil sample from a geological site consisting of acquiring the reflection and / or photoluminescence signature of said sample using said calibrated field equipment, - and to proceed to the estimation of the characterization of the pollutants by processing said signature by a learning engine exploiting the data from the database created during the learning sequence.

[0021] Advantageously the analysis system according to the invention comprises a probe having at least one optical fiber for transmitting light between the analysis area of ​​said probe on the one hand, and the light source, in particular Xenon or Halogen, and said at least one sensor on the other hand.

[0022] According to an optional variant, said equipment further comprises a means of physico-chemical analysis. Description of a non-limiting example of the invention

[0023] The present invention will be better understood upon reading the following description, with reference to the accompanying drawings concerning non-limiting examples of embodiment, where: [fig. 1] Figure 1 represents the physical architecture of an example of an implementation of the invention [fig.2] Figure 2 represents the functional diagram of the invention [fig.3] Figure 3 represents the functional architecture [fig.4] Figure 4 represents the optical diagram of a variant embodiment of the optical system. General context of the invention

[0024] The invention relates to the characterization of soil samples by coring to determine the qualitative and quantitative presence of constituents of interest (pollutants, in particular plastics, hydrocarbons, metals...) to provide a real-time measurement tool for the nature of pollutants on polluted land recovery sites.

[0025] The aim is to provide a solution for generating, if possible in real time and on-site, a detailed pollution map to facilitate and secure the implementation of selective sorting of excavated material based on its pollution level, directly on the construction site using a real-time measurement tool. The result is a three-dimensional map of the terrain providing geolocated information on pollution, in x,y coordinates with a resolution of a few square meters to a few hundred square meters, and in z-depth, thus enabling informed decisions regarding optimal remediation measures. Optionally, the analysis of core samples can be supplemented by additional remote analysis using a hyperspectral camera to quantify pollutants delivered to analysis centers for real-time monitoring of the contaminated soil they receive.Thus, the proposed system guarantees soil quality, identifies its pollutants, in order to allow its recycling.

[0026] To this end, the invention enables the instrumentation of drilling machines and construction equipment to allow the integration of real-time analyses and accelerate the process by eliminating iterative steps and sources of financial uncertainty.

[0027] Thus, when pollution not initially identified is detected, real-time measurements would make it possible to direct the excavated material to the corresponding recovery channel without the delay of laboratory analysis (optimization of real-time decision-making). Hardware architecture

[0028] The equipment according to one embodiment of the invention consists of a field device (1), portable in the described example, comprising a backpack-type case containing a broad-spectrum light source, for example a Xenon lamp (10), and a power supply, for example batteries. The light source (10) is associated by an optical fiber (2) to a lance (3) which transmits light to the ground and reflects light to sensors (11) whose electrical signals are transmitted to a computer which can be housed in the casing or fixed in the form of a tablet (4) on the handle (5) of the lance (3).

[0029] The sensors are hyperspectral sensors with a sensitivity range between 100 microns and 200 nanometers. They may be a hyperspectral camera, a multispectral camera, or an assembly of sensors forming a composite multispectral sensor.

[0030] The lance includes one or more optical fibers to transmit the light emitted by the source (10) to a measuring end, and to collect the reflected light or fluorescence light from the sample towards the end of the lance (3). The fiber may include a lens or collimating optics at its end.

[0031] The tablet (4) includes a touch interface (6) equipped with a geolocation module (13) (GPS or Galileo) and a 5G SIM mobile phone card.

[0032] This equipment further comprises a computer (12) and radio communication means which enable, on the one hand, the processing of data and the provision of a real-time diagnosis of the soil condition and pollution (lithological characteristics, type of pollutants, quantity of pollutants, 3D soil mapping, etc.); and on the other hand, the transmission of data to a cloud storage space (30). The data is available locally for real-time decision-making but also on an online platform to allow the project manager, equipped with a connected terminal (20) and present at the control center, to monitor operations live and collect the data acquired in the field. Implementation of the invention

[0033] A core sample is taken by an operator equipped with the aforementioned equipment at a site suspected of contamination. The location of the borehole is probed by coring or tapping using an instrument equipped with a geolocation module, and its geographic coordinates are recorded. Several sections approximately 1 meter deep are taken at the borehole location, and several boreholes are drilled at the site.

