Risk assessment method for influence of water source soil on water source water quality environment

Abstract

The invention is suitable for the technical field of water source environment management, and provides a risk assessment method for the influence of water source soil on a water source water quality environment, and the method achieves the risk assessment of the influence of the water source soil on the water source water quality environment through basic information investigation, risk identification, migration flux calculation, consequence calculation and risk assessment. The method is suitable for the conditions that surface water source soil environment quality investigation is carried out, the problem of exceeding the standard exists, and water source water quality risk assessment needs to be carried out, and the amount of pollutants released in soil and migrated into a water source water body can be quantitatively analyzed; key parameters are obtained in combination with an experimental method, a release process evaluation model suitable for the actual situation is constructed for consequence calculation, and the influence degree and the influence range of the risk source on the water quality of the water source are obtained. The method breaks through the dilemma that the existing method cannot evaluate the risk that the water source soil exceeds the standard to influence the water source water quality environment, and promotes the water source environment quality management to be scientific, efficient and refined.

Description

Technical Field

[0001] The present invention belongs to the technical field of water source environmental management, and in particular relates to a risk assessment method for the impact of water source soil on the water quality environment. Background Art

[0002] Water source environmental risk assessment is the core link of water source environmental management, and its accuracy is directly related to the improvement of water supply quality safety and management efficiency.

[0003] Existing methods primarily assess potential hazards arising from anthropogenic sources, such as industrial storage tanks and sewage outfalls, hazardous material transport vehicles and pipelines, and farmland. These anthropogenic risk sources can be eliminated through standardized water source management. These risk sources are often located in specific locations, with a certain scope and scale. Pollutants released into the water source pose a threat only when exposed to specific human activities, such as leaks and explosions.

[0004] The "Guidelines for Environmental Protection of Centralized Drinking Water Sources (Trial Implementation)," issued by the Ministry of Ecology and Environment in 2012, assess the potential environmental risks posed by sudden environmental pollution incidents surrounding water sources, including fixed sources such as industrial enterprises and sewage outfalls, mobile sources such as transportation roads, and non-point sources such as agricultural non-point sources. This system forms a risk assessment framework consisting of "risk identification - source phase analysis - consequence calculation - risk calculation - risk assessment." This system primarily analyzes risk sources by calculating the probability of sudden environmental incidents such as leaks and explosions and the rate of pollutant release. It also uses theoretical mathematical models of pollutant diffusion to calculate the extent and scope of the impact of sudden water pollution incidents on water source quality and conducts consequence calculations. However, it fails to fully consider water environmental risks posed by soil quality exceeding standards in the surrounding area of ​​a water source, a risk source that is difficult to eliminate and widely distributed.

[0005] The Chinese patent with publication number CN119692818A discloses a method and system for assessing the environmental risk of drinking water sources. This method is evaluated by quantitatively characterizing water source characteristics, pollution source activity data, and pollutant migration capacity. Specifically, the comprehensive characteristic value of the water source is obtained by combining the basic information of the water source with meteorological information, the pollutant migration capacity value and the risk assessment range value are determined based on hydrological data, the potential pollution risk value is calculated by the area occupied by the potential pollution source and the linear distribution distance, and finally the comprehensive environmental risk assessment result is obtained by combining the above indicators to judge the size of the environmental risk of the water source. However, this method has shortcomings. It mainly involves long time scales and uses the relatively stable operating conditions and basic hydrological and meteorological conditions of the water source as the basis for calculating the environmental risk value. It fails to fully consider the atmospheric rainfall-related characteristics that are most likely to cause environmental risks brought by pollutants in the soil around the water source, especially the impact of extreme rainfall processes on the environmental risks of the water source.

[0006] Furthermore, soil environmental quality surveys at water sources across the country indicate that soil environmental quality at water sources exceeds standards due to environmental issues or historical human activities, posing a potential threat to water quality. However, current industry technical documentation lacks targeted assessment techniques, and existing water source environmental risk assessment methods fail to consider the assessment and management of risks arising from soil environmental quality exceeding standards in protected areas. Therefore, the present invention proposes a risk assessment method for the impact of water source soil on water quality. Summary of the Invention

[0007] The purpose of the present invention is to provide a risk assessment method for the impact of water source soil on the water quality environment, aiming to solve the problems raised in the above background technology.

