A method of detecting a petroleum hydrocarbon soil contamination plume

Abstract

The application discloses a method for detecting a petroleum hydrocarbon soil pollution plume, and is suitable for a polluted site, especially a service site pollution plume sketching. The application realizes preliminary sketching of a petroleum hydrocarbon pollution plume by coupling a high-density resistance method with a portable modular soil gas stratified sampling method. The portable modular soil gas stratified sampling method uses a portable modular soil gas stratified sampling device to perform stratum sampling, and sets an air inlet interval protection device. When the air inlet interval protection device is not opened, the air inlet interval protection device is in a non-breathable state. Only when the air inlet interval protection device is opened, the air inlet interval protection device has air inlet conditions. The method guarantees sampling accuracy, and has the advantages of low price, high efficiency and improved efficiency.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection, and in particular relates to a method for detecting petroleum hydrocarbon soil pollution plumes. Background Technology

[0002] The development of the petroleum and petrochemical industry has led to petroleum hydrocarbon pollution at various sites. Upstream oil and gas development primarily pollutes well sites, with crude oil being the main contaminant. Downstream refining and chemical processes mainly pollute refinery areas, with gasoline, diesel, and other refined oil products, as well as various intermediate products. Gas station sales sites are oil depots and gas stations, with gasoline and diesel fuel as the primary pollutants. Petroleum-contaminated soil can cause changes in soil structure and properties, vegetation destruction, alterations in microbial communities, reduced soil enzyme activity, and water and soil pollution, damaging land use functions and seriously threatening human health and the ecological environment.

[0003] With increasingly stringent environmental protection requirements, the need for site investigations to determine whether petroleum hydrocarbon contamination has occurred in soil is growing. Currently, conventional soil investigation techniques include:

[0004] (1) Soil in-situ sampling and laboratory testing methods

[0005] Soil samples are obtained from different locations and depths using tools such as Luoyang shovels and hand drills, or more advanced in-situ soil sampling drills (such as GeoProbe). The samples are then preserved and transferred in accordance with national standards and sent to the laboratory for testing using high-precision instruments such as gas chromatography.

[0006] (2) Membrane Interface Probe Method (MIP)

[0007] The GeoProbe is equipped with a MIP (Membrane Interface Probe) module, which allows for the collection of underground volatile organic compounds (VOCs) through a permeable membrane on the drill bit while the drilling rig is drilling. This enables on-site GC testing to determine the petroleum hydrocarbon content at different depths. It features FID, PID, and XSD detectors. FID detects the total amount of non-halogenated organic compounds, XSD detects the total amount of halogenated organic compounds, and PID detects the total amount of organic compounds containing functional groups such as benzene rings.

[0008] In conventional soil survey techniques, systematic sampling, random sampling, and zonal sampling are commonly used in field applications. Systematic sampling, also known as grid sampling, is primarily used for sites with unclear soil pollution characteristics or severely damaged original conditions. The site is divided into several equal-sized plots, with one sampling point placed in each plot. The accuracy of systematic sampling is affected by the grid size; smaller grids result in higher sampling precision. For large contaminated sites with similar soil characteristics and uses, random sampling is typically used when initially establishing monitoring points. Soil sampling using the random sampling method has certain requirements for the site area to be tested and is not suitable for areas with complex soil environments. Furthermore, due to the randomness of the sampling points, the results are also highly random and lack strong representativeness of the overall soil condition. The zonal sampling method is mainly suitable for areas where the original soil condition is well preserved, the functions of each block are clearly defined, and the survey area is large. It divides the site into relatively uniform areas based on its original functional properties, and sampling points are placed according to these areas. This method can reveal potential contaminated areas within the testing area; however, the division of areas significantly impacts the results. Currently, the commonly used sampling size in existing technologies is generally 40m*40m. The resulting boundaries of the contaminated area often have significant uncertainty, thus increasing remediation costs and reducing the efficiency of contaminated site remediation.

