CN106018004B - A kind of passive type soil gas acquisition method - Google Patents

Abstract

The invention discloses a passive soil gas collection method. The passive soil gas collection device includes: a housing with micropores for soil gas to pass through; a gas adsorption column core fixed in the housing; a suspension, The suspension part is connected with the housing. The soil gas collection system includes: casing, the pipe wall of the casing has air holes; pipe plug, the pipe plug is installed on the top of the casing; passive soil gas collection device; connection line, the connection line is connected to hang the passive soil gas collection device on the casing inside the tube. The passive soil gas collection device and system of the present invention have the advantages of small size, easy to carry and use, low cost, and are suitable for soil gas collection in sites with low permeability and high moisture content such as clay; at the same time, the accuracy of data collected by the gas collection method is high, It can collect soil gas for a long time, and its data can better reflect the harm caused by soil gas concentration to human body when calculating risk assessment.

Description

A passive soil gas collection method

technical field

The invention belongs to the technical field of polluted site investigation and health risk assessment, and in particular relates to a passive soil gas collection method.

Background technique

With the rapid development of industry and agriculture in our country, the pollution of soil and groundwater is becoming more and more serious. Soil and groundwater are not only important agricultural production resources, but also important environmental elements and the basis for human survival. It not only restricts agricultural production and industrial development more and more, but also affects people's health. Among them, organic pollution is characterized by its persistence, high toxicity, accumulation, and fluidity. It will accumulate for a long time and is difficult to remove through natural degradation processes. It will also migrate to other environments under natural or artificial conditions, which is extremely harmful. .

At present, the organic pollutants in the soil of the site mainly come from the following three aspects: First, the chemical pollution enterprises such as chemical factories and pesticide factories, the raw materials and pollutants caused by the production workshop, subpackaging workshop, drug storage warehouse and transportation in the factory area. Drug leakage, as well as raw materials and wastewater discharged from printing, building materials, spraying and other industries; second, oil discharge or spillage caused by improper operation or accidental leakage during oil exploration and exploitation, storage and transportation; third, oil, The ground oil formed in chemical production areas, gas stations and other places, the discharge of oily production sewage and the leakage of oil pipelines.

If timely detection and treatment are not carried out, it will lead to more serious pollution, and the cost and difficulty of treatment will increase exponentially in the future. At present, the domestic collection of volatile organic pollutant gases in polluted sites is mainly to build gas wells, and then use vacuum pumps to pump the volatile organic compound gases (soil gas) in the wells into air sampling tanks or adsorption tubes equipped with adsorbents. Because it needs extra electricity, the operation is cumbersome, the equipment is complicated, and the sample can only be collected for a short time, and the cost is high, so its disadvantages are increasingly exposed in the collection of soil gas. At the same time, the existing active soil gas sampling method is not suitable for sites dominated by permeability such as clay and sites with shallow groundwater depth.

Contents of the invention

The first purpose of the present invention is to provide a passive soil gas collection device; the second purpose of the present invention is to provide a passive soil gas collection system; the third purpose of the present invention is to provide a passive soil gas collection method to solve Existing equipment and methods are cumbersome to operate, complex in equipment, expensive in cost, can only collect samples for a short period of time, and are not suitable for sites with shallow permeability of clay and other grounds and shallow buried depth of groundwater.

In order to achieve the above-mentioned first purpose, the present invention provides a passive soil gas collection device, which includes:

The casing, the casing has micropores for soil gas to pass through, and the micropores can effectively prevent water vapor from passing through;

A gas adsorption column core fixed in the housing for adsorbing pollutants in the soil gas;

a suspension part, the suspension part is connected with the housing.

In the passive soil gas collection device as described above in the present invention, further, the housing is a cylindrical housing, and the surface of the housing is loaded with a porous waterproof polymer, and the waterproof polymer can allow pollutants in the soil gas to pass through it. The micropores enter the shell, but at the same time, it can effectively prevent water vapor from entering the shell.

In the passive soil gas collection device as described above in the present invention, further, the suspension member is a U-shaped hook, and the hook is installed on the top of the housing.

