An apparatus for determining the rate of exchange of gases between soil, a sampling method and applications

Abstract

A device for measuring the gas exchange rate between soil, comprising a first sampling part, a second sampling part, a connecting pipe and a valve, the first sampling part and the second sampling part are communicated through the hollow connecting pipe, the first sampling part comprises a first sampling box and a first base, a plurality of first sampling ports are arranged on the first sampling box, the second sampling part comprises a second sampling box and a second base, the second sampling box is provided with a plurality of second sampling ports, the valve is arranged on the connecting pipe, the connecting pipe is provided with a third sampling port and a fourth sampling port, and the third sampling port and the fourth sampling port are arranged on the two sides of the valve. The present application can collect samples and calculate the rate of gas exchange between soil and air and between soil and soil under in-situ conditions in the field, which is accurate and controllable, and can measure the gas diffusion and release or absorption rate between different soils.

Description

Technical Field

[0001] This invention relates to the field of greenhouse gas emission monitoring technology in farmland soil, and in particular to a device, sampling method and application for measuring the gas exchange rate between soils. Specifically, it relates to a sampling device and method for measuring the gas release and absorption rates between farmland soil and the atmosphere, as well as between soils, based on collected samples under in-situ field conditions. Background Technology

[0002] Due to human activities such as fertilization, irrigation, and crop growth, farmland ecosystems experience more frequent material exchange at the soil-atmosphere interface than natural ecosystems. This includes the emission and absorption of greenhouse gases such as methane, nitrous oxide, and carbon dioxide. Therefore, quantitative observations are needed on the exchange of gaseous substances at the soil-atmosphere interface in farmland ecosystems and between soils under different management conditions. This is to assess the impact of farmland ecosystems under different planting management models on the ecological environment and the release and absorption rates of gaseous substances between soils. In particular, methane and nitrous oxide, two greenhouse gases, have a greenhouse effect far greater than that of carbon dioxide and are important research subjects for greenhouse gas emission reduction in crop farming.

[0003] Traditional rice production requires prolonged flooding, resulting in extremely anaerobic conditions in paddy field soils, which promotes the formation and emission of the greenhouse gas methane. In contrast, dryland soils in terrestrial ecosystems have an oxidative absorption capacity for atmospheric methane. Paddy field soils under dry-management conditions also exhibit a strong oxidative absorption capacity for atmospheric methane, especially when dry-management paddy fields are interspersed within flooded rice cultivation areas. This is because the methane oxidation and absorption capacity of dry-management paddy field soils reduces the atmospheric methane concentration at the soil surface, creating a methane concentration depression. Based on the principle of gas concentration gradient diffusion, this accelerates the diffusion rate of high-concentration atmospheric methane to the dry-management paddy field area. To clarify the methane release rate of flooded paddy fields and the methane absorption rate of dry-management paddy fields when they are adjacent, and their reduction effect on canopy atmospheric methane concentration, and to eliminate the interference of meteorological factors such as wind direction and force, it is necessary to use a closed-loop system to measure the methane emission dynamics of flooded paddy fields and the methane absorption dynamics of dry-management paddy fields, and to quantitatively assess the absorption effect of dry-management paddy fields on atmospheric methane in the environment of flooded rice cultivation areas. On the other hand, farmland soils treated with chemical fertilizers have higher nitrous oxide emission fluxes, and soil microorganisms can also absorb and metabolize atmospheric nitrous oxide under suitable conditions. Therefore, similar apparatus and methods are needed to determine the release and absorption rates of methane, nitrous oxide, and other gaseous components between different soils. However, no similar complete apparatus or method has yet been found that can measure the gas exchange rate between soils in situ in the field. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the first aspect of the present invention provides an apparatus for determining the net methane emission rate between soils, comprising a first sampling unit, a second sampling unit, a connecting pipe, and a valve. The first sampling unit and the second sampling unit are connected by a hollow connecting pipe. The first sampling unit includes a first sampling box and a first base, and the first sampling box is provided with a plurality of first sampling ports. The second sampling unit includes a second sampling box and a second base, and the second sampling box is provided with a plurality of second sampling ports. The valve is disposed on the connecting pipe, and the connecting pipe is provided with a third sampling port and a fourth sampling port, and the third sampling port and the fourth sampling port are disposed on both sides of the valve.

