A rapid assessment method for groundwater pollution risk based on interface processes

Abstract

The present invention discloses a method for rapid assessment of groundwater pollution risk based on interface processes, comprising the following steps: S1, conducting a survey on site pollution status and hydrogeological conditions; S2, constructing a site conceptual model based on the survey results of the site pollution status and hydrogeological conditions, determining the distance between the contaminated soil and the groundwater aquifer, querying the groundwater function classification in the area where the site is located, and determining the groundwater protection target value; S3, calculating the attenuation coefficient of the pollutant distribution process in different soil types; S4, calculating the attenuation coefficient of the transmission process of the vadose zone soil layer; S5, calculating the total attenuation coefficient of the pollutants entering the groundwater aquifer; S6, calculating the concentration of the pollutants entering the groundwater; S7, evaluating whether the pollutants in the soil will cause groundwater pollution after entering the groundwater; and S8, calculating the soil remediation target value for the case where the assessment result shows that the pollutants will cause groundwater pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of site pollution risk assessment, and in particular to a method for rapid groundwater pollution risk assessment based on interface processes. Background Art

[0002] Since 2008, national and local governments have gradually formulated relevant laws, regulations, and technical standards to ensure the safe use of contaminated land, generally adhering to a management philosophy centered on risk control. The assessment methods and models in these supporting technical standards are primarily used to quantify the health risks posed to the public by soil and groundwater contamination. However, under the influence of rainfall leaching and other factors, pollutants previously present only in the soil may infiltrate into groundwater with rainfall, causing groundwater contamination. Furthermore, with the continued implementation of groundwater pressure extraction and artificial recharge, groundwater levels in many urban agglomerations have risen significantly, coming into contact with contaminated soil previously in the vadose zone, leading to groundwater contamination. Current technical specifications lack appropriate assessment methods for the environmental risks posed by this type of soil contamination to groundwater. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for rapid assessment of groundwater pollution risk based on interface processes to solve the problems raised in the above background technology.

[0004] To achieve the above objectives, the present invention provides a method for rapid assessment of groundwater pollution risk based on interface processes, comprising the following steps:

[0005] S1. Conduct site pollution status and hydrogeological condition investigation;

[0006] S2. Based on the site pollution status and hydrogeological condition survey results, construct a conceptual model of the site, determine the distance between the contaminated soil and the groundwater aquifer, query the groundwater function classification in the site area, and determine the groundwater protection target value;

[0007] S3. Calculate the attenuation coefficient of the pollutant distribution process in different soil types;

[0008] S4. Calculate the attenuation coefficient of the aeration zone soil layer during the transmission process;

[0009] S5. Calculate the total attenuation coefficient of pollutants entering the groundwater aquifer;

[0010] S6. Calculate the concentration of pollutants entering the groundwater;

[0011] S7. Assess whether pollutants in the soil will cause groundwater pollution after entering the groundwater;

[0012] S8. Calculate the soil remediation target value for pollutants that are assessed to cause groundwater pollution.

[0013] In a preferred embodiment, in step S1, an investigation of the site pollution status and hydrogeological conditions is carried out, including: according to technical specifications, sampling and testing to clarify the type and concentration of pollutants, spatial distribution, contaminated area and the length of the contaminated area parallel to the groundwater flow direction, and through data collection and analysis, geophysical exploration, indoor geotechnical tests, and on-site pumping tests, to clarify the hydrogeological conditions of the contaminated area, including groundwater depth, interannual variation of groundwater level, average annual rainfall, soil infiltration rate, vertical stratum distribution, and dry density, total porosity, water porosity, and organic carbon content of soil in different strata.

[0014] In a preferred embodiment, in step S3, the attenuation coefficient of the pollutant distribution process in different soil types is calculated using formula (1):

[0015]

[0016] Among them, AF swi is the attenuation coefficient of the pollutant distribution process in the i-th soil type, dimensionless; ρ b is the soil dry density, in kg / L; θ w is the soil water porosity, dimensionless; f oc is the soil organic carbon content, dimensionless; K oc is the organic carbon-water partition coefficient of the pollutant, in L / kg; n is the total porosity of the soil, dimensionless; K H is the pollutant Henry constant, dimensionless.

