High temporal-spatial resolution risk assessment method for agricultural non-point source pollution in plain river network region

Abstract

The invention discloses a high temporal-spatial resolution risk assessment method for agricultural non-point source pollution in a plain river network region. The method comprises the following steps: selecting an assessment region; dividing evaluation units; selecting an evaluation time period; basic data collection and necessary supplementary monitoring of an evaluation area; agricultural non-point source pollution in-river load accounting; evaluating the bearing capacity of the riverway on non-point source pollution; calculating evaluation indexes; carrying out risk grade delimiting; compiling a priority treatment area list; agricultural non-point source pollution control measures are implemented; and evaluating agricultural non-point source pollution prevention and control performance. The polder area and the irrigation and drainage area are used as agricultural non-point source pollution risk last-stage evaluation units, so that the spatial resolution of agricultural non-point source pollution risk evaluation is greatly improved; a monthly risk assessment method is provided, and the time resolution of agricultural non-point source pollution risk assessment is greatly improved; a land and water linkage evaluation index system is adopted, excessive adoption of weights is avoided, the index meaning is clear, and targeted accurate recognition of a key source area is achieved through mutual verification of different indexes.

Description

Technical Field

[0001] The invention relates to the technical field of pollution prevention and control, and in particular to a high temporal and spatial resolution risk assessment method for agricultural non-point source pollution in plain river network areas. Background Art

[0002] In recent years, the country has attached great importance to the work related to the prevention and control of agricultural non-point source pollution.

[0006] At present, the existing schemes fail to fully consider the river network and agricultural production characteristics in plain river network areas, and are not closely linked to the practice of agricultural non-point source pollution prevention and control. The following main problems exist:

[0007] (1) Unclear evaluation unit: Existing agricultural non-point source pollution risk assessment (key source area identification) methods mostly use watersheds and sub-watersheds as evaluation units. However, plain river network areas are low-lying and the relationship between the upstream and downstream of the river is unclear. The boundaries and outlets of the watersheds in plain river network areas are unclear, and it is impossible to strictly divide the watersheds or sub-watersheds. The concept of watershed is not applicable. Therefore, the evaluation units used in the above methods are not applicable in plain river network areas.

[0008] (2) Basic data is difficult to collect: Existing methods mostly quantify the influencing factors related to precipitation, soil and topography through formula calculation or model simulation, and superimpose various influencing indicators through weighting method to carry out risk assessment. There is a lot of basic data to be collected, the evaluation results lack clear physical meaning, the calculation is difficult, and the accuracy is difficult to verify.

[0009] (3) The time scale is not precise enough: the existing methods are not precise enough in the time scale of agricultural non-point source risk assessment. Most of them adopt an annual assessment method or even a static assessment. However, the risk caused by agricultural non-point source pollution has obvious seasonal fluctuation characteristics. There are significant differences between the flood season and the non-flood season, and the farming season and the non-farming season. There is a lack of more refined assessment methods on a monthly scale.

[0010] (4) The concepts are abstract and impractical: Some methods are difficult to propose specific work goals for transforming high-risk areas of agricultural non-point source pollution into medium- or low-risk areas through the implementation of control measures. This is because the existing methods do not fully consider the actual emission intensity of non-point source pollution with high temporal and spatial resolution and the surrounding water environment capacity. The resulting evaluation indicators are relatively abstract and difficult to guide pollution control practices. Summary of the invention

[0011] The purpose of the present invention is to solve the technical problems of improving the spatiotemporal resolution of risk assessment of agricultural non-point source pollution in plain river network areas and the shortcomings that the traditional method uses watershed / sub-watershed or administrative area as the evaluation unit in terms of spatial scale, which is no longer applicable in plain river network areas. The proposed high spatiotemporal resolution risk assessment method for agricultural non-point source pollution in plain river network areas directly addresses the relatively weak links in current management and research work, and is the first to propose a refined risk assessment method for agricultural non-point source pollution suitable for plain river network areas. It has also carried out example applications in three typical research areas in Shanghai, drawn risk zoning maps at the scale of the town's polder area and irrigation and drainage area, and guided the practice of agricultural non-point source pollution prevention and control.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions:

[0013] The high spatiotemporal resolution risk assessment method for agricultural non-point source pollution in plain river network areas includes the following specific steps:

[0014] S1: Selection of assessment area: The assessment area is the town (village, street) level or above administrative unit in the plain river network area. The assessment area can be selected as: a single or multiple provinces (or administrative units of the same level, such as municipalities, etc., the same below), a single or multiple towns (or administrative units of the same level, such as townships, streets, etc., the same below) located in the plain river network area; if multiple administrative units of the same level are used as the assessment area, each administrative unit can belong to different upper-level administrative units;

[0015] S2: Division of evaluation units: The evaluation units are the town (township, street) level or above administrative units, polder areas (water conservancy control units), and irrigation and drainage areas (agricultural production units) in plain river network areas, and agricultural non-point source pollution risk assessment is carried out for the same level / same evaluation units; the boundaries of administrative units shall be based on the information released by government departments, the boundaries of polder areas shall be based on the information held by water affairs (water conservancy) departments, and the boundaries of irrigation and drainage areas shall be based on the information held by agricultural and rural departments; the area of ​​administrative units at all levels should be larger than the area of ​​polder areas and irrigation and drainage areas. In some plain river network areas, the area of ​​polder areas or irrigation and drainage areas is larger than that of administrative units such as towns, and towns are no longer used as evaluation units;

[0016] S3: Selection of assessment period: One month or multiple consecutive months, one natural year or multiple consecutive natural years are used as the assessment period. It is recommended to conduct agricultural non-point source pollution risk assessment on a monthly basis, so as to compare and analyze the agricultural non-point source pollution risks during the flood season and non-flood season, crop cultivation period and fallow period, aquaculture pond cleaning period, and different seasons.

[0017] S4: Collection of basic data and necessary supplementary monitoring in the assessment area: Collect basic data such as agricultural production data (planting, aquatic products and livestock and poultry breeding), water conservancy industry data, hydrological data, water quality data, geographic information data, agricultural non-point source pollution-related data, basic data of the ecological environment industry, surveying and mapping data, meteorological data, soil data, engineering planning data, and the establishment of various demonstration pilot projects in the assessment area, and conduct necessary supplementary monitoring of river water quality, water level and flow, localized inflow coefficient of agricultural non-point source pollution in the assessment area during the assessment period, and important information on necessary agricultural production activities;

[0018] S5: Calculation of agricultural non-point source pollution into river load: The river inflow coefficient method (also known as the export coefficient method) is used to calculate the river inflow load of non-point source pollution from the crop industry (including paddy fields, dry land, greenhouses, gardens, woodlands and grasslands, etc.), aquatic products and livestock and poultry breeding industries in each assessment unit. The river inflow coefficients of various types of agricultural land in the assessment area are calculated and filled in the localized river inflow coefficient list. Then, the river inflow load of the crop industry, aquatic products and livestock and poultry breeding industries is estimated based on the area of ​​each agricultural land, the output of breeding ponds or the stock / output of livestock and poultry breeding. The calculation method of the agricultural non-point source pollution into river load of the assessment unit is as follows. The monthly river inflow load of agricultural non-point source pollution of a certain water quality factor of the assessment unit is calculated using formula (1):

[0019] L eu =L p +L a +L 1 (1);

[0020] S5.1: Calculation of the river load of agricultural non-point source pollution: Select typical river discharge outlets in the evaluation unit to set up monitoring points for measurement, and use Doppler flowmeters to automatically monitor the real-time flow of the river discharge outlets online at high frequency to fully capture the entire process of agricultural non-point source pollution discharge events. In terms of water quality, automatic sampling or automatic monitoring is recommended, and manual sampling is also acceptable; the relevant calculation formula is as follows: The monthly river load calculation formula for agricultural non-point source pollution of a certain water quality factor in the evaluation unit is as follows:

[0021]

[0022] S5.2: Calculation of river load of non-point source pollution from aquaculture: The calculation of the coefficient of non-point source pollution from aquaculture also adopts the coordinated monitoring method of hydrology and water quality. Monitoring points are set up at typical river discharge outlets in the evaluation unit for calculation. The relevant calculation formula is as follows. The monthly calculation formula of non-point source pollution from aquaculture for a certain water quality factor in the evaluation unit is as follows:

[0023]

[0024] S5.3: Calculation of non-point source pollution from livestock and poultry breeding into river load: The calculation method of non-point source pollution from livestock and poultry breeding into river load on a monthly basis is as follows. The calculation formula of non-point source pollution from livestock and poultry breeding into river load on a certain water quality factor of the assessment unit is as follows:

[0025]

[0026] S6: Assessment of the carrying capacity of rivers for non-point source pollution: The carrying capacity of rivers for non-point source pollution is characterized by the water environment capacity of rivers. The water environment capacity of the river (river section) shared by two assessment units at the boundary is calculated half in each of the two assessment units; the accuracy of the calculation of the water environment capacity of each assessment unit mainly depends on the density of water quality monitoring points in the assessment area. All polder areas should have at least 3 water quality monitoring points, and all irrigation and drainage areas should have at least 1 water quality monitoring point. The seasonal fluctuation characteristics of river hydrology and water quality in plain river network areas are more significant. Refer to the overall compliance method for calculating the water environment capacity of small and medium-sized river networks with one-way flow specified in DB32 / T 4542, and calculate the water environment capacity of each level of assessment unit on a monthly basis. The specific method is as follows:

[0027] W i =2.592aQ(C s -C o )+3×10 -5 AHr s (5)

[0028]

[0029] S7: Calculation of evaluation indicators: Water quality coefficient, load coefficient and risk coefficient are used as the risk assessment indicators of agricultural non-point source pollution in Shanghai. The above three evaluation indicators respectively represent the comprehensive quality of river water environment, the intensity of land non-point source pollution emissions and the impact of non-point source pollution emissions on river water environment. The evaluation unit is used as the object of evaluation indicator calculation. The risk zoning and grading assessment results within the assessment period are comprehensively determined based on the calculation results of the evaluation indicators.