[0005] Preferably, the first sampling box is detachably connected to the first base;

[0006] Preferably, the first sampling box is hollow and has an opening at the bottom;

[0007] Preferably, the second sampling box is detachably connected to the second base;

[0008] Preferably, the second sampling box is hollow and has an opening at the bottom;

[0009] Preferably, one or more of the first sampling port, the second sampling port, the third sampling port and the fourth sampling port are provided with silicone plugs.

[0010] Preferably, the system further includes a sampler, which is detachably connected to the first sampling port, the second sampling port, the third sampling port, and the fourth sampling port, respectively.

[0011] Preferably, the sampler includes a syringe, a three-way valve, and a needle, wherein the syringe is connected to the needle via the three-way valve.

[0012] Preferably, the first sampling box is equipped with a first temperature sensor;

[0013] Preferably, the second sampling box is equipped with a second temperature sensor. The first and second temperature sensors are existing technologies and can be purchased on the market.

[0014] Preferably, the first base has a first liquid seal groove on the edge of the side facing the first sampling box;

[0015] Preferably, the second base has a second liquid seal groove on the edge of the side facing the second sampling box.

[0016] Preferably, it also includes a light-shielding sleeve, which is detachably mounted on the first sampling box and / or the second sampling box and / or the connecting pipe.

[0017] Preferably, it further includes a first temperature control component, which is connected to the first sampling box;

[0018] Preferably, it further includes a second temperature control component, which is connected to the second sampling box.

[0019] Preferably, the valve includes a valve stem and a butterfly plate, the butterfly plate being disposed inside the connecting pipe and rotating within the connecting pipe, and the valve stem being disposed outside the connecting pipe and connected to the butterfly plate;

[0020] Preferably, the valve further includes a sealing ring, which is fitted onto the side wall of the butterfly plate.

[0021] Preferably, the third sampling port and the fourth sampling port are equidistant from the valve.

[0022] Preferably, the plurality of first sampling ports are evenly distributed along the height of the first sampling box;

[0023] Preferably, the plurality of second sampling ports are evenly distributed along the height of the second sampling box;

[0024] Preferably, the first sampling port and the corresponding second sampling port are symmetrically distributed.

[0025] A second aspect of the present invention provides a method for determining the net methane emission rate between soils, wherein the net methane emission rate between soils is determined using the aforementioned apparatus for determining the net methane emission rate between soils.

[0026] Preferably, it includes the following steps:

[0027] A1) Place the first base and the second base into the first soil and the second soil, respectively;

[0028] A2) Connect the first sampling box and the second sampling box to the first base and the second base respectively, and seal them;

[0029] A3) Open the valve and collect gas samples from the first, second, third, and fourth sampling ports at different times. Analyze the concentration at each sampling port during different time periods, and then calculate the net methane emission rate F1 between the first and second soil samples and the atmosphere. For sampling accuracy, at least three samplings can be performed at each sampling port.

[0030] Preferably, in step A3), the net methane emission rate F1 between the first soil and the second soil and the atmosphere is calculated according to formula (1):

[0031] The formula (1) is: F1=ΔS / Δt × 273 / (A1×(273+T1)) (1)

[0032] Where: F1 is the net methane emission rate between the first soil and the second soil and the atmosphere, in mg / m³. -2 h -1 ΔS / Δt is the slope of the change in the total mass S1 of the gas inside the device with time t; A1 is the area inside the base of the soil gas release end, in meters. 2 T1 is the average temperature inside the device, in °C; when both the first and second soils release gas, A1 is the sum of the areas of the first and second bases; when only the first soil releases gas, A1 is the area of ​​the first base; when only the second soil releases gas, A1 is the area of ​​the second base.

[0033] The total mass S1 of the gas inside the device is calculated according to formula (2):

[0034] The formula (2) is: S1 = ΣC i × V i ×( M / 22.4)(2)

[0035] Where: S1 is the total mass of the gas components within the device at a sampling time t, in mg; C i V is the gas concentration at point i, in ppm; i It is the allocated volume represented by point i, m 3 M is the molecular weight of the gaseous component.

