A multilayer soil gas sampler and sampling method

Abstract

This invention discloses a multi-layer soil gas sampler and sampling method. The sampler comprises: several layers of plastic protective shells, adjacent layers being connected by threads; each plastic protective shell has a cavity and several small holes on its sidewall; a partition is provided between adjacent layers; a cylindrical plastic pipe having a cavity, passing through the cavity of each plastic protective shell and extending to the protective end cap of the bottom plastic protective shell, where it is fixed; several waterproof and breathable flexible hoses, each disposed within each plastic protective shell and wrapped around the outer wall of the cylindrical plastic pipe; and several airtight polyurethane tubes, passing through the cavity of the cylindrical plastic pipe, with their bottom ends connected to one end of the waterproof and breathable flexible hoses, and their top ends extending from the top of the cylindrical plastic pipe, and equipped with a two-way valve. The sampler of this invention can simultaneously collect gases from multiple layers of soil and is convenient to use.

Description

Technical Field

[0001] This invention relates to a soil gas sampler, specifically to a multi-layer soil gas sampler and sampling method. Background Technology

[0002] Soil microorganisms decompose soil organic matter and organic nitrogen through mineralization, producing greenhouse gases such as CO2, CH4, and N2O. These greenhouse gases are either released into the atmosphere through diffusion, dissolved in soil solution, remain in soil pores, or are further decomposed and reduced by microorganisms.

[0003] Chamber samplers have been widely used by researchers both domestically and internationally to monitor greenhouse gas emission fluxes from soil. However, the gas samples collected by chamber samplers represent the apparent net flux after various soil processes have concluded, failing to reveal the gas's circulation within the soil. Therefore, various soil gas samplers have been developed. For example, Chinese patent CN201710127750.9 discloses a simple deep soil gas sampler and its sampling method. This device buries a waterproof and breathable membrane in the soil at the required depth, then uses a gas delivery tube to evacuate and seal the sampler. Once the gas from the soil pores passes through the waterproof and breathable membrane into the sampler, the sample can be retrieved and taken back to the laboratory for analysis. This device can only collect gas samples from one soil layer at a time and requires a vacuum pump for evacuation, making it relatively cumbersome. Chinese patent CN201720263552.0 discloses a soil gas sampler, which is mainly used to collect gas samples by drilling holes in relatively hard soil, cement ground, or asphalt roads. It also requires a vacuum pump and battery, making operation rather cumbersome. Chinese patent CN201620792990.1 discloses a soil gas sampling device equipped with a telescopic cylinder, motor, drill bit, and transmission rod, making operation even more cumbersome and less portable.

[0004] In summary, existing soil gas samplers are cumbersome to operate, inconvenient to carry, and do not consider stratified gas sample collection. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-layer soil gas sampler and sampling method. This sampler solves the problem that existing samplers can only collect gas from one soil layer at a time, and can collect gas from multiple soil layers simultaneously, making it convenient to use.

[0006] To achieve the above objectives, the present invention provides a multi-layer soil gas sampler, comprising: several layers of plastic protective shells, adjacent layers being connected by threads, and protective end caps fixed to the ends of the top and bottom layers of plastic protective shells; each plastic protective shell having a cavity and several small holes on its sidewall; a partition between adjacent layers; a cylindrical plastic pipe having a cavity, passing through the cavity of each layer of plastic protective shell and extending to the protective end cap of the bottom layer of plastic protective shell, and being fixed thereon; several waterproof and breathable hoses, each disposed within each layer of plastic protective shell and wound around the outer wall of the cylindrical plastic pipe, the length of which is set according to the required gas sample volume, and the volume of which is equal to the required gas sample volume; and several airtight polyurethane tubes, passing through the cavity of the cylindrical plastic pipe, the bottom end of which is connected to one end of the waterproof and breathable hose, the top end of which extends from the top end of the cylindrical plastic pipe, and equipped with a two-way valve.

[0007] In this design, each layer of the plastic protective shell contains a waterproof and breathable flexible hose that is connected to two airtight polyurethane tubes, and the two ends of the waterproof and breathable flexible hose are respectively connected to the bottom ends of the two airtight polyurethane tubes.

[0008] Preferably, the waterproof and breathable hose is a PTFE waterproof and breathable hose.

[0009] Preferably, the height of the top of the cylindrical plastic pipe is higher than the water surface height at the sampling point.

[0010] Preferably, the airtight polyurethane tube is black.

[0011] Preferably, the cylindrical plastic pipe has a threading hole on the side wall inside each layer of plastic protective shell, through which the airtight polyurethane pipe passes and communicates with the end of the waterproof and breathable hose.