[0030] S7.1: Water quality factor: The water quality factor for the evaluation unit is calculated as follows:

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039] S7.2: Load Factor: The load factor for the evaluation unit is calculated as follows:

[0040]

[0041] S7.3: Risk Factor: The risk factor for the evaluation unit is calculated as follows:

[0042]

[0043] S7.4: Comprehensive risk indicators: First, normalize and calculate the three types of risk assessment indicators:

[0044]

[0045]

[0046]

[0047] The comprehensive index of agricultural non-point source pollution risk of the assessment unit is calculated as follows:

[0048] I i =a·I' Ri +b·I' Wi +c·I' Li (20);

[0049] S8: Risk level delineation: Sort the water quality coefficient, load coefficient, risk coefficient or comprehensive risk index of each evaluation unit in the assessment area from large to small, and determine the risk level by comparing their ranking order. The evaluation units ranked 0%-25%, 25%-50% (including 25%), 50%-75% (including 50%) and 75%-100% (including 75%) are respectively classified as low risk, medium risk, high risk and extremely high risk units; for evaluation units with negative water environment capacity, those with load coefficient values ​​greater than or equal to 1 are directly classified as extremely high risk areas, and those with load coefficient values ​​less than 1 are directly classified as high risk areas, and the risk level is no longer determined based on the ranking of the evaluation indicators;

[0050] S9: Preparation of the list of priority control areas: The list of priority control areas for agricultural non-point source pollution should include all extremely high-risk units as much as possible. Some high-risk assessment units can be added in combination with the actual needs of agricultural non-point source pollution reduction and river water quality improvement. At the same time, the priority control areas should be finally determined after comprehensive evaluation based on the short-term and medium-term work goals and supporting fund budget of agricultural non-point source pollution prevention and control in the assessment area. After the agricultural non-point source pollution prevention and control work is carried out in the priority control areas, the effectiveness of agricultural non-point source pollution control can be dynamically evaluated based on the dynamically updated risk assessment results, and the list of priority control areas can be continuously updated until the risk levels of extremely high-risk and high-risk areas are reduced to medium and low risks, and the list of priority control areas is gradually cleared;

[0051] S10: Implementation of agricultural non-point source pollution prevention and control measures: All relevant departments should coordinate multiple departments, take all factors and chains into consideration from the perspectives of green and high-quality agricultural development, recovery of river and lake ecological environment, construction of ecological civilization in the agricultural and rural areas, and optimization of national ecological space, and take comprehensive measures without affecting normal agricultural production activities and flood and drought prevention. Priority should be given to the implementation of low-impact agricultural non-point source pollution prevention and control measures with low input costs, low operation and maintenance costs, and closely related to existing work. The risk assessment methods proposed in S1-S9 can be used to determine the agricultural non-point source pollution load reduction targets, river water quality improvement targets, and water environment capacity (or water surface rate) improvement targets that must be achieved to reduce the risk level of the evaluation unit, so as to implement agricultural non-point source pollution prevention and control measures in a targeted manner in priority control areas. If agricultural non-point source pollution prevention and control funds have been secured, supporting prevention and control measures will be implemented in priority control areas according to the funding situation. If there is a funding gap, simultaneous application and implementation in stages can be made. If agricultural non-point source pollution prevention and control funds cannot be secured, non-point source pollution prevention and control can be promoted in combination with existing work, and existing work that promotes non-point source pollution reduction and river water quality improvement will be given priority in priority control areas.

[0052] S11: Performance evaluation of agricultural non-point source pollution prevention and control: During the implementation of agricultural non-point source pollution prevention and control measures, the prevention and control performance evaluation should be carried out in accordance with the technical methods of this guideline, and the evaluation results should be used to provide timely guidance for agricultural non-point source pollution prevention and control work, and to objectively evaluate the final work results to achieve a closed-loop work system.

[0053] As a further technical solution of the present invention, in S2, the main river channels, main roads (except elevated roads and bridges) and other elements should be combined to divide the evaluation units of the same level as the existing polder areas in the gravity flow area of ​​the assessment area, and the main factors such as agricultural production conditions, distribution of planting and rotation patterns, locations of irrigation water intakes and discharge outlets into rivers should be combined to divide the evaluation units of the same level as the existing irrigation and drainage areas in the agricultural land areas not included in the irrigation and drainage areas.

[0054] As a further technical solution of the present invention, in S5, the load of various agricultural non-point source pollution entering the river should adopt a unified accounting method system as much as possible, or refer to the existing emission coefficient list from the same official data source;

[0055] In formula (1): L eu is the monthly river load of agricultural non-point source pollution in a certain evaluation unit, in kilograms per month (kg / mo);

[0056] L p The monthly river load of non-point source pollution from crop production within the evaluation unit, in kilograms per month (kg / mo);

[0057] L a It is the monthly river load of non-point source pollution from aquaculture industry in the evaluation unit, in kilograms per month (kg / mo);

[0058] L l To evaluate the monthly river load of non-point source pollution from livestock and poultry breeding industry within the unit (excluding non-point source pollution from crop farming industry caused by returning biogas slurry to fields), the unit is kilogram per month (kg / mo).

[0059] As a further technical solution of the present invention, in S5.1, the method for calculating the coefficient of non-point source pollution entering the river from the planting industry (including paddy fields, dry land, gardens, greenhouses, woodlands and grasslands, etc.) refers to the hydrological and water quality collaborative monitoring method recommended in the "Technical Guidelines for Monitoring Non-point Source Pollution in Farmland in Plain River Network Areas (Trial) (Shanghai Environmental Science

[2023] No. 9)" issued by the Shanghai Municipal Ecological Environment Bureau;

[0060] In formula (2): i is the ordinal number of the plots (farmland) with the same land use type, planting type and rotation pattern in the evaluation unit;

[0061] I pi is the coefficient of non-point source pollution from crop production in the i-th plot within the evaluation unit, in kilograms per hectare per month (kg / (ha·mo));

[0062] A i is the area of ​​the ith plot in the evaluation unit, in hectares (ha);

[0063] n is the number of blocks in the evaluation unit.

[0064] As a further technical solution of the present invention, in S5.2, in formula (3):

[0065] i is the ordinal number of the plots (aquaculture ponds) with the same land use type and aquaculture species within the assessment unit;

[0066] I ai is the coefficient of aquaculture non-point source pollution entering the river for the ith plot, in kilograms per ton (kg / t);

[0067] q ai is the aquatic product output of the ith plot in one aquaculture cycle, in tons (t);

[0068] C ap It is the distribution coefficient of the river load of aquaculture non-point source pollution in a certain month (compared to a breeding cycle), and the unit is per month ( / month). It is recommended to determine the distribution coefficient based on the proportion of monthly discharge of aquaculture ponds, and the distribution coefficient of the month in which the pond cleaning period (fishing season) is located should be a high value;

[0069] n is the number of blocks in the evaluation unit.

[0070] As a further technical solution of the present invention, in S5.3, livestock and poultry farm waste shall not be discharged directly into the environment without treatment. The return of livestock and poultry manure to the fields shall be converted into non-point source pollution of the planting industry under the condition of complying with the Shanghai local standard DB31 / T 1137, and included in the scope of non-point source pollution into the river load of the planting industry, and the non-point source pollution caused by the direct discharge of livestock and poultry waste shall be ignored; if it does not meet the above specifications, it is necessary to consider the intensity of direct discharge of livestock and poultry pollutants into the environment separately, and its non-point source pollution into the river coefficient shall refer to the livestock and poultry scale breeding pollution coefficient and livestock and poultry breeder breeding pollution coefficient in the "Manual of Emission Source Statistical Survey Pollution Accounting Methods and Coefficients" (Announcement No. 24 of 2021) issued by the Ministry of Ecology and Environment in 2021, and converted into a monthly river entry coefficient;

[0071] In formula (4): i is the ordinal number of the plots (livestock and poultry breeding sheds) with the same land use type and livestock species within the evaluation unit;

[0072] I li规模 is the river entry coefficient of the ith plot of the large-scale livestock and poultry farm, in kilograms per head / feather (kg / (head / feather));

[0073] q li规模 is the stock / output quantity of the ith plot of livestock and poultry in large-scale breeding farms, in units of heads / feathers;

[0074] I li养殖户 is the river entry coefficient of the i-th plot of livestock and poultry farmers, in kilograms per head / feather per month (kg / (head / feather));

[0075] q li养殖户 is the stock / output quantity of livestock and poultry farmers in the ith plot, in units of heads / feathers;

[0076] C lp规模 It is the load distribution coefficient of livestock and poultry breeding non-point source pollution into the river for a certain type of livestock in a large-scale livestock and poultry breeding farm in a certain month (compared with the whole year), in units of per month ( / month);

[0077] C lp养殖户It is the load distribution coefficient of livestock and poultry breeding non-point source pollution into the river for a certain livestock and poultry breeding variety of livestock and poultry farmers in a certain month (compared with the whole year), in units of per month ( / month);

[0078] n is the number of blocks in the evaluation unit.