[0036] A4) Close valve (4), collect gas from the first sampling port (5), the second sampling port (6), the third sampling port (7), and the fourth sampling port (8) respectively, and analyze the concentration of each sampling port. Calculate the methane source release rate F2 between the soil and the atmosphere in the first sampling box (11) and the methane sink absorption rate F3 between the soil and the atmosphere in the second sampling box (21). Then calculate the net methane emission rate between the first soil and the second soil and the atmosphere F′1 = F2 + F3.

[0037] Preferably, in step A4), the release rate F2 of the methane source between the first soil and the atmosphere and the absorption rate F3 of the methane sink between the second soil and the atmosphere are calculated according to formula (3):

[0038] The formula (3) is: Fj= ΔSj / Δt × 273 / (Aj×(273+Tj)(3)

[0039] Where: Fj is the gas exchange rate between the first soil or the second soil and the atmosphere, mg / m³ -2 h -1ΔSj / Δt is the slope of the change in the total gas mass Sj in the first or second sampling box with time t; Aj is the internal area of ​​the first or second base, in meters. 2 Tj is the temperature inside the first or second sampling box, in °C; j is selected from 2 or 3;

[0040] The total mass Sj of the gas in the first and second sampling boxes is calculated according to formula (4):

[0041] The formula (4) is: Sj = ΣC k × V k ×( M / 22.4 )(4 )

[0042] Where: Sj is the total mass of the gas components in the first or second sampling chamber at a sampling time t, in mg; C k V is the gas concentration at point k, in ppm; k It is the distribution volume represented by point k, m 3 M is the molecular weight of the gas component, and j is selected from 2 or 3.

[0043] The third aspect of the present invention provides the application of the above-described method for determining the net methane emission rate between soils in determining the gas exchange rate between soil and atmosphere under different planting management modes or in determining the gas exchange rate between soils under different planting management modes.

[0044] The present invention has the following technical effects:

[0045] This invention provides a connected sampling device and method for monitoring the rate of greenhouse gas exchange between different farmland soils. It can collect samples and calculate the rate of gas exchange between soil and atmosphere and between soils under in-situ conditions in the field. The process is simple, accurate and controllable, and can measure the rate of gas diffusion, release or absorption between different soils. Attached Figure Description

[0046] Figure 1 The diagram shows the structure of the apparatus used to determine the net methane emission rate between soils in this invention.

[0047] Figure 2 The diagram shows a schematic of the valve being closed in the apparatus used to determine the net methane emission rate between soils in this invention.

[0048] Figure 3 The diagram shows a schematic of the valve opening in the apparatus for measuring the net methane emission rate between soils in this invention.

[0049] Figure 4 This diagram shows the change in total methane volume when the valve is opened in the apparatus used to determine the net methane emission rate between soils according to the present invention.

[0050] Figure 5 This diagram shows the change in methane levels at the emission end of the apparatus used to determine the net methane emission rate between soils in this invention.

[0051] Figure 6 This diagram shows the change in the amount of methane at the absorber end of the apparatus used to determine the net methane emission rate between soils in this invention.

[0052] Component designation explanation

[0053] 1. First sampling unit;

[0054] 11. First sampling box;

[0055] 12. First base;

[0056] 2. Second sampling unit;

[0057] 21. Second sampling box;

[0058] 22. Second base;

[0059] 3. Connecting pipe;

[0060] 4. Valves;

[0061] 41. Valve stem;

[0062] 42. Butterfly board;

[0063] 43. Sealing ring;

[0064] 5. First sampling port;

[0065] 6. Second sampling port;

[0066] 7. Third sampling port;

[0067] 8. Fourth sampling port;

[0068] 9. Silicone stopper;

[0069] 10. First temperature control component;

[0070] 13. Second temperature control component;

[0071] 14. First liquid seal tank;

