Risk assessment methods for the impact of water source soil on water quality environment

Abstract

This invention relates to the field of water source environmental management technology, providing a risk assessment method for the impact of water source soil on water quality. This method, through basic information investigation, risk identification, migration flux calculation, consequence calculation, and risk assessment, achieves a risk assessment of the impact of water source soil on water quality. This invention is applicable to situations where surface water source soil environmental quality surveys have been conducted and exceedances exist, requiring water quality risk assessment. It can quantitatively analyze the amount of pollutants released from the soil and migrate into the water source; and, combined with experimental methods, obtain key parameters to construct a release process assessment model suitable for the actual situation for consequence calculation, determining the degree and scope of the risk source's impact on water quality. This invention overcomes the limitations of existing methods in assessing the risk of water source soil exceeding standards, promoting the scientific, efficient, and refined management of water source environmental quality.

Description

Technical Field

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

[0002] As a core component of water source environmental management, the accuracy of water source environmental risk assessment directly affects the safety of water supply quality and the improvement of management efficiency.

[0003] Existing methods primarily assess potential hazards from anthropogenic sources, such as industrial storage tanks, sewage outlets, hazardous material transport vehicles and pipelines, and farmland. These anthropogenic risk sources can be eliminated through standardized management of water sources. These risk sources often have specific locations, ranges, and scales, and only release pollutants that harm water sources under the influence of specific human activities such as leaks and explosions.

[0004] The "Guidelines for the Protection of Centralized Drinking Water Sources (Trial)" issued by the Ministry of Ecology and Environment in 2012 assesses the potential environmental risks posed by sudden environmental pollution incidents from stationary sources such as industrial enterprises and sewage outlets around water sources, mobile sources such as transportation roads, and non-point sources such as agricultural non-point sources. It establishes a risk assessment system comprising "risk identification - source phase analysis - consequence calculation - risk calculation - risk evaluation." This system primarily analyzes the source phase by calculating the probability of sudden environmental incidents such as leaks and explosions and the rate of pollutant release. It uses theoretical mathematical models of pollutant diffusion to calculate the degree and scope of impact of sudden water pollution incidents on water source quality. However, it fails to adequately consider the water environment risks caused by surrounding soil environmental quality exceeding relevant standards. These risk sources are characterized by being difficult to eliminate and having a wide distribution.

[0005] Chinese patent CN119692818A discloses a method and system for environmental risk assessment of drinking water sources. This method assesses the risk by quantitatively characterizing water source features, pollution source activity data, and pollutant migration capacity. Specifically, it combines basic information and meteorological information of the water source to derive comprehensive characteristic values, determines pollutant migration capacity values ​​and risk assessment range values ​​based on hydrological data, calculates potential pollution risk values ​​by the area occupied by potential pollution sources and their linear distribution distance, and finally synthesizes the above indicators to obtain a comprehensive environmental risk assessment result, thereby determining the magnitude of the environmental risk of the water source. However, this method has shortcomings. It mainly involves long-term timescales, relying on relatively stable operating conditions and basic hydrological and meteorological conditions of the water source as the basis for calculating environmental risk values. It fails to fully consider the atmospheric precipitation-related characteristics that most easily trigger environmental risks from pollutants in the surrounding soil of the water source, especially the impact of extreme rainfall events on the environmental risk of the water source.

[0006] Furthermore, nationwide surveys of soil environmental quality in water source areas indicate that soil environmental quality in these areas exceeds relevant standards due to environmental background issues or historical human activities, posing a potential threat to water quality. However, current industry technical documents lack specific assessment methods, and existing environmental risk assessment methods for water source areas do not consider the assessment and management of risks arising from soil environmental quality exceeding standards in protected areas. Therefore, this invention proposes a risk assessment method for the impact of soil pollution on water source quality. Summary of the Invention

[0007] The purpose of this invention is to provide a risk assessment method for the impact of soil in water source areas on the water quality environment, aiming to solve the problems mentioned in the background art.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] The risk assessment method for the impact of soil from water source areas on the water quality environment includes the following steps:

[0010] Step 1: Basic Information Survey; Obtain basic environmental data of the water source area;

[0011] Step 2: Risk Identification; Based on basic information, pollutants that pose a potential risk to the water source quality are screened as potential pollutants, their types and concentration distribution are identified, and risk factors and types are determined;

[0012] Step 3: Calculate migration flux; determine rainfall erosivity factor, soil erodibility factor, slope length factor, slope factor, vegetation cover factor and potential pollutant factor, convert them into uniform resolution raster data, calculate pollutant migration modulus under routine management conditions and extreme rainfall conditions, and merge raster data to obtain the migration flux of potential pollutants from soil in water source area to reservoir water body.