[0079] As a further technical solution of the present invention, in said S6, if the density of existing river water quality monitoring points cannot meet the calculation accuracy requirements of water environment capacity of the scale evaluation unit of the polder area and the irrigation and drainage area, water quality intensive monitoring should be carried out, and when selecting water quality monitoring points, the distribution of points in each evaluation unit should be ensured as much as possible; the water environment capacity is calculated based on the Class III and Class V water standards specified in GB3838 during the non-flood season and flood season respectively; if the Class III phenomenon of river water quality is relatively common during the flood season, the water environment capacity can be calculated based on the Class V water standard;

[0080] The seasonal fluctuation characteristics of river hydrology and water quality in plain river network areas are more obvious. Refer to the overall compliance method for calculating water environmental capacity in small and medium-sized river network areas with one-way flow specified in DB32 / T 4542, and calculate the water environmental capacity of each level of evaluation unit on a monthly basis. For details, see Appendix D formula (D.1) and formula (D.2);

[0081] In formula (5):

[0082] i is the ordinal number of the water body within the evaluation unit;

[0083] W i is the monthly water environment capacity of the ith water body in the evaluation unit, in kilograms per month (kg / mo);

[0084] a is the water body non-uniformity coefficient (dimensionless), for specific values, refer to Appendix B of DB32 / T 4542;

[0085] Q is the flow rate under the design hydrological conditions, in cubic meters per second (m 3 / s);

[0086] V is the volume of water under the design hydrological conditions, in cubic meters (m 3 );

[0087] C s is the water quality target for the functional area, expressed in milligrams per liter (mg / L);

[0088] C 0 is the pollutant concentration of upstream water, in milligrams per liter (mg / L);

[0089] In formula (6): Weu is the monthly water environment capacity of the evaluation unit, in kilograms per month (kg / mo);

[0090] n is the number of water bodies in the evaluation unit.

[0091] As a further technical solution of the present invention, in S7.1, in formulas (7)-(14):

[0092] RPI i,TP is the total phosphorus coefficient (dimensionless) of the ith water quality section in the evaluation unit. The water quality section here refers to the water quality section of the river located in a certain evaluation unit or at the boundary (the same below);

[0093] c i,TP is the total phosphorus concentration of the ith water quality section in the assessment unit (mg / L);

[0094] c t,TP is the water quality concentration threshold of total phosphorus, in milligrams per liter (mg / L), which is 0.2 mg / L according to the Class III water standard of GB 3838;

[0095] c i,NH4 is the ammonia nitrogen concentration of the ith water quality section in the evaluation unit (mg / L);

[0096] c t,NH4 is the water quality concentration threshold of ammonia nitrogen, in milligrams per liter (mg / L), which is 1.0 mg / L according to the Class III water standard of GB 3838;

[0097] c i,TN is the total nitrogen concentration of the ith water quality section in the evaluation unit (mg / L);

[0098] c t,TN is the water quality concentration threshold of total nitrogen, in milligrams per liter (mg / L), and is taken as 2.0 mg / L with reference to GB 3838;

[0099] RPI i,TP is the total phosphorus coefficient (dimensionless) of the ith water quality section in the evaluation unit;

[0100] RPI i,TN is the total nitrogen coefficient (dimensionless) of the ith water quality section in the evaluation unit;

[0101] RPI i,NH4 is the ammonia nitrogen coefficient of the ith water quality section in the evaluation unit (dimensionless);

[0102] RPI TP is the total phosphorus coefficient of the evaluation unit (dimensionless);

[0103] RPI TN is the total nitrogen coefficient of the evaluation unit (dimensionless);

[0104] RPI NH4is the ammonia nitrogen coefficient of the evaluation unit (dimensionless);

[0105] I w is the water quality coefficient of the evaluation unit (dimensionless); when total phosphorus, total nitrogen and ammonia nitrogen factors are considered, formula (13) is used; when total phosphorus and ammonia nitrogen factors are considered, formula (14) is used.

[0106] As a further technical solution of the present invention, in S7.2-S7.4, in formulas (15)-(20):

[0107] I L is the load factor of the evaluation unit (dimensionless);

[0108] L eu is the agricultural non-point source pollution load into the river of the assessment unit, in kilograms per month (kg / mo);

[0109] A eu is the area of ​​the evaluation unit in hectares (ha);

[0110] L is the agricultural non-point source pollution load into the river at the next higher administrative unit, in kilograms per month (kg / mo);

[0111] A is the area of ​​the upper level assessment unit or the entire assessment area, in hectares (ha);

[0112] I R is the risk factor of the evaluation unit (dimensionless);

[0113] L eu is the agricultural non-point source pollution load into the river of the assessment unit, in kilograms per month (kg / mo);

[0114] W eu The water environment capacity of the assessment unit, in kilograms per month (kg / mo). If it is less than or equal to 0, it will not be calculated;

[0115] I' Ri is the normalized risk coefficient of the ith evaluation unit (dimensionless);

[0116] I' Rmin , I' Rmax are the minimum and maximum (dimensionless) normalized risk coefficients of the i-th evaluation unit and the evaluation units of the same level;

[0117] I' Wi is the normalized water quality coefficient (dimensionless) of the ith evaluation unit;

[0118] I' Wmin , I' Wmaxare the minimum and maximum values ​​(dimensionless) of the normalized water quality coefficient of the i-th evaluation unit among the evaluation units of the same level;

[0119] I' Li is the normalized load factor of the ith evaluation unit (dimensionless);

[0120] I' Lmin , I' Lmax are the minimum and maximum (dimensionless) normalized load factors of the i-th evaluation unit and the evaluation units of the same level;

[0121] I i is the comprehensive risk index of the ith evaluation unit (dimensionless);

[0122] a is the risk factor weight (dimensionless); b is the water quality factor weight (dimensionless); c is the load factor weight (dimensionless); it is recommended to take: a=0.5, b=0.2, c=0.3 in areas where the water quality in the water environment functional zone meets the standards better, and take: a=0.5, b=0.3, c=0.2 in areas where the water quality in the water environment functional zone meets the standards worse.

[0123] As a further technical solution of the present invention, in S10, the preventive and control measures that can be implemented include but are not limited to: (ecological) high-standard farmland construction related to the work of agricultural and rural departments, new fertilization technologies and methods such as soil testing and formulation and side deep fertilization, optimization and adjustment of fertilizer nitrogen and phosphorus ratios, measures for returning biogas slurry to the field combined with farming and breeding, optimization of appropriate planting types and rotation patterns, promotion and application of water-saving and drought-resistant rice, agricultural green / organic certification, incentive measures for demonstration creation such as ecological farms and agricultural subsidy incentives, etc.; ecological clean small watershed construction, soil and water conservation measures, water-saving irrigation measures, drainage control measures, optimization and adjustment of field ditch and pond layout, river dredging and regulation, optimization and adjustment of river network water system and river blue line, local area river water dynamics enhancement and Duantou Bay connectivity, etc. related to the ecological environment department; ecological compensation fund incentives, river discharge outlet management, creation of "two mountains" bases, etc., agricultural non-point source pollution pilot monitoring and evaluation, etc.; comprehensive land improvement in the entire region, optimization of ecological space layout and ecological restoration of national land space, etc. related to the planning and resources department.

[0124] The beneficial effects of the present invention are:

[0125] 1. Taking the polder area (the basic unit of water conservancy control, with an average area of ​​about 5,000-10,000 mu) and the irrigation and drainage area (the basic unit of agricultural production, with an average area of ​​about 200-500 mu) as the evaluation units, the spatial resolution of the risk assessment of agricultural non-point source pollution can be greatly improved, and the assessment conclusions formed on this basis can guide the relevant departments to implement non-point source pollution prevention and control measures and river water quality improvement measures in a specific small area; conducting agricultural non-point source pollution risk assessment on a monthly basis can guide the precise implementation of pollution prevention and control policies, accurately identify the key source areas and high-risk periods of agricultural non-point source pollution, concentrate superior resources to fully reduce the non-point source pollution risks in high-risk areas during high-risk periods, and form non-point source pollution reduction targets and water environment capacity improvement targets for non-point source pollution prevention and control, providing technical support for the green and high-quality development of agriculture with one policy in one area.

[0126] 2. In terms of time scale, a method of conducting monthly risk assessment of agricultural non-point source pollution is proposed to take into account the impact of the seasonality of agricultural production and the seasonality of hydrological and meteorological conditions on the risk of agricultural non-point source pollution. Compared with previous annual assessment or static assessment methods, the temporal resolution of agricultural non-point source pollution risk assessment has been greatly improved.

[0127] 3. The evaluation indicators have clear concepts and strong operability. They can directly form the work objectives of non-point source pollution prevention and control, and have practical guiding significance for work practice. An evaluation indicator system based on water quality coefficient, load coefficient and risk coefficient is proposed to fully achieve water-land linkage and point-surface combination. Different indicators can verify each other, which is convenient for analyzing the impact of non-point source pollution emissions on the surrounding river water environment. Compared with existing methods, it avoids the use of complex model tools. Most of the basic data and data are mastered by relevant departments such as agriculture and rural areas, water affairs, ecological environment, planning resources, etc., which is very practical and convenient for subsequent promotion and application and transformation of patent results. BRIEF DESCRIPTION OF THE DRAWINGS

[0128] Figure 1 This is a diagram of the risk assessment method system for agricultural non-point source pollution in plain river network areas;

[0129] Figure 2 A map of joint prevention and control measures for various departments in areas with (extremely) high risk of agricultural non-point source pollution;

[0130] Figure 3 This is a flow chart for risk assessment of agricultural non-point source pollution in plain river network areas;

[0131] Figure 4 Apply the technology roadmap for this method case;

[0132] Figure 5 This is the risk factor (TP) map of irrigation and drainage area scale in Town 1;

[0133] Figure 6is the scale risk coefficient of irrigation and drainage area of ​​town 1 (NH 4 + -N) graph;

[0134] Figure 7 This is the risk factor (TP) map of irrigation and drainage area scale in Town 2;

[0135] Figure 8 is the irrigation and drainage area scale risk coefficient of town 2 (NH 4 + -N) graph;

[0136] Fig. 9 This is the irrigation and drainage area scale risk factor (TP) map of Town 3;

[0137] Fig.10 is the irrigation and drainage area scale risk coefficient of town 3 (NH 4 + -N) graph;

[0138] Fig.11 This is the application result diagram of town 3. DETAILED DESCRIPTION

[0139] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0140] Key terms explanation:

[0141] (1) Plain river network area: an area with dense river networks, crisscrossing water systems, flat and low-lying terrain, insufficient native water power, and where water conservancy engineering measures are often used for water conservancy regulation.