[0034] Spectral analysis of all the core samples is performed. This is done by removing the half-core samples, which are split lengthwise, and acquiring data on several half-core samples simultaneously, which is possible due to the rapid acquisition speed of the imaging. Extracting sub-images corresponding to a half-core sample is facilitated by the placement of digitally recognized QR codes on the corners of the sections. Imaging can be carried out on-site with a camera in a vehicle or container. A pre-trained predictive model can be used at this stage, based on a sufficient amount of data in the database for the pre-trained model (on this data) to produce a real-time diagnosis.

[0035] Subsample selection is performed using imaging data. Statistical methods, supervised (Machine Learning) or unsupervised (end-member extraction, feature extraction, novelty detection, etc.), are used to select areas for subsampling in order to represent the heterogeneity of the geological formations present at the site. Spectrometer data can be used alternatively. Subsampling can be carried out immediately (in the case of volatile pollutants) or later in the laboratory (the half-cores are hermetically sealed with plastic film and stored in a cold room for preservation).

[0036] Chemical analyses consist of extracting pollutants using various methods, including solvent extraction (water, hexane, ether), agitation, solid-phase microextraction, microwave extraction, headspace extraction, etc. The analytical techniques used are chromatography (ICP-AES, ion chromatography, HS-GS / MS). Analyses are performed on-site (in a container) or in the laboratory, on subsamples of core samples or on provided and / or non-selectable samples (e.g., those collected by auger).

[0037] Predictive model training is performed using a database and reference samples. A first processing model consists of converting raw data from the reflectance sensor. This step is called normalization, referring to the current method which uses raw data measured on a reference material with >99% reflectance (Spectralon(R)) and electronic noise data measured without an illuminant (source) to normalize the sample data between these two spectra (i.e., 0 and 100% reflectance). In order to eliminate these measurements prior to acquisition, a model is generated from the prior recording of this raw reference data. Raw data measured on eight reference materials (from 2% to 99% reflectance) and electronic noise are used; a model can be trained for each combination of device parameters.A second level of processing predicts the variables of interest (soil composition, presence of pollutants, and pollutant quantity) based on the reflection of a sample. Several training databases are used: published training databases (pure spectral compound libraries, e.g., the USGS Spectral Library), data produced on artificial samples produced in the laboratory, or data produced on samples analyzed in the laboratory. If a batch of analyzed samples comes from a specific site, a model can be trained on that batch only, or that batch can be used to improve a pre-trained model based on an existing database using transfer learning.

[0038] Data processing is applied to imaging data; data from analyzed subsamples allow for the interpretation or refinement of a first interpretation. Core sampling is performed. The model generated with spectrometer data allows for real-time analyses, including analyses referenced to data from COFRAC-certified laboratories. The combination of on-site imaging and spectrometry addresses both the diagnostic phase of a site and the subsequent construction phase. Selective sorting of excavated soil based on its waste classification is possible. Quality control of recycled soil at the landfill is performed using provided samples, either artificial or semi-artificial (samples provided diluted or artificially enhanced to cover a wider range of concentrations and improve the model).

[0039] Mapping the results constitutes a third level of interpretation based on a Machine Learning model. Interpolation in the space of variables of interest measured on different boreholes allows for the generation of a map. Gaussian process modeling methods are used. Geophysical data measured at the time of drilling are used in the mapping by data fusion methods.

[0040] In-situ measurements can be considered. Data acquisition using a fiber optic spectrometer makes it possible to probe the ground and produce a profile of the variables of interest as a function of depth. (Note: a distinction has been made between in-situ and on-site: Imaging can be carried out on-site with a camera in a vehicle or container. The term "in-situ" refers to the use of equipment comprising a fiber optic probe with one or more spectrometers in the portable version described above). Functional diagram

[0041] The first step (100) consists of taking a core sample of a length determined by the depth of ground to be analyzed using the probe (4). The core sample is geolocated by the GPS module (13) of the equipment.