In order to achieve the above-mentioned second purpose, the present invention provides a passive soil gas collection system, which includes:

A casing, the pipe wall of the casing has air holes;

a pipe plug mounted on top of the casing;

A passive soil gas collection device, which includes: a casing, the surface of the casing is loaded with a waterproof polymer with micropores, and the polymer has a microporous structure, allowing pollutants in the soil gas to enter the casing through the casing and prevent the water vapor in the soil gas from entering the shell; the gas adsorption column core, the gas adsorption column core is fixed in the housing, and is used to adsorb pollutants in the soil gas; the suspension, the suspension is connected to the housing;

A connection line, the connection line is connected between the pipe plug and the suspension part of the passive soil gas collection device, and suspends the passive soil gas collection device in the casing.

In the passive soil gas collection system as described above in the present invention, further, a connecting hook is installed at the lower end of the pipe plug for connecting with a connecting line.

The advantages of the passive soil gas collection device and collection system of the present invention are:

The soil gas collection device and collection system of the present invention are passive samplers, which have the advantages of small size, convenient portability, simple on-site installation, and low cost, and can be applied to large-area polluted site investigations due to low cost. At the same time, it is also suitable for sites with clay-based soil permeability and sites with shallow groundwater depth. Due to the removal of active pumping equipment such as vacuum pumps, the device or system of the present invention can collect samples for a long time, and can calculate the time-weighted concentration. Therefore, for human health risk assessment, it can better reflect the impact of long-term exposure on human health. influences.

In order to achieve the above-mentioned third purpose, the present invention provides a passive soil gas collection method, comprising the following steps:

S1, preparing the soil sampling hole;

Step 1, remove the surface soil at the selected monitoring point of the site to be tested; use a drilling tool to prepare a sampling hole;

Step 2, put the porous casing into the sampling hole;

Step 3, seal the upper opening of the casing with a pipe plug, and cover the top of the pipe plug with a layer of soil;

Step 4. After the sampling hole is sealed, it should be stable for more than 48 hours;

S2, collecting the gas in the soil sampling hole;

Open the pipe plug, put the passive soil gas collection device into the sampling hole, and the depth of insertion is about half of the depth of the sampling hole. The passive soil gas collection device is the soil gas collection device as described above; soil gas collection;

S3, soil gas concentration detection;

Step 1. After the collection is completed, take out the soil gas collection device, put the gas adsorption column core in a sealed plastic bag or glass tube, and then wrap and seal it with a transparent polyethylene bag;

Step 2, continue to seal the sampling hole with a pipe plug, cover the upper layer with a layer of soil, and mark it;

Step 3, send the gas adsorption column core to the laboratory for testing.

In the soil gas collection method as described above in the present invention, preferably: in S2, the collection time period is calculated and determined according to formula 1;

In Equation 1 above:

t is the sampling time (min);

M _min is the laboratory detection limit (pg) of the target compound;

C _RBSL is the human health risk screening value (μg/m ³ );

UR ₁ is the laboratory absorption rate (ml/min) of the compound.

In the above-mentioned passive soil gas collection method of the present invention, preferably: also include the following steps: in the process of preparing sampling holes, set up gas wells at the site to be measured, measure soil gas concentration C in a traditional way, the number of gas wells is sampling The number of holes is 10% to 20%;

Use formula 2 to correct the absorption rate of the passive soil gas sampling device at the site to be tested:

In Equation 2 above:

UR ₂ is the site-corrected absorption rate;

m is the mass of soil gas absorbed by the passive sampler;

_C1 is the soil gas concentration measured by the traditional method;

t is the sampling time;

Finally, calculate the soil gas concentration C ₂ using Equation 3:

The beneficial effects of the passive soil gas collection method of the present invention are:

Due to the use of the above-mentioned passive soil gas collection and system of the present invention, active pumping equipment such as vacuum pumps are removed, so that the collection method of the present invention can collect samples for a long time, and can calculate the time-weighted concentration, so it is suitable for human health risk assessment. It can better reflect the impact of long-term exposure on human health. In addition, since the soil gas concentration is calculated using the site-corrected absorption rate UR ₂ , the calculation results can be more accurate.