[0009] In existing technologies, CN105203599A discloses a rapid diagnostic method for contaminated soil at a site. This method involves using high-density electrical resistivity tomography (EDS) to test the soil resistivity in a preliminary investigation area within a potentially contaminated zone. This identifies areas with abnormal resistivity distribution, thus determining key investigation areas for further exploration. The method then tests the resistivity of contaminated soil in these key investigation areas and assesses the degree of contamination based on the rate of change of resistivity in these areas relative to uncontaminated areas. However, using EDS to quickly identify abnormal contamination areas has limitations. EDS has specific applicability and is not suitable for sites with heterogeneous hydrogeological conditions. In such cases, EDS alone cannot quickly screen out the contamination status. CN107544097A discloses a method for precise location and accurate assessment of soil contamination based on geophysical exploration technology. This invention utilizes a combination of geophysical exploration technologies—an electromagnetic induction meter, a high-density resistivity meter, and ground-penetrating radar—to accurately locate suspected contaminated areas or points in the soil. It rationally arranges sampling points and combines rapid on-site contamination screening with borehole sampling and analysis to construct a soil contamination investigation process that progresses from surface to line to point and finally back to surface. The use of integrated geophysical methods for detection has yielded some results. Experiments have shown that for organically contaminated sites, high-density electrical resistivity methods can infer the potential contamination levels by analyzing differences in resistivity. However, high density alone cannot truly characterize the pollution plume, and its accuracy is not high. CN108548888A discloses a method for precise monitoring and assessment of volatile petroleum hydrocarbons in organically contaminated sites. This invention still determines pollutant concentrations through internal standards between the laboratory and the site, but it is mainly used for later-stage precise investigations and cannot quickly and effectively locate pollution plumes during the initial investigation phase.

[0010] According to existing survey techniques, accurately characterizing pollution plumes requires a large number of densely distributed sampling points, which is not only costly but also unsuitable for enterprises in operation, posing significant safety risks. Therefore, this invention proposes a method for detecting petroleum hydrocarbon soil pollution plumes at petroleum hydrocarbon contaminated sites. This method is applicable to the characterization of pollution plumes at in-service sites contaminated with petroleum hydrocarbons. It can achieve preliminary characterization of petroleum hydrocarbon pollution plumes in organically contaminated sites by using a high-density resistivity method coupled with a portable modular soil gas stratification sampling method. The advantages include low cost, high efficiency, and improved efficiency. Summary of the Invention

[0011] To address the aforementioned technical problems, this invention provides a method for detecting petroleum hydrocarbon soil pollution plumes. This method enables the preliminary characterization of petroleum hydrocarbon pollution plumes in organically contaminated sites by coupling a high-density resistivity method with a portable modular soil gas stratification sampling method. The advantages include low cost, high efficiency, and improved efficiency.

[0012] A method for detecting petroleum hydrocarbon soil pollution plumes, the method comprising the following steps:

[0013] Step 1: Lay out survey lines and determine survey points within the survey area;

[0014] Step 2: Obtain the resistivity of the measuring point using a high-density electrical resistivity tomography (EDT) device;

[0015] Step 3: Obtain the formation resistivity of the measuring point by inversion based on the resistivity of the measuring point;

[0016] Step 4: Compare the formation resistivity at the measuring point with the corresponding normal formation resistivity value to obtain the comparison result;

[0017] Step 5: Determine whether the area corresponding to the measuring point is a suspected contaminated area based on the comparison results;

[0018] Step 6: Deploy sampling points in the suspected contaminated area, and use a high-density resistivity method coupled with a portable modular soil gas stratification sampling method to delineate the three-dimensional distribution of soil gas pollution from the sampling points in the suspected contaminated area. Determine the range of the pollution plume through real-time dynamic adjustments.