[0017] In a preferred embodiment, in step S4, the attenuation coefficient of the aeration zone soil layer transmission process is calculated using formula (2):

[0018]

[0019] Among them, AF vai is the attenuation coefficient of the pollutant in the i-th soil layer during transmission in the vadose zone, dimensionless; λ is the pollutant degradation rate, unit is 1 / d; D0 is the thickness of the contaminated soil, unit is m; D is the thickness of the vadose zone between the contaminated soil and groundwater, unit is m; v is the soil infiltration rate, unit is m / d; R is the retardation factor of the pollutant in the vadose zone soil during transmission, dimensionless, and is calculated using formula (3):

[0020]

[0021] In a preferred embodiment, in step S5, the total attenuation coefficient of pollutants entering the groundwater aquifer is calculated using formula (4):

[0022] AF T =AF swa ×AFvaa …(4);

[0023] Among them, AF T AF is the total attenuation coefficient of pollutants in soil entering groundwater, dimensionless; swa AF is the comprehensive attenuation coefficient of the pollutant distribution process in the soil of the contaminated area, dimensionless; vaa is the comprehensive attenuation coefficient of pollutants during transmission in the vadose zone soil, dimensionless;

[0024] Formula (5) is used to calculate the average attenuation coefficient weighted by the volume of different contaminated soils as the comprehensive attenuation coefficient of the pollutant distribution process in the soil:

[0025]

[0026] Where N is the number of soil types in the contaminated area, determined based on the hydrogeological survey results in step 1; V i is the volume of the i-th soil type in the contaminated area, in m 3 ;AF swi is the attenuation coefficient of the distribution process of the i-th soil pollutant in the polluted area, calculated using formula (1);

[0027] Formula (6) is used to calculate the average attenuation coefficient weighted by the thickness of soil layers with different properties as the comprehensive attenuation coefficient during the transmission process of the vadose zone:

[0028]

[0029] Where M is the number of soil layers with different properties in the vadose zone between the contaminated soil and groundwater, dimensionless; d i AF is the thickness of soil layers of different properties in the vadose zone, in m; vai is the attenuation coefficient of the pollutant in the i-th soil layer of the vadose zone, calculated using formula (2).

[0030] In a preferred embodiment, in step S6, the concentration of pollutants entering the groundwater is calculated using formula (7):

[0031]

[0032] Among them, C T is the concentration of target pollutants in the soil, in mg / kg; C w It is the concentration of pollutants entering groundwater, in mg / L.

[0033] In a preferred embodiment, in step S6, the sample collection interval in the vertical direction of each monitoring point during the pollution status survey in step S1 is combined to generalize the soil in the contaminated area into contaminated soil layers of equal thickness in the vertical direction, and then use formula (8) to calculate the concentration C of the target pollutant in the soil of the entire contaminated area. T :

[0034]

[0035] Wherein, z is the zth layer of contaminated soil after generalization, dimensionless; Q is the number of contaminated soil layers after generalization, dimensionless; x is the xth monitoring point in the zth layer, dimensionless; P is the number of soil monitoring points in the zth layer, dimensionless; A x The area of ​​contaminated soil represented by the x-th monitoring point in the z-th layer, in m 2 ; A z is the area of ​​the zth layer of contaminated soil, in m 2 ; C x It is the concentration of target pollutant in the soil at the x-th monitoring point in the z-th layer, in mg / kg.

[0036] In a preferred embodiment, in step S7, the evaluation of whether the pollutants in the soil will cause groundwater pollution after entering the groundwater includes: combining the groundwater function classification of the polluted land area, determining the groundwater evaluation standard C of the target pollutant. ws , if C w If the value is lower than the assessment standard, the assessment result is that the possibility of pollutants in the soil causing groundwater pollution is low; otherwise, the assessment result is that pollutants in the soil will cause groundwater pollution on the site.

