Method for ecological risk assessment of trace organic contaminants in sediments

Abstract

The present application relates to the field of pollution risk assessment, and discloses a method for ecological risk assessment of trace organic pollutants in sediments, comprising: collecting fresh sediment samples in lake or reservoir type water environment, collecting the latitude and longitude information of the sampling point, and measuring the mass fraction of organic carbon, water content and density; pretreating the fresh sediment samples, measuring the concentration of target trace organic pollutants, obtaining pore water samples and measuring the concentration of pollutants; constructing a model to calculate the exchange flux of unit area sediment and pore water; importing the data into a geographic information system and calculating the total exchange flux using the Kriging interpolation method; calculating the concentration increment of pollutants in the lake or reservoir type water environment according to the total exchange flux and the total volume of the water area, and determining the predicted no-effect concentration in water; and determining the potential ecological risk grade of the pollutants using the risk quotient method. The present application effectively assesses the ecological risk according to the potential of trace organic pollutants released from the surface sediment to the overlying water body.

Description

Technical Field

[0001] This invention relates to the field of pollution risk assessment, and more specifically to an ecological risk assessment method for trace organic pollutants in sediments. Background Technology

[0002] Lakes and reservoirs are important freshwater resource reservoirs and components of ecosystems. With the rapid development of industry and agriculture, large amounts of organic pollutants enter water bodies through runoff and discharge. Among them, trace organic pollutants (TrOCs), such as persistent organic pollutants, pharmaceuticals and personal care products, and pesticides, have attracted much attention due to their biotoxicity, recalcitrant nature, and bioaccumulation. Although their concentrations in water bodies are low, they can still have carcinogenic, teratogenic, and mutagenic effects on aquatic organisms and disrupt their endocrine system, posing a long-term threat to the health and stability of the entire aquatic ecosystem.

[0003] In aquatic environments, sediments serve as both important sinks and potential sources of TrOCs. Most hydrophobic organic pollutants rapidly adsorb onto suspended particulate matter and eventually settle into sediments. Through physical, chemical, and biological processes, these pollutants enriched in sediments can be released back into overlying water bodies via desorption and resuspension, causing secondary pollution, thus prolonging their environmental exposure period and exacerbating ecological risks. Therefore, assessing the release potential of TrOCs from sediments into overlying water bodies is a crucial step in accurately diagnosing aquatic ecological risks.

[0004] Currently, traditional methods for ecological risk assessment of organic pollutants in aquatic environments mainly focus on directly measuring the concentration of pollutants in overlying water bodies, or on the total concentration in sediments, by comparing it with sediment quality benchmarks.

[0005] However, these methods have obvious limitations: First, the complex physicochemical processes at the sediment-water interface were not effectively coupled, and the core mechanism of dynamic exchange of pollutants between the solid and liquid phases was ignored. Secondly, assessment methods based on total sediment concentration cannot distinguish between bioavailable and non-bioavailable forms of pollutants, which may overestimate their actual risks. Finally, existing technologies lack an efficient and universal framework that combines point monitoring data with the spatial characteristics of the entire lake and reservoir area to quantify the overall pollutant release flux and classify risks. Summary of the Invention

[0006] The purpose of this invention is to provide an ecological risk assessment method for trace organic pollutants in sediments, thereby solving the technical problem that it is difficult to assess the potential ecological risks caused by the release of trace organic pollutants from sediments into overlying water bodies in the prior art.

[0007] The objective of this invention can be achieved through the following technical solutions: An ecological risk assessment method for trace organic pollutants in sediments, comprising the following steps: S1. Collect fresh sediment samples from lake or reservoir water environments, collect latitude and longitude information of sampling points, and determine the organic carbon mass fraction, water content and density of the fresh sediment samples. S2. Pre-treat the fresh sediment sample, determine the concentration of the target pollutant in the fresh sediment sample, and simultaneously obtain a pore water sample from the fresh sediment sample and determine the concentration of the target pollutant in the pore water. S3. Based on the distribution balance theory of the target pollutant, calculate the exchange flux of the target pollutant between sediment and pore water per unit area; S4. Import the exchange flux data of sediment and pore water per unit area into the geographic information system, and use the Kriging interpolation method to calculate the total exchange flux of the target pollutant in the study area. S5. Calculate the concentration increment of the target pollutant in the lake or reservoir water environment based on the total exchange flux and the total water volume, and determine the predicted invalid concentration of the target pollutant in the water based on the toxicological data of fish, aquatic invertebrates and algae of the target pollutant. S6. Use the risk quotient method to determine the potential ecological risk level of the target pollutant, and conduct analysis based on the risk level classification.