[0008] The purpose of the present invention is achieved through the following technical solutions: The risk assessment method for the impact of water source soil on water quality environment includes the following steps: Step 1: Basic information survey; obtain basic environmental status data of the water source area; Step 2: Risk identification: Based on basic information, select pollutants that pose potential risks to water quality as potential pollutants, clarify their types and concentration distribution, and determine risk factors and types; Step 3: Migration flux calculation: Determine the rainfall erosivity factor, soil erodibility factor, slope length factor, slope gradient factor, vegetation cover factor, and potential pollutant factor, convert them into uniform resolution raster data, calculate the pollutant migration modulus under daily management and extreme rainfall conditions, and merge the raster data to obtain the migration flux of potential pollutants from the water source soil to the reservoir water body; Step 4: Calculate the consequences. For extreme rainfall events, the elevated concentrations of pollution indicators are calculated by combining pollutant migration, flood discharge, and effective reservoir volume. For daily management, a numerical model of potential pollutant release patterns in sediments is obtained through fitting the release kinetics of sediment samples. The elevated concentrations of pollution indicators for local and overall reservoir volumes are calculated by combining circulation time and annual soil erosion. Step 5: Risk assessment: Based on the consequence calculation results, use the single factor index method or the maximum value method to assess the risk level and determine whether the risk value exceeds the acceptable risk level.

[0009] Furthermore, the migration flux is calculated based on the following formula: ; ; Where A is the potential pollutant migration modulus; a is the soil erosion modulus; p is a potential pollutant factor; R is the rainfall erosivity factor;K is the soil erodibility factor; L is the slope length factor; S is the slope factor; C is the vegetation cover factor.

[0010] Furthermore, the rainfall erosivity factor R Including rainfall erosivity factors under daily management and rainfall erosivity factor , Calculated based on semi-monthly or monthly rainfall data, Calculated based on rainfall on extreme rainfall days.

[0011] Furthermore, in the consequence calculation, the calculation formula under extreme rainfall conditions is: ; Where: Elevated concentrations for single pollution indicators affected by potential contaminants in the soil; The amount of potential pollutant migration in the soil on that day under extreme rainfall conditions; The reservoir discharge volume on that day under extreme rainfall conditions; is the effective volume of the reservoir.

[0012] Furthermore, in the consequence calculation, the numerical model of the release law of potential pollutants in sediments under daily management is fitted by the following formula: or ; Where: is the concentration in the solution at time t; a , b is a constant, which is obtained from the numerical simulation model of potential pollutant release law; To release time; The impact of sediment in the reservoir on the water quality of the local area is calculated using the following formula: or ; Where: To increase the concentration of a single pollution indicator in a local area affected by potential pollutants in the soil; a , b is a constant, which is obtained from the numerical simulation model of potential pollutant release law; It is the time required for one actual storage capacity cycle under normal reservoir operation; The formula for calculating the concentration of pollutants diffused from a local area to the entire reservoir capacity is as follows: ; ; Where: is the annual soil erosion; For the i Annual soil erosion modulus of each grid; n is the number of grids; s is the grid projection area; Increased concentration of a single pollution indicator affected by potential pollutants in the soil; is the effective volume of the reservoir; Solid-liquid ratio used for pollutant release kinetics experiments.

[0013] Furthermore, in the risk assessment, if there are multiple potential pollutants, the water source soil environmental risk index calculation formula is as follows: ; Where: r is the soil environmental risk index of water source areas; Potential soil pollutants i The single factor risk index is To increase the concentration of a single pollution indicator affected by potential pollutants in the soil, Potential pollutants i evaluation criteria; According to the water source soil environmental risk index r , the results of soil environmental risk assessment at water source areas are divided into: no risk, r ≤1; mild risk, 1< r ≤2; moderate risk, 2< r ≤3; severe risk, r >3.

[0014] A risk assessment system for the impact of water source soil on water quality environment implementing the above-mentioned method comprises: Data acquisition module, used to obtain basic environmental status data of water sources; The risk identification module is used to screen pollutants that pose potential risks to water quality as potential pollutants based on basic information, clarify their types and concentration distribution, and determine risk factors and types; Migration flux calculation module, used to calculate the migration flux of potential pollutants from soil in water source areas to reservoir water bodies under daily management and extreme rainfall conditions; Consequence calculation module, used to calculate the elevated concentrations of pollution indicators under daily management conditions and extreme rainfall conditions; Risk assessment module is used to evaluate risk levels and output results.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention addresses the potential environmental risks to water quality posed by soil environmental quality exceeding standards in protected areas. It proposes a quantitative analysis method for the release and migration of pollutants from soil into water bodies, used to assess the risk level of such environmental issues. This method is applicable to situations where a soil environmental quality survey has been conducted at a surface water source and there are problems with exceeding standards, requiring a water quality risk assessment. It addresses the challenge of assessing the risk of water quality deterioration caused by such issues in surface water sources, including reservoir-type water sources. It focuses on soil erosion with atmospheric precipitation as the primary release and migration pathway for pollutants. Based on a combination of basic information on the water source, hydrometeorological information, and pollution source information, it incorporates atmospheric precipitation characteristics as a key influencing factor. By quantitatively analyzing the amount of pollutants released from the soil and migrating into the water body, it achieves a quantitative analysis of the source phase. Furthermore, experimental methods are used to obtain key parameters of the release model, constructing a release process assessment model applicable to actual conditions for consequence calculation, and thereby determining the extent and scope of the impact of the risk source on water quality. This invention fills the gap in related technologies at home and abroad, breaks through the dilemma that existing water source environmental risk assessment methods are unable to predict and assess the risks caused by excessive soil environmental quality, and promotes the scientific, efficient and refined management of water source environmental quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Flow chart of the method of the present invention.