[0072] 15. Second liquid seal tank. Detailed Implementation

[0073] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0074] Please see Figure 1-6It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art and are not intended to limit the scope of the invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, adjustments to size, or increases or decreases in the number of sampling ports, without affecting the effectiveness and objectives of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0075] like Figure 1-3 As shown, an apparatus for determining the net methane emission rate in soil includes a first sampling unit 1, a second sampling unit 2, a connecting pipe 3, and a valve 4. The first sampling unit 1 and the second sampling unit 2 are connected by a hollow connecting pipe 3. The first sampling unit 1 includes a first sampling box 11 and a first base 12. The first sampling box 11 is provided with a plurality of first sampling ports 5. The second sampling unit 2 includes a second sampling box 21 and a second base 22. The second sampling box 21 is provided with a plurality of second sampling ports 6. The valve 4 is located on the connecting pipe 3. The connecting pipe 3 is provided with a third sampling port 7 and a fourth sampling port 8, and the third sampling port 7 and the fourth sampling port 8 are located on both sides of the valve 4.

[0076] The atmosphere and soil surface generally have a function of releasing and absorbing atmospheric components, such as the emission and absorption of greenhouse gases like methane and nitrous oxide from paddy fields. To clarify the gas exchange process between different soil types, especially the absorption effect and dynamics of methane emitted from flooded paddy fields by dry-managed paddy fields, this invention elucidates the "source / sink" relationship of methane emission and absorption between the two types of paddy fields and the potential of dry-managed paddy fields to absorb atmospheric methane. The invention sets up a first sampling port 5, a second sampling port 6, a third sampling port 7, and a fourth sampling port 8 at different heights above the field surface and along the gas diffusion path in the first sampling box 11 and the second sampling box 21, at certain distances. By collecting gas samples from different locations at different time periods, monitoring changes in gas concentration, and based on methane diffusion dynamics and methane flux changes, the absorption potential of dry-managed paddy fields for methane emitted from flooded paddy fields can be assessed.

[0077] In a preferred embodiment, the first sampling box 11 is detachably connected to the first base 12, and the second sampling box 21 is detachably connected to the second base 22. The first sampling box 11 is hollow and has an opening at the bottom; the second sampling box 21 is hollow and has an opening at the bottom.

[0078] In this invention, the first sampling unit 1, the second sampling unit 2, and the connecting pipe 3 are made of transparent materials such as acrylic. The connection points of the first sampling unit 1, the second sampling unit 2, and the connecting pipe 3 are connected with a soft silicone tube to ensure airtightness, allowing gas exchange between different soil surfaces to occur under sealed conditions. In use, the first base 12 and the second base 22 are first placed in the soil to be tested, and then the first sampling box 11 and the second sampling box 21 are placed on the first base 12 and the second base 22 respectively and sealed. The first sampling box 11 and the second sampling box 21 are connected by the connecting pipe 3, and then measurements are taken. Because the first base 12 and the second base 22 are hollow, the crops in the soil to be tested are surrounded by the first base 12 and the second base 22. The number of crops surrounded is determined by the planting density. The height and size of the first sampling box 11 and the second sampling box 21 in this invention can be designed according to actual conditions. For example, the first sampling box 11 and the second sampling box 21 can be divided into a top box and an extension box. When there are no plants in the first sampling box 11 and the second sampling box 21 or the plants are small, only the top box is used. The number of extension boxes can be increased according to the height of crop growth.

[0079] In a preferred embodiment, one or more of the first sampling port 5, the second sampling port 6, the third sampling port 7, and the fourth sampling port 8 are provided with silicone plugs 9. The silicone plugs 9 are consistent in size and shape with the first sampling port 5, the second sampling port 6, the third sampling port 7, and the fourth sampling port 8, which facilitates the insertion of the gas sampler and ensures airtightness.

[0080] In a preferred embodiment, the system further includes a sampler detachably connected to the first sampling port 5, the second sampling port 6, the third sampling port 7, and the fourth sampling port 8. The sampler includes a syringe, a three-way valve, and a needle. The syringe is connected to the needle via the three-way valve. In use, the needle is inserted into the silicone stopper 9 in each of the first sampling port 5, the second sampling port 6, the third sampling port 7, and the fourth sampling port 8. Gas collection is controlled by opening and closing the three-way valve. After collection, the collected gas is injected into a sample vial for subsequent analysis.