[0037] In a preferred embodiment, in step S8, for the case where the assessment result is that the pollutant will cause groundwater pollution, the allowable weighted average concentration of the target pollutant in the soil is calculated using formula (9):

[0038]

[0039] Among them, C RT is the target value for remediation of target pollutants in soil, in mg / kg; C ws It is the assessment standard for pollutants in groundwater, and the unit is mg / L.

[0040] In a preferred embodiment, step S8 further includes: first setting the initial remediation target value PC of the contaminated area soil RT , the concentration of target pollutants in the soil of the contaminated area is higher than PC RT The concentration of the sample was determined by PC RT Substitute the remaining sample concentrations into formula (8) to calculate the concentration of the target pollutant in the soil of the entire contaminated area, CT and C calculated by formula (9) RT Compare, if higher than C RT , then reduce PC RT Then substitute (8) to calculate the concentration C of the target pollutant in the soil of the entire contaminated area. T , and again with formula (9) to calculate the C RT Compare until it is not higher than the C calculated by formula (8) RT , the corresponding PC RT It can be regarded as the ultimate remediation target value of target pollutants in soil.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention combines a conceptual pollution model of pollutants in site soil entering groundwater under the influence of rainfall leaching and other factors, and establishes an analytical model for calculating pollutant attenuation factors based on interfacial processes. This allows relevant technical personnel to quickly assess whether pollutants in the soil will cause groundwater pollution after leaching into groundwater based on a small number of on-site measured parameters and without the help of complex numerical simulation professional software. This fills the methodological gap of current relevant technical specifications that only focus on human health risk assessment, and can provide important technical support for the prevention and control of groundwater pollution.

[0043] Due to the heterogeneity of soil and the anisotropy of strata, as well as the uneven spatial distribution of pollutants, the present invention further proposes a method for calculating the comprehensive attenuation coefficient of the distribution process based on the weighted volume of soil of different soil types in the contaminated area, a method for calculating the comprehensive attenuation coefficient of the transmission process based on the weighted thickness of different soil layers in the vertical aeration zone, a method for calculating the concentration of target pollutants in the soil based on the weighted area of ​​stratified sampling points, and a method for calculating the soil remediation target value based on the qualified weighted average value, which improves the accuracy of the evaluation results and avoids the formulation of overly conservative remediation target values, resulting in unnecessary remediation and waste of remediation funds. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the method flow of the present invention;

[0045] Figure 2 This is the conceptual site model of implementation case 2 of the present invention. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present invention are described clearly and completely below. The embodiments of the present invention and all other embodiments obtained by persons of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0047] Example 1

[0048] like Figures 1 to 2 As shown, the method for rapid assessment of groundwater pollution risk based on interface process of the present invention comprises the following steps:

[0049] Step S1: Conduct an investigation into the site pollution status and hydrogeological conditions, including: according to technical specifications, clarify the type and concentration of pollutants, spatial distribution, contaminated area and the length of the contaminated area parallel to the groundwater flow through sampling and testing, and clarify the hydrogeological conditions of the contaminated area through data collection and analysis, geophysical exploration, indoor geotechnical tests, and on-site pumping tests, including groundwater depth, interannual fluctuation of groundwater levels, average annual rainfall, soil infiltration rate, vertical stratum distribution, and soil dry density, total porosity, water porosity, and organic carbon content in different strata.

[0050] Step S2: Based on the site pollution status and hydrogeological condition survey results, a site conceptual model is constructed to determine the distance between the contaminated soil and the groundwater aquifer, query the groundwater function classification in the area where the site is located, and determine the groundwater protection target value.