[0008] As a further technical solution, step S1 specifically includes: S11. Determine the sampling time and location, use a gravity sediment sampler to collect sediment samples, and record the latitude and longitude information of the sampling point; S12. Determine the total organic carbon content of the sediment sample and obtain its organic carbon mass fraction; S13. Determine the water content of the sediment sample; S14. Calculate the volume and density of the sediment sample; Among them, sediment volume Through formula Calculated; where, The depth of the sediment; The sampler diameter; Sediment density Through formula Calculated; where, The mass of the sediment sample.

[0009] As a further technical solution, the method for obtaining the pore water sample in step S2 is as follows: After thoroughly mixing the fresh sediment sample, centrifuge it at 4500–6000 r / min for 10–20 minutes, take the supernatant, and then filter it through a 0.2–0.7 μm glass fiber membrane to obtain the pore water sample.

[0010] As a further technical solution, step S3 specifically includes: S31. Based on the octanol-water partition coefficient of the target pollutant. The normalized partition coefficient of the target pollutant between sediment and pore water was derived. The derivation formula is as follows: ; in, , These are empirical coefficients, obtained based on statistical analysis of experimental data. S32, Based on the standardized allocation coefficients The actual concentration of the target pollutant in the sediment. The organic carbon mass fraction of the sediment Moisture content and pore water density Calculate the theoretical concentration of the target pollutant in the pore water when the sediment and pore water are in equilibrium. The calculation formula is: ; S33. Calculate the actual concentration of the target pollutant in the pore water. With equilibrium theoretical concentration The difference The formula is: ; S34, Based on the concentration difference The density of the sediment The depth of the sediment The water content of the sediment sample The pore water density Based on the water area or the bottom area of ​​the reservoir, a model is constructed to calculate the sediment-pore water exchange flux per unit area.

[0011] As a further technical solution, the sediment-pore water exchange flux per unit area The calculation model is as follows: ;in, The area is measured in units of water area.

[0012] As a further technical solution, step S4 specifically includes: S41. Draw a base map of the study area in the geographic information system, and import the latitude and longitude information of the sampling points and the corresponding exchange flux data per unit area. S42. Divide the total area of ​​the study region into several calculation intervals and calculate the conversion factor for each interval. The formula is: ,in, To calculate the total number of units; S43, Convert the interval conversion factors as described above The corresponding calculation interval contains the exchange flux. and the number of units Substituting into the calculation model, the total switching throughput is obtained. The calculation model is as follows: .

[0013] As a further technical solution, step S5 specifically includes: S51. Calculate the concentration increment of the target pollutant. The concentration increment is a negative number representing the ratio of the total exchange flux to the total volume of the water body. S52. Review the toxicological data of the target pollutant on fish, aquatic invertebrates, and algae, including concentrations with no observed effect. LD50 or half-effect concentration And based on this, the evaluation factors are determined. ; S53. Calculate the predicted invalid concentration of the target pollutant. The calculation formula is: .

[0014] As a further technical solution, step S6 specifically includes: S61. The potential ecological risk level of the pollutant is determined using the risk quotient method, wherein the calculation formula for the risk quotient method is: ; in, The risk quotient of the target pollutant; S62, Based on the aforementioned risk quotient Risk levels are classified when If the risk level is greater than the first risk threshold, the target pollutant is considered high-risk; if the risk level is less than or equal to the second risk threshold... When the risk level is ≤ the first risk threshold, the target pollutant is classified as medium risk; when If the risk level is less than the second risk threshold, the target pollutant is considered low risk.