The passive sampler used in this method is simple and portable, and its use does not require special training, and can greatly reduce equipment costs and labor costs when used in large-area polluted sites. The collection method in the present invention can collect volatile organic gas samples that are more representative and more reflective of the real situation in the polluted area, making the investigation and risk assessment of the polluted site more objective and scientific, and satisfying the need for a more objective survey of the polluted site. Pollution investigation and health risk assessment needs.

Description of drawings

The above and/or other aspects and advantages of the present invention will become clearer and easier to understand through the detailed description made in conjunction with the following drawings, which are only schematic and do not limit the present invention, wherein:

Fig. 1 is a schematic diagram of a passive soil gas collection device according to an embodiment of the present invention;

Fig. 2 is a schematic diagram of a passive soil gas acquisition system according to an embodiment of the present invention;

Fig. 3 is a flowchart of a passive soil gas collection method according to an embodiment of the present invention.

In the accompanying drawings, the list of parts represented by each label is as follows:

10. Passive soil gas collection device, 1. Shell, 2. Gas adsorption column core, 3. Suspension piece, 4. Sleeve, 5. Air hole, 6. Pipe plug, 7. Connecting wire, 8. Connecting hook.

Detailed ways

Hereinafter, embodiments of a passive soil gas collection device, a gas collection system, and a gas collection method of the present invention will be described with reference to the accompanying drawings.

The examples described here are specific specific implementations of the present invention, and are used to illustrate the concept of the present invention. They are all explanatory and exemplary, and should not be construed as limiting the implementation of the present invention and the scope of the present invention. In addition to the embodiments described here, those skilled in the art can also adopt other obvious technical solutions based on the claims of the application and the contents disclosed in the description, and these technical solutions include adopting any obvious changes made to the embodiments described here. Replacement and modified technical solutions.

The accompanying drawings in this specification are schematic diagrams, which assist in explaining the concept of the present invention, and schematically represent the shapes of various parts and their interrelationships. Please note that in order to clearly show the structures of the components in the embodiments of the present invention, the drawings are not drawn in the same scale. The same reference numerals are used to designate the same parts.

Fig. 1 shows a passive soil gas acquisition device 10 of an embodiment of the present invention, which includes:

Housing 1, the surface of the housing 1 is loaded with a waterproof polymer, and the waterproof polymer is a porous structure, which can allow pollutants in the soil gas to enter the shell through it and prevent water vapor from entering; the housing is columnar, and its cross-section The shape can be round, oval, square, etc. In a preferred embodiment, as shown in FIG. 1 , the housing 1 is a cylindrical housing, and its cross-sectional shape may be circular. The shell 1 is made of plastic, and has holes, and the surface of the shell is loaded with a porous waterproof polymer to cover the holes. For example, the shell is made of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) or acrylonitrile-butadiene-styrene copolymer (ABS), waterproof polymer The main substance is polydimethylsiloxane.

The gas adsorption column core 2, which is fixed in the shell 1, is used to absorb the pollutants in the soil gas; in the field application process, the corresponding adsorption column core will be selected according to the target pollutants in the soil gas of the site , For example, activated carbon can be selected for benzene series and chlorinated hydrocarbons, Tenaxe TA can be selected as the adsorption column core for phenolic compounds, and Carbopack X can be selected as the adsorption column core for 1,3-butadiene/isoprene.

The suspension part 3 is connected with the casing 1 . In a preferred embodiment, as shown in FIG. 1 , the suspension member is a U-shaped hook, and the hook is installed on the top of the housing.

In the above embodiment, the first function of the shell is to provide a cavity for installing the gas adsorption column core, so as to prevent the direct contact of the gas adsorption column core with the soil from being polluted, and the second function is to allow the gas to pass through the micropores, which is convenient Gas adsorption column core absorption.