[0051] Step S3: Calculate the attenuation coefficient of the pollutant distribution process in different soil types using formula (1):

[0052]

[0053] Among them, AF swi is the attenuation coefficient of the pollutant distribution process in the i-th soil type, dimensionless; ρ b is the soil dry density, in kg / L; θ w is the soil water porosity, dimensionless; f oc is the soil organic carbon content, dimensionless; K oc is the organic carbon-water partition coefficient of the pollutant, in L / kg; n is the total porosity of the soil, dimensionless; K H is the pollutant Henry constant, dimensionless.

[0054] Step S4: Calculate the attenuation coefficient of the aeration zone soil layer during the transmission process using formula (2):

[0055]

[0056] Among them, AF vai is the attenuation coefficient of the pollutant in the i-th soil layer during transmission in the vadose zone, dimensionless; λ is the pollutant degradation rate, unit is 1 / d; D0 is the thickness of the contaminated soil, unit is m; D is the thickness of the vadose zone between the contaminated soil and groundwater, unit is m; v is the soil infiltration rate, unit is m / d; R is the retardation factor of the pollutant in the vadose zone soil during transmission, dimensionless, and is calculated using formula (3):

[0057]

[0058] Step S5: Calculate the total attenuation coefficient of pollutants entering the groundwater aquifer using formula (4):

[0059] AF T =AF swa ×AF vaa ……(4);

[0060] Among them, AF T AF is the total attenuation coefficient of pollutants in soil entering groundwater, dimensionless; swa AF is the comprehensive attenuation coefficient of the pollutant distribution process in the soil of the contaminated area, dimensionless; vaa is the comprehensive attenuation coefficient of pollutants during transmission in the vadose zone soil, dimensionless;

[0061] Furthermore, formula (5) is used to calculate the average attenuation coefficient weighted by the volume of different contaminated soils as the comprehensive attenuation coefficient of the pollutant distribution process in the soil:

[0062]

[0063] Where N is the number of soil types in the contaminated area, determined based on the hydrogeological survey results in step 1; V i is the volume of the i-th soil type in the contaminated area, in m 3 ;AF swi is the attenuation coefficient of the distribution process of the i-th soil pollutant in the polluted area, calculated using formula (1);

[0064] Formula (6) is used to calculate the average attenuation coefficient weighted by the thickness of soil layers with different properties, which is used as the comprehensive attenuation coefficient during the transmission process of the vadose zone:

[0065]

[0066] Where M is the number of soil layers with different properties in the vadose zone between the contaminated soil and groundwater, dimensionless; d i AF is the thickness of soil layers of different properties in the vadose zone, in m; vai is the attenuation coefficient of the pollutant in the i-th soil layer of the vadose zone, calculated using formula (2).

[0067] Step S6: Calculate the concentration of pollutants entering the groundwater using formula (7):

[0068]

[0069] Among them, C T is the concentration of target pollutants in the soil, in mg / kg; C wIt is the concentration of pollutants entering groundwater, in mg / L.

[0070] Furthermore, in combination with the sample collection spacing in the vertical direction of each monitoring point during the pollution status investigation in step S1, the soil in the contaminated area is generalized into contaminated soil layers of equal thickness in the vertical direction, and then the concentration C of the target pollutant in the soil of the entire contaminated area is calculated using formula (8): T :

[0071]

[0072] Wherein, z is the zth layer of contaminated soil after generalization, dimensionless; Q is the number of contaminated soil layers after generalization, dimensionless; x is the xth monitoring point in the zth layer, dimensionless; P is the number of soil monitoring points in the zth layer, dimensionless; A x The area of ​​contaminated soil represented by the x-th monitoring point in the z-th layer, in m 2 ; A z is the area of ​​the zth layer of contaminated soil, in m 2 ; C x It is the concentration of target pollutant in the soil at the x-th monitoring point in the z-th layer, in mg / kg.

[0073] Step S7: assess whether the pollutants in the soil will cause groundwater pollution after entering the groundwater, including: combining the groundwater function classification of the polluted land area, determining the groundwater assessment standard C of the target pollutant ws , if C w If the value is lower than the assessment standard, the assessment result is that the possibility of pollutants in the soil causing groundwater pollution is low; otherwise, the assessment result is that pollutants in the soil will cause groundwater pollution on the site.