[0042] The next step (200) consists of carrying out an analysis of the core over the length of the core by measuring the hyperspectral reflection measured by the sensors (11) when illuminated with the source (10).

[0043] The data obtained during the analysis step are recorded locally and in the cloud, and are then subjected to a step (300) of selecting a subset of samples to carry out either model training (steps 400, 500, 600), or on-site analysis (steps 450, 550, 650). Variant of the learning stage

[0044] Learning can be shared from laboratory analyses, using equipment fitted with a high-performance hyperspectral camera to record the spectral signatures of a large number of reference samples, and provide a database accessible to a plurality of field devices equipped with sensors less efficient and less expensive.

[0045] To account for technical and optical differences, each field instrument is calibrated using reference samples whose spectral signature has been previously recorded in the database. A correction function is calculated to allow the database content to be used with equipment different from that used for the initial analysis.

[0046] The samples are distinguished on the one hand by the nature of the substrate, and on the other hand by the nature of the pollutants present.

[0047] The substrates are characterized by meta-descriptors based on variables such as: - The chemical nature of the mineral and organic constituents - Water content - Oxide content - The pH - Particle size - Belonging to one or more mineral classes according to the Strunz classification - The oxidation-reduction potential (REDOX).

[0048] The reference substrate can be characterized by physicochemical analyses. It can also be prepared from predetermined components to prepare substrates by assembly.

[0049] Reference pollutants are characterized by their chemical composition.

[0050] Next, for each reference sample, the spectral signature is recorded by exposing it to illumination from a light source, for example a xenon lamp, and the reflected light as well as the light emitted by photoluminescence is captured in a wavelength range extending from thermal infrared to ultraviolet UVC. The data are recorded for each sample with a reference sample identifier and the physicochemical characteristics.

[0051] According to a preferred alternative, spectral acquisition of the sample or the entire core is carried out first, then a (sub-)sample (or several) is extracted for physico-chemical analysis. Spectral acquisition

[0052] Figure 4 shows the optical diagram of an alternative embodiment of the optical system. The configuration consists of two separate channels operated by a fiber bundle connected to a xenon lamp (10) which irradiates soil samples (60) and collects the reflected light in each channel by means of an optical switch (50). A monochromator (51) placed in the optical path provides a beam se- secondary excitation of fluorescence.

[0053] The first reflectance channel is intended for the simultaneous collection of photons on two separate spectrometers: - A spectrometer (61) in the visible and ultraviolet band - A spectrometer (62) in the infrared band.

[0054] The second channel is intended for collecting fluorescence photons in the UV-Visible-PIR range: the monochromatic incident light is selected by means of a monochromator connected to the Xenon lamp and photons are collected on the UV-Visible-PIR spectrometer (61).

Claims

Demands

1.

2. A method for analyzing soil contamination by pollutants, particularly organic pollutants, by hyperspectral analysis of reflection and / or photoluminescence, characterized in that said analysis is carried out with a first setup involving the illumination of a sample by a light source and by at least one spectral sensor sensitive over a spectrum ranging from thermal infrared to ultraviolet, characterized in that it comprises: a learning sequence consisting of analyzing a plurality of reference samples and recording them in a training database a) of the spectral reflection signature acquired by spectral analysis b) known values ​​of the variables representing the contaminants present in each of said reference samples c) known values ​​of the variables representing the substrates of each of said samples reference a calibration sequence of field analysis equipment against said first equipment, said field equipment comprising a light source and a spectral sensor, analysis sequences of a soil sample from a geological site consisting of acquiring the reflection signature and / or photoluminescence signature of said sample using said field equipment thus calibrated, and proceeding to estimate the characterization of pollutants by processing said signature by a learning engine exploiting the data from the database created during the learning sequence. Method for analyzing soil contamination by pollutants, particularly organic matter according to claim 1 characterized in that, during the analysis of a site, at least one core sample is taken and in that a plurality of samples distributed over the site are analyzed core height to characterize contaminants at different depths.

3. Method for analyzing soil contamination by pollutants, in particular organic pollutants according to claim 1 characterized in that it further comprises steps of physical and / or chemical analysis of at least a part of said samples.

Images