[0142] (2) Agricultural non-point source pollution: The pollution caused by the use of agricultural inputs such as fertilizers and pesticides, and the untimely or improper treatment of aquatic and livestock and poultry wastes, crop straw, etc. in the agricultural production process, which enters the receiving water body under the driving force of precipitation and irrigation, causes pollution to the ecological environment. The patent of this invention refers to agricultural non-point source pollution in a narrow sense, and focuses on the impact of non-point source pollution emissions on the river water environment, including planting industry (paddy fields, dry land and orchards, etc.), aquatic and livestock and poultry breeding, forestry and grassland non-point source pollution, but does not include rural domestic sewage and pollution caused by surface runoff from village houses.

[0143] (3) Polder area: A relatively closed flood control and drainage protection area formed by building embankments, sluice gates, pumping stations and other water conservancy projects in plain river networks or low-lying and flood-prone areas along rivers and lakes to prevent floods from outside and drain water from inside.

[0144] (4) Irrigation and drainage area: an area of ​​farmland with a certain guaranteed water source, a unified management entity, and controlled by a relatively complete irrigation and drainage engineering system.

[0145] (5) Evaluation unit: the basic unit for conducting risk assessment of agricultural non-point source pollution.

[0146] The agricultural non-point source pollution risk assessment units referred to in the patent of this invention are: administrative units of different levels such as provinces (municipalities, etc.), prefecture-level cities, urban districts (counties) and towns (townships, streets), water conservancy management and control units such as polder areas and gravity-flow areas, and agricultural production units such as irrigation and drainage areas and contiguous agricultural land.

[0147] (6) Export coefficient of farmland non-point source pollution discharged into the river: the amount of non-point source pollutants discharged into the downstream river through river outlets from farmland (including paddy fields, dry land, gardens and greenhouses), woodland or grassland of the same planting type per unit area per unit time.

[0148] (7) Export coefficient of aquaculture non-point source pollution discharged into the river: Under normal aquaculture production conditions, the amount of pollutants produced by one ton of aquatic products in one breeding cycle, which is directly discharged into the river through different discharge pathways.

[0149] (8) Export coefficient of livestock non-point source pollution discharged into the river: Under normal production and management conditions, the amount of original pollutants generated by a single livestock and poultry farm in one natural year that are not recycled and reduced by treatment facilities or are directly discharged into the river without being treated and utilized. It is divided into the export coefficient of livestock non-point source pollution discharged into the river by large-scale livestock and poultry farms and the export coefficient of livestock and poultry farmers.

[0150] (9) Environmental capacity of water bodies: The maximum amount of a pollutant that a water body can accommodate when the water quality target requirements of the calculated water body are met under the designed hydrological conditions (also known as the pollution absorption capacity).

[0151] (10) Risk grading: After evaluating the agricultural non-point source pollution risk assessment indicators of the assessment units, the risk level of the impact of agricultural non-point source pollution emissions on the water environment quality of surrounding rivers at each level of assessment units is divided into different regions.

[0152] (11) Critical source area: The area where the impact of agricultural non-point source pollution on the water environment quality of surrounding rivers exceeds a certain threshold. It is determined through comprehensive analysis and comparison based on the risk zoning and classification of the assessment unit.

[0153] The high spatiotemporal resolution risk assessment method for agricultural non-point source pollution in plain river network areas includes the following specific steps:

[0154] S1: Selection of assessment area: The assessment area is the town (village, street) level or above administrative unit in the plain river network area. The assessment area can be selected as: a single or multiple provinces (or administrative units of the same level, such as municipalities, etc., the same below), a single or multiple towns (or administrative units of the same level, such as townships, streets, etc., the same below) located in the plain river network area; if multiple administrative units of the same level are used as the assessment area, each administrative unit can belong to different upper-level administrative units;

[0155] S2: Division of evaluation units: The evaluation units are the town (township, street) level or above administrative units, polder areas (water conservancy control units), and irrigation and drainage areas (agricultural production units) in plain river network areas, and agricultural non-point source pollution risk assessment is carried out for the same level / same evaluation units; the boundaries of administrative units shall be based on the information released by government departments, the boundaries of polder areas shall be based on the information held by water affairs (water conservancy) departments, and the boundaries of irrigation and drainage areas shall be based on the information held by agricultural and rural departments; the area of ​​administrative units at all levels should be larger than the area of ​​polder areas and irrigation and drainage areas. In some plain river network areas, the area of ​​polder areas or irrigation and drainage areas is larger than that of administrative units such as towns, and towns are no longer used as evaluation units;

[0156] The assessment units of the same level as the existing polder areas should be divided in the gravity flow area of ​​the assessment area in combination with the main river channels and main roads (except elevated roads and bridges). The assessment units of the same level as the existing polder areas should be divided in the agricultural land areas not included in the irrigation and drainage areas in combination with the main factors such as agricultural production conditions, distribution of planting and rotation patterns, and locations of irrigation water intakes and river discharge outlets.

[0157] S3: Selection of assessment period: One month or multiple consecutive months, one natural year or multiple consecutive natural years are used as the assessment period. It is recommended to conduct agricultural non-point source pollution risk assessment on a monthly basis, so as to compare and analyze the agricultural non-point source pollution risks during the flood season and non-flood season, crop cultivation period and fallow period, aquaculture pond cleaning period, and different seasons.

[0158] S4: Collection of basic data and necessary supplementary monitoring in the assessment area: Collect basic data such as agricultural production data (planting, aquatic products and livestock and poultry breeding), water conservancy industry data, hydrological data, water quality data, geographic information data, agricultural non-point source pollution-related data, basic data of the ecological environment industry, surveying and mapping data, meteorological data, soil data, engineering planning data, and the establishment of various demonstration pilot projects in the assessment area, and conduct necessary supplementary monitoring of river water quality, water level and flow, localized inflow coefficient of agricultural non-point source pollution in the assessment area during the assessment period, and important information on necessary agricultural production activities;

[0159] The list of basic data required is shown in Table 1. For those marked with “*” and for which no data are available, appropriate supplementary monitoring should be carried out.

[0160] Table 1 Data required for risk assessment of agricultural non-point source pollution in plain river network areas

[0161]

[0162] Table 1 Data required for risk assessment of agricultural non-point source pollution in plain river network areas

[0163]

[0164] Table 1 Data required for risk assessment of agricultural non-point source pollution in plain river network areas

[0165]

[0166] S5: Calculation of river load of agricultural non-point source pollution: The river load of non-point source pollution entering the river of the crop industry (including paddy fields, dry land, greenhouses, gardens, woodlands and grasslands, etc.), aquatic products and livestock and poultry breeding industries in each assessment unit is calculated using the river load coefficient method (also known as the export coefficient method). The river load of various agricultural lands in the assessment area is calculated and filled in the localized river load coefficient list. Then, the river load of the crop industry, aquatic products and livestock and poultry breeding industries is estimated according to the area of ​​each agricultural land, the output of breeding ponds or the stock / output of livestock and poultry breeding.

[0167] The seasonal fluctuation characteristics of agricultural non-point source pollution emissions in plain river network areas are more significant. In order to refine the assessment of agricultural non-point source pollution risks in different time periods (such as flood season and non-flood season, crop cultivation period and fallow period, aquaculture pond cleaning period, different seasons, etc.), the agricultural non-point source pollution into the river coefficient is calculated monthly. If the time scale for calculating the river into the coefficient cannot meet the monthly requirements, the river into the coefficient can also be calculated on a yearly time scale, thereby forming a monthly river into the coefficient list;

[0168] The river loads of various agricultural non-point source pollution should adopt a unified accounting method system as much as possible, or refer to the existing emission coefficient list from the same official data source;

[0169] The calculation method of agricultural non-point source pollution load into the river of the evaluation unit is as follows. The monthly agricultural non-point source pollution load into the river of a certain water quality factor of the evaluation unit is calculated using formula (1):

[0170] L eu =L p +L a +L 1 (1);

[0171] In formula (1): L eu is the monthly river load of agricultural non-point source pollution in a certain evaluation unit, in kilograms per month (kg / mo);

[0172] L p The monthly river load of non-point source pollution from crop production within the evaluation unit, in kilograms per month (kg / mo);

[0173] L a It is the monthly river load of non-point source pollution from aquaculture industry in the evaluation unit, in kilograms per month (kg / mo);

[0174] L l To evaluate the monthly river load of non-point source pollution from livestock and poultry breeding in the unit (excluding non-point source pollution from crop farming caused by returning biogas slurry to fields), in kilograms per month (kg / mo);

[0175] S5.1: Calculation of non-point source pollution entering the river from the planting industry: The calculation method of the non-point source pollution entering the river from the planting industry (including paddy fields, dry land, gardens, greenhouses, woodlands and grasslands, etc.) refers to the hydrological and water quality coordinated monitoring method recommended in the "Technical Guidelines for Monitoring Non-point Source Pollution in Farmland in Plain River Network Areas (Trial) (Shanghai Environmental Protection Bureau

[2023] No. 9)" issued by the Shanghai Municipal Ecological Environment Bureau;

[0176] In the evaluation unit, typical river discharge outlets are selected to set up monitoring points for measurement. The real-time flow of the river discharge outlets is automatically monitored online with a Doppler flowmeter at high frequency to fully capture the entire process of agricultural non-point source pollution emission events. In terms of water quality, automatic sampling or automatic monitoring is recommended, and manual sampling is also acceptable.