[0074] Step S8: For pollutants that are assessed to cause groundwater pollution, the allowable weighted average concentration of the target pollutant in the soil is calculated using formula (9):

[0075]

[0076] Among them, C RT is the target value for remediation of target pollutants in soil, in mg / kg; C ws It is the assessment standard for pollutants in groundwater, and the unit is mg / L.

[0077] Furthermore, step S8 also includes: first setting the initial remediation target value PC of the contaminated area soil RT , the concentration of target pollutants in the soil of the contaminated area is higher than PC RT The concentration of the sample was determined by PC RTSubstitute the remaining sample concentrations, and then substitute into formula (8) to calculate the concentration of the target pollutant in the soil of the entire contaminated area, C T and C calculated by formula (9) RT Compare, if higher than C RT , then reduce PC RT Then substitute (8) to calculate the concentration C of the target pollutant in the soil of the entire contaminated area. T , and again with formula (9) to calculate the C RT Compare until it is not higher than the C calculated by formula (9) RT , the corresponding PC RT It can be regarded as the ultimate remediation target value of target pollutants in soil.

[0078] Example 2

[0079] The following describes the method of the present invention in detail by taking the pollution risk assessment of groundwater caused by benzene and methyl tert-butyl ether in the soil of a gas station as an example and setting of remediation target values.

[0080] Example: A gas station with a total area of ​​about 5000m 2 , of which the underground storage tank area is about 1000m 2 According to relevant management requirements, it is necessary to conduct an investigation and risk assessment of the soil and groundwater pollution status in the gas station area to ensure that the land can be used safely.

[0081] Step S1: According to the requirements of the technical specifications, 30 soil sampling points were arranged throughout the gas station. A soil sample was collected at intervals of 1 meter in the vertical direction of each sampling point for analysis and testing. No pollutants were detected at each sampling point, and a total of 200 soil samples were tested. The results showed that at 15 points in the tank area, a total of 30 soil samples were found to contain characteristic pollutants, benzene and methyl tert-butyl ether, within a depth of 3-5 meters above the ground. No pollutants were detected in the soil below 5 meters. The specific concentrations are shown in Tables 1 and 2, respectively. The results of the hydrogeological survey showed that the soil in the contaminated area was mainly clay at 3-4 meters and silt at 4-5 meters. The soil in the vadose zone between the contaminated area and the groundwater was mainly fine sand at 5-8 meters, mainly silt clay at 8-10 meters, and mainly clay silt at 10-12 meters. The groundwater level was buried at a depth of approximately 12 meters below the ground. The statistical results of the average values ​​of the physical and chemical parameters of soils of different textures are shown in Table 3.

[0082] Table 1 Benzene concentration in soil of contaminated area (unit: mg / kg)

[0083] Point number <![CDATA[Represented area (m 2 )]]> 3-4m 4-5m 5-6m 6-7m S1 35 1.5 0.5 Not detected Not detected S2 33 3.1 1.8 0.5 Not detected S3 33 10.5 4.5 0.5 Not detected S4 28 4.2 1.2 0.2 Not detected S5 31 1.1 0.2 Not detected Not detected S6 35 1.5 0.8 Not detected Not detected S7 38 0.8 0.2 Not detected Not detected S8 20 2.2 0.5 Not detected Not detected S9 28 2.9 0.3 Not detected Not detected S10 36 0.8 0.2 Not detected Not detected S11 32 6.1 2.1 1.5 Not detected S12 38 0.8 0.2 Not detected Not detected S13 22 3.2 1.1 0.4 Not detected S14 25 2.1 0.8 Not detected Not detected S15 29 1.3 0.6 Not detected Not detected

[0084] Table 2 Concentration of MTBE in soil of contaminated area (unit: mg / kg)

[0085]

[0086]