In a specific embodiment, the housing is 60 mm high and has an outer diameter of 16 mm. Different designs of the dimensions can produce different absorption rates. The gas adsorption column core is 60mm long and has a diameter of 4.8mm or 5.8mm. The gas adsorption column core has many different types of adsorbents for sampling different types of compounds. The gas adsorption column core is usually disposable and used for thermal analysis. Except for the adsorption cartridge. The principle of this passive sampling device is molecular diffusion. Due to the concentration gradient between the gas compound concentration at the shell and the gas adsorption column core, the compound gas diffuses from the shell to the adsorption column core, and then is absorbed by the specific adsorbent at the adsorption column core. Absorbed and fixed.

Fig. 2 shows the soil gas collection system of an embodiment of the present invention, it comprises:

The casing 4, the pipe wall of the casing 4 has air holes 5; the effect of the casing is to reinforce the surrounding soil of the sampling hole to prevent the sampling hole from collapsing; at the same time, the air holes in the casing wall help the gas in the soil to diffuse into the casing;

Pipe plug 6, the pipe plug 6 is installed on the top of the casing 4; as shown in FIG.

Soil gas collection device 10, which includes: housing 1, the housing 1 has micropores for soil gas to pass through; gas adsorption column core 2, gas adsorption column core 2 is fixed in the housing 1 for absorbing soil gas; a suspension part 3 connected to the casing 1 .

The connection line 7 is connected between the pipe plug 6 and the suspension part 3 of the soil gas collection device, and suspends the soil gas collection device 10 in the casing 4 .

Below in conjunction with Fig. 3, the passive soil gas acquisition method of the present embodiment is illustrated, comprising the following steps:

S1, preparing the soil sampling hole;

Step 1. Remove the surface soil at the selected monitoring point of the site to be tested; use a drilling tool to prepare a sampling hole; specifically, use a small military shovel to remove the surface soil with a diameter of about 10 cm and a depth of 2 cm. A sampling hole with a diameter of 4-5 cm and a depth of 0.5-0.7 m was drilled with an electric hammer impact drill (16×350 mm).

Step 2, put the porous sleeve into the sampling hole to strengthen the stability of the sampling hole structure.

Step 3, seal the upper opening of the casing with a pipe plug, and cover the pipe plug with a layer of soil to prevent human interference and damage.

Step 4. After the sampling hole is sealed, it should be stable for more than 48 hours;

S2, collecting the gas in the soil sampling hole;

Open the pipe plug, put the soil gas collection device into the sampling hole, the depth of insertion is about half of the depth of the sampling hole, and the soil gas collection device is the soil gas collection device described in the above embodiment;

Soil gas collection is carried out within the collection time period; the collection time period is calculated and determined according to formula 1;

In Equation 1 above:

t is the sampling time (min);

M _min is the laboratory detection limit (pg) of the target compound;

C _RBSL is the human health risk screening value (μg/m ³ );

UR ₁ is the laboratory absorption rate (ml/min) of the compound.

In a preferred embodiment, the VOC concentration in the sampling hole is initially measured using a portable PID, and the readings are recorded. If the on-site PID reading is relatively high, the length of the acquisition time period calculated by formula 1 should be appropriately shortened to avoid the saturation of the adsorbent in the passive sampler due to long-term sampling, resulting in large errors in the final calculation results.

S3, soil gas concentration detection;

Step 1. After the collection is completed, take out the soil gas collection device, put the gas adsorption column core in a sealed plastic bag or glass tube, and seal the outside with a transparent polyethylene bag;

In step 2, the sampling hole continues to be sealed with a pipe plug, and the upper layer is covered with a layer of soil, which is marked for possible reuse in the future.

Step 3, send the gas adsorption column core to the laboratory for testing. Before detection, use CS2 or thermal desorption to analyze the gas adsorption column core, and then measure the mass m of the soil gas absorbed by the passive sampler by GC/MC.