[0013] Step 4: Consequence Calculation; For extreme rainfall scenarios, calculate the increased concentration of pollution indicators by combining pollutant migration, flood discharge, and effective reservoir volume; For routine management scenarios, obtain a numerical model of the release pattern of potential pollutants in sediments by fitting sediment sample release kinetics experiments, and calculate the increased concentration of pollution indicators in local and overall reservoir capacity by combining cycle time and annual soil erosion.

[0014] Step 5: Risk assessment; Based on the consequences 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.

[0015] Furthermore, the migration flux calculation is based on the following formula:

[0016] ;

[0017] ;

[0018] In the formula, A is the potential pollutant migration modulus; a is the soil erosion modulus; p As a potential pollutant factor; R It is the erosivity factor of rainfall; K It is a soil erodibility factor; L Slope length factor; S Slope factor; C This refers to vegetation cover factors.

[0019] Furthermore, the rainfall erosivity factor R Including rainfall erosivity factors under routine management conditions and rainfall erosivity factor , Calculated based on bi-weekly or monthly rainfall data, Calculated based on daily rainfall during extreme rainfall events.

[0020] Furthermore, in the consequence calculation, the calculation formula for extreme rainfall scenarios is as follows:

[0021] ;

[0022] In the formula: The concentration of a single pollution indicator is increased due to the influence of potential pollutants in the soil. This represents the amount of potential pollutants that migrated from the soil on a given day under extreme rainfall conditions. This refers to the reservoir's discharge flow rate on that day under extreme rainfall conditions. This refers to the effective volume of the reservoir.

[0023] Furthermore, in the consequence calculation, the numerical model of the potential pollutant release pattern in sediments under routine management conditions is fitted using the following formula:

[0024] or ;

[0025] In the formula: Let t be the concentration in the solution. a , b This is a constant, derived from a numerical simulation model of the potential pollutant release pattern; Release time;

[0026] The impact of sediments in the reservoir on the water quality of the local water source area is calculated using the following formula:

[0027] or ;

[0028] In the formula: The concentration of a single pollution indicator increased in a localized area due to the influence of potential pollutants in the soil. a , b This is a constant, derived from a numerical simulation model of the potential pollutant release pattern; The time required for one actual reservoir capacity cycle under normal operating conditions;

[0029] The formula for calculating the concentration of pollutants that have diffused from a local area to the entire reservoir capacity is as follows:

[0030] ;

[0031] ;

[0032] In the formula: This refers to the annual soil erosion. For the first i The annual soil erosion modulus of each grid cell; n The number of grid cells; s The grid projection area; The concentration of a single pollution indicator increases due to the influence of potential pollutants in the soil. The effective volume of the reservoir; The solid-liquid ratio used to conduct pollutant release kinetics experiments.

[0033] Furthermore, in the aforementioned risk assessment, if multiple potential pollutants exist, the formula for calculating the soil environmental risk index of the water source area is as follows:

[0034] ;

[0035] In the formula: r The soil environmental risk index for water source areas; Potential soil pollutants i The single-factor risk index, among which The concentration of a single pollution indicator increases due to the influence of potential pollutants in the soil. as potential pollutants i Evaluation criteria;

[0036] According to the soil environmental risk index of water source areas r The results of the soil environmental risk assessment for water sources are divided into: no risk, r ≤1; Mild risk, 1 < r ≤2; Moderate risk, 2 < r ≤3; Severe risk. r >3.

[0037] A risk assessment system for the impact of water source soil on water quality environment, implementing the method described above, includes:

[0038] The data acquisition module is used to acquire basic environmental status data of the water source area;

[0039] The risk identification module is used to screen pollutants that pose a potential risk to the quality of water sources based on basic information, identify their types and concentration distribution, and determine the risk factors and types.

[0040] The migration flux calculation module is used to calculate the migration flux of potential pollutants from the soil of the water source to the reservoir water body under routine management conditions and extreme rainfall conditions;

[0041] The consequences calculation module is used to calculate the increase in pollution index concentrations under routine management conditions and extreme rainfall conditions;