[0087] Table 3 Summary of soil physical and chemical parameters at different depths

[0088]

[0089] Step S2: Based on the pollution and hydrogeological survey results from step S1, a conceptual model of the site was constructed. In this case study, benzene contamination was present in the soil at a depth of 3-6 meters, so the thickness of the benzene-contaminated soil layer, D0, was 3 meters. MTBE contamination was present in the soil at a depth of 3-7 meters, so the thickness of the MTBE-contaminated soil layer, D0, was 4 meters. The groundwater depth at the case study site was 12 meters, so the thickness of the vadose zone, D, between the benzene-contaminated soil and the groundwater was 6 meters, and the thickness of the vadose zone, D, between the MTBE-contaminated soil and the groundwater was 5 meters. Because the case study site is located within a groundwater drinking water source protection zone, the corresponding drinking water quality standards were used as the protection target values ​​for benzene and MTBE in groundwater: 10 μg / L for benzene and 2000 μg / L for MTBE.

[0090] Step S3: By consulting the technical specifications, the organic carbon-water partition coefficient K of benzene oc 150L / kg, Henry coefficient K H The organic carbon-water partition coefficient K of methyl tert-butyl ether is 0.23. oc The Henry coefficient K is 12L / kg. H The comprehensive attenuation coefficients of benzene and MTBE in the 3-4 m clay and 4-5 m silt soil, respectively, were calculated using formulas (1) and (5). The results are shown in Tables 4 and 5. The comprehensive attenuation coefficients of benzene in the contaminated soil were 3.86, and those of MTBE were 1.07.

[0091] Table 4 Comprehensive attenuation coefficient of benzene distribution process in contaminated soil

[0092]

[0093] Table 5 Comprehensive attenuation coefficient of the distribution process of MTBE in the soil of the contaminated area

[0094]

[0095] Step S4: Using formula (2) and formula (6), calculate the attenuation coefficients of benzene and methyl tert-butyl ether during the transmission process in the aeration zone soil layer. The degradation coefficient λ of benzene is 0.005d -1The degradation coefficient λ of MTBE is 0. The results are shown in Tables 6 and 7. Among them, the comprehensive attenuation coefficient of benzene transmission process is 3.86, and that of MTBE is 1.07.

[0096] Table 6 Comprehensive attenuation coefficients of benzene and MTBE during transmission in the aeration zone soil layer

[0097]

[0098]

[0099] Step S5: using formula (4) to calculate the total attenuation coefficient of benzene and methyl tert-butyl ether entering the groundwater from the contaminated soil layer, where the attenuation coefficient of benzene is 7622.342 and the attenuation coefficient of methyl tert-butyl ether is 3.32.

[0100] Step S6: Calculate the concentration C of the target pollutant in the soil of the entire contaminated area using (8). T , among which, the C of benzene T The value is 1.47 mg / kg, and the C T The value is 4.73 mg / kg. Further calculation using formula (7) shows that the concentration of benzene entering the groundwater is 0.99 μg / L, and the concentration of MTBE entering the groundwater is 7310 μg / L.

[0101] Step S7: Compare the concentrations of benzene and MTBE entering the groundwater with the groundwater protection targets of 10 μg / L for benzene and 2000 μg / L for MTBE, respectively. It can be seen that benzene pollution in the soil of the case site will not cause groundwater pollution, but MTBE can cause groundwater pollution under the action of rainfall leaching. Compared with the current soil benzene standard of 1 mg / kg based on the protection of human health, it can be seen that if the case site only considers human health risks and the benzene is repaired to no more than 1 mg / kg, the residual benzene in the soil will not cause groundwater pollution. However, the soil standard value of MTBE based on the protection of human health is 47 mg / kg. If corresponding management measures are formulated based on only human health risks, the MTBE remaining in the soil may still leach and migrate, causing groundwater pollution.

[0102] Step S8: Calculate the weighted average concentration C of MTBE allowed in soil using formula (9): RT 1mg / kg.