[0081] In a preferred embodiment, the first sampling box 11 is provided with a first temperature sensor, and the second sampling box 21 is provided with a second temperature sensor. The first and second temperature sensors are existing technologies and can be purchased on the market.

[0082] In a preferred embodiment, the first base 12 has a first liquid seal groove 14 on its edge facing the first sampling box 11, and the second base 22 has a second liquid seal groove 15 on its edge facing the second sampling box 21. In use, water is injected into the first liquid seal groove 14 and the second liquid seal groove 15 to prevent the first sampling section 1 and the second sampling section 2 from exchanging with the atmosphere and affecting the accuracy of sample collection.

[0083] In a preferred embodiment, a light-shielding sleeve is also included. The light-shielding sleeve is detachably mounted on the first sampling box 11 and / or the second sampling box 21 and / or the connecting pipe 3. The entire sampling device is covered by the light-shielding sleeve to prevent the temperature of the sampling device from rising due to sunlight.

[0084] In a preferred embodiment, the system further includes a first temperature control element 10 connected to the first sampling box 11, and a second temperature control element 13 connected to the second sampling box 21. When the first temperature sensor and the second temperature sensor detect that the temperature in the first sampling box 11 and / or the second sampling box 21 is too high or too low, the first temperature control element 10 and the second temperature control element 13 can be used for adjustment. More preferably, the first temperature control element 10 and the second temperature control element 13 can be a temperature-controlled refrigerator, which is prior art and commercially available.

[0085] In a preferred embodiment, the valve 4 includes a valve stem 41 and a butterfly plate 42. The butterfly plate 42 is disposed inside the connecting pipe 3 and rotates within the connecting pipe 3. The valve stem 41 is disposed outside the connecting pipe 3 and connected to the butterfly plate 42. Preferably, the valve 4 further includes a sealing ring 43, which is sleeved on the side wall of the butterfly plate 42. When the butterfly plate 42 is perpendicular to the connecting pipe 3, the sealing ring 43 fits against the inner wall of the connecting pipe 3 to achieve a sealing effect. When the position of the butterfly plate 42 and the connecting pipe 3 is rotated, the first sampling box 11 and the second sampling box 21 can be connected. When the butterfly plate 42 is parallel to the center line of the connecting pipe 3, gas diffusion is almost unimpeded, and the gas in the first sampling box 11 and the second sampling box 21 can be freely exchanged through the connecting pipe 3.

[0086] In a preferred embodiment, the third sampling port 7 and the fourth sampling port 8 are equidistant from the valve 4, the first sampling port 5 is evenly distributed along the height of the first sampling box 11, and the second sampling port 6 is evenly distributed along the height of the second sampling box 21. The first sampling port 5 and the corresponding second sampling port 6 are symmetrically distributed, meaning that the first sampling port 5 and the corresponding second sampling port 6 are at the same height from the soil.

[0087] Example 1

[0088] Users obtain such Figure 1 The device shown is a connected sampling device for measuring the net methane emission rate between soils. It measures the release or absorption of gases by soil under different management conditions. Two days before the start of the measurement, the first base 12 and the second base 22 are fixed in the soil of the flooded paddy field and the dry-managed paddy field to be measured, respectively. The measurement is carried out during the peak methane emission period of the flooded paddy field.

[0089] Preparations before testing

[0090] Before the formal measurement, the first sampling box 11 and the second sampling box 21 are firstly fitted onto the first base 12 and the second base 22 respectively to seal them. Specifically, the lower ends of the side walls of the first sampling box 11 and the second sampling box 21 are respectively fitted into the first liquid seal tank 14 and the second liquid seal tank 15. Rice plants are then placed inside the first sampling box 11 and the second sampling box 21, and water is poured into the first liquid seal tank 14 and the second liquid seal tank 15 to liquid seal the first sampling box 11 and the second sampling box 21, preventing them from exchanging gases with the outside environment and affecting the accuracy of the measurement results. Then, the connecting pipe 3 is used to connect the first sampling box 11... The first sampling box 11 and the second sampling box 21 are sealed at the connection point, making the first sampling box 11, the second sampling box 21 and the connecting pipe 3 a closed system. Samplers are inserted into the first sampling port 5, the second sampling port 6, the third sampling port 7 and the fourth sampling port 8 respectively, and the samplers are kept in the closed state. Preferably, the sampler used in this embodiment is a three-way sampler. When in use, the connecting sampling device used to determine the gas exchange rate between soils is covered with a light-shielding material to prevent internal heating. When the first temperature sensor and the second temperature sensor detect that the temperature of the device is too high, the first temperature control component 10 and the second temperature control component 13 can be used to assist in controlling the internal temperature of the device.