[0042] The risk assessment module is used to evaluate the risk level and output the results.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] This invention addresses the potential environmental risks to water quality posed by soil environmental quality exceeding relevant standards in water source protection areas. It proposes a quantitative analysis method for assessing the risk level of pollutants released from soil and migrating into water sources. This method is applicable to situations where soil environmental quality surveys of surface water sources have been conducted and exceedances are identified, requiring water quality risk assessment. It solves the challenge of assessing the risk of water quality deterioration caused by such issues in surface water sources, including reservoir-type sources. The method focuses on soil erosion via atmospheric precipitation as the primary release and migration pathway for pollutants. Based on basic information about the water source, hydrological and meteorological information, and pollution source information, it incorporates atmospheric precipitation characteristics as a crucial influencing factor. By quantitatively analyzing the amount of pollutants released from soil and migrating into water sources, it achieves quantitative analysis of the source phase. Simultaneously, it combines experimental methods to obtain key parameters of the release model, constructing a release process assessment model suitable for actual conditions for consequence calculation, thereby determining the degree and scope of the risk source's impact on water quality. This invention fills a gap in related technologies both domestically and internationally, overcomes the predicament that existing water source environmental risk assessment methods cannot predict and assess the risks arising from excessive soil environmental quality, and promotes the scientific, efficient, and refined management of water source environmental quality. Attached Figure Description

[0045] Figure 1 This is a flowchart of the method of the present invention.

[0046] Figure 2 For the slope length factor in the evaluation area in Example 1 L With slope factor S The product of the two is 30m×30m raster data.

[0047] Figure 3 For the vegetation cover factor in the evaluation area in Example 1 C 30m×30m raster data.

[0048] Figure 4 For the potential pollutant factors assessed in Example 1 p 30m×30m raster data.

[0049] Figure 5 The data is a 30m×30m raster of soil erosion modulus a in the evaluation area in Example 1.

[0050] Figure 6 The data is a 30m×30m raster of potential pollutant migration modulus A under routine management conditions in the evaluation area in Example 1.

[0051] Figure 7 The data is a 30m*30m raster of potential pollutant migration modulus A under extreme rainfall conditions in the evaluation area in Example 1. Detailed Implementation

[0052] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0053] One embodiment of the present invention provides a risk assessment method for the impact of soil in water source areas on the water quality environment, the flowchart of which is shown below. Figure 1 As shown, the method includes the following steps:

[0054] Step 1: Basic Information Survey;

[0055] Through basic data collection, on-site surveys, and interviews, basic environmental data of the water source area were obtained. The data mainly included key information such as natural geographical overview, socio-economic overview, basic information of the protected area, reservoir operation status, reservoir water quality status, soil status of the protected area, and environmental risk sources in and around the protected area, laying the foundation for subsequent risk assessment work.

[0056] ① Data collection;

[0057] Before conducting a risk assessment, relevant data must first be collected and analyzed. Data sources primarily include the daily management departments of water source protection areas, environmental authorities, and the internet. Specific data is as follows:

[0058] a) Natural geographical overview: including the location of the water source area, topography, rivers flowing into the reservoir, hydrogeological conditions, climate and meteorological characteristics, etc.

[0059] b) Socioeconomic overview: This includes the population size and distribution, economic scale, industrial structure, leading industries, and industrial planning layout of the area where the water source is located;

[0060] c) Basic information about the protected area: This includes the historical delineation of the water source protection area, details of the current status of the water source protection area, the current land use status within the protected area, vegetation cover and species, soil and water conservation assessment and measures, etc.

[0061] d) Reservoir operation status: including reservoir design and construction data, water source diversion, water storage, water supply and flood discharge data, distribution of water source intakes, water supply destination, reservoir catchment area, internal pollution status of the reservoir, and construction status of water quality protection projects;

[0062] e) Reservoir water quality status: This includes information such as reservoir water quality monitoring points, monitoring frequency, monitoring items and water quality status, as well as information on inflow rivers and external water diversion monitoring sections and their water quality status.

[0063] f) Soil conditions in the protected area: This includes soil types, textures, organic matter content, soil structure, permeability, and other physical and chemical properties within the protected area, as well as the results of a detailed survey of the soil environmental quality of the water source area conducted in accordance with relevant technical specifications.

[0064] g) Environmental risk sources within and around the protected area: including the types, distribution, emission characteristics, industry types, production and discharge destinations, and environmental infrastructure construction of pollution sources within and around the water source protected area.

[0065] ②On-site inspection;

[0066] When risk assessment units conduct on-site inspections, the key targets include:

[0067] a) Actual land use patterns and soil types within the water source protection area;

[0068] b) Areas within and around water source protection zones that are related to human production and daily life activities, as well as sites where toxic and harmful substances are used, treated, stored, or disposed of;

[0069] c) Whether the soil within the water source protection area may be affected by environmental risk sources within and around the protection area, and clarify the locational relationship between the environmental risk sources and the protection area and the reservoir water area;

[0070] d) Vegetation cover and species within the water source protection area, and soil and water conservation assessment and measures.

[0071] ③ Interviews with personnel;

[0072] The interviewees were selected from people who knew about the current situation or history of the water source, such as personnel from the water source protection area management agency and local government, staff of the water supply system unit, and third parties familiar with the water source (such as nearby staff and residents).