[0012] The present invention also provides a multi-layer soil gas sampling method, which employs the aforementioned multi-layer soil gas sampler and includes:

[0013] During sampling, the multi-layer soil gas sampler is buried in the soil at the sampling point, and the top of the cylindrical plastic pipe is placed in the air;

[0014] Fill the waterproof and breathable hose with nitrogen and close the two-way valve at the top of the airtight polyurethane tube. After the nitrogen in the waterproof and breathable hose exchanges with the gas in the soil / sediment pores at the sampling point and reaches equilibrium, connect the nitrogen to the air inlet of the airtight polyurethane tube and the sampling vacuum bottle to the air outlet of the airtight polyurethane tube. Open the two-way valve to collect the gas and measure the greenhouse gas concentration of the collected gas, which is the greenhouse gas concentration at equilibrium in the soil / sediment pores.

[0015] Preferably, the method for filling the waterproof and breathable hose with nitrogen is as follows: connect nitrogen to the air inlet of the airtight polyurethane tube, connect the sampling vacuum bottle to the air outlet of the airtight polyurethane tube, open the two-way valve, drain the air from the waterproof and breathable hose through the sampling vacuum bottle, and fill the waterproof and breathable hose with nitrogen.

[0016] Preferably, the sampling vacuum bottle is obtained by evacuating the sampling bottle.

[0017] Preferably, the pressure inside the sampling vacuum bottle is measured.

[0018] The multi-layer soil gas sampler of the present invention solves the problem that existing samplers can only collect gas from one soil layer at a time, and has the following advantages:

[0019] (1) The sampler of the present invention can simultaneously collect gas samples from different soil depths at the same location, thereby revealing the distribution characteristics of soil / sediment pore gas in the vertical direction.

[0020] (2) The sampler of the present invention uses a PTFE waterproof and breathable hose, which can achieve waterproofing while gas sampling, and is suitable for collecting soil pore gas samples from paddy fields, wetlands and other places with high soil moisture.

[0021] (3) The sampler of the present invention can be used for long-term location monitoring of soil / sediment pore gas concentration at different times, and can also be used for monitoring the respiration gas of marked plant roots;

[0022] (4) The sampler of the present invention has good sealing performance, is easy to operate, and helps to reduce experimental errors;

[0023] (5) The sampler of the present invention is simple and reasonable in design, low in cost, easy to carry and very simple to operate, and is suitable for field sampling. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the multi-layer soil gas sampler of the present invention.

[0025] Figure 2 This is a three-dimensional schematic diagram of the multi-layer soil gas sampler of the present invention. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] A multi-layer soil gas sampler, such as Figure 1 The diagram shown is a structural schematic of the multi-layer soil gas sampler of the present invention. Figure 2 The diagram shown is a three-dimensional schematic of the multi-layer soil gas sampler of the present invention. The sampler comprises: several layers of plastic protective shells 2, adjacent layers being connected by threads, and protective end caps fixed to the ends of the top and bottom layers of plastic protective shells 2; each plastic protective shell 2 having a cavity and several small holes on its sidewalls; and partitions between adjacent layers; and a cylindrical plastic pipe 4 having a cavity, which passes through the cavity of each layer of plastic protective shell 2 and extends to the bottom layer of plastic protective shell 2. The protective end cap of body 2 is fixed; several waterproof and breathable hoses 1 are installed inside each layer of plastic protective shell 2 and wrapped around the outer wall of cylindrical plastic pipe 4. Their length is set according to the required gas sample volume, and their volume is equal to the required gas sample volume; and several airtight polyurethane tubes 3 are inserted into the cavity of cylindrical plastic pipe 4. Their bottom end is connected to one end of the waterproof and breathable hose 1 and sealed (to ensure that the connection does not leak air). Their top end extends from the top end of cylindrical plastic pipe 4 and is equipped with a two-way valve.

[0028] In this case, the waterproof and breathable hose 1 in each layer of the plastic protective shell 2 is connected to two airtight polyurethane tubes 3, and the two ends of the waterproof and breathable hose 1 are respectively connected to the bottom ends of the two airtight polyurethane tubes 3.

[0029] Furthermore, the waterproof and breathable hose 1 is made of PTFE.

[0030] Furthermore, the height of the top of the cylindrical plastic pipe 4 is higher than the water surface height at the sampling point.

[0031] Furthermore, the airtight polyurethane tube 3 is black.

[0032] Furthermore, on the cylindrical plastic pipe 4, a threading hole is provided on the side wall inside each layer of plastic protective shell 2, through which the airtight polyurethane pipe 3 passes and communicates with the end of the waterproof and breathable hose 1.