[0177] The relevant calculation formula is as follows: The calculation formula for the monthly river load of non-point source pollution from the planting industry for a certain water quality factor in the evaluation unit is as follows:

[0178]

[0179] In formula (2): i is the ordinal number of the plots (farmland) with the same land use type, planting type and rotation pattern in the evaluation unit;

[0180] I pi is the coefficient of non-point source pollution from crop production in the i-th plot within the evaluation unit, in kilograms per hectare per month (kg / (ha·mo));

[0181] A i is the area of ​​the ith plot in the evaluation unit, in hectares (ha);

[0182] n is the number of plots in the evaluation unit;

[0183] Table 2 List of localized river entry coefficients of agricultural non-point source pollution

[0184]

[0185] Table 2 List of localized river entry coefficients of agricultural non-point source pollution

[0186]

[0187] S5.2: Calculation of river load of non-point source pollution from aquaculture: The calculation of the coefficient of non-point source pollution from aquaculture also adopts the coordinated monitoring method of hydrology and water quality. Monitoring points are set up at typical river discharge outlets in the evaluation unit for calculation. The relevant calculation formula is as follows. The monthly calculation formula of non-point source pollution from aquaculture for a certain water quality factor in the evaluation unit is as follows:

[0188]

[0189] In formula (3):

[0190] i is the ordinal number of the plots (aquaculture ponds) with the same land use type and aquaculture species within the assessment unit;

[0191] I ai is the coefficient of aquaculture non-point source pollution entering the river for the ith plot, in kilograms per ton (kg / t);

[0192] q ai is the aquatic product output of the ith plot in one aquaculture cycle, in tons (t);

[0193] C apIt is the distribution coefficient of the river load of aquaculture non-point source pollution in a certain month (compared to a breeding cycle), and the unit is per month ( / month). It is recommended to determine the distribution coefficient based on the proportion of monthly discharge of aquaculture ponds, and the distribution coefficient of the month in which the pond cleaning period (fishing season) is located should be a high value;

[0194] n is the number of plots in the evaluation unit;

[0195] S5.3: Calculation of non-point source pollution entering rivers from livestock and poultry breeding: Waste from livestock and poultry farms shall not be discharged directly into the environment without treatment. The return of livestock and poultry manure to the fields shall be converted into non-point source pollution from the crop industry if it complies with the Shanghai local standard DB31 / T 1137 and is included in the scope of non-point source pollution entering rivers from the crop industry, while non-point source pollution caused by direct discharge of livestock and poultry breeding waste shall not be taken into account. If the above standards are not met, the intensity of direct discharge of livestock and poultry pollutants into the environment shall be considered separately, and the non-point source pollution entering rivers coefficient shall refer to the pollution discharge coefficient of large-scale livestock and poultry breeding and the pollution discharge coefficient of livestock and poultry breeders in the "Handbook of Pollution Calculation Methods and Coefficients for Emission Source Statistical Surveys" (Announcement No. 24 of 2021) issued by the Ministry of Ecology and Environment in 2021, and converted into a monthly river discharge coefficient;

[0196] The calculation method of the monthly river load of livestock and poultry breeding non-point source pollution is as follows. The calculation formula of the monthly river load of livestock and poultry breeding non-point source pollution for a certain water quality factor of the evaluation unit is as follows:

[0197]

[0198] In formula (4): i is the ordinal number of the plots (livestock and poultry breeding sheds) with the same land use type and livestock species within the evaluation unit;

[0199] I li规模 is the river entry coefficient of the ith plot of the large-scale livestock and poultry farm, in kilograms per head / feather (kg / (head / feather));

[0200] q li规模 is the stock / output quantity of the ith plot of livestock and poultry in large-scale breeding farms, in units of heads / feathers;

[0201] I li养殖户 is the river entry coefficient of the i-th plot of livestock and poultry farmers, in kilograms per head / feather per month (kg / (head / feather));

[0202] q li养殖户 is the stock / output quantity of livestock and poultry farmers in the ith plot, in units of heads / feathers;

[0203] C lp规模 It is the load distribution coefficient of livestock and poultry breeding non-point source pollution into the river for a certain type of livestock in a large-scale livestock and poultry breeding farm in a certain month (compared with the whole year), in units of per month ( / month);

[0204] Clp养殖户 It is the load distribution coefficient of livestock and poultry breeding non-point source pollution into the river for a certain livestock and poultry breeding variety of livestock and poultry farmers in a certain month (compared with the whole year), in units of per month ( / month);

[0205] n is the number of plots in the evaluation unit;

[0206] S6: Assessment of the carrying capacity of rivers for non-point source pollution: The carrying capacity of rivers for non-point source pollution is characterized by the water environment capacity of rivers. The water environment capacity of the river (river section) shared by two evaluation units at the boundary is calculated half in each of the two evaluation units. The accuracy of the calculation of the water environment capacity of each evaluation unit mainly depends on the density of water quality monitoring points in the evaluation area. All polder areas should have at least 3 water quality monitoring points, and all irrigation and drainage areas should have at least 1 water quality monitoring point. Existing water quality assessment sections;

[0207] If the density of existing river water quality monitoring points cannot meet the accuracy requirements for calculating the water environment capacity of the evaluation unit at the scale of the polder area and irrigation and drainage area, water quality intensification monitoring should be carried out, and the distribution of points in each evaluation unit should be as uniform as possible when selecting water quality monitoring points; the water environment capacity should be calculated based on the Class III and Class V water standards specified in GB 3838 during the non-flood season and flood season respectively; if the phenomenon of Class III water quality in the river during the flood season is relatively common, the water environment capacity can be calculated based on the Class V water standard;

[0208] The seasonal fluctuation characteristics of river hydrology and water quality in plain river network areas are more obvious. Refer to the overall compliance method for calculating water environmental capacity in small and medium-sized river network areas with one-way flow specified in DB32 / T 4542, and calculate the water environmental capacity of each level of evaluation unit on a monthly basis. For details, see Appendix D formula (D.1) and formula (D.2);

[0209] The seasonal fluctuation characteristics of river hydrology and water quality in plain river network areas are more obvious. Referring to the overall compliance method for calculating water environmental capacity in small and medium-sized river network areas with one-way flow specified in DB32 / T 4542, the water environmental capacity of each level of evaluation unit is calculated monthly. The specific method is as follows:

[0210] W i =2.592aQ(C s -C o )+3×10 -5 AHr s (5)

[0211] In formula (5):

[0212] i is the ordinal number of the water body within the evaluation unit;

[0213] W i is the monthly water environment capacity of the ith water body in the evaluation unit, in kilograms per month (kg / mo);

[0214] a is the water body non-uniformity coefficient (dimensionless), for specific values, refer to Appendix B of DB32 / T 4542;

[0215] Q is the flow rate under the design hydrological conditions, in cubic meters per second (m 3 / s);

[0216] V is the volume of water under the design hydrological conditions, in cubic meters (m 3 );

[0217] C s is the water quality target for the functional area, expressed in milligrams per liter (mg / L);

[0218] C 0 is the pollutant concentration of upstream water, in milligrams per liter (mg / L);

[0219]

[0220] In formula (6): Weu is the monthly water environment capacity of the evaluation unit, in kilograms per month (kg / mo);

[0221] n is the number of water bodies in the evaluation unit;

[0222] S7: Calculation of evaluation indicators: Water quality coefficient, load coefficient and risk coefficient are used as the risk assessment indicators of agricultural non-point source pollution in Shanghai. The above three evaluation indicators respectively represent the comprehensive quality of river water environment, the intensity of land non-point source pollution emissions and the impact of non-point source pollution emissions on river water environment. The evaluation unit is used as the object of evaluation indicator calculation. The risk zoning and grading assessment results within the assessment period are comprehensively determined based on the calculation results of the evaluation indicators.

[0223] S7.1: Water quality factor: The water quality factor for the evaluation unit is calculated as follows:

[0224]

[0225]

[0226]

[0227]

[0228]

[0229]

[0230]

[0231]

[0232] In formulas (7)-(14):

[0233] RPI i,TP is the total phosphorus coefficient (dimensionless) of the ith water quality section in the evaluation unit. The water quality section here refers to the water quality section of the river located in a certain evaluation unit or at the boundary (the same below);

[0234] c i,TP is the total phosphorus concentration of the ith water quality section in the assessment unit (mg / L);

[0235] c t,TP is the water quality concentration threshold of total phosphorus, in milligrams per liter (mg / L), which is 0.2 mg / L according to the Class III water standard of GB 3838;

[0236] c i,NH4 is the ammonia nitrogen concentration of the ith water quality section in the evaluation unit (mg / L);

[0237] c t,NH4 is the water quality concentration threshold of ammonia nitrogen, in milligrams per liter (mg / L), which is 1.0 mg / L according to the Class III water standard of GB 3838;

[0238] c i,TN is the total nitrogen concentration of the ith water quality section in the evaluation unit (mg / L);

[0239] c t,TN is the water quality concentration threshold of total nitrogen, in milligrams per liter (mg / L), and is taken as 2.0 mg / L with reference to GB 3838;

[0240] RPI i,TP is the total phosphorus coefficient (dimensionless) of the ith water quality section in the evaluation unit;

[0241] RPI i,TN is the total nitrogen coefficient (dimensionless) of the ith water quality section in the evaluation unit;

[0242] RPI i,NH4 is the ammonia nitrogen coefficient of the ith water quality section in the evaluation unit (dimensionless);

[0243] RPI TP is the total phosphorus coefficient of the evaluation unit (dimensionless);

[0244] RPI TN is the total nitrogen coefficient of the evaluation unit (dimensionless);