[0073] Step 2: Risk Identification;

[0074] Based on the data collected during the basic information survey, risk identification work was carried out. The specific process and information obtained are as follows:

[0075] a) Organize and analyze detailed data and historical information related to water sources, covering the operation status of water supply reservoirs, water diversion and storage and flood discharge, water quality, delineation of water source protection areas, and current status of aquatic ecology;

[0076] b) Collect environmental sample data such as soil within the protected area, and based on the detailed survey results of soil environmental quality, screen out pollutants that pose a potential risk to water quality and require risk assessment, and identify them as potential pollutants;

[0077] c) Obtain concentration data and distribution range of potential pollutants;

[0078] d) Collect and analyze the physicochemical properties of the soil within the protected area;

[0079] e) Compile information and data on the climate, hydrology, and geological characteristics of the water source area (or its location);

[0080] f) Collect information on the topography, land use types, and vegetation cover of the protected area.

[0081] Through the above work, we can fully understand the types and concentration distribution of pollutants that pose potential risks to the soil environment due to environmental background and sources of toxic and harmful substances within and around drinking water source protection areas and catchment areas, identify risk factors and risk types, and provide a basis for subsequent risk assessment work.

[0082] Step 3: Calculate migration flux;

[0083] Based on risk identification, migration flux calculation is carried out, and the specific process is as follows:

[0084] 1. Calculation basis and formula;

[0085] Migration flux is calculated based on the following formula:

[0086] Formula 1: ;

[0087] Formula 2: ;

[0088] In the formula, This represents the potential pollutant migration modulus, expressed in milligrams per hectare (mg / hm). 2 ); 'a' represents the soil erosion modulus, expressed in tons per hectare (t / hm). 2 ); p As a potential pollutant, the unit is milligrams per kilogram (mg / kg); R The erosivity factor is measured in megajoules per millimeter per hectare per hour (MJ·mm / hm). 2 ·h); K It is a soil erodibility factor; L Slope length factor; S Slope factor; C This refers to vegetation cover factors.

[0089] 2. The methods for obtaining rainfall erosivity factors, soil erodibility factors, slope length factors, slope gradient factors, vegetation cover factors, and potential pollutant factors are as follows:

[0090] ①Rainfall erosivity factor R Rainfall erosivity factors are divided into those under routine management conditions. Rainfall erosivity factor under extreme rainfall conditions .

[0091] a) It can be obtained through two methods:

[0092] The formula is calculated based on bi-weekly rainfall data, as follows:

[0093] Formula 3: ;

[0094] Formula 4: ;

[0095] In the formula: The annual rainfall erosivity factor is expressed in megajoules per millimeter per hectare per hour per year (MJ·mm / hm). 2 ·h·a); For the first k The erosivity of rainfall over one and a half months is measured in megajoules per millimeter per hectare per hour per year (MJ·mm / hm). 2 ·h·a); k It consists of 24 and a half months in the middle of the year. k =1,2,…,24; i The year in which the rainfall data was used. i =1,2,…, n , n The number of years for which rainfall data was used; j For the first i Year k The number of days with erosive rainfall in one and a half months, j =1,2,…,m , m For the first i Year k The number of days with erosive rainfall in one and a half months; α For parameters, during the warm season α =0.3937, during the cold season α =0.3101. Generally, June to August is considered the warm season, December to February of the following year is the cold season, and other months are transitional seasons. The transitional season can be selected using either the warm season or cold season parameter value based on the specific daily average temperature.

[0096] The formula is calculated based on monthly rainfall data, as follows:

[0097] Formula 5: ;

[0098] In the formula: The annual rainfall erosivity factor is expressed in megajoules per millimeter per hectare per hour per year (MJ·mm / hm). 2 ·h·a); i Which month of the year? i =1,2,…,12; For the first i Monthly rainfall, in millimeters (mm); P Annual rainfall, expressed in millimeters (mm).

[0099] b) The method to obtain it is as follows:

[0100] Formula 6: ;

[0101] In the formula: This refers to the daily rainfall erosivity factor under extreme rainfall conditions, expressed in megajoules per millimeter per hectare per hour per day (MJ·mm / hm). 2 (·h·d); α For parameters, during the warm season α =0.3937, during the cold season α =0.3101; This represents the local daily rainfall at the time of the extreme rainfall event, expressed in millimeters (mm).

[0102] ② Soil erodibility factors K The method to obtain it is as follows:

[0103] a) The calculation data comes from the China 1:1,000,000 Soil Database and was calculated using a spreadsheet tool. K Values ​​are then calculated, and using the soil type map as the base map, the values ​​are processed in ArcGIS software. KThe values ​​are connected to the base map, and then converted into a soil erodibility factor raster map using the vector-to-raster tool in the Conversion Tools. Specifically... K The calculation method for the value is shown in Equations 7 and 8.