[0017] Figure 2 is the slope length factor in the evaluation area in Example 1 L and slope factor S The product of the two is a 30m×30m grid data.

[0018] Figure 3 The vegetation coverage factor in the evaluation area in Example 1 C 30m×30m grid data.

[0019] Figure 4 The potential pollutant factors in the evaluation area in Example 1 p 30m×30m grid data.

[0020] Figure 5 This is the 30m×30m grid data of the soil erosion modulus a in the assessment area in Example 1.

[0021] Figure 6 This is the 30m×30m grid data of the potential pollutant migration modulus A under daily management in the assessment area in Example 1.

[0022] Figure 7This is the 30m*30m grid data of the potential pollutant migration modulus A under extreme rainfall conditions in the assessment area in Example 1. DETAILED DESCRIPTION

[0023] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0024] One embodiment of the present invention provides a risk assessment method for the impact of water source soil on water quality environment, the flow chart of which is as follows: Figure 1 As shown, the method includes the following steps: Step 1: Basic information investigation; Through basic data collection, on-site surveys and personnel interviews, basic environmental status data of water sources are obtained. The data obtained mainly include: physical geographical overview, socio-economic overview, basic situation of the protected area, reservoir operation status, reservoir water quality status, soil status of the protected area, environmental risk sources in and around the protected area, and other key information, laying the foundation for subsequent risk assessment work.

[0025] ①Data collection; Before conducting risk assessment, relevant data collection and analysis should be carried out first. The data collection sources mainly include the daily management department of the water source protection area, the environmental authorities, the Internet, etc. The specific data are as follows: a) Physical geography: including the location of the water source, topography, rivers flowing into the reservoir, hydrogeological conditions, climate and meteorological characteristics, etc. b) Socio-economic overview: including population size and distribution, economic scale, industrial structure, leading industries and industrial planning layout of the region where the water source is located; c) Basic information on the protected area: including the historical demarcation of the water source protection area, details of the current status of the water source protection area, the current land use status within the protection area, vegetation cover and types, soil and water conservation assessments and measures, etc.; d) Reservoir operation status: including reservoir design and construction data, water diversion, water storage, water supply, and flood discharge data at the water source, distribution of water intakes at the water source, water supply destination, reservoir catchment area, internal pollution status of the reservoir, and construction status of water quality assurance projects; e) Reservoir water quality: including information on reservoir water quality monitoring points, monitoring frequency, monitoring items, water quality status, etc., as well as information on inflowing rivers and external water diversion monitoring sections and water quality status; f) Soil conditions in the protected area: including soil type, texture, organic matter content, soil structure, permeability and other physical and chemical properties within the protected area, and detailed results of a soil environmental quality survey of the water source area conducted in accordance with relevant technical specifications; g) Environmental risk sources in and around the protected area: including the types, distribution, emission characteristics, industry types, pollution production and discharge destinations, and environmental infrastructure construction status of pollution sources in and around the water source protection area.

[0026] ② On-site investigation; When the risk assessment unit conducts on-site investigation, the key targets include: a) Actual land use patterns and soil types within the water source protection area; b) Areas related to human production and living activities within and around water source protection areas, as well as places where toxic and hazardous substances are used, processed, stored, and disposed of; c) Whether the soil within the water source protection zone is likely to be affected by environmental risk sources within and around the protection zone, and clarify the location relationship between the environmental risk sources and the protection zone and reservoir waters; d) Vegetation coverage and types within water source protection areas, soil and water conservation assessment and measures.