[0091] Using the device for measuring the gas exchange rate between soils that has been prepared and installed, butterfly valve 4 was opened, and then 20 ml of gas samples were collected from the first sampling box 11 and the second sampling box 21 in sequence from bottom to top according to the sampling port position at 5 min, 15 min, 30 min and 60 min respectively. At the same time, the temperature inside the first sampling box 11 and the second sampling box 21 was read.

[0092] The methane concentration in the sampled gas was determined by gas chromatography to obtain the methane concentration at different locations and sampling times within the apparatus. The trend of the total methane mass S1 within the apparatus was calculated according to formula (2). Figure 4 )

[0093] The formula (2) is: S1 = ΣC i × V i ×( M / 22.4 )

[0094] Where: S1 is the total mass of the gas components within the device at a sampling time t, in mg; C i V is the gas concentration at point i, in ppm; i It is the allocated volume represented by point i, m 3 M is the molecular weight of the gaseous component.

[0095] According to formula (1), F1 = ΔS / Δt × 273 / (A1 × (273 + T1)).

[0096] Where: F1 is the net methane emission rate between the first soil and the second soil and the atmosphere, in mg / m³. -2 h -1 ΔS / Δt is the slope of the change in the total mass S1 of the gas inside the device with time t; A1 is the area inside the base of the soil gas release end, in meters. 2 Average temperature inside device T1, °C;

[0097] The calculated net methane emission rate F1 when the first sampling box 11 and the second sampling box 21 are connected is 29.0 mg / m³. -2 h -1 .

[0098] Example 2

[0099] In Example 1, after sampling for 60 minutes, valve (4) was slowly closed to isolate the first sampling box (11) and the second sampling box (21). Then, 20 ml of gas samples were collected from the box for analysis at 5 min, 15 min, 30 min, 60 min and 120 min after the butterfly valve was closed. At the same time, the temperature inside the first sampling box (11) and the second sampling box (21) was read.

[0100] (a) Analysis of methane sources and sinks

[0101] According to formula (4), S2=ΣC k × V k ×( M / 22.4 )

[0102] Where: S2 (mg) is the total mass of the gas components in the first sampling box 11 during a certain sampling time period t; C k V is the gas concentration (ppm) at point k; kThe volume (m) represented by point k 3 M is the molecular weight of the gaseous component, and the trend diagram of methane content in paddy soil under flood management is obtained. Figure 5 ).

[0103] According to formula (4), S3 = ΣC k × V k ×( M / 22.4 )

[0104] Where: S3 (mg) is the total mass of the gas components in the second sampling box 21 during a certain sampling time period t; C k V is the gas concentration (ppm) at point k; k The volume (m) represented by point k 3 M is the molecular weight of the gaseous component, and the trend of methane content in the soil of dry-planted paddy fields is obtained ( Figure 6 ).

[0105] You can see Figure 5 The methane levels shown are on an upward trend, indicating that the flooded paddy field soil is releasing methane and is a methane source. Figure 6 The methane levels shown are decreasing, indicating that the soil in dry-planted rice paddies absorbs methane and acts as a methane sink.

[0106] (ii) Analysis of methane exchange rate

[0107] According to formula (3), F2 = ΔS2 / Δt × 273 / (A2 × (273 + T2))

[0108] Where: F2 (mg m -2 h -1 ) is the release rate of the methane source between the first sampling box 11 and the atmosphere; ΔS2 / Δt is the slope of the change in the total mass S2 of the gas in the first sampling box 11 over time; A2 (m 2 ) is the internal area of ​​the first base 12; Tj is the temperature (°C) inside the first sampling box, and the release rate F2 of the methane source in the flooded paddy soil is calculated.