The calculation method of soil gas concentration is as follows:

In the process of preparing sampling holes, establish gas wells at the site to be tested, and measure the soil gas concentration C according to the traditional method. The number of gas wells is 10% to 20% of the number of sampling holes;

Since the laboratory absorption rate UR ₁ of the compound is obtained through exposure chamber experiments in the laboratory, the soil gas concentration obtained by directly applying it to the polluted site cannot truly reflect the actual situation, so on-site correction is required . Use formula 2 to correct the absorption rate of the passive soil gas sampling device at the site to be tested:

In Equation 2 above:

UR ₂ is the site-corrected absorption rate;

m is the mass of soil gas absorbed by the passive sampler;

_C1 is the soil gas concentration measured by the traditional method;

t is the sampling time;

Finally, calculate the soil gas concentration C ₂ using Equation 3:

In the above-mentioned embodiments of the present invention, in order to meet the requirements of quality control during the sampling process, appropriate parallel samples need to be collected. Since the sampling hole for accommodating passive samplers is relatively small, it is not enough to accommodate 2 passive samplers. At the same time, placing 2 passive samplers at the same time may form competitive adsorption with each other and cause interference. Preferably, a sampler is drilled at a distance of 0.2 meters around the sampling hole to collect parallel samples.

The present invention provides a method capable of collecting passive soil gas for a long period of time. Using the collection device and collection system described in the present invention to collect volatile organic compounds in the soil, analyze the concentration of the pollutants concerned, and then substitute into the corresponding The migration model calculates the exposure concentration in different situations, and finally combines the corresponding risk calculation model for subsequent health risk calculations, which can simulate the health risks caused by long-term exposure to the human body and overcome the short-term transient effects calculated by traditional methods.

The technical features disclosed above are not limited to the disclosed combination with other features, and those skilled in the art can also make other combinations among the technical features according to the purpose of the invention, so as to achieve the purpose of the present invention.

Claims (4)

1. a kind of passive type soil gas acquisition method, includes the following steps:

S1 prepares soil sampling hole；

Step 1, monitoring site topsoil selected by place to be measured is removed；Thieff hatch is prepared using drilling tool；

Step 2, porous casing is put into thieff hatch；

Step 3, with pipe close by casing sealing suitable for reading, one layer of soil is covered above pipe close；

After step 4, thieff hatch are sealed, stablize 48h or more；

S2 acquires the gas in soil sampling hole；

Pipe close is opened, passive type soil gas harvester is put into thieff hatch, is put into depth probably the one of sampling hole depth Half, the passive type soil gas harvester includes shell, the shell have for soil gas by micropore, while it is micro- Hole effectively can prevent aqueous vapor from passing through；

Gas absorption column core, gas absorption column core is fixed in the shell, for adsorbing the pollutant in soil gas；Suspension Part, the suspender are connect with the shell；Soil gas acquisition is carried out in acquisition time section；Acquisition time section is according to formula 1 calculates determination；

In above-mentioned formula 1：

T is the sampling time；

M_minFor the laboratory detection limit of target compound；

C_RBSLFor human health risk screening value；

UR₁For the laboratory absorption rate of compound；

S3, soil gas Concentration Testing；

Step 1, passive type soil gas harvester is taken out after acquisition, by polybag of the gas absorption column core loaded on sealing Or in glass tube, outside is again with transparent polyethylene bags environmental sealing；

Step 2, thieff hatch continues to be sealed with pipe close, and upper layer covers one layer of soil, marks；

Step 3, gas absorption column core laboratory is sent to be detected.

2. passive type soil gas acquisition method according to claim 1, which is characterized in that the shell is column shell Body, surface of shell load the water proofing property polymer for having micropore, and water proofing property polymer can be such that the pollutant in soil gas passes through Microchannel thereon enters in shell, but can effectively prevent steam again simultaneously and enter in shell.

3. passive type soil gas acquisition method according to claim 1, which is characterized in that the suspender is U-shaped Hook, it is described hook mounted on the shell top.

4. passive type soil gas acquisition method according to claim 1, it is characterised in that：It is further comprising the steps of： During preparing thieff hatch, gas well is established in place to be measured, conventionally measures soil gas concentration C, gas well quantity Be for sampling hole number 10%~20%；

Absorption rate using the correction passive type SOIL GAS sampling apparatus of formula 2 in place to be measured：

In above-mentioned formula 2：

UR₂For the absorption rate of place correction；

M is the quality for the SOIL GAS that passive sample devices absorb；

C₁The soil gas concentration measured for conventional method；

T is the sampling time；

Finally formula 3 is utilized to calculate SOIL GAS concentration C₂：