[0027] ③ Personnel interviews; Respondents for the personnel interviews were selected from people who knew the current situation or history of the water source, such as personnel from water source protection area management agencies and local government, staff from water supply system units, and third parties who were familiar with the water source (such as nearby staff and residents).

[0028] Step 2: Risk identification; Based on the information collected from the basic information survey, risk identification work was carried out. The specific process and information obtained are as follows: a) Organize and analyze detailed data and historical information related to water sources, including the operation of water supply reservoirs, water diversion and flood discharge, water quality, water source protection zone demarcation, and water ecological status; b) Collect data on soil and other environmental samples within the protected area, and based on the detailed soil environmental quality survey results, screen out pollutants that pose potential risks to water quality and require risk assessment, and identify them as potential pollutants; c) Obtaining concentration data and distribution range of potential pollutants; d) Collect and analyze data on the physical and chemical properties of soil within the protected area; e) Organize information on climate, hydrology, and geological characteristics and related data of the water source (or location); f) Collect information on the topography, land use types, vegetation cover, etc. of the land within the protected area.

[0029] Through the above work, we can fully understand the types of pollutants and their concentration distribution that pose potential risks to the soil environment due to environmental background and toxic and hazardous substance emission sources within, around and within the drinking water source protection area, and clarify the risk factors and risk types, providing a basis for subsequent risk assessment work.

[0030] Step 3: Migration flux calculation; Based on risk identification, migration flux calculation is carried out. The specific process is as follows: 1. Calculation basis and formula; The migration flux calculation is based on the following formula: Formula 1: ; Formula 2: ; Where, is the potential pollutant migration modulus, in milligrams per hectare (mg / hm 2 ); a is the soil erosion modulus, in tons per hectare (t / hm 2 ); p is the potential contaminant factor, in milligrams per kilogram (mg / kg); R is the rainfall erosivity factor, expressed in megajoules millimeters per hectare hour (MJ mm / hm 2 h); K is the soil erodibility factor; L is the slope length factor; S is the slope factor; C is the vegetation cover factor.

[0031] 2. The methods for obtaining the rainfall erosivity factor, soil erodibility factor, slope length factor, slope gradient factor, vegetation cover factor, and potential pollutant factor are as follows: ① Rainfall erosion factor R Divided into rainfall erosivity factors under daily management and rainfall erosivity factors under extreme rainfall conditions .

[0032] a) There are two ways to obtain: Based on half-month rainfall data, the formula is as follows: Formula 3: ; Formula 4: ; Where: is the annual rainfall erosivity factor, expressed in megajoules millimeters per hectare hour year (MJ mm / hm 2 ·h·a); For the k The erosivity of rainfall for a month and a half is expressed in megajoules / millimeters per hectare / hour / year (MJ·mm / hm 2 ·h·a); k The 24 and a half months in a year, k =1,2,…,24; i is the year of rainfall data used,i =1,2,…, n , n is the number of years of rainfall data used; j For the i Year k The number of days with erosive rainfall in a month and a half, j =1,2,…, m , m For the i Year k Number of days with erosive rainfall in a month and a half; α As parameter, in warm season α =0.3937, cold season α =0.3101. Generally, June to August is the warm season, December to February is the cold season, and the remaining months are the transition season. The transition season can use either the warm or cold season parameter values ​​based on the specific daily average temperature.

[0033] Based on monthly rainfall data, the formula is as follows: Formula 5: ; Where: is the annual rainfall erosivity factor, expressed in megajoules millimeters per hectare hour year (MJ mm / hm 2 ·h·a); i For the months of the year, i =1,2,…,12; For the i Monthly rainfall, in millimeters (mm); P It is the annual rainfall in millimeters (mm).

[0034] b) The method to obtain is as follows: Formula 6: ; Where: The single-day rainfall erosivity factor under extreme rainfall conditions is expressed in megajoules / millimeters per hectare / hour / day (MJ·mm / hm 2 ·h·d); α As parameter, in warm season α =0.3937, cold season α =0.3101; It is the local daily rainfall when the extreme rainfall event occurs, in millimeters (mm).

[0035] ②Soil erodibility factor K The method to obtain is as follows: a) The calculation data comes from the China 1:1 million soil database and is calculated in the table tool KThen use the soil type map as the working base map and use ArcGIS software to K The values ​​are connected to the base map and converted into a soil erodibility factor raster map using the vector to raster tool in the Conversion Tools. K The value calculation method is shown in Equation 7 and Equation 8.

[0036] Formula 7: ; Where: K is the corrected soil erodibility factor; K EPIC is the soil erodibility factor before correction.