[0015] The beneficial effects of this invention are: (1) This invention combines theoretical calculations with measured data to quantitatively characterize the potential for trace organic pollutants to be released from sediments to overlying water bodies or to accumulate in the reverse direction. It uses the exchange potential of trace organic matter between pore water in sediments and overlying water bodies as a basis to effectively assess the aquatic ecological risk of sediments in lake or reservoir water environments. This invention breaks through the limitations of traditional methods that rely solely on static concentrations in sediments or water bodies for assessment. It can more realistically reflect the migration and transformation behavior of pollutants in the environment and the actual exposure risk, making the risk assessment results more accurate. (2) In calculating the exchange potential of trace organic pollutants in sediment pore water and overlying water, this invention uses Kriging interpolation to combine the exchange flux data of sediment and pore water per unit area with the base map of the study area, and then calculates the total exchange flux of trace organic pollutants through data analysis. This method can be well applied to different scenarios. Kriging interpolation quantifies the uncertainty of the estimate and makes full use of the data to quantify spatial autocorrelation. In areas with dense data points, it can naturally reduce the mutual weight between clusters, thereby avoiding the over-biasing of the estimate to dense data clusters. Therefore, it is suitable for studies where the data has spatial autocorrelation, the reliability of the estimate needs to be assessed, and the data has trends or anisotropy. Attached Figure Description

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1 As shown, this invention provides an ecological risk assessment method for trace organic pollutants in sediments, which includes the following steps: S1. Collect fresh sediment samples from lake or reservoir water environments, collect latitude and longitude information of sampling points, and determine the organic carbon mass fraction, water content and density of the fresh sediment samples. S2. Pre-treat the fresh sediment sample, determine the concentration of the target pollutant in the fresh sediment sample, and simultaneously obtain a pore water sample from the fresh sediment sample and determine the concentration of the target pollutant in the pore water. S3. Based on the distribution balance theory of the target pollutant, calculate the exchange flux of the target pollutant between sediment and pore water per unit area; S4. Import the exchange flux data of sediment and pore water per unit area into a geographic information system such as ArcGIS platform, and use Kriging interpolation to calculate the total exchange flux of the target pollutant in the study area. S5. Calculate the concentration increment of the target pollutant in the lake or reservoir water environment based on the total exchange flux and the total water volume, and determine the predicted invalid concentration of the target pollutant in the water based on the toxicological data of fish, aquatic invertebrates and algae of the target pollutant. S6. Use the risk quotient method to determine the potential ecological risk level of the target pollutant, and conduct analysis based on the risk level classification.

[0020] Step S1 specifically includes: S11. Determine the sampling time and location, use a gravity sediment sampler to collect sediment samples, and record the latitude and longitude information of the sampling point; S12. Determine the total organic carbon content of the sediment sample and obtain its organic carbon mass fraction; S13. Determine the water content of the sediment sample; S14. Calculate the volume and density of the sediment sample; Among them, sediment volume Through formula Calculated; where, The depth of the sediment is expressed in centimeters. The sampler diameter is in cm; the sediment volume is... The unit is cm 3 ; Sediment density Through formula Calculated; where, This refers to the mass of the sediment sample. Sediment density. The unit is g / cm³ 3 or kg / L; In step S2, the method for obtaining the pore water sample is as follows: After thoroughly mixing the fresh sediment sample, centrifuge at 5000 r / min for 15 minutes, collect the supernatant, and then filter it through a 0.45 μm glass fiber membrane to obtain the pore water sample.

[0021] By pretreatment, the original concentration of the pollutants in the sediment can be determined as accurately as possible to avoid significant impact on subsequent risk assessment; at the same time, pore water samples can be obtained using accurate methods to lay the foundation for calculating exchange flux.