[0103] Furthermore, set the initial repair target value PC RT The concentration of the samples in Table 2 with a concentration higher than 2 mg / kg is 2 mg / kg, and the C is calculated by substituting it into formula (8). T The value is 1.6 mg / kg, which is higher than the C calculated by formula (9). RT1mg / kg. Therefore, it reduces PC RT The concentration of the samples in Table 2 with a concentration higher than 1.1 mg / kg is 1.1 mg / kg, and the C is calculated by substituting it into formula (8). T The value is 1.0 mg / kg, which is not higher than the C calculated by formula (9). RT Therefore, the final remediation target value of MTBE in the soil of the case site can be set at 1.1 mg / kg to ensure that the MTBE remaining in the soil after remediation will not pollute groundwater due to rainfall leaching.

[0104] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A rapid assessment method for groundwater pollution risk based on interface processes, characterized by: The steps include: S1. Conduct site pollution status and hydrogeological condition investigation; S2. Based on the site pollution status and hydrogeological condition survey results, construct a conceptual model of the site, determine the distance between the contaminated soil and the groundwater aquifer, query the groundwater function classification in the site area, and determine the groundwater protection target value; S3. Calculate the attenuation coefficient of the pollutant distribution process in different soil types; S4. Calculate the attenuation coefficient of the aeration zone soil layer during the transmission process; S5. Calculate the total attenuation coefficient of pollutants entering the groundwater aquifer; S6. Calculate the concentration of pollutants entering the groundwater; S7. Assess whether pollutants in the soil will cause groundwater pollution after entering the groundwater; S8. Calculate soil remediation target values ​​for pollutants that are assessed to cause groundwater pollution; In step S3, the attenuation coefficient of the pollutant distribution process in different soil types is calculated using formula (1): Among them, AF swi is the attenuation coefficient of the pollutant distribution process in the i-th soil type, dimensionless; ρ b is the soil dry density, in kg / L; θ w is the soil water porosity, dimensionless; f oc is the soil organic carbon content, dimensionless; K oc is the organic carbon-water partition coefficient of the pollutant, in L / kg; n is the total porosity of the soil, dimensionless; K H is the pollutant Henry constant, dimensionless; In step S4, the attenuation coefficient of the aeration zone soil layer transmission process is calculated using formula (2): Among them, AF vai is the attenuation coefficient of the pollutant in the i-th soil layer during transmission in the vadose zone, dimensionless; λ is the pollutant degradation rate, unit is 1 / d; D0 is the thickness of the contaminated soil, unit is m; D is the thickness of the vadose zone between the contaminated soil and groundwater, unit is m; v is the soil infiltration rate, unit is m / d; R is the retardation factor of the pollutant in the vadose zone soil during transmission, dimensionless, and is calculated using formula (3): In step S5, the total attenuation coefficient of pollutants entering the groundwater aquifer is calculated using formula (4): OF T =OFF swa ×AF vaa ……(4); Among them, AF T AF is the total attenuation coefficient of pollutants in soil entering groundwater, dimensionless; swa AF is the comprehensive attenuation coefficient of the pollutant distribution process in the soil of the contaminated area, dimensionless; vaa is the comprehensive attenuation coefficient of pollutants during transmission in the vadose zone soil, dimensionless; Formula (5) is used to calculate the average attenuation coefficient weighted by the volume of different contaminated soils as the comprehensive attenuation coefficient of the pollutant distribution process in the soil: Where N is the number of soil types in the contaminated area, determined based on the hydrogeological survey results in step 1; V i is the volume of the i-th soil type in the contaminated area, in m 3 ;AF swi is the attenuation coefficient of the distribution process of the i-th soil pollutant in the polluted area, calculated using formula (1); Formula (6) is used to calculate the average attenuation coefficient weighted by the thickness of soil layers with different properties as the comprehensive attenuation coefficient during the transmission process of the vadose zone: Where M is the number of soil layers with different properties in the vadose zone between the contaminated soil and groundwater, dimensionless; d i AF is the thickness of soil layers of different properties in the vadose zone, in m; vai is the attenuation coefficient of the pollutant in the i-th soil layer of the vadose zone, calculated using formula (2).