[0019] Further, in step 4, the specific method for comparing the formation resistivity of the measuring point with the corresponding normal value of formation resistivity is as follows: when there are no metal pipelines, cement walls, or groundwater layers in the survey area, the normal value of formation resistivity of the formation type corresponding to the measuring point is compared with the formation resistivity of the measuring point. If the comparison result exceeds at least one order of magnitude, the comparison result is considered an apparent resistivity anomaly; when there are metal pipelines, cement walls, or groundwater layers in the survey area, the normal value of formation resistivity of the formation type corresponding to the measuring point is compared with the formation resistivity of the measuring point. If the comparison result exceeds at least three orders of magnitude, the comparison result is considered an apparent resistivity anomaly.

[0020] Furthermore, in step 5, the method for identifying suspected contaminated areas is as follows: when the formation resistivity of the measuring point is higher than the corresponding normal value of formation resistivity, it is considered that there is no pollution from fresh gasoline and diesel or weathered crude oil, but there is suspected pollution from weathered gasoline and diesel or fresh crude oil; when the formation resistivity of the measuring point is lower than the corresponding normal value of formation resistivity, it is considered that there is suspected pollution from fresh gasoline and diesel or weathered crude oil, but there is no pollution from weathered gasoline and diesel or fresh crude oil.

[0021] Furthermore, the spacing between the measuring lines in step 1 is 2-5 meters.

[0022] Furthermore, the portable modular soil gas stratification sampling method described in step 6 utilizes a portable modular soil gas stratification sampling device for formation sampling. The specific sampling method is as follows:

[0023] Step 6.1: Drill a borehole into the formation using a drilling device, ensuring that no groundwater is encountered and that the borehole width is greater than the diameter of the portable modular soil gas stratification sampling device;

[0024] Step 6.2: Assemble the portable modular soil gas stratification sampling device, insert the sampling device into the borehole, and freely control the insertion depth according to the actual depth requirements;

[0025] Step 6.3: Turn on the air inlet barrier protection device in the portable modular soil gas stratification sampling device. After the air inlet barrier protection device is fully turned on, use a vacuum pump to draw air from two different gas sampling tubes. After the temperature of the portable modular soil gas stratification sampling device is balanced and stable, record the reading.

[0026] Step 6.4: Close the air intake barrier protection device. After the air intake barrier protection device is completely closed, slowly pull out the portable modular soil gas stratification sampling device to complete the soil gas sampling.

[0027] Furthermore, the drilling depth in step 6.1 is 1.5m.

[0028] Furthermore, the portable modular soil gas stratification sampling device consists of a detachable probe module, a detection module, a sampling module, and a metal spiral head. Multiple sampling modules can be assembled. The detection module, probe module, sampling module, and metal spiral head are connected sequentially from top to bottom. The probe module consists of a probe, a motor start switch, and a motor control connection line. The motor start switch is located on the probe and is connected to the motor via the motor control connection line to control the operation of the sampling module. The detection module is connected to the sampling module via a gas guide tube.

[0029] Furthermore, the sampling module comprises a gas sampling probe, a bentonite filling layer, an air intake layer, a chassis, an air intake isolation protection device, an air duct connector, a motor connector, and filter material. The bentonite filling layer, air intake layer, and chassis are arranged sequentially from top to bottom. The filter material is located at the bottom of the air intake layer and is close to the top of the chassis. The gas sampling probe is located in the filter material and is connected to the detection module through an air duct. An air duct connector is provided at the end of the air duct to facilitate the connection between air ducts. The chassis is composed of concrete and a motor. The air intake isolation protection device covers the outer wall of the sampling module. The motor start switch controls the motor in the chassis to realize the switching of the air intake isolation protection device. Motor connectors are provided at the top and bottom of the sampling module, and the two motor connectors are connected through a motor control connection line.

[0030] Furthermore, the portable modular soil air stratification sampling device has a cylindrical structure with a diameter of 3-10 cm and a sampling range of 0.5-6 m.

[0031] Furthermore, the thickness of the bentonite filling layer is 2-5 cm.

[0032] Furthermore, the air intake diaphragm protection device is supported by a titanium alloy frame and is made of soft anti-corrosion material, and has an umbrella-shaped structure.

[0033] Furthermore, the sidewall of the air intake layer is made of perforated polytetrafluoroethylene material, which is airtight when the air intake layer protection device is not activated, and only allows air intake when the air intake layer protection device is activated.