[0022] For example, when the pollutant is an organic pesticide, the pretreatment method for the sediment sample is to stir it evenly, freeze-dry it, pass it through a 100-mesh sieve, and freeze it at -40°C for later use; take 2g of the above sediment sample and 8g of diatomaceous earth, mix them evenly, transfer them to an accelerated solvent extraction cell with a 0.45μm glass fiber filter membrane, and add 50ng of tracer isotope internal standards of 31 typical pesticides respectively; let the mixture stand overnight to ensure sufficient wetting, and then place it in an ASE350 for accelerated solvent extraction.

[0023] Step S3 specifically includes: S31. Based on the octanol-water partition coefficient of the target pollutant. The normalized partition coefficient of the target pollutant between sediment and pore water was derived. The derivation formula is as follows: ; in, , These are empirical coefficients, obtained based on statistical analysis of experimental data. It is 1.03. It is 0.61; , The unit is L / kg; It should be noted that, based on the physicochemical properties of organic pollutants, the target pollutant will eventually reach a partition equilibrium between the sediment (solid phase) and pore water (liquid phase), at which point a standardized octanol-water partition coefficient exists. ; S32, Based on the standardized allocation coefficients The actual concentration of the target pollutant in the sediment. The organic carbon mass fraction of the sediment Moisture content and pore water density Calculate the theoretical concentration of the target pollutant in the pore water when the sediment and pore water are in equilibrium. The calculation formula is: ; in, This indicates the theoretical concentration of the pollutant in the pore water when the pollutant reaches equilibrium between the sediment and the pore water, expressed in ng / L. This indicates the actual concentration of the pollutant in the sediment, expressed in μg / kg; This represents the mass fraction of organic carbon in sediments and is dimensionless. The standardized partition coefficient of the target pollutant between sediment and pore water is expressed in L / kg. Indicates the water content of a sediment sample; dimensionless. This indicates the density of pore water, expressed in kg / L. It should be noted that after determining the standardized allocation coefficient, and combining the measured actual concentration of the target pollutant in the sediment, as well as the organic carbon mass fraction and water content of the sediment, the theoretical concentration of the pollutant in the pore water when the sediment and pore water reach equilibrium can be calculated by substituting the values ​​into the formula. S33. Calculate the actual concentration of the target pollutant in the pore water. With equilibrium theoretical concentration The difference The formula is: ; S34, Based on the concentration difference The density of the sediment The depth of the sediment The water content of the sediment sample The pore water density Based on the water area or the bottom area of ​​the reservoir, a model is constructed to calculate the sediment-pore water exchange flux per unit area.

[0024] As one implementation method, when When >0, the target pollutant can be considered to have mainly accumulated in the sediment; when When = 0, the target pollutant can be considered to be relatively balanced in its distribution at the sediment-pore water interface; while when When <0, the target pollutant can be considered to be mainly present in pore water.

[0025] For example, the sample mass before and after centrifugation can be measured, and then the moisture content can be calculated using the following method: ; in, Indicates the water content of a sediment sample; dimensionless. This indicates the mass of the sediment sample, expressed in kg. This indicates the mass of the sediment sample after centrifugation, expressed in kg.

[0026] The sediment-pore water exchange flux per unit area The calculation model is as follows: ; in, The area is measured in km² (unit of water area). 2 ; The unit is ng / cm 2 Or 100kg / km 2 Concentration difference The unit is ng / L; pore water density The unit is g / cm³ 3 Sediment density The unit is kg / cm² 3 .

[0027] The above scheme constructs a relatively complete calculation model for sediment-pore water exchange flux per unit area, effectively realizing the quantification of the material exchange capacity between sediments and pore water.

[0028] As a further technical solution, step S4 specifically includes: S41. Draw a base map of the study area in the geographic information system, and import the latitude and longitude information of the sampling points and the corresponding exchange flux data per unit area. S42. Divide the total area of ​​the study region into several calculation intervals and calculate the conversion factor for each interval. The formula is: ,in, To calculate the total number of units; S43, Convert the interval conversion factors as described above The corresponding calculation interval contains the exchange flux. and the number of units Substituting into the calculation model, the total switching throughput is obtained. The calculation model is as follows: .