[0245] RPI NH4 is the ammonia nitrogen coefficient of the evaluation unit (dimensionless);

[0246] Iw is the water quality coefficient of the evaluation unit (dimensionless); when total phosphorus, total nitrogen and ammonia nitrogen factors are considered, formula (13) is used; when total phosphorus and ammonia nitrogen factors are considered, formula (14) is used;

[0247] S7.2: Load Factor: The load factor for the evaluation unit is calculated as follows:

[0248]

[0249] S7.3: Risk Factor: The risk factor for the evaluation unit is calculated as follows:

[0250]

[0251] S7.4: Comprehensive risk indicators: First, normalize and calculate the three types of risk assessment indicators:

[0252]

[0253]

[0254]

[0255] The comprehensive index of agricultural non-point source pollution risk of the assessment unit is calculated as follows:

[0256] I i =a·I' Ri +b·I' Wi +c·I' Li (20);

[0257] In formulas (15)-(20):

[0258] I L is the load factor of the evaluation unit (dimensionless);

[0259] L eu is the agricultural non-point source pollution load into the river of the assessment unit, in kilograms per month (kg / mo);

[0260] A eu is the area of ​​the evaluation unit in hectares (ha);

[0261] L is the agricultural non-point source pollution load into the river at the next higher administrative unit, in kilograms per month (kg / mo);

[0262] A is the area of ​​the upper level assessment unit or the entire assessment area, in hectares (ha);

[0263] I R is the risk factor of the evaluation unit (dimensionless);

[0264] L eu is the agricultural non-point source pollution load into the river of the assessment unit, in kilograms per month (kg / mo);

[0265] W eu The water environment capacity of the assessment unit, in kilograms per month (kg / mo). If it is less than or equal to 0, it will not be calculated;

[0266] I' Ri is the normalized risk coefficient of the ith evaluation unit (dimensionless);

[0267] I' Rmin , I' Rmax are the minimum and maximum (dimensionless) normalized risk coefficients of the i-th evaluation unit and the evaluation units of the same level;

[0268] I' Wi is the normalized water quality coefficient (dimensionless) of the ith evaluation unit;

[0269] I' Wmin , I' Wmax are the minimum and maximum values ​​(dimensionless) of the normalized water quality coefficient of the i-th evaluation unit among the evaluation units of the same level;

[0270] I' Li is the normalized load factor of the ith evaluation unit (dimensionless);

[0271] I' Lmin , I' Lmax are the minimum and maximum (dimensionless) normalized load factors of the i-th evaluation unit and the evaluation units of the same level;

[0272] I i is the comprehensive risk index of the ith evaluation unit (dimensionless);

[0273] a is the risk factor weight (dimensionless); b is the water quality factor weight (dimensionless); c is the load factor weight (dimensionless); it is recommended that in areas where the water quality of the water environment functional zone meets the standard better, a=0.5, b=0.2, c=0.3 are used; in areas where the water quality of the water environment functional zone meets the standard worse, a=0.5, b=0.3, c=0.2 are used;

[0274] The risk assessment method system of agricultural non-point source pollution in plain river network areas is as follows: Figure 1 As shown;

[0275] S8: Risk level delineation: Sort the water quality coefficient, load coefficient, risk coefficient or comprehensive risk index of each evaluation unit in the assessment area from large to small, and determine the risk level by comparing their ranking order. The evaluation units ranked 0%-25%, 25%-50% (including 25%), 50%-75% (including 50%) and 75%-100% (including 75%) are respectively classified as low risk, medium risk, high risk and extremely high risk units; for evaluation units with negative water environment capacity, those with load coefficient values ​​greater than or equal to 1 are directly classified as extremely high risk areas, and those with load coefficient values ​​less than 1 are directly classified as high risk areas, and the risk level is no longer determined based on the ranking of the evaluation indicators;

[0276] S9: Preparation of a list of priority areas for governance: The list of priority areas for governance of agricultural non-point source pollution should include as many extremely high-risk units as possible. In combination with the actual needs of agricultural non-point source pollution reduction and river water quality improvement, some high-risk assessment units can be added. At the same time, the priority governance areas should be finally determined after comprehensive evaluation based on the short-term and medium-term work objectives and supporting funding budget of the agricultural non-point source pollution prevention and control in the assessment area. After carrying out agricultural non-point source pollution prevention and control work in the priority governance areas, the effectiveness of agricultural non-point source pollution control can be dynamically evaluated based on the dynamically updated risk assessment results, and the list of priority governance areas can be continuously updated until the risk levels of extremely high-risk and high-risk areas are reduced to medium and low risks, and the list of priority governance areas is gradually cleared.

[0277] S10: Implementation of agricultural non-point source pollution prevention and control measures: All relevant departments should coordinate multiple departments, take all factors and chains into consideration from the perspectives of green and high-quality agricultural development, recovery of river and lake ecological environment, construction of ecological civilization in the agricultural and rural areas, and optimization of national ecological space, and take comprehensive measures without affecting normal agricultural production activities and flood and drought prevention. Priority should be given to the implementation of low-impact agricultural non-point source pollution prevention and control measures with low input costs, low operation and maintenance costs, and closely related to existing work. The risk assessment methods proposed in S1-S9 can be used to determine the agricultural non-point source pollution load reduction targets, river water quality improvement targets, and water environment capacity (or water surface rate) improvement targets that must be achieved to reduce the risk level of the evaluation unit, so as to implement agricultural non-point source pollution prevention and control measures in a targeted manner in priority control areas. If agricultural non-point source pollution prevention and control funds have been secured, supporting prevention and control measures will be implemented in priority control areas according to the funding situation. If there is a funding gap, simultaneous application and implementation in stages can be made. If agricultural non-point source pollution prevention and control funds cannot be secured, non-point source pollution prevention and control can be promoted in combination with existing work, and existing work that promotes non-point source pollution reduction and river water quality improvement will be given priority in priority control areas.

[0278] The feasible prevention and control measures include but are not limited to: (ecological) high-standard farmland construction, soil testing and formulation, side deep fertilization and other new fertilization technologies and methods, fertilizer nitrogen and phosphorus ratio optimization, farming and breeding combined biogas slurry return to the field measures, appropriate planting types and rotation mode optimization, promotion and application of water-saving and drought-resistant rice, agricultural green / organic certification, ecological farms and other demonstration creation incentives and agricultural subsidy incentives related to the work of the agricultural and rural departments; ecological clean small watershed construction, soil and water conservation measures, water-saving irrigation measures, drainage control measures, field ditch and pond layout optimization and adjustment, river dredging and regulation, river network and river blue line optimization and adjustment, local area river water dynamics enhancement and Duantou Bay connection related to the ecological environment department; ecological compensation fund incentives, river discharge outlet management, "two mountains" base creation, agricultural non-point source pollution pilot monitoring and evaluation related to the planning and resources department; comprehensive land improvement in the whole region, ecological space layout optimization and national land space ecological restoration related to the planning and resources department; see for details. Figure 2 .

[0279] S11: Performance evaluation of agricultural non-point source pollution prevention and control: During the implementation of agricultural non-point source pollution prevention and control measures, the prevention and control performance evaluation should be carried out in accordance with the technical methods of this guideline, and the evaluation results should be used to provide timely guidance for agricultural non-point source pollution prevention and control work, and to objectively evaluate the final work results to achieve a closed-loop work system.

[0280] Workflow and case application results: Risk assessment process of agricultural non-point source pollution in plain river network areas Figure 3 ;

[0281] The method proposed in this patent has been applied in three different areas: Town 1, Town 2 and Town 3. The technical route is as follows: Figure 4 ;

[0282] The application results of the three towns are as follows: Figure 5-11 .