[0037] Formula 8: ; Where: is the soil erodibility factor before correction; m c is the percentage content of clay particles (<0.002mm); It is the percentage content of powder particles (0.002~0.05mm); m s is the percentage content of sand particles (0.05~2mm); is the percentage content of organic carbon.

[0038] b) Use the soil erodibility factor of the region in the "Guidelines for Calculating Soil Loss in Production and Construction Projects" (SL773-2018) K Reference value.

[0039] ③ Slope length factor L and slope factor S Get the product of the two as follows: Obtain a 30*30mDEM elevation dataset. Select the elevation dataset in ArcGIS software, and under the Neighborhood menu in the Spatial Analyst Tools menu bar, use the Focus Statistics tool and set the Statistic Type to MAXIMUM and MINIMUM to obtain the maximum and minimum raster data of the elevation dataset. Under the Map Algebra menu in the Spatial Analyst Tools menu bar, use the Raster Calculator tool to calculate the difference between the two raster data to obtain the terrain relief, that is, the slope length factor. L and slope factor S Product raster plot.

[0040] ④Vegetation cover factor C The method to obtain it is as follows: Paddy fields, wetlands, towns, and deserts are assigned values ​​of 0, 0, 0.01, and 0.7, respectively; dry land is converted according to vegetation coverage, as shown in Equation 9; the remaining ecosystem types are assigned values ​​according to different vegetation coverage (see Table 1).

[0041] Formula 9: ; Where: is the vegetation cover factor of dry land; The vegetation cover is in decimal form.

[0042] Table 1 Vegetation cover factor assignments for different ecosystem types

[0043] ⑤ Potential pollutant factors p The linear model method in the Geostatistical Wizard module of ArcGIS software was used to obtain the pollutant data from the soil environmental quality survey points in the protected area and perform geostatistical analysis and interpolation to determine the concentration distribution of potential pollutants.

[0044] 3. Migration flux calculation process; The above factors were unified into 30-meter-resolution raster data. Under the Map Algebra menu in the Spatial Analyst Tools menu, the Raster Calculator tool was used to calculate the pollutant migration modulus for each raster according to Equations 1 and 2 (using two rainfall erosivity factors to calculate the pollutant migration modulus under extreme rainfall conditions and routine management conditions, respectively). All raster data were then merged to ultimately determine the migration flux of potential pollutants from the soil at the water source to the reservoir water body.

[0045] Step 4: Calculate the consequences; Based on risk identification and migration flux calculation, consequence calculations were conducted for extreme rainfall conditions and daily management situations. The specific process is as follows: 1. Calculating the consequences of extreme rainfall requires the collection of detailed data and historical information on water sources. This information includes meteorological data (daily rainfall, etc.), basic information on water supply reservoirs (total storage capacity, effective storage capacity, etc.), water diversion and storage supply conditions (inflow flow, supply flow, designed flood discharge flow, circulation time, etc.), water quality conditions, the distribution of potentially risky plots in protected areas for soil environment, and key areas of potential pollutant migration. The calculation formula is as follows: Formula 10: ; Where: The elevated concentration of a single pollution indicator affected by potential pollutants in the soil is expressed in milligrams per liter (mg / L); The amount of potential pollutant migration in the soil on that day under extreme rainfall conditions, in milligrams (mg); The reservoir discharge volume on the day of extreme rainfall is in cubic meters (m 3 ); is the effective volume of the reservoir, in cubic meters (m 3 ).

[0046] 2. Calculate the consequences under daily management. Collect relevant data and historical information on water sources required for the calculation of the consequences of soil environmental risk assessments under daily supervision. Relevant information includes meteorological data (daily rainfall, etc.), basic information on water supply reservoirs (total storage capacity, effective storage capacity, etc.), water diversion and storage supply conditions (inflow flow, water supply flow, designed flood discharge flow, circulation time, etc.), water quality conditions, the distribution of potential soil environmental risk plots in the protected area, key areas of potential pollutant migration distribution, and data related to the daily operation of water supply reservoirs (wet and dry seasons, operating storage capacity, etc.). Based on this, carry out the calculation according to the following steps: ①Collection and processing of sediment samples from water sources; a) Sampling points for sediment samples at water sources should be located using professional judgment. For more than five sampling points, additional sampling points should be appropriately added if the reservoir area is large or the situation is complex. Sampling points should be located based on representativeness, with a focus on key areas near potential soil environmental risk areas and near water intakes at water sources.