[0104] Formula 7: ;

[0105] In the formula: K The corrected soil erodibility factor; K EPIC The soil erodibility factor is as shown before correction.

[0106] Formula 8: ;

[0107] In the formula: Soil erodibility factors before correction; m c Percentage content of clay particles (<0.002 mm); The percentage content of powder particles (0.002~0.05mm); m s This refers to the percentage content of sand particles (0.05~2mm); This represents the percentage content of organic carbon.

[0108] b) The soil erodibility factor in this area is adopted from the "Guidelines for Soil Loss Measurement in Production and Construction Projects" (SL773-2018). K Reference value.

[0109] ③ Slope length factor L With slope factor S To obtain the product of the two, follow these steps:

[0110] Obtain a 30*30m DEM elevation dataset. In ArcGIS software, select the elevation dataset. Under the Neighborhood menu in the Spatial Analyst Tools menu, 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. Then, under the Map Algebra menu in the Spatial Analyst Tools menu, use the Raster Calculator tool to calculate the difference between the two raster data sets, obtaining the terrain relief, i.e., the slope length factor. L With slope factor S Product raster image.

[0111] ④Vegetation cover factor C The method to obtain it is as follows:

[0112] Paddy fields, wetlands, towns, and deserts were assigned values ​​of 0, 0, 0.01, and 0.7, respectively; dry land was converted according to vegetation cover, and the specific method is shown in Equation 9; other ecosystem types were assigned values ​​according to different vegetation cover (see Table 1).

[0113] Formula 9: ;

[0114] In the formula: Vegetation cover factor for dry land; Vegetation coverage is expressed as a decimal.

[0115] Table 1. Vegetation cover factor assignments for different ecosystem types

[0116]

[0117] ⑤ Potential pollutant factors p In ArcGIS software, the linear model method in the Geostatistical Wizard module was used to obtain pollutant data from soil environmental quality survey sites in the protected area. Geostatistical interpolation was then performed to determine the concentration distribution of potential pollutants.

[0118] 3. Migration flux calculation process;

[0119] All the above factors were unified into 30m resolution raster data. In the Spatial Analyst Tools menu, under the Map Algebra menu, the Raster Calculator tool was used to calculate the pollutant migration modulus of 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 finally obtain the migration flux of potential pollutants from the soil of the water source to the reservoir water body.

[0120] Step 4: Calculate the consequences;

[0121] Based on risk identification and migration flux calculation, consequence calculations are performed for both extreme rainfall scenarios and routine management scenarios. The specific process is as follows:

[0122] 1. Calculating the consequences of extreme rainfall requires collecting detailed data and historical information about the water source. This data includes meteorological data (daily rainfall, etc.), basic information about the water supply reservoir (total capacity, effective capacity, etc.), water diversion and supply conditions (inflow rate, supply rate, design discharge rate, circulation time, etc.), water quality status, distribution of potentially hazardous soil areas within the protected area, and key areas for the migration and distribution of potential pollutants. The calculation formula is as follows:

[0123] Formula 10: ;

[0124] In the formula: Elevated concentration of a single pollution index affected by potential pollutants in the soil, expressed in milligrams per liter (mg / L). This represents the amount of potential pollutants that migrate from the soil on a given day under extreme rainfall conditions, expressed in milligrams (mg). This refers to the reservoir discharge flow rate on that day under extreme rainfall conditions, expressed in cubic meters (m³). 3 ); The effective volume of the reservoir is expressed in cubic meters (m³). 3 ).

[0125] 2. Calculation of consequences under routine management: Collect relevant data and historical information on water sources required for calculating the consequences of soil environmental risk assessment under routine supervision. Relevant data includes meteorological data (daily rainfall, etc.), basic information on water supply reservoirs (total storage capacity, effective storage capacity, etc.), water diversion and supply conditions (inflow rate, supply rate, design discharge rate, circulation time, etc.), water quality status, distribution of potentially risky soil environmental sites within the protected area, key areas for potential pollutant migration and distribution, and relevant data on the daily operation of water supply reservoirs (dry and high water seasons, operating storage capacity, etc.). Based on this, calculations are carried out according to the following steps:

[0126] ① Collection and processing of sediment samples from water sources;

[0127] a) The sampling points for sediment samples from water sources are determined by professional judgment, with more than 5 sampling points. The number of sampling points may be increased appropriately when the reservoir area is large or the situation is complex. Sampling points are arranged based on representativeness, with a focus on key areas adjacent to potentially hazardous soil environments and near water intake points.