Claims

1. A high spatiotemporal resolution risk assessment method for agricultural non-point source pollution in plain river network areas, characterized by: The specific steps include: S1: Selection of assessment area: The assessment area is the town (village, street) level or above administrative unit in the plain river network area. The assessment area can be selected as: a single or multiple provinces (or administrative units of the same level, such as municipalities, etc., the same below), a single or multiple towns (or administrative units of the same level, such as townships, streets, etc., the same below) located in the plain river network area; if multiple administrative units of the same level are used as the assessment area, each administrative unit can belong to different upper-level administrative units; S2: Division of evaluation units: The evaluation units are the town (township, street) level or above administrative units, polder areas (water conservancy control units), and irrigation and drainage areas (agricultural production units) in plain river network areas, and agricultural non-point source pollution risk assessment is carried out for the same level / same evaluation units; the boundaries of administrative units shall be based on the information released by government departments, the boundaries of polder areas shall be based on the information held by water affairs (water conservancy) departments, and the boundaries of irrigation and drainage areas shall be based on the information held by agricultural and rural departments; the area of ​​administrative units at all levels should be larger than the area of ​​polder areas and irrigation and drainage areas. In some plain river network areas, the area of ​​polder areas or irrigation and drainage areas is larger than that of administrative units such as towns, and towns are no longer used as evaluation units; S3: Selection of assessment period: One month or multiple consecutive months, one natural year or multiple consecutive natural years are used as the assessment period. It is recommended to conduct agricultural non-point source pollution risk assessment on a monthly basis, so as to compare and analyze the agricultural non-point source pollution risks during the flood season and non-flood season, crop cultivation period and fallow period, aquaculture pond cleaning period, and different seasons. S4: Collection of basic data and necessary supplementary monitoring in the assessment area: Collect basic data such as agricultural production data (planting, aquatic products and livestock and poultry breeding), water conservancy industry data, hydrological data, water quality data, geographic information data, agricultural non-point source pollution-related data, basic data of the ecological environment industry, surveying and mapping data, meteorological data, soil data, engineering planning data, and the establishment of various demonstration pilot projects in the assessment area, and conduct necessary supplementary monitoring of river water quality, water level and flow, localized inflow coefficient of agricultural non-point source pollution in the assessment area during the assessment period, and important information on necessary agricultural production activities; S5: Calculation of agricultural non-point source pollution into river load: The river inflow coefficient method (also known as the export coefficient method) is used to calculate the river inflow load of non-point source pollution from the crop industry (including paddy fields, dry land, greenhouses, gardens, woodlands and grasslands, etc.), aquatic products and livestock and poultry breeding industries in each assessment unit. The river inflow coefficients of various types of agricultural land in the assessment area are calculated and filled in the localized river inflow coefficient list. Then, the river inflow load of the crop industry, aquatic products and livestock and poultry breeding industries is estimated based on the area of ​​each agricultural land, the output of breeding ponds or the stock / output of livestock and poultry breeding. The calculation method of the agricultural non-point source pollution into river load of the assessment unit is as follows. The monthly river inflow load of agricultural non-point source pollution of a certain water quality factor of the assessment unit is calculated using formula (1): L eu =L p +L a +L1 (1); S5.1: Calculation of the river load of agricultural non-point source pollution: Select typical river discharge outlets in the evaluation unit to set up monitoring points for measurement, and use Doppler flowmeters to automatically monitor the real-time flow of the river discharge outlets online at high frequency to fully capture the entire process of agricultural non-point source pollution discharge events. In terms of water quality, automatic sampling or automatic monitoring is recommended, and manual sampling is also acceptable; the relevant calculation formula is as follows: The monthly river load calculation formula for agricultural non-point source pollution of a certain water quality factor in the evaluation unit is as follows: S5.2: Calculation of river load of non-point source pollution from aquaculture: The calculation of the coefficient of non-point source pollution from aquaculture also adopts the coordinated monitoring method of hydrology and water quality. Monitoring points are set up at typical river discharge outlets in the evaluation unit for calculation. The relevant calculation formula is as follows. The monthly calculation formula of non-point source pollution from aquaculture for a certain water quality factor in the evaluation unit is as follows: S5.3: Calculation of non-point source pollution from livestock and poultry breeding into river load: The calculation method of non-point source pollution from livestock and poultry breeding into river load on a monthly basis is as follows. The calculation formula of non-point source pollution from livestock and poultry breeding into river load on a certain water quality factor of the assessment unit is as follows: S6: Assessment of the carrying capacity of rivers for non-point source pollution: The carrying capacity of rivers for non-point source pollution is characterized by the water environment capacity of rivers. The water environment capacity of the river (river section) shared by two assessment units at the boundary is calculated half in each of the two assessment units; the accuracy of the calculation of the water environment capacity of each assessment unit mainly depends on the density of water quality monitoring points in the assessment area. All polder areas should have at least 3 water quality monitoring points, and all irrigation and drainage areas should have at least 1 water quality monitoring point. The seasonal fluctuation characteristics of river hydrology and water quality in plain river network areas are more significant. Refer to the overall compliance method for calculating the water environment capacity of small and medium-sized river networks with one-way flow specified in DB32 / T 4542, and calculate the water environment capacity of each level of assessment unit on a monthly basis. The specific method is as follows: W i =2.592aQ(C s -C o )+3×10 -5 aKVC s (5) S7: Calculation of evaluation indicators: Water quality coefficient, load coefficient and risk coefficient are used as the risk assessment indicators of agricultural non-point source pollution in Shanghai. The above three evaluation indicators respectively represent the comprehensive quality of river water environment, the intensity of land non-point source pollution emissions and the impact of non-point source pollution emissions on river water environment. The evaluation unit is used as the object of evaluation indicator calculation. The risk zoning and grading assessment results within the assessment period are comprehensively determined based on the calculation results of the evaluation indicators. S7.1: Water quality factor: The water quality factor for the evaluation unit is calculated as follows: S7.2: Load Factor: The load factor for the evaluation unit is calculated as follows: S7.3: Risk Factor: The risk factor for the evaluation unit is calculated as follows: S7.4: Comprehensive risk indicators: First, normalize and calculate the three types of risk assessment indicators: The comprehensive index of agricultural non-point source pollution risk of the assessment unit is calculated as follows: S8: Risk level delineation: Sort the water quality coefficient, load coefficient, risk coefficient or comprehensive risk index of each evaluation unit in the assessment area from large to small, and determine the risk level by comparing their ranking order. The evaluation units ranked 0%-25%, 25%-50% (including 25%), 50%-75% (including 50%) and 75%-100% (including 75%) are respectively classified as low risk, medium risk, high risk and extremely high risk units; for evaluation units with negative water environment capacity, those with load coefficient values ​​greater than or equal to 1 are directly classified as extremely high risk areas, and those with load coefficient values ​​less than 1 are directly classified as high risk areas, and the risk level is no longer determined based on the ranking of the evaluation indicators; S9: Preparation of the list of priority control areas: The list of priority control areas for agricultural non-point source pollution should include all extremely high-risk units as much as possible. Some high-risk assessment units can be added in combination with the actual needs of agricultural non-point source pollution reduction and river water quality improvement. At the same time, the priority control areas should be finally determined after comprehensive evaluation based on the short-term and medium-term work goals and supporting fund budget of agricultural non-point source pollution prevention and control in the assessment area. After the agricultural non-point source pollution prevention and control work is carried out in the priority control areas, the effectiveness of agricultural non-point source pollution control can be dynamically evaluated based on the dynamically updated risk assessment results, and the list of priority control areas can be continuously updated until the risk levels of extremely high-risk and high-risk areas are reduced to medium and low risks, and the list of priority control areas is gradually cleared; S10: Implementation of agricultural non-point source pollution prevention and control measures: All relevant departments should coordinate multiple departments, take all factors and chains into consideration from the perspectives of green and high-quality agricultural development, recovery of river and lake ecological environment, construction of ecological civilization in the agricultural and rural areas, and optimization of national ecological space, and take comprehensive measures without affecting normal agricultural production activities and flood and drought prevention. Priority should be given to the implementation of low-impact agricultural non-point source pollution prevention and control measures with low input costs, low operation and maintenance costs, and closely related to existing work. The risk assessment methods proposed in S1-S9 can be used to determine the agricultural non-point source pollution load reduction targets, river water quality improvement targets, and water environment capacity (or water surface rate) improvement targets that must be achieved to reduce the risk level of the evaluation unit, so as to implement agricultural non-point source pollution prevention and control measures in a targeted manner in priority control areas. If agricultural non-point source pollution prevention and control funds have been secured, supporting prevention and control measures will be implemented in priority control areas according to the funding situation. If there is a funding gap, simultaneous application and implementation in stages can be made. If agricultural non-point source pollution prevention and control funds cannot be secured, non-point source pollution prevention and control can be promoted in combination with existing work, and existing work that promotes non-point source pollution reduction and river water quality improvement will be given priority in priority control areas. S11: Performance evaluation of agricultural non-point source pollution prevention and control: During the implementation of agricultural non-point source pollution prevention and control measures, the prevention and control performance evaluation should be carried out in accordance with the technical methods of this guideline, and the evaluation results should be used to provide timely guidance for agricultural non-point source pollution prevention and control work, and to objectively evaluate the final work results to achieve a closed-loop work system.

2. The high spatiotemporal resolution risk assessment method for agricultural non-point source pollution in plain river network areas according to claim 1 is characterized in that: In S2, the main river channels, main roads (except elevated roads and bridges) and other elements should be combined to divide the evaluation units of the same level as the existing polder areas in the gravity flow area of ​​the assessment area. The main factors such as agricultural production conditions, distribution of planting and rotation patterns, locations of irrigation water intakes and discharge outlets into rivers should be combined to divide the evaluation units of the same level as the existing irrigation and drainage areas in the agricultural land areas not included in the irrigation and drainage areas.

3. The high spatiotemporal resolution risk assessment method for agricultural non-point source pollution in plain river network areas according to claim 1 is characterized in that: In S5, the river loads of various agricultural non-point source pollution should adopt a unified accounting method system as much as possible, or refer to the existing emission coefficient list from the same official data source; In formula (1): L eu is the monthly river load of agricultural non-point source pollution in a certain evaluation unit, in kilograms per month (kg / mo); L p The monthly river load of non-point source pollution from crop production within the evaluation unit, in kilograms per month (kg / mo); L a It is the monthly river load of non-point source pollution from aquaculture industry in the evaluation unit, in kilograms per month (kg / mo); L l To evaluate the monthly river load of non-point source pollution from livestock and poultry breeding industry within the unit (excluding non-point source pollution from crop farming industry caused by returning biogas slurry to fields), the unit is kilogram per month (kg / mo).

4. The high spatiotemporal resolution risk assessment method for agricultural non-point source pollution in plain river network areas according to claim 1 is characterized in that: In S5.1, the calculation method of the coefficient of non-point source pollution entering the river from the planting industry (including paddy fields, dry land, gardens, greenhouses, woodlands and grasslands, etc.) refers to the hydrological and water quality coordinated monitoring method recommended in the "Technical Guidelines for Monitoring Non-point Source Pollution in Farmland in Plain River Network Areas (Trial) (Shanghai Environmental Protection Bureau [2023] No. 9)" issued by the Shanghai Municipal Ecological Environment Bureau; In formula (2): i is the ordinal number of the plots (farmland) with the same land use type, planting type and rotation pattern in the evaluation unit; I pi is the coefficient of non-point source pollution from crop production in the i-th plot within the evaluation unit, in kilograms per hectare per month (kg / (ha·mo)); A i is the area of ​​the ith plot in the evaluation unit, in hectares (ha); n is the number of blocks in the evaluation unit.