[0034] Furthermore, the filter material is composed of quartz sand.

[0035] Furthermore, the probe of the device is made of aluminum or titanium alloy, and has a round bottom that allows for threaded connection.

[0036] Beneficial Effects: This invention provides a method for detecting petroleum hydrocarbon soil pollution plumes. It enables the preliminary characterization of petroleum hydrocarbon pollution plumes in organically contaminated sites by coupling a high-density electrical resistivity method with a portable modular soil gas stratification sampling method. Advantages include low cost, high efficiency, and improved efficiency. While some existing patents mention using high-density electrical resistivity to delineate pollution areas, these methods often suffer from limited effectiveness in heterogeneous subsurfaces. This invention solves this problem by coupling high-density electrical resistivity to delineate with a self-developed portable modular soil gas stratification sampling method. The portable modular soil gas stratification sampling method utilizes a portable modular soil gas stratification sampling device for ground sampling. An air intake barrier protection device is installed, ensuring an airtight state when the device is closed and allowing air intake only when the device is open. This guarantees sampling accuracy. Attached Figure Description

[0037] Figure 1 A schematic diagram of the structure of a method for detecting petroleum hydrocarbon soil pollution plumes according to the present invention;

[0038] Figure 2 A schematic diagram of the initial structure of the air intake diaphragm protection device of the present invention;

[0039] Figure 3 A schematic diagram of the probe module structure of the device of the present invention;

[0040] Figure 4 A schematic diagram of the detection module structure of the present invention;

[0041] Figure 5 A schematic diagram of the sampling module structure of the present invention;

[0042] Figure 6 A schematic diagram of the metal spiral head structure of the present invention;

[0043] Figure 7 A schematic diagram of the high-density electrical resistivity tomography principle of this invention;

[0044] Figure 8 Schematic diagram of high-density electrical resistivity tomography (EDT) sampling points;

[0045] Figure 9 A schematic diagram of the high-density electrical resistivity tomography (EDT) side-line arrangement of this invention;

[0046] Figure 10 1. High-density electrical resistivity tomography cross-section of side line Z1 in this embodiment of the invention;

[0047] Figure 11 The image shows a three-dimensional distribution map of pollution at a petrochemical site in a real-world example of this invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments.

[0049] A method for detecting petroleum hydrocarbon soil pollution plumes involves: laying out measuring lines within a survey area to determine measuring points, with the spacing between the measuring lines typically ranging from 2 to 5 meters; acquiring the resistivity of each measuring point; obtaining the formation resistivity of each measuring point by inversion based on its resistivity; comparing the formation resistivity of each measuring point with its corresponding normal value to obtain a comparison result; determining whether the area corresponding to the measuring point is a suspected pollution area based on the comparison result; deploying sampling points in the suspected pollution area; using portable modular soil gas stratification sampling to delineate the three-dimensional distribution of soil gas pollution from the sampling points in the suspected pollution area; and determining the range of the pollution plume through real-time dynamic adjustments.

[0050] Further, the step of comparing the formation resistivity of the measuring point with the corresponding normal value of formation resistivity includes: when there are no metal pipelines, cement walls, or groundwater layers in the survey area, the normal value of formation resistivity for the corresponding formation type of the measuring point is compared with the formation resistivity of the measuring point; if the difference exceeds by at least one order of magnitude, the comparison result is an apparent resistivity anomaly; when there are metal pipelines, cement walls, or groundwater layers in the survey area, the normal value of formation resistivity for the corresponding formation type of the measuring point is compared with the formation resistivity of the measuring point; if the difference exceeds by at least three orders of magnitude, the comparison result is an apparent resistivity anomaly. The comparison result is as follows: when the formation resistivity of the measuring point is higher than the corresponding normal value of formation resistivity, there is no fresh gasoline / diesel or weathered crude oil contamination, but there is suspected contamination of weathered gasoline / diesel or fresh crude oil; when the formation resistivity of the measuring point is lower than the corresponding normal value of formation resistivity, there is suspected contamination of fresh gasoline / diesel or weathered crude oil, but no contamination of weathered gasoline / diesel or fresh crude oil.