[0128] (b) Sediment samples from water sources should be collected using grab buckets, mud samplers, or drilling equipment. Surface sediment samples should be collected near the sediment-water interface. The sampling equipment should be designed to avoid disturbance during collection, sample loss, or washing away sample components or organisms at the mud-water interface. After collection, samples should be immediately placed in a sample preservation container. Containers made of polyethylene, fluoroplastics, or carbonates can be used when the potential contaminants are inorganic (e.g., heavy metals). Glass containers can be used when the potential contaminants are organic (e.g., organic). The containers should be clearly labeled with the sampling time, location, and sample number. Appropriate packaging and refrigeration should be used during sample transportation to prevent sample degradation. Quality control methods, such as using full-procedure blank samples and on-site parallel samples, should be employed during the sampling process.

[0129] ② Pollutant release kinetics experiment;

[0130] Using collected sediment samples, a potential pollutant release kinetic experiment was conducted under simulated reservoir operating conditions to determine the concentration of potential pollutants in the liquid phase. The experimental results were fitted according to Equation 11 or Equation 12. Based on the pollutant release kinetic experiment results, a kinetic equation that conforms to the actual pollutant release process was selected for description, and the fitted equation was used as a numerical model of the potential pollutant release law in sediments.

[0131] Formula 11: ;

[0132] In the formula: The concentration of the solution at time t is expressed in milligrams per liter (mg / L). a , b This is a constant, derived from a numerical simulation model of the potential pollutant release pattern; For release time.

[0133] Formula 12: ;

[0134] In the formula: The concentration of the solution at time t is expressed in milligrams per liter (mg / L). a , b This is a constant, derived from a numerical simulation model of the potential pollutant release pattern; For release time.

[0135] ③ Concentration calculation and impact assessment;

[0136] The impact of sediments in the reservoir on the water quality of the local area was calculated using a kinetic model of the adsorption and desorption process of potential pollutants. Based on the fitting results of the pollutant release kinetic equation, a suitable kinetic model for the adsorption and desorption process was selected for calculation, as shown in Equation 13 or Equation 14 (if Equation 11 is selected, then Equation 13 is selected for concentration calculation; if Equation 12 is selected, then Equation 14 is selected for concentration calculation).

[0137] Formula 13: ;

[0138] In the formula: The concentration of a single pollution index in a localized area affected by potential pollutants in the soil is elevated, expressed in milligrams per liter (mg / L). a , b This is a constant, derived from a numerical simulation model of the potential pollutant release pattern; This refers to the time required for one actual reservoir capacity cycle under normal operating conditions.

[0139] Formula 14: ;

[0140] In the formula: The concentration of a single pollution index in a localized area affected by potential pollutants in the soil is elevated, expressed in milligrams per liter (mg / L). a , b This is a constant, derived from a numerical simulation model of the potential pollutant release pattern; This refers to the time required for one actual reservoir capacity cycle under normal operating conditions.

[0141] Based on this, the concentration of pollutants diffused from the local area to the entire reservoir capacity is calculated. The method is shown in Equations 15 and 16.

[0142] Formula 15: ;

[0143] In the formula: This represents the annual soil erosion, expressed in tons (t). For the first i The annual soil erosion modulus of each grid cell, expressed in tons per hectare (t / hm²). 2 ); n The number of grid cells; s This represents the grid projection area, in square meters (m²). 2 ).

[0144] Formula 16: ;

[0145] In the formula: The concentration of a single pollution index increased due to the influence of potential pollutants in the soil is expressed in milligrams per liter (mg / L). This represents the annual soil erosion, expressed in tons (t). The effective volume of the reservoir is expressed in cubic meters (m³). 3 ); The solid-liquid ratio used to conduct pollutant release kinetics experiments.

[0146] Step 5: Risk assessment;

[0147] Based on the consequences calculation, a risk assessment is conducted, and the specific process is as follows:

[0148] The evaluation criteria are the Class II standard values ​​for surface water specified in the "Surface Water Environmental Quality Standard" (GB 3838-2002) and the specific item standard limits for centralized drinking water surface water sources (or other standard documents used for water source quality management).

[0149] Evaluation method:

[0150] For the evaluation of a water source, if only one potential pollutant exists, the single-factor index method is used for calculation, as shown in the following formula:

[0151] Equation 17: ;

[0152] In the formula: Potential soil pollutants i Single-factor risk index; The concentration of a single pollution index increased due to the influence of potential pollutants in the soil is expressed in milligrams per liter (mg / L). as potential pollutants i The evaluation standard is expressed in milligrams per liter (mg / L).