[0109] According to formula (3), F3 = ΔS2 / Δt × 273 / (A3 × (273 + T3))

[0110] Among them: F3 (mg m -2 h -1 ) is the absorption rate of the methane sink between the second sampling box 21 and the atmosphere; ΔS3 / Δt is the slope of the change in the total mass S3 of the gas in the second sampling box 21 over time; A3 (m 2T1 is the internal area of ​​the second base 22; T2 is the temperature (°C) inside the second sampling box. The absorption rate F3 of the methane sink in the soil of the dry-planted paddy field is calculated.

[0111] Based on the methane release rate F2 in the flooded paddy soil and the methane sink absorption rate F3 in the dry-managed paddy soil, the methane emission and absorption potential of paddy soil under different management conditions was quantitatively assessed. The measured methane release rate F2 was 29.9 mg / m³. -2 h -1 The absorption rate F3 of the methane sink is: -0.9 mg m -2 h -1 Furthermore, the sum of the two net methane emission rates F′1 is equal to the net methane emission rate F1 obtained in Example 1.

[0112] After sampling, the internal and external temperatures and atmospheric pressure of the first sampling box 11 and the second sampling box 21 are recorded. The temperature change of the first sampling box 11 and the second sampling box 21 is ≤2℃ and the atmospheric pressure is 101.325 kPa, as determined by the first temperature sensor and the second temperature sensor.

[0113] As can be seen from the above soil gas sampling method, the sampling device and method of the present invention provide for the first time an in-situ monitoring method for the gas exchange rate between soils under different field management conditions, obtain the release or absorption dynamics of gas components between soil and atmosphere, truly reflect the gas dynamics under the actual farmland environment, and the monitoring results are accurate.

[0114] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for determining the net methane emission rate between soils, characterized in that, The net methane emission rate between soils is measured using an apparatus for measuring the net methane emission rate between soils. The apparatus includes a first sampling unit (1), a second sampling unit (2), a connecting pipe (3), and a valve (4). The first sampling unit (1) and the second sampling unit (2) are connected by a hollow connecting pipe (3). The first sampling unit (1) includes a first sampling box (11) and a first base (12). The first sampling box (11) is provided with a plurality of first sampling ports (5). The second sampling unit (2) includes a second sampling box (21) and a second base (22). The second sampling box (21) is provided with a plurality of second sampling ports (6). The valve (4) is located on the connecting pipe (3). The connecting pipe (3) is provided with a third sampling port (7) and a fourth sampling port (8). The third sampling port (7) and the fourth sampling port (8) are located on both sides of the valve (4). The first sampling box (11) is hollow and has an opening at the bottom; The second sampling box (21) is hollow and has an opening at the bottom; The method includes the following steps: A1) Place the first base (12) and the second base (22) in the first soil and the second soil respectively; A2) Connect the first sampling box (11) and the second sampling box (21) to the first base (12) and the second base (22) respectively, and seal them; A3) Open the valve (4) and collect gas from the first sampling port (5), the second sampling port (6), the third sampling port (7) and the fourth sampling port (8) at different times, and analyze the concentration of each sampling port at different time periods. Then calculate the net methane emission rate F1 between the first soil and the second soil and the atmosphere. The first soil is the soil from a flooded paddy field, and the second soil is the soil from a dry paddy field.

2. The method for determining the net methane emission rate between soils as described in claim 1, characterized in that, The first sampling box (11) is detachably connected to the first base (12); The second sampling box (21) is detachably connected to the second base (22); One or more of the first sampling port (5), the second sampling port (6), the third sampling port (7) and the fourth sampling port (8) are provided with silicone plugs (9); It also includes a sampler, which is detachably connected to the first sampling port (5), the second sampling port (6), the third sampling port (7) and the fourth sampling port (8); The first sampling box (11) is equipped with a first temperature sensor; The second sampling box (21) is equipped with a second temperature sensor; The first base (12) has a first liquid seal groove (14) on the edge of the side facing the first sampling box (11). The second base (22) has a second liquid seal groove (15) on the edge of the side facing the second sampling box (21); It also includes a light-shielding sleeve, which is detachably mounted on the first sampling box (11), the second sampling box (21), and the connecting pipe (3); It also includes a first temperature control component (10), which is connected to the first sampling box (11); It includes a second temperature control unit (13), which is connected to the second sampling box (21).