[0047] b) Sediment samples from water sources should be collected using grab buckets, mud samplers, or drilling equipment. Surface sediment samples near the interface between sediment and water should be collected. Sample collection devices should be used to avoid causing disturbances during the collection process, sample loss, or washing away sample components or organisms at the mud-water interface. After sample collection, the sample should be immediately placed in a sample storage container. When potential pollutants are inorganic substances such as heavy metals, the sample storage container can be made of polyethylene, fluoroplastics, and carbonates. When potential pollutants are organic substances, the sample storage container can be made of glass. Labels should be affixed to record the sampling time, location, and sample number. Sample transportation should use appropriate packaging, refrigeration, and other means to prevent changes in the sample. Quality control methods such as full-procedure blank samples and on-site parallel samples should be used during the sampling process.

[0048] ② Pollutant release kinetics experiment; Using collected sediment samples, potential pollutant release kinetics experiments were conducted under simulated reservoir operating conditions to measure potential pollutant concentrations in the liquid phase. The experimental results were fitted using Equation 11 or Equation 12. Based on the experimental results, a kinetic equation that fits the actual pollutant release process was selected to describe the process. This fitted equation was used as the numerical model for potential pollutant release patterns in sediments.

[0049] Formula 11: ; Where: is the concentration in the solution at time t, in milligrams per liter (mg / L); a , b is a constant, which is obtained from the numerical simulation model of potential pollutant release law; To release time.

[0050] Formula 12: ; Where: is the concentration in the solution at time t, in milligrams per liter (mg / L); a , b is a constant, which is obtained from the numerical simulation model of potential pollutant release law; To release time.

[0051] ③Concentration calculation and impact assessment; A kinetic model of the adsorption and desorption processes of potential pollutants was used to calculate the impact of sediment in a reservoir on local water quality. Based on the results of the pollutant release kinetic equation, an appropriate adsorption and desorption kinetic model was selected for calculation, as shown in Equation 13 or Equation 14. (If Equation 11 is selected, Equation 13 is used for concentration calculation. If Equation 12 is selected, Equation 14 is used for concentration calculation.)

[0052] Formula 13: ; Where: The elevated concentration of a single pollution indicator in a local area affected by potential pollutants in the soil, expressed in milligrams per liter (mg / L); a , b is a constant, which is obtained from the numerical simulation model of potential pollutant release law; It is the time required for an actual storage capacity cycle under normal reservoir operation.

[0053] Equation 14: ; Where: The elevated concentration of a single pollution indicator in a local area affected by potential pollutants in the soil, expressed in milligrams per liter (mg / L); a , bis a constant, which is obtained from the numerical simulation model of potential pollutant release law; It is the time required for an actual storage capacity cycle under normal reservoir operation.

[0054] On this basis, the concentration of pollutants in the local area that diffuse into the entire reservoir capacity is calculated. The method is shown in Equations 15 and 16.

[0055] Equation 15: ; Where: is the annual soil erosion amount, in tons (t); For the i The annual soil erosion modulus of each grid is in tons per hectare (t / hm 2 ); n is the number of grids; s is the grid projection area, in square meters (m 2 ).

[0056] Equation 16: ; Where: The elevated concentration of a single pollution indicator affected by potential pollutants in the soil, expressed in milligrams per liter (mg / L); is the annual soil erosion amount, in tons (t); is the effective volume of the reservoir, in cubic meters (m 3 ); Solid-liquid ratio used for pollutant release kinetics experiments.

[0057] Step 5: Risk assessment; Based on the consequence calculation, risk assessment is carried out. The specific process is as follows: The Class II surface water standard values ​​and specific item standard limits for centralized drinking water surface water sources specified in the "Surface Water Environmental Quality Standard" (GB 3838-2002) (or other standard documents for water source water quality management) are used as evaluation criteria.

[0058] Evaluation method: For the evaluation of a water source, if there is only one potential pollutant, the single factor index method is used for calculation, and the formula is as follows: Equation 17: ; Where: Potential soil pollutants i Single factor risk index; The elevated concentration of a single pollution indicator affected by potential pollutants in the soil, expressed in milligrams per liter (mg / L); Potential pollutants iThe evaluation standard is in milligrams per liter (mg / L).

[0059] When evaluating a water source, if there are multiple potential soil pollutants, the maximum value method is used. First, the single factor index method is used to calculate them, and then the maximum value of the single factor index is taken to determine the water source soil environmental risk index. The formula is as follows: Equation 18: ; Where: is the soil environmental risk index of water source areas; Potential soil pollutants i The single factor risk index.

[0060] According to the calculated water source soil environmental risk index r The soil environmental risk assessment results of water sources are divided into 4 levels, as shown in Table 2.