[0029] Alternatively, in addition to Kriging interpolation, the method for calculating total exchange throughput on the ArcGIS 10.8.2 platform can also be the radial basis function method or the inverse distance weight method, depending on the actual size of the study area and the number of samples.

[0030] Optionally, before using Kriging interpolation, you can check whether the data meets the normal distribution using a histogram. If not, you can use logarithmic transformation to process the data. When setting parameters, the z-value field is set to the sediment-pore water exchange flux per unit area at each sampling point, the semi-variogram model is selected as a spherical function, the output cell size can be set to 0.00005, and the number of points in the cell is set to 100 horizontally and 200 vertically.

[0031] As one implementation scheme, after step S4, the method further includes: Given that the concentration of pollutants in pore water is higher than that in the overlying water, and that pore water is a key pathway for material exchange between sediments and overlying water, the exchange flux at the sediment-pore water interface can be used to approximate the exchange potential between sediments and overlying water. when When the value is greater than 0, the target pollutant is considered to have the potential to accumulate in the sediment from pore water; when... When = 0, the distribution of the target pollutant is considered balanced; while when When the value is less than 0, the target pollutant is considered to have the potential to be released from sediments into pore water.

[0032] The total exchange flux was calculated using ArcGIS 10.8.2. The operation was simple and the results were accurate. At the same time, the exchange flux at the sediment-pore water interface can well represent the exchange potential between sediments and overlying water, ensuring the scientific nature of the overall work.

[0033] Step S5 specifically includes: S51. Calculate the concentration increment of the target pollutant. The concentration increment is a negative number representing the ratio of the total exchange flux to the total volume of the water body. S52. Review the toxicological data of the target pollutant on fish, aquatic invertebrates, and algae, including concentrations with no observed effect. LD50 or half-effect concentration And based on this, the evaluation factors are determined. ; S53. Calculate the predicted invalid concentration of the target pollutant. The calculation formula is: .

[0034] in The unit is ng / cm 3 ; The unit is mg / L; LC50 or EC50 The unit is mg / L; also, The principle of the calculation is: if a certain organism exists... If so, then it will be selected as the preferred method for calculation. The basis for this should be determined by the toxicological data of the organisms most sensitive to the target pollutant.

[0035] For example, the principle for determining the evaluation factors is: no organism among the three categories of organisms—fish, aquatic invertebrates, and algae—is included. At the same time, at least one type of organism exists. or hour, Take 1000; any one of the three types of organisms exists. hour, Take 100; any two organisms exist among the three categories of organisms. hour, Take 50; coexisting in the three types of organisms. hour, Take 10.

[0036] Step S6 specifically includes: S61. The potential ecological risk level of the pollutant is determined using the risk quotient method, wherein the calculation formula for the risk quotient method is: ; in, The risk quotient of the target pollutant; S62, Based on the aforementioned risk quotient Risk levels are classified when If the risk level is greater than the first risk threshold, the target pollutant is considered high-risk; if the risk level is less than or equal to the second risk threshold... When the risk level is ≤ the first risk threshold, the target pollutant is classified as medium risk; when When the risk level is less than the second risk threshold, the target pollutant is considered low risk; the first risk threshold is 1, and the second risk threshold is 0.1.

[0037] In one embodiment, step S1 includes: selecting Fengshuba Reservoir as the research object, setting up 5 sampling points, collecting sediment samples from each point during the summer low water period, and determining their organic carbon mass fraction, water content and density.

[0038] In this embodiment, step S2 includes: selecting bifenthrin as the target pollutant, and measuring the concentration of the substance in the sediment at each point as 7.630 μg / kg, 8.272 μg / kg, 8.131 μg / kg, 10.118 μg / kg and 8.685 μg / kg, and the concentration of the substance in the pore water at each point as 171.310 ng / L, 135.681 ng / L, 178.802 ng / L, 125.813 ng / L and 150.572 ng / L.