2. The method for rapid assessment of groundwater pollution risk based on interface processes according to claim 1 is characterized by: In step S1, an investigation of the site pollution status and hydrogeological conditions is carried out, including: according to technical specifications, sampling and testing to clarify the type and concentration of pollutants, spatial distribution, contaminated area and the length of the contaminated area parallel to the groundwater flow direction; and through data collection and analysis, geophysical exploration, indoor geotechnical tests, and on-site pumping tests, to clarify the hydrogeological conditions of the contaminated area, including groundwater depth, interannual fluctuation of groundwater level, average annual rainfall, soil infiltration rate, vertical stratum distribution, and dry density, total porosity, water porosity, and organic carbon content of soil in different strata.

3. The method for rapid assessment of groundwater pollution risk based on interface processes according to claim 1 is characterized by: In step S6, the concentration of pollutants entering the groundwater is calculated using formula (7): Among them, C T is the concentration of target pollutants in the soil, in mg / kg; C w It is the concentration of pollutants entering groundwater, in mg / L.

4. The method for rapid assessment of groundwater pollution risk based on interface processes according to claim 3 is characterized by: In step S6, the sample collection interval in the vertical direction of each monitoring point during the pollution status investigation in step S1 is combined to generalize the soil in the contaminated area into contaminated soil layers of equal thickness in the vertical direction, and then use formula (8) to calculate the concentration C of the target pollutant in the soil of the entire contaminated area. T : Wherein, z is the zth layer of contaminated soil after generalization, dimensionless; Q is the number of contaminated soil layers after generalization, dimensionless; x is the xth monitoring point in the zth layer, dimensionless; P is the number of soil monitoring points in the zth layer, dimensionless; A x The area of ​​contaminated soil represented by the x-th monitoring point in the z-th layer, in m 2 ; A z is the area of ​​the zth layer of contaminated soil, in m 2 ; C x It is the concentration of target pollutant in the soil at the x-th monitoring point in the z-th layer, in mg / kg.

5. The method for rapid assessment of groundwater pollution risk based on interface processes according to claim 4 is characterized in that: In step S7, it is evaluated whether the pollutants in the soil will cause groundwater pollution after entering the groundwater, including: combining the groundwater function classification of the polluted land area, determining the groundwater assessment standard C of the target pollutant ws , if C w If the value is lower than the assessment standard, the assessment result is that the possibility of pollutants in the soil causing groundwater pollution is low; otherwise, the assessment result is that pollutants in the soil will cause groundwater pollution on the site.

6. The method for rapid assessment of groundwater pollution risk based on interface processes according to claim 5 is characterized by: In step S8, for pollutants that are assessed to cause groundwater pollution, the allowable weighted average concentration of the target pollutant in the soil is calculated using formula (9): Among them, C RT is the target value for remediation of target pollutants in soil, in mg / kg; C ws It is the assessment standard for pollutants in groundwater, and the unit is mg / L.

7. The method for rapid assessment of groundwater pollution risk based on interface processes according to claim 6 is characterized in that: Step S8 also includes: first setting the initial remediation target value PC of the contaminated area soil RT , the concentration of target pollutants in the soil of the contaminated area is higher than PC RT The concentration of the sample was detected by PC RT Substitute the remaining sample concentrations, and then substitute into formula (8) to calculate the concentration of the target pollutant in the soil of the entire contaminated area, C T and C calculated by formula (9) RT Compare, if higher than C RT , then reduce PC RT Then substitute (8) to calculate the concentration C of the target pollutant in the soil of the entire contaminated area. T , and again with formula (9) to calculate the C RT Compare until it is not higher than the C calculated by formula (9) RT , the corresponding PC RT It can be regarded as the ultimate remediation target value of target pollutants in soil.

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