[0061] Table 2 Results of soil environmental risk assessment at water source areas

[0062] The risk level is used to determine whether the risk of potential soil pollutants to water quality is within an acceptable range. If the risk level is mild or above, risk management measures are implemented, and monitoring and daily management are strengthened.

[0063] Another embodiment of the present invention provides a risk assessment system for the impact of water source soil on water quality environment, which implements the above-mentioned method, including: Data acquisition module, used to obtain basic environmental status data of water sources; The risk identification module is used to screen pollutants that pose potential risks to water quality as potential pollutants based on basic information, clarify their types and concentration distribution, and determine risk factors and types; Migration flux calculation module, used to calculate the migration flux of potential pollutants from soil in water source areas to reservoir water bodies under daily management and extreme rainfall conditions; Consequence calculation module, used to calculate the elevated concentrations of pollution indicators under daily management conditions and extreme rainfall conditions; Risk assessment module is used to evaluate risk levels and output results.

[0064] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0065] Example 1: Risk assessment of the impact of soil in a water source on the water quality environment in 2020; (1) Carry out basic information investigation and risk identification according to the above method of the present invention, and determine heavy metal mercury as the pollutant involved in the assessment.

[0066] (2) Migration flux calculation; ① Calculate the rainfall erosivity factor according to Equations 5 and 6 R Rainfall erosivity factor under daily management 465.7 MJ·mm / hm 2 h·a, rainfall erosivity factor under extreme rainfall conditions 1296 MJ·mm / hm 2 ·h·d.

[0067] ②Soil erodibility factor K Use the above acquisition method b) to obtain the soil erodibility factor K It is 0.0032.

[0068] ③ Slope length factor L and slope factor S Obtain the product of the two and obtain the slope length factor in the assessment area according to the above method of the present invention L and slope factor S The product of the two is a 30m×30m grid data, such as Figure 2 shown.

[0069] ④Vegetation cover factor C According to formula 9, the vegetation coverage factor in the assessment area is obtained. C 30m×30m grid data, such as Figure 3 shown.

[0070] ⑤ Potential pollutant factors p According to the above method of the present invention, the potential pollutant factors in the assessment area are obtained. p 30m×30m grid data, such as Figure 4 shown.

[0071] ⑥ After obtaining the above data, the rainfall erosion factor R , soil erodibility factor K , slope length factor L and slope factor S The product of vegetation cover factor C The 30m×30m grid data is unified and calculated according to Formula 2 to obtain the 30m×30m grid data of the soil erosion modulus a in the assessment area, as shown in Figure 5 shown.

[0072] Will Figure 5 The soil erosion modulus a and potential pollutant factor in the assessment area are obtained p The 30m×30m grid data of potential pollutant migration modulus A under daily management in the assessment area is calculated according to formula 1, as shown in Figure 6shown.

[0073] Combining the above 30m x 30m grid data, we calculated an annual potential pollutant migration flux of 411.9g / a. This result is consistent with previous scientific research on the water source, which found an annual potential pollutant migration flux of 0.41kg / a.

[0074] According to the above calculation method, the rainfall erosion factor R Replaced by rainfall erosivity factor under extreme rainfall conditions , calculate the 30m*30m grid data of potential pollutant migration modulus A under extreme rainfall conditions in the assessment area, such as Figure 7 shown.

[0075] The above 30m*30m grid data were combined and calculated, and the potential pollutant migration flux under extreme rainfall conditions was obtained to be 1146.35g / d.

[0076] (3) Calculation of consequences; According to the above method of the present invention, under daily management, the concentration of heavy metal Hg index increased to 0.000038 mg / L; under extreme rainfall conditions, the concentration of heavy metal Hg index increased to 0.00012 mg / L.

[0077] (4) Risk assessment; According to the above method of the present invention, the evaluation criteria used were the Class II surface water standard values ​​specified in the "Surface Water Environmental Quality Standard" (GB 3838-2002), and the heavy metal mercury evaluation standard was 0.00005 mg / L. According to Equation 17, under routine management, the environmental risk of heavy metal Hg was 0.76, with a risk level of no risk. This risk assessment result is consistent with the actual situation of routine management. Under extreme rainfall conditions, the environmental risk of heavy metal Hg was 2.4, with a risk level of moderate risk.