[0039] In this embodiment, the sediment-pore water exchange flux per unit area of ​​the target pollutant at each point is calculated to be -1.819 ng / cm³ using the method provided in step S3. 2 -1.441ng / cm 2 -1.899ng / cm 2 -1.336ng / cm 2 and -1.599ng / cm 2 .

[0040] In this embodiment, step S4 includes: setting the latitude and longitude of each point and the sediment-pore water exchange flux per unit area as x, y and z field data respectively, importing them into the ArcGIS 10.8.2 platform, and obtaining the total exchange flux of bifenthrin during the summer normal water period of Fengshuba Reservoir as -0.262 kg.

[0041] In this embodiment, step S5 includes: calculating the concentration increment of the target pollutant as 0.226 ng / L, and determining the predicted invalid concentration of the target pollutant as 0.000099 ng / cm³ using data retrieved from the ECOSAR database. 3 .

[0042] In this embodiment, step S6 includes: calculating the risk quotient of the target pollutant as 2.280, and determining it as high risk.

[0043] The commonly used method for assessing the ecological risk of pollutants in sediments is to calculate the predicted non-effect concentration (PNEC) of a specific pollutant in the sediment using the equilibrium allocation method, and then determine the risk quotient (RQ) based on the ratio of the two.

[0044] ; ; ; in, The concentration is measured in the environment and the unit is μg / kg dry weight. The predicted invalid concentration of the target pollutant in the sediment is expressed in μg / kg dry weight. The predicted invalid concentration of the target pollutant in water is expressed in μg / L. and The densities of wet suspended matter and solid particles are respectively taken as 1150 kg / m³. 3 and 2500kg / m 3 ; and These represent the volume fractions of water and solids in the suspension, respectively, and are taken as 0.9 and 0.1. The partition coefficient of organic carbon-water is expressed in L / kg. The partition coefficient of suspended solids-water is dimensionless. The percentage of organic carbon in suspended solids is 0.1%.

[0045] Table 1 compares the risk quotients calculated by the method described above with those calculated by conventional methods.

[0046] As shown in Table 1, the risk quotients calculated by the proposed method are generally higher than those calculated by conventional methods, especially for pollutants such as bifenthrin, methoxyfenozide, and lambda-cyhalothrin. This indicates that the proposed method can more sensitively reflect the migration potential and ecological risks of pollutants at the sediment-water interface. Furthermore, conventional methods, based on equilibrium distribution theory, assume a state of equilibrium between sediment and pore water, neglecting the dynamic exchange process of pollutants at the interface. In contrast, the proposed method, by directly calculating the exchange flux between sediment and pore water and combining it with spatial interpolation techniques, can more realistically simulate the migration behavior of pollutants under different hydrological periods (such as normal water levels, dry seasons, and wet seasons). Simultaneously, the introduction of Kriging interpolation allows the proposed method to effectively integrate spatial variability information, thereby more accurately assessing the distribution pattern of pollutant exchange fluxes at the regional scale.

[0047] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for ecological risk assessment of trace organic pollutants in sediments, characterized in that, The method includes the following steps: S1. Collect fresh sediment samples from lake or reservoir water environments, collect latitude and longitude information of sampling points, and determine the organic carbon mass fraction, water content and density of the fresh sediment samples; S2. Pre-treat the fresh sediment sample, determine the concentration of the target pollutant in the fresh sediment sample, and simultaneously obtain a pore water sample from the fresh sediment sample and determine the concentration of the target pollutant in the pore water. S3. Based on the distribution balance theory of the target pollutant, calculate the exchange flux of the target pollutant between sediment and pore water per unit area; S4. Import the exchange flux data of sediment and pore water per unit area into the geographic information system, and use the Kriging interpolation method to calculate the total exchange flux of the target pollutant in the study area. S5. Calculate the concentration increment of the target pollutant in the lake or reservoir water environment based on the total exchange flux and the total water volume, and determine the predicted invalid concentration of the target pollutant in the water based on the toxicological data of fish, aquatic invertebrates and algae of the target pollutant. S6. Use the risk quotient method to determine the potential ecological risk level of the target pollutant, and conduct analysis based on the risk level classification.