[0051] The steps for portable modular soil air stratification sampling are as follows: Figure 1 As shown, this device includes a probe module, a detection module, a sampling module, and a metal spiral head, which includes two sampling modules. The total length is approximately 1 meter. These five modules are first assembled to form... Figure 1 The method for using this device to perform soil air stratification sampling is as follows:

[0052] Step 1: Drill to a depth of 1.5 meters using a drilling device, ensuring that no groundwater is present and that the borehole width is greater than the diameter of the device.

[0053] Step 2: Assemble the sampling device to Figure 1 The sampling device is inserted into the borehole, leaving only the probe module outside the hole. This can be freely controlled according to the actual depth requirements.

[0054] Step 3: Turn on the air intake barrier protection device 6. After the device is fully turned on, use a vacuum pump to draw air from the two different gas sampling pipes. After the portable device temperature is balanced and stable, record the reading.

[0055] Step 4: Close the air inlet barrier protection device 6. After the device is completely closed, slowly pull out the equipment and disassemble the module. Soil gas sampling is complete.

[0056] The portable modular soil gas stratification sampling method mainly utilizes a portable modular soil gas stratification sampling device, characterized by the modules shown in the figure: Figure 3 The image shows the probe module of the device. Figure 4 The image shows the detection module. Figure 5 The image shows the sampling module. Figure 6The diagram shows a metal spiral head. The probe module is threadedly connected to the sampling module via connecting pipe 17. The detection module is threadedly connected to the metal spiral head, and the detection module is connected to the sampling module via a gas guide tube. The main components include a metal spiral head 1, a gas sampling probe 2, a bentonite filling layer 3, an air inlet layer 4, a sampling module chassis 5, an air inlet partition protection device 6, a gas guide tube 7, a probe 8, a detection module 9, a gas guide tube connector 10, a motor start switch 11, a motor control connection cable 12, a motor connector 13, and filter material 14. The entire device is cylindrical, with a diameter between 3cm and 10cm. Due to its modular design, the length of the entire device can be flexibly adjusted. However, the detection range is generally between 0.5 meters and 6 meters. The probe is made of aluminum or titanium alloy, with a circular bottom and threaded connection. A connecting rod can be added as needed to adjust the length. The four modules can be disassembled at any time, and multiple sampling modules can be assembled. The sampling module can also be connected to a connecting rod, and then to the sampling module; the detection module is connected to the detector via a gas guide tube. The detector includes conventional soil testing equipment, such as PID and portable gas phase instruments, and can also be connected to a gas bag or a suma canister; the sampling module consists of a gas sampling probe 2, a bentonite filling layer 3, an air intake layer 4, a sampling module chassis 5, an air intake partition protection device 6, a gas guide tube 7, a gas guide tube connector 10, a motor control connection cable 12, a motor connector 13, and filter material 14; the sampling module chassis 5 is composed of concrete and a motor, and the motor controls the on / off state of the air intake partition protection device 6; the air intake partition protection device 6 is controlled by a motor start switch 11 to open and close, and when opened... Figure 2 In the indicated state, the air intake isolation protection device 6 is open and tightly attached to the outer wall 16 of the soil hole. Gas in the soil enters the air intake layer through the air inlet 15, effectively blocking cross-contamination of gases at different levels. The air intake isolation protection device 6 is supported by a titanium alloy frame and is composed of soft, corrosion-resistant materials. Similar to an umbrella-shaped structure, it has strong strength and good containment. The motor connector 13 and the air duct connector 10 in the sampling module can be effectively connected to other modules, facilitating modular disassembly. The sidewall of the air intake layer 4 is composed of perforated polytetrafluoroethylene material. It is airtight when the air intake isolation protection device 6 is not open, and only allows air intake when the air intake isolation protection device 6 is open. The entire motor device is powered by a battery. The bentonite filling layer 3 is between 2-5 cm and is located above the air intake layer. The filter material 14 in module 3 is composed of quartz sand.