[0078] The above are only preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, several variations and improvements can be made without departing from the concept of the present invention. These should also be regarded as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A risk assessment method for the impact of water source soil on water quality environment, characterized by: The following steps are involved: Step 1: Basic information survey; obtain basic environmental status data of the water source area; Step 2: Risk identification; Based on basic information, we screen pollutants that pose potential risks to source water quality as potential pollutants, clarify their types and concentration distribution, and determine risk factors and types; Step 3: Migration flux calculation: Determine the rainfall erosivity factor, soil erodibility factor, slope length factor, slope gradient factor, vegetation cover factor, and potential pollutant factor, convert them into uniform resolution raster data, calculate the pollutant migration modulus under daily management and extreme rainfall conditions, and merge the raster data to obtain the migration flux of potential pollutants from the water source soil to the reservoir water body; Step 4: Calculate the consequences. For extreme rainfall events, the elevated concentrations of pollution indicators are calculated by combining pollutant migration, flood discharge, and effective reservoir volume. For daily management, a numerical model of potential pollutant release patterns in sediments is obtained through fitting the release kinetics of sediment samples. The elevated concentrations of pollution indicators for local and overall reservoir volumes are calculated by combining circulation time and annual soil erosion. Step 5: Risk assessment: Based on the consequence calculation results, use the single factor index method or the maximum value method to assess the risk level and determine whether the risk value exceeds the acceptable risk level.

2. The risk assessment method for the impact of water source soil on water quality environment according to claim 1 is characterized in that: The migration flux calculation is based on the following formula: ； ； Where A is the potential pollutant migration modulus; a is the soil erosion modulus; p is a potential pollutant factor; R is the rainfall erosivity factor; K is the soil erodibility factor; L is the slope length factor; S is the slope factor; C is the vegetation cover factor.

3. The risk assessment method for the impact of water source soil on water quality environment according to claim 2 is characterized in that: The rainfall erosivity factor R Including rainfall erosivity factors under daily management and rainfall erosivity factor , Calculated based on semi-monthly or monthly rainfall data, Calculated based on rainfall on extreme rainfall days.

4. The risk assessment method for the impact of water source soil on water quality environment according to claim 1 is characterized in that: In the consequence calculation, the calculation formula for extreme rainfall is: ； Where: Elevated concentrations for single pollution indicators affected by potential contaminants in the soil; The amount of potential pollutant migration in the soil on that day under extreme rainfall conditions; The reservoir discharge volume on that day under extreme rainfall conditions; is the effective volume of the reservoir.

5. The risk assessment method for the impact of water source soil on water quality environment according to claim 1 is characterized in that: In the consequence calculation, the numerical model of the potential pollutant release pattern of sediments under daily management is fitted by the following formula: or ; Where: is the concentration in the solution at time t; a , b is a constant, which is obtained from the numerical simulation model of potential pollutant release law; To release time; The impact of sediment in the reservoir on the water quality of the local area is calculated using the following formula: or ; Where: To increase the concentration of a single pollution indicator in a local area affected by potential pollutants in the soil; a , b is a constant, which is obtained from the numerical simulation model of potential pollutant release law; It is the time required for one actual storage capacity cycle under normal reservoir operation; The formula for calculating the concentration of pollutants diffused from a local area to the entire reservoir capacity is as follows: ； ； Where: is the annual soil erosion; For the i Annual soil erosion modulus of each grid; n is the number of grids; s is the grid projection area; Increased concentration of a single pollution indicator affected by potential pollutants in the soil; is the effective volume of the reservoir; Solid-liquid ratio used for pollutant release kinetics experiments.

6. The risk assessment method for the impact of water source soil on water quality environment according to claim 1 is characterized in that: In the risk assessment, if there are multiple potential pollutants, the water source soil environmental risk index calculation formula is as follows: ； Where: r is the soil environmental risk index of water source areas; Potential soil pollutants i The single factor risk index is To increase the concentration of a single pollution indicator affected by potential pollutants in the soil, Potential pollutants i evaluation criteria; According to the water source soil environmental risk index r , the results of soil environmental risk assessment at water source areas are divided into: no risk, r ≤1; mild risk, 1< r ≤2; moderate risk, 2< r ≤3; severe risk, r >3.

7. A risk assessment system for the impact of water source soil on water quality environment that implements the method according to any one of claims 1 to 6, characterized in that: include: Data acquisition module, used to obtain basic environmental status data of water sources; The risk identification module is used to screen pollutants that pose potential risks to water quality as potential pollutants based on basic information, clarify their types and concentration distribution, and determine risk factors and types; Migration flux calculation module, used to calculate the migration flux of potential pollutants from soil in water source areas to reservoir water bodies under daily management and extreme rainfall conditions; Consequence calculation module, used to calculate the elevated concentrations of pollution indicators under daily management conditions and extreme rainfall conditions; Risk assessment module is used to evaluate risk levels and output results.

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