5. The high spatiotemporal resolution risk assessment method for agricultural non-point source pollution in plain river network areas according to claim 1 is characterized in that: In the S5.2, in formula (3): i is the ordinal number of the plots (aquaculture ponds) with the same land use type and aquaculture species within the assessment unit; I ai is the coefficient of aquaculture non-point source pollution entering the river for the ith plot, in kilograms per ton (kg / t); q ai is the aquatic product output of the ith plot in one aquaculture cycle, in tons (t); C ap It is the distribution coefficient of the aquaculture non-point source pollution into the river load in a certain month (compared to a breeding cycle), and the unit is per month ( / month). It is recommended to determine the distribution coefficient based on the proportion of monthly discharge of aquaculture ponds, and the distribution coefficient of the month in which the pond cleaning period (fishing season) is located should be a high value; n is the number of blocks in the evaluation unit.

6. The high spatiotemporal resolution risk assessment method for agricultural non-point source pollution in plain river network areas according to claim 1 is characterized in that: In S5.3, waste from livestock and poultry farms shall not be discharged directly into the environment without treatment. The return of livestock and poultry manure to the fields shall be converted into non-point source pollution of the crop industry under the condition of complying with Shanghai local standard DB31 / T 1137, and included in the scope of non-point source pollution into the river load of the crop industry, and the non-point source pollution caused by the direct discharge of livestock and poultry waste shall not be taken into account; if it does not meet the above standards, it is necessary to consider the intensity of direct discharge of livestock and poultry pollutants into the environment separately, and its non-point source pollution into the river coefficient shall refer to the pollution discharge coefficient of large-scale livestock and poultry breeding and the pollution discharge coefficient of livestock and poultry farmers in the "Handbook of Pollution Calculation Methods and Coefficients for Emission Source Statistical Survey" (Announcement No. 24 of 2021) issued by the Ministry of Ecology and Environment in 2021, and converted into a monthly river discharge coefficient; In formula (4): i is the ordinal number of the plots (livestock and poultry breeding sheds) with the same land use type and livestock species within the evaluation unit; I li规模 is the river entry coefficient of the ith plot of the large-scale livestock and poultry farm, in kilograms per head / feather (kg / (head / feather)); q li规模 is the stock / output quantity of the ith plot of livestock and poultry in large-scale breeding farms, in units of heads / feathers; I li养殖户 is the river entry coefficient of the i-th plot of livestock and poultry farmers, in kilograms per head / feather per month (kg / (head / feather)); q li养殖户 is the stock / output quantity of livestock and poultry farmers in the ith plot, in units of heads / feathers; C lp规模 It is the load distribution coefficient of livestock and poultry breeding non-point source pollution into the river for a certain type of livestock in a large-scale livestock and poultry breeding farm in a certain month (compared with the whole year), the unit is per month ( / month); C lp养殖户 It is the load distribution coefficient of livestock and poultry breeding non-point source pollution into the river for a certain livestock and poultry breeding variety of livestock and poultry farmers in a certain month (compared with the whole year), in units of per month ( / month); n is the number of blocks in the evaluation unit.

7. The high spatiotemporal resolution risk assessment method for agricultural non-point source pollution in plain river network areas according to claim 1 is characterized in that: In S6, if the density of existing river water quality monitoring points cannot meet the accuracy requirements for calculating the water environment capacity of the evaluation unit of the polder area and irrigation and drainage area, water quality intensification monitoring should be carried out, and the points in each evaluation unit should be evenly distributed as much as possible when selecting water quality monitoring points; the water environment capacity is calculated based on the Class III and Class V water standards specified in GB 3838 during the non-flood season and flood season respectively; if the phenomenon of Class III water quality in the river during the flood season is relatively common, the water environment capacity can be calculated based on the Class V water standard; The seasonal fluctuation characteristics of river hydrology and water quality in plain river network areas are more obvious. Refer to the overall compliance method for calculating water environmental capacity in small and medium-sized river network areas with one-way flow specified in DB32 / T 4542, and calculate the water environmental capacity of each level of evaluation unit on a monthly basis. For details, see Appendix D formula (D.1) and formula (D.2); In formula (5): i is the ordinal number of the water body within the evaluation unit; W i is the monthly water environment capacity of the ith water body in the evaluation unit, in kilograms per month (kg / mo); a is the water body non-uniformity coefficient (dimensionless), for specific values, refer to Appendix B of DB32 / T 4542; Q is the flow rate under the design hydrological conditions, in cubic meters per second (m 3 / s); V is the volume of water under the design hydrological conditions, in cubic meters (m 3 ); C s is the water quality target for the functional area, expressed in milligrams per liter (mg / L); C0 is the pollutant concentration of upstream water, in milligrams per liter (mg / L); In formula (6): Weu is the monthly water environment capacity of the evaluation unit, in kilograms per month (kg / mo); n is the number of water bodies in the evaluation unit.

8. The high spatiotemporal resolution risk assessment method for agricultural non-point source pollution in plain river network areas according to claim 1 is characterized in that: In S7.1, in formulas (7)-(14): RPI i,TP is the total phosphorus coefficient (dimensionless) of the ith water quality section in the evaluation unit. The water quality section here refers to the water quality section of the river located in a certain evaluation unit or at the boundary (the same below); c i,TP is the total phosphorus concentration of the ith water quality section in the assessment unit (mg / L); c t,TP is the water quality concentration threshold of total phosphorus, in milligrams per liter (mg / L), which is 0.2 mg / L according to the Class III water standard of GB 3838; c i,NH4 is the ammonia nitrogen concentration of the ith water quality section in the evaluation unit (mg / L); c t,NH4 is the water quality concentration threshold of ammonia nitrogen, in milligrams per liter (mg / L), which is 1.0 mg / L according to the Class III water standard of GB 3838; c i,TN is the total nitrogen concentration of the ith water quality section in the evaluation unit (mg / L); c t,TN is the water quality concentration threshold of total nitrogen, in milligrams per liter (mg / L), and is taken as 2.0 mg / L with reference to GB 3838; RPI i,TP is the total phosphorus coefficient (dimensionless) of the ith water quality section in the evaluation unit; RPI i,TN is the total nitrogen coefficient (dimensionless) of the ith water quality section in the evaluation unit; RPI i,NH4 is the ammonia nitrogen coefficient of the ith water quality section in the evaluation unit (dimensionless); RPI TP is the total phosphorus coefficient of the evaluation unit (dimensionless); RPI TN is the total nitrogen coefficient of the evaluation unit (dimensionless); RPI NH4 is the ammonia nitrogen coefficient of the evaluation unit (dimensionless); I w is the water quality coefficient of the evaluation unit (dimensionless); when total phosphorus, total nitrogen and ammonia nitrogen factors are considered, formula (13) is used; when total phosphorus and ammonia nitrogen factors are considered, formula (14) is used.

9. The high spatiotemporal resolution risk assessment method for agricultural non-point source pollution in plain river network areas according to claim 1 is characterized in that: In S7.2-S7.4, in formula (15)-(20): I L is the load factor of the evaluation unit (dimensionless); L eu is the agricultural non-point source pollution load into the river of the assessment unit, in kilograms per month (kg / mo); A eu is the area of ​​the evaluation unit in hectares (ha); L is the agricultural non-point source pollution load into the river at the next higher administrative unit, in kilograms per month (kg / mo); A is the area of ​​the upper level assessment unit or the entire assessment area, in hectares (ha); I R is the risk factor of the evaluation unit (dimensionless); L eu is the agricultural non-point source pollution load into the river of the assessment unit, in kilograms per month (kg / mo); W eu The water environment capacity of the assessment unit, in kilograms per month (kg / mo). If it is less than or equal to 0, it will not be calculated; is the normalized risk coefficient of the ith evaluation unit (dimensionless); are the minimum and maximum (dimensionless) normalized risk coefficients of the i-th evaluation unit and the evaluation units of the same level; is the normalized water quality coefficient (dimensionless) of the ith evaluation unit; are the minimum and maximum values ​​(dimensionless) of the normalized water quality coefficient of the i-th evaluation unit among the evaluation units of the same level; is the normalized load factor of the ith evaluation unit (dimensionless); are the minimum and maximum (dimensionless) normalized load factors of the i-th evaluation unit and the evaluation units of the same level; I i is the comprehensive risk index of the ith evaluation unit (dimensionless); a is the risk factor weight (dimensionless); b is the water quality factor weight (dimensionless); c is the load factor weight (dimensionless); it is recommended to take: a=0.5, b=0.2, c=0.3 in areas where the water quality in the water environment functional zone meets the standards better, and take: a=0.5, b=0.3, c=0.2 in areas where the water quality in the water environment functional zone meets the standards worse.

10. The high spatiotemporal resolution risk assessment method for agricultural non-point source pollution in plain river network areas according to claim 1 is characterized in that: In the S10, the preventive and control measures that can be implemented include but are not limited to: (ecological) high-standard farmland construction related to the work of the agricultural and rural departments, new fertilization technologies and methods such as soil testing and formulation and side deep fertilization, optimization and adjustment of fertilizer nitrogen and phosphorus ratios, measures for returning biogas slurry to the fields combined with farming and breeding, optimization of appropriate planting types and rotation patterns, promotion and application of water-saving and drought-resistant rice, agricultural green / organic certification, incentive measures for demonstration creation such as ecological farms and agricultural subsidy incentives, etc.; ecological clean small watershed construction, soil and water conservation measures, water-saving irrigation measures, drainage control measures, optimization and adjustment of field ditch and pond layout, river dredging and regulation, optimization and adjustment of river network water system and river blue line, local area river water dynamics enhancement and Duantou Bay connection, etc. related to the ecological environment department; ecological compensation fund incentives, river discharge outlet management, "two mountains" base creation, agricultural non-point source pollution pilot monitoring and evaluation, etc. related to the planning and resources department; comprehensive land improvement in the entire region, optimization of ecological space layout and ecological restoration of national land space, etc.

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