[0033] This invention also provides a multi-layer soil gas sampling method, wherein the multi-layer soil gas sampler used in this method comprises:

[0034] During sampling, the multi-layer soil gas sampler is buried in the soil at the sampling point, and the top of the cylindrical plastic pipe 4 is placed in the air;

[0035] Fill the waterproof and breathable hose 1 with nitrogen and close the double-way valve at the top of the impermeable polyurethane tube 3. After the nitrogen in the waterproof and breathable hose 1 exchanges with the gas in the soil / sediment pores at the sampling point and reaches equilibrium, connect the nitrogen to the air inlet of the impermeable polyurethane tube 3 and the sampling vacuum bottle to the air outlet of the impermeable polyurethane tube 3. Open the double-way valve to collect the gas and measure the greenhouse gas concentration of the collected gas, which is the greenhouse gas concentration in the soil / sediment pores at equilibrium.

[0036] Furthermore, the method for filling the waterproof and breathable hose 1 with nitrogen is as follows: connect nitrogen to the air inlet of the airtight polyurethane tube 3, connect the sampling vacuum bottle to the air outlet of the airtight polyurethane tube 3, open the double-way valve, evacuate the air in the waterproof and breathable hose 1 through the sampling vacuum bottle, and fill the waterproof and breathable hose 1 with nitrogen.

[0037] Furthermore, the sampling vacuum bottle is obtained by evacuating the sampling bottle.

[0038] Furthermore, the pressure inside the sampling vacuum bottle was measured.

[0039] Example 1

[0040] A multi-layer soil gas sampler comprises: a PTFE waterproof and breathable hose 1, a three-layer plastic protective shell 2, an airtight polyurethane tube 3, and a cylindrical plastic pipe 4. Each layer of the plastic protective shell 2 has a cavity and several small holes on its sidewall. Adjacent layers of the plastic protective shell 2 are connected by threads. The ends of the top and bottom layers of the plastic protective shell 2 are fixed (possibly by threaded connection) with protective end caps to protect the internal hose. The cylindrical plastic pipe 4 has a cavity, passes through the cavities of each layer of the plastic protective shell 2, and extends to the protective end cap of the bottom layer of the plastic protective shell 2, where it is fixed. The protective end cap of the top layer of the plastic protective shell 2 has a perforation through which the cylindrical plastic pipe 4 passes. The PTFE waterproof and breathable hose 1 is wound around the outer wall of the cylindrical plastic pipe 4, and its length is set according to the required gas sample volume. There are 6 airtight polyurethane tubes 3, which are inserted into the cavity of the cylindrical plastic pipe 4. The bottom ends of every two tubes are connected to both ends of the PTFE waterproof and breathable hose 1, and the top ends extend from the top of the cylindrical plastic pipe 4. Each tube is equipped with a double-way valve.

[0041] Specifically, cylindrical plastic pipes 4 have thread holes on the side walls of each layer, and two airtight polyurethane pipes 3 pass through the thread holes and connect with PTFE waterproof and breathable hoses 1.

[0042] The length of the PTFE waterproof and breathable hose 1 is set according to the required gas sample volume. Its volume is equal to the required gas sample volume and can be replaced each time according to the volume of the sampling bottle. It is used for the balanced exchange of soil / sediment gas and gas inside the hose. It can also achieve waterproof gas sampling at the same time. It is suitable for collecting soil pore gas samples from paddy fields, wetlands and other soils with high soil moisture.

[0043] The plastic protective shell 2 is used to protect the PTFE waterproof and breathable hose 1 while allowing air to pass through, ensuring the flow of gas in the pores of the soil / sediment for collecting gas samples from different soil layers.

[0044] The airtight polyurethane tube 3 is black to avoid direct sunlight and any possible photochemical reactions. It is connected to the PTFE waterproof and breathable hose 1 and is used to transport the gas sample inside the PTFE waterproof and breathable hose 1. The two-way valve at its end facilitates sealing and gas sample collection.

[0045] Cylindrical plastic pipe 4 is used to protect the airtight polyurethane pipe 3, and its height can be determined according to whether the sampling site is flooded and the flood level.

[0046] The method of using the multi-layer soil gas sampler of the present invention is as follows:

[0047] During sampling, first dig a pit at the desired sampling point, bury the multi-layer soil gas sampler of the present invention in the soil, and cover it with soil to ensure that the top of the cylindrical plastic pipe 4 is exposed to the air.

[0048] Take a nitrogen-filled gas bag and a sampling bottle, evacuate the gas bag and measure the pressure inside. The volume of the sampling bottle should be the same as the volume of the PTFE waterproof and breathable hose 1. Connect the nitrogen gas bag to the inlet of the airtight polyurethane tube 3, and connect the vacuum bottle to the outlet of the airtight polyurethane tube 3. Open the double-way valve. At this time, the vacuum sampling bottle will evacuate the air from the PTFE waterproof and breathable hose 1 and introduce nitrogen into the PTFE hose. Nitrogen filling is used to remove the target gas (i.e., the target gas to be measured, such as CO2, CH4, or N2O) remaining in the hose. In this way, the measured gas concentration is the concentration at soil / sediment physical equilibrium, not the concentration that remained in the hose before. Immediately close the double-way valve of the inlet and outlet after sampling. Different soil layers should be treated in the same way, and the inlet / outlet of each airtight polyurethane tube 3 and the soil layer from which it comes should be clearly marked.