3. The method for determining the net methane emission rate between soils as described in claim 1 or 2, characterized in that, The valve (4) includes a valve stem (41) and a butterfly plate (42). The butterfly plate (42) is located inside the connecting pipe (3) and rotates in the connecting pipe (3). The valve stem (41) is located outside the connecting pipe (3) and connected to the butterfly plate (42). The valve (4) also includes a sealing ring (43), which is sleeved on the side wall of the butterfly plate (42); The third sampling port (7) and the fourth sampling port (8) are equidistant from the valve (4); Several of the first sampling ports (5) are evenly distributed along the height of the first sampling box (11); Several second sampling ports (6) are evenly distributed along the height of the second sampling box (21); The first sampling port (5) and the corresponding second sampling port (6) are symmetrically distributed.

4. The method for determining the net methane emission rate between soils as described in claim 2, characterized in that, The sampler includes a syringe, a three-way valve, and a needle, with the syringe connected to the needle via the three-way valve.

5. The method for determining the net methane emission rate between soils as described in claim 1, characterized in that, In step A3), the net methane emission rate F1 between the first soil and the second soil and the atmosphere is calculated according to formula (1): The formula (1) is: F1=ΔS / Δt × 273 / (A1×(273+T1))(1) Where: F1 is the net methane emission rate between the first soil and the second soil and the atmosphere, in mg / m³. -2 h -1 ΔS / Δt is the slope of the change in the total mass S1 of the gas inside the device with time t; A1 is the area inside the base of the soil gas release end, in meters. 2 Average temperature inside device T1, °C; The total mass S1 of the gas inside the device is calculated according to formula (2): The formula (2) is: S1 = ΣC i × V i ×( M / 22.4)(2) Where: S1 is the total mass of the gas components within the device at a sampling time t, in mg; C i V is the gas concentration at point i, in ppm; i It is the allocated volume represented by point i, m 3 M is the molecular weight of the gaseous component.

6. The method for determining the net methane emission rate between soils as described in claim 1, characterized in that, It also includes the following steps: A4) Close valve (4), collect gas from the first sampling port (5), the second sampling port (6), the third sampling port (7), and the fourth sampling port (8) respectively, and analyze the concentration of each sampling port. Calculate the release rate F2 of the methane source between the soil and the atmosphere in the first sampling box (11) and the absorption rate F3 of the methane sink between the soil and the atmosphere in the second sampling box (21). Then calculate the net methane emission rate F′1 = F2 + F3 between the first soil and the second soil and the atmosphere.

7. The method for determining the net methane emission rate between soils as described in claim 6, characterized in that, In step A4), the release rate F2 of the methane source between the first soil and the atmosphere and the absorption rate F3 of the methane sink between the second soil and the atmosphere are calculated according to formula (3): The formula (3) is: Fj= ΔSj / Δt × 273 / (Aj×(273+Tj)(3) Where: Fj is the gas exchange rate between the first soil or the second soil and the atmosphere, mg / m³ -2 h -1 ΔSj / Δt is the slope of the change in the total gas mass Sj in the first or second sampling box with time t; Aj is the internal area of ​​the first or second base, in meters. 2 Tj is the temperature inside the first or second sampling box, in °C; j is selected from 2 or 3; The total mass Sj of the gas in the first and second sampling boxes is calculated according to formula (4): The formula (4) is: Sj = ΣC k × V k ×( M / 22.4 )(4 ) Where: Sj is the total mass of the gas components in the first or second sampling chamber at a sampling time t, in mg; C k V is the gas concentration at point k, in ppm; k It is the distribution volume represented by point k, m 3 M is the molecular weight of the gas component, and j is selected from 2 or 3.

8. The method for determining the net methane emission rate between soils according to any one of claims 1-7 is applied to determining the gas exchange rate between soil and atmosphere under different planting management models, and to determining the gas exchange rate between soils under different planting management models.

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