[0153] For the evaluation of a water source, if multiple potential soil pollutants exist, the maximum value method is used for assessment. First, the single-factor index method is used to calculate the risk, and then the maximum value among the single-factor indices is taken to determine the soil environmental risk index of the water source. The formula is as follows:

[0154] Formula 18: ;

[0155] In the formula: The soil environmental risk index for water source areas; Potential soil pollutants i The single-factor risk index.

[0156] Based on the calculated soil environmental risk index of water source areas r The results of the soil environmental risk assessment for water sources are divided into four levels, as shown in Table 2.

[0157] Table 2 Results of Soil Environmental Risk Assessment for Water Sources

[0158]

[0159] 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 low or above, risk control measures are implemented, including enhanced monitoring and daily management.

[0160] Another embodiment of the present invention provides a risk assessment system for the impact of water source soil on water quality environment to implement the above-described method, comprising:

[0161] The data acquisition module is used to acquire basic environmental status data of the water source area;

[0162] The risk identification module is used to screen pollutants that pose a potential risk to the quality of water sources based on basic information, identify their types and concentration distribution, and determine the risk factors and types.

[0163] The migration flux calculation module is used to calculate the migration flux of potential pollutants from the soil of the water source to the reservoir water body under routine management conditions and extreme rainfall conditions;

[0164] The consequences calculation module is used to calculate the increase in pollution index concentrations under routine management conditions and extreme rainfall conditions;

[0165] The risk assessment module is used to evaluate the risk level and output the results.

[0166] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0167] Example 1: Risk assessment of the impact of soil from a water source area on the water quality environment in 2020;

[0168] (1) Conduct basic information investigation and risk identification according to the above method of the present invention, and determine that heavy metal mercury is a pollutant to be included in the assessment.

[0169] (2) Calculation of migration flux;

[0170] ① Calculate the rainfall erosivity factor according to Equations 5 and 6. R Rainfall erosivity factor under routine management conditions 465.7 MJ·mm / hm 2 •h·a, rainfall erosivity factor under extreme rainfall conditions 1296 MJ·mm / hm 2 ·h·d.

[0171] ② Soil erodibility factors K Soil erodibility factor was obtained using method b) described above. K It is 0.0032.

[0172] ③ Slope length factor L With slope factor S The product of the two is obtained according to the method described above in this invention, thus yielding the slope length factor within the evaluation area. L With slope factor S The product of the two is a 30m×30m raster data, such as Figure 2 As shown.

[0173] ④Vegetation cover factor C The vegetation cover factor within the assessment area was obtained by calculating according to Equation 9. C 30m×30m raster data, such as Figure 3 As shown.

[0174] ⑤ Potential pollutant factors p Potential pollutant factors within the assessment area are obtained according to the method described above in this invention. p 30m×30m raster data, such as Figure 4 As shown.

[0175] ⑥ After obtaining the above data, the rainfall erosivity factor R Soil erodibility factors K Slope length factor L With slope factor S The product of vegetation cover factor C The data was standardized to 30m × 30m raster data. Calculations were performed according to Equation 2 to obtain the 30m × 30m raster data for the soil erosion modulus *a* within the assessment area. Figure 5 As shown.

[0176] Will Figure 5 The obtained soil erosion modulus a and potential pollutant factors in the assessment area p The 30m×30m raster data, calculated according to Equation 1, yields the 30m×30m raster data of the potential pollutant migration modulus A under routine management conditions within the assessment area, such as... Figure 6 As shown.

[0177] Combining the above 30m×30m grid data, the annual potential pollutant migration flux is calculated to be 411.9 g / a. This result is consistent with the previous scientific research findings for this water source area, which showed an annual potential pollutant migration flux of 0.41 kg / a.

[0178] According to the above calculation method, the rainfall erosivity factor R Replace with rainfall erosivity factor under extreme rainfall conditions The 30m*30m raster data of the potential pollutant migration modulus A under extreme rainfall conditions in the assessment area were calculated, such as... Figure 7 As shown.

[0179] By combining the above 30m*30m grid data, the potential pollutant migration flux under extreme rainfall conditions is calculated to be 1146.35g / d.

[0180] (3) Calculation of consequences;

[0181] According to the method described above, under normal management conditions, the concentration of heavy metal Hg increases by 0.000038 mg / L; under extreme rainfall conditions, the concentration of heavy metal Hg increases by 0.00012 mg / L.

[0182] (4) Risk assessment;

[0183] According to the method described above in this invention, the evaluation standard is selected from the Class II standard value of surface water specified in the "Surface Water Environmental Quality Standard" (GB 3838-2002), and the evaluation standard for heavy metal mercury is 0.00005 mg / L. Calculated according to Equation 17, under normal management conditions, the environmental risk of heavy metal Hg is 0.76, with a risk level of no risk, and the risk assessment result is consistent with the actual situation of daily management; under extreme rainfall conditions, the environmental risk of heavy metal Hg is 2.4, with a risk level of moderate risk.