[0049] Gases in the soil undergo diffusion. The PTFE waterproof and breathable hose 1 allows the gas to move inside and outside the hose. After the nitrogen in the PTFE waterproof and breathable hose 1 exchanges with the gas in the soil / sediment pores and reaches equilibrium, gas samples can be collected again using a vacuum bottle and nitrogen bag. The operation for gas sample collection is the same as the operation for filling the PTFE waterproof and breathable hose 1 with nitrogen. At this time, the greenhouse gas concentration is measured, which is the greenhouse gas concentration in the soil / sediment pores at equilibrium. After each gas sample collection, the double-way valve should be closed to keep the device in a sealed state.

[0050] After collecting the gas, it can be analyzed using gas chromatography or other instruments.

[0051] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A multi-layer soil gas sampler, characterized in that, This sampler includes: Several layers of plastic protective shells (2), with adjacent layers connected by threads, and the ends of the top and bottom layers of plastic protective shells (2) are fixed with: protective end caps, each plastic protective shell (2) has a cavity, and its side wall is provided with several: small holes, and adjacent layers are provided with: partitions; A cylindrical plastic pipe (4) has a cavity, and it passes through the cavity of each layer of plastic protective shell (2) and extends to the protective end cap of the bottom plastic protective shell (2) and is fixed thereon; Several waterproof and breathable flexible hoses (1) are provided inside each layer of plastic protective shell (2) and wrapped around the outer wall of the cylindrical plastic pipe (4). Their length is set according to the required gas sample volume, and their volume is equal to the required gas sample volume; and Several airtight polyurethane tubes (3) are inserted into the cavity of the cylindrical plastic pipe (4), with their bottom ends connected to one end of the waterproof and breathable hose (1), and their top ends extending from the top of the cylindrical plastic pipe (4), and equipped with a two-way valve. In this case, the waterproof and breathable hose (1) in each layer of the plastic protective shell (2) is connected to two airtight polyurethane tubes (3), and the two ends of the waterproof and breathable hose (1) are respectively connected to the bottom ends of the two airtight polyurethane tubes (3). The waterproof and breathable hose (1) is made of PTFE.

2. The multi-layer soil gas sampler according to claim 1, characterized in that, The height of the top of the cylindrical plastic pipe (4) is higher than the water surface height at the sampling point.

3. The multi-layer soil gas sampler according to claim 1, characterized in that, The airtight polyurethane tube (3) is black.

4. The multi-layer soil gas sampler according to claim 3, characterized in that, On the cylindrical plastic pipe (4), a threading hole is provided on the side wall inside each layer of plastic protective shell (2), through which the airtight polyurethane pipe (3) passes and communicates with the end of the waterproof and breathable hose (1).

5. A multi-layer soil gas sampling method, characterized in that, This method employs a multi-layer soil gas sampler as described in any one of claims 1-4, comprising: During sampling, the multi-layer soil gas sampler is buried in the soil at the sampling point, and the top of the cylindrical plastic pipe (4) is placed in the air; Fill the waterproof and breathable hose (1) with nitrogen and close the double-way valve at the top of the impermeable polyurethane tube (3). After the nitrogen in the waterproof and breathable hose (1) and the gas in the soil / sediment pores at the sampling point have reached equilibrium through mutual exchange, connect the nitrogen to the air inlet of the impermeable polyurethane tube (3), connect the sampling vacuum bottle to the air outlet of the impermeable polyurethane tube (3), open the double-way valve to collect the gas, and measure the greenhouse gas concentration of the collected gas, which is the greenhouse gas concentration when the soil / sediment pores are in equilibrium.

6. The multi-layer soil gas sampling method according to claim 5, characterized in that, The method for filling the waterproof and breathable hose (1) with nitrogen is as follows: connect nitrogen to the air inlet of the airtight polyurethane tube (3), connect the sampling vacuum bottle to the air outlet of the airtight polyurethane tube (3), open the double-way valve, drain the air in the waterproof and breathable hose (1) through the sampling vacuum bottle, and fill the waterproof and breathable hose (1) with nitrogen.

7. The multi-layer soil gas sampling method according to claim 5, characterized in that, The sampling vacuum bottle is obtained by evacuating the sampling bottle.

8. The multi-layer soil gas sampling method according to claim 5, characterized in that, The pressure inside the sampling vacuum bottle is measured.

Images