[0057] Specific implementation case 1:

[0058] For a decommissioned petrochemical site in northern China, the soil has become contaminated with petroleum hydrocarbons due to years of production. It is necessary to determine the distribution range of this contamination for subsequent remediation. To determine the distribution of petroleum hydrocarbon contamination in the underground space, high-density electrical resistivity tomography (EDS) was used to locate the contamination plume in the area.

[0059] The high-density electrical resistivity tomography (EDT) data acquisition device is a Wenner quadrupole device. A schematic diagram of the high-density EDT principle is shown below. Figure 7 .

[0060] from Figure 10 As can be seen, at three locations along survey line 01, from 13m to 25m, 34m to 35m, and 45m to 50m, at depths from the surface to a burial depth of about 1.3m, there are obvious relatively high resistivity anomaly traps, which are particularly evident in the 13m to 25m section.

[0061] Through multiple lateral line inversions, the contamination area can be preliminarily defined. Based on the contamination area, sampling points are deployed in the contaminated area of ​​the site, and a portable modular soil air stratification sampling method is used for detection.

[0062] A total of 30 sampling points were set up within the contaminated area. Soil gas was collected at 12 depths at each point, with each sample spaced half a meter apart. Soil gas screening was carried out using a portable modular soil gas stratification sampling method. The final three-dimensional distribution map is shown below. Figure 11 .

[0063] Numerical simulations and some field tests on the petroleum hydrocarbon-contaminated strata model demonstrate that the high-density electrical resistivity tomography coupled with portable modular soil gas stratification sampling method is effective in identifying petroleum hydrocarbon contamination in strata, and is feasible and applicable. It can serve as a method and approach for addressing this type of pollution problem.

[0064] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for detecting petroleum hydrocarbon soil pollution plumes, characterized in that, The method includes the following steps: Step 1: Lay out survey lines and determine survey points within the survey area; Step 2: Obtain the resistivity of the measuring point using a high-density electrical resistivity tomography (EDT) device; Step 3: Obtain the formation resistivity of the measuring point by inversion based on the resistivity of the measuring point; Step 4: Compare the formation resistivity at the measuring point with the corresponding normal formation resistivity value to obtain the comparison result; The specific method for comparing the formation resistivity of the measuring point with the corresponding normal value of formation resistivity is as follows: When there are no metal pipelines, cement walls, or groundwater layers in the survey area, the normal value of formation resistivity of the corresponding formation type of the measuring point is compared with the formation resistivity of the measuring point. If the comparison result exceeds at least one order of magnitude, the comparison result is considered an apparent resistivity anomaly. When there are metal pipelines, cement walls, or groundwater layers in the survey area, the normal value of formation resistivity of the corresponding formation type of the measuring point is compared with the formation resistivity of the measuring point. If the comparison result exceeds at least three orders of magnitude, the comparison result is considered an apparent resistivity anomaly. Step 5: Determine whether the area corresponding to the measuring point is a suspected contaminated area based on the comparison results; Step 6: Deploy sampling points in the suspected contaminated area, and use a high-density resistivity method coupled with a portable modular soil gas stratification sampling method to delineate the three-dimensional distribution of soil gas pollution from the sampling points in the suspected contaminated area. Determine the range of the pollution plume through real-time dynamic adjustment. The sampling module consists of a gas sampling probe, a bentonite filling layer, an air intake layer, a chassis, an air intake isolation protection device, an air duct connector, a motor connector, and filter material. The bentonite filling layer, air intake layer, and chassis are arranged sequentially from top to bottom. The filter material is located in the lower part of the air intake layer and is close to the upper part of the chassis. The gas sampling probe is located in the filter material and is connected to the detection module through an air duct. An air duct connector is provided at the end of the air duct to facilitate the connection between air ducts. The chassis is composed of concrete and a motor. The air intake isolation protection device covers the outer wall of the sampling module. The motor start switch controls the motor in the chassis to realize the switching of the air intake isolation protection device. Motor connectors are provided at the upper and lower ends of the sampling module, and the two motor connectors are connected through a motor control connection line.