2. The method for ecological risk assessment of trace organic pollutants in sediments according to claim 1, characterized in that, Step S1 specifically includes: S11. Determine the sampling time and location, use a gravity sediment sampler to collect sediment samples, and record the latitude and longitude information of the sampling point; S12. Determine the total organic carbon content of the sediment sample and obtain its organic carbon mass fraction; S13. Determine the water content of the sediment sample; S14. Calculate the volume and density of the sediment sample; Among them, sediment volume Through formula Calculated; where, The depth of the sediment; The sampler diameter; Sediment density Through formula Calculated; where, The mass of the sediment sample.

3. The method for ecological risk assessment of trace organic pollutants in sediments according to claim 1, characterized in that, In step S2, the method for obtaining the pore water sample is as follows: After thoroughly mixing the fresh sediment sample, centrifuge it at 4500–6000 r / min for 10–20 minutes, collect the supernatant, and then filter it through a 0.2–0.7 μm glass fiber membrane to obtain the pore water sample.

4. The method for ecological risk assessment of trace organic pollutants in sediments according to claim 2, characterized in that, Step S3 specifically includes: S31. Based on the octanol-water partition coefficient of the target pollutant. The normalized partition coefficient of the target pollutant between sediment and pore water was derived. The derivation formula is as follows: ; in, , These are empirical coefficients, obtained based on statistical analysis of experimental data; S32, Based on the standardized allocation coefficients The actual concentration of the target pollutant in the sediment. The organic carbon mass fraction of the sediment Moisture content and pore water density Calculate the theoretical concentration of the target pollutant in the pore water when the sediment and pore water are in equilibrium. The calculation formula is: ; S33. Calculate the actual concentration of the target pollutant in the pore water. With equilibrium theoretical concentration The difference The formula is: ; S34, Based on the concentration difference The density of the sediment The depth of the sediment The water content of the sediment sample The pore water density Based on the water area or the bottom area of ​​the reservoir, a model is constructed to calculate the sediment-pore water exchange flux per unit area.

5. The method for ecological risk assessment of trace organic pollutants in sediments according to claim 4, characterized in that, The sediment-pore water exchange flux per unit area The calculation model is as follows: ;in, The area is measured in units of water area.

6. The method for ecological risk assessment of trace organic pollutants in sediments according to claim 1, characterized in that, Step S4 specifically includes: S41. Draw a base map of the study area in the geographic information system, and import the latitude and longitude information of the sampling points and the corresponding exchange flux data per unit area. S42. Divide the total area of ​​the study region into several calculation intervals and calculate the conversion factor for each interval. The formula is: ,in, To calculate the total number of units; S43, Convert the conversion factors of each interval The corresponding calculation interval contains the exchange flux. and the number of units Substituting into the calculation model, the total switching throughput is obtained. The calculation model is as follows: .

7. The method for ecological risk assessment of trace organic pollutants in sediments according to claim 1, characterized in that, Step S5 specifically includes: S51. Calculate the concentration increment of the target pollutant. The concentration increment is a negative number representing the ratio of the total exchange flux to the total volume of the water body. S52. Review the toxicological data of the target pollutant on fish, aquatic invertebrates, and algae, including concentrations with no observed effect. LD50 or half-effect concentration And based on this, the evaluation factors are determined. ; S53. Calculate the predicted invalid concentration of the target pollutant. The calculation formula is: .

8. The method for ecological risk assessment of trace organic pollutants in sediments according to claim 7, characterized in that, Step S6 specifically includes: S61. The potential ecological risk level of the pollutant is determined using the risk quotient method, wherein the calculation formula for the risk quotient method is: ; in, The risk quotient of the target pollutant; S62, Based on the aforementioned risk quotient Risk levels are classified when If the risk level is greater than the first risk threshold, the target pollutant is considered high-risk; if the risk level is less than or equal to the second risk threshold... When the risk level is ≤ the first risk threshold, the target pollutant is classified as medium risk; when If the risk level is less than the second risk threshold, the target pollutant is considered low risk.

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