[0184] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A risk assessment method for the impact of soil from water source areas on the water quality environment, characterized in that, Includes the following steps: Step 1: Basic Information Survey; Obtain basic environmental data of the water source area; Step 2: Risk Identification; Based on basic information, pollutants that pose a potential risk to the quality of water sources are screened as potential pollutants, their types and concentration distribution are identified, and risk factors and types are determined. Step 3: Calculate migration flux; determine rainfall erosivity factor, soil erodibility factor, slope length factor, slope factor, vegetation cover factor and potential pollutant factor, convert them into uniform resolution raster data, calculate pollutant migration modulus under routine management conditions and extreme rainfall conditions, and merge raster data to obtain the migration flux of potential pollutants from soil in water source area to reservoir water body. Step 4: Consequence Calculation; For extreme rainfall scenarios, calculate the increased concentration of pollution indicators by combining pollutant migration, flood discharge, and effective reservoir volume; For routine management scenarios, obtain a numerical model of the release pattern of potential pollutants in sediments by fitting sediment sample release kinetics experiments, and calculate the increased concentration of pollution indicators in local and overall reservoir capacity by combining cycle time and annual soil erosion. Step 5: Risk assessment; Based on the consequences 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; In the calculation of the consequences, the formula for extreme rainfall scenarios is as follows: ； In the formula: The concentration of a single pollution indicator is increased due to the influence of potential pollutants in the soil. This represents the amount of potential pollutants that migrated from the soil on a given day under extreme rainfall conditions. This refers to the reservoir's discharge flow rate on that day under extreme rainfall conditions. The effective volume of the reservoir; In the consequence calculation, the numerical model for the release pattern of potential pollutants from sediments under routine management conditions is fitted using the following formula: or ; In the formula: t represents the concentration in the solution at time t; a and b are constants derived from a numerical simulation model of the release patterns of potential pollutants. Release time; The impact of sediments in the reservoir on the water quality of the local water source area is calculated using the following formula: or ; In the formula: The concentration of a single pollution indicator increases in a localized area due to the influence of potential pollutants in the soil; a and b are constants derived from a numerical simulation model of the release pattern of potential pollutants. The time required for one actual reservoir capacity cycle under normal operating conditions; The formula for calculating the concentration of pollutants that have diffused from a local area to the entire reservoir capacity is as follows: ； ； In the formula: This refers to the annual soil erosion. Let be the annual soil erosion modulus of the i-th grid; n be the number of grids; and s be the projected area of ​​the grid. The concentration of a single pollution indicator increases due to the influence of potential pollutants in the soil. The effective volume of the reservoir; The solid-liquid ratio used to conduct pollutant release kinetics experiments.

2. The risk assessment method for the impact of water source soil on water quality environment according to claim 1, characterized in that, The migration flux calculation is based on the following formula: ； ； In the formula, A is the potential pollutant migration modulus; a is the soil erosion modulus; p is the 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; and 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, characterized in that, The rainfall erosivity factor R includes the rainfall erosivity factor under routine management conditions. and rainfall erosivity factor , Calculated based on bi-weekly or monthly rainfall data, Calculated based on daily rainfall during extreme rainfall events.

4. The risk assessment method for the impact of water source soil on water quality environment according to claim 1, characterized in that, In the aforementioned risk assessment, if multiple potential pollutants exist, the formula for calculating the soil environmental risk index of the water source area is as follows: ； In the formula: r is the soil environmental risk index of the water source area; This is a single-factor risk index for potential soil pollutant i, where The concentration of a single pollution indicator increases due to the influence of potential pollutants in the soil. The evaluation criteria for potential pollutant i; Based on the soil environmental risk index r of water source areas, the soil environmental risk assessment results of water source areas are divided into: no risk, r≤1; slight risk, 1<r≤2; moderate risk, 2<r≤3; and severe risk, r>3.

5. A risk assessment system for the impact of water source soil on water quality environment, implementing the method of any one of claims 1-4, characterized in that, include: The data acquisition module is used to acquire basic environmental status data of the water source area; The risk identification module is used to screen pollutants that pose a potential risk to the quality of water sources based on basic information, identify their types and concentration distribution, and determine the risk factors and types. The migration flux calculation module is used to calculate the migration flux of potential pollutants from the soil of the water source to the reservoir water body under routine management conditions and extreme rainfall conditions; The consequences calculation module is used to calculate the increase in pollution index concentrations under routine management conditions and extreme rainfall conditions; The risk assessment module is used to evaluate the risk level and output the results.

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