2. The method for detecting petroleum hydrocarbon soil pollution plumes according to claim 1, characterized in that, In step 5, the method for identifying suspected contaminated areas is as follows: when the formation resistivity of the measuring point is higher than the corresponding normal value of formation resistivity, it is considered that there is no pollution from fresh gasoline and diesel or weathered crude oil, but there is suspected pollution from weathered gasoline and diesel or fresh crude oil; when the formation resistivity of the measuring point is lower than the corresponding normal value of formation resistivity, it is considered that there is suspected pollution from fresh gasoline and diesel or weathered crude oil, but there is no pollution from weathered gasoline and diesel or fresh crude oil.

3. The method for detecting petroleum hydrocarbon soil pollution plumes according to claim 1, characterized in that, The spacing of the measuring lines in step 1 is 2-5 meters.

4. The method for detecting petroleum hydrocarbon soil pollution plumes according to claim 1, characterized in that, The portable modular soil gas stratification sampling method described in step 6 utilizes a portable modular soil gas stratification sampling device for formation sampling. The specific sampling method is as follows: Step 6.1: Drill a borehole into the formation using a drilling device, ensuring that no groundwater is encountered and that the borehole width is greater than the diameter of the portable modular soil gas stratification sampling device; Step 6.2: Assemble the portable modular soil gas stratification sampling device, insert the sampling device into the borehole, and freely control the insertion depth according to the actual depth requirements; Step 6.3: Turn on the air inlet barrier protection device in the portable modular soil gas stratification sampling device. After the air inlet barrier protection device is fully turned on, use a vacuum pump to draw air from two different gas sampling tubes. After the temperature of the portable modular soil gas stratification sampling device is balanced and stable, record the reading. Step 6.4: Close the air intake barrier protection device. After the air intake barrier protection device is completely closed, slowly pull out the portable modular soil gas stratification sampling device to complete the soil gas sampling.

5. The method for detecting petroleum hydrocarbon soil pollution plumes according to claim 4, characterized in that, In step 6.1, the depth of the drilling hole is 1.5m.

6. The method for detecting petroleum hydrocarbon soil pollution plumes according to claim 4, characterized in that, The portable modular soil gas stratification sampling device consists of a detachable probe module, a detection module, a sampling module, and a metal spiral head. Multiple sampling modules can be assembled. The detection module, probe module, sampling module, and metal spiral head are connected sequentially from top to bottom. The probe module consists of a probe, a motor start switch, and a motor control connection cable. The motor start switch is located on the probe and is connected to the motor via the motor control connection cable to control the operation of the sampling module. The detection module is connected to the sampling module via a gas guide tube.

7. The method for detecting petroleum hydrocarbon soil pollution plumes according to claim 4, characterized in that, The portable modular soil air stratification sampling device has a cylindrical structure with a diameter of 3-10 cm and a sampling range of 0.5-6 m.

8. The method for detecting petroleum hydrocarbon soil pollution plumes according to claim 1, characterized in that, The thickness of the bentonite filling layer is 2-5 cm.

9. The method for detecting petroleum hydrocarbon soil pollution plumes according to claim 1, characterized in that, The air intake diaphragm protection device is supported by a titanium alloy frame and is made of soft, corrosion-resistant material, and has an umbrella-shaped structure.

10. The method for detecting petroleum hydrocarbon soil pollution plumes according to claim 1, characterized in that, The sidewall of the air intake layer is made of porous polytetrafluoroethylene material. It is airtight when the air intake layer protection device is not activated, and air intake is only possible when the air intake layer protection device is activated.

11. The method for detecting petroleum hydrocarbon soil pollution plumes according to claim 1, characterized in that, The filter material is composed of quartz sand.

12. The method for detecting petroleum hydrocarbon soil pollution plumes according to claim 6, characterized in that, The probe of the device is made of aluminum or titanium alloy, and has a round bottom that allows for threaded connection.

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