Comprehensive environmental nitrogen threshold evaluation method and system

Abstract

The invention provides a comprehensive environmental nitrogen threshold evaluation method and system, and relates to the technical field of environmental nitrogen threshold evaluation. The method comprises the following steps: identifying a main nitrogen pollution problem; selecting a nitrogen threshold standard corresponding to each pollution problem; acquiring a preliminary evaluation value based on the monitoring data and model simulation; correcting the preliminary evaluation value to obtain a corrected evaluation value; comparing the correction value with a threshold value, and calculating emission reduction; and outputting an emission reduction target and a suggestion or recording a standard reaching state. The accuracy of an evaluation result and the scientificity of a management decision are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental nitrogen threshold assessment, and in particular to a comprehensive environmental nitrogen threshold assessment method and system. Background Art

[0002] The extensive use of chemical nitrogen fertilizers is an important means of increasing grain production. However, irrational nitrogen fertilizer application has led to a series of environmental problems, such as eutrophication of water bodies, increased greenhouse gas emissions, soil acidification, excessive nitrates in groundwater, and biodiversity loss, seriously threatening human health and sustainable socioeconomic development. Currently, research on environmental nitrogen thresholds is relatively limited, primarily focusing on nitrogen deposition and surface water nitrogen pollution. These studies suffer from a single indicator and a lack of systematic and comprehensive analysis.

[0003] Patent application number CN201410442797.0 discloses a method for calculating nitrogen input thresholds for farmland. The method includes the following steps: comparing planting data and collecting statistical data; using the statistical results to determine the nitrogen threshold for crop yields and the environmental nitrogen input threshold for farmland; determining farmland soil type and soil fertility levels based on the crop yield nitrogen threshold and the environmental nitrogen input threshold for regional farmland, and revising the determined nitrogen input threshold; and finally, calculating the nitrogen input threshold for farmland. This technique only considers the nitrogen input threshold for farmland and fails to fully account for the environmental impacts of nitrogen loss. It also lacks systematicity and comprehensiveness. Furthermore, this technique does not cover the entire atmosphere-water-soil multi-media process and lacks a universal quantitative correction mechanism. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a comprehensive environmental nitrogen threshold assessment method and system, which effectively improves the accuracy of the assessment results and the scientific nature of management decisions.

[0005] To achieve the above object, the present invention provides the following solutions: A comprehensive approach to environmental nitrogen threshold assessment, including: Identify major nitrogen pollution issues based on the environmental characteristics and pollution status of the target area; For each of the nitrogen pollution problems, the corresponding nitrogen threshold standard CL(i) is selected with reference to the preset environmental quality standards and literature research; where i represents the i-th indicator; The preliminary evaluation value N of each indicator is obtained by using monitoring data and model simulation pre (i); For the initial evaluation value N pre (i) Perform correction to obtain the corrected evaluation value N cor (i); The corrected evaluation value N cor(i) Compare with the nitrogen threshold standard CL(i) of the corresponding threshold and calculate the nitrogen load reduction E(i) of each indicator; If E(i)>0, the sub-item emission reduction targets and recommended measures for the corresponding indicators are output; if E(i)=0, it is recorded as a compliance status.

[0006] Preferably, the major nitrogen pollution problems include: atmospheric nitrogen deposition, total nitrogen load to surface water, groundwater nitrate, atmospheric ammonia emissions and nitrous oxide emissions.

[0007] Preferably, for each of the nitrogen pollution problems, the corresponding nitrogen threshold standard CL(i) is selected with reference to the preset environmental quality standards and literature research, including: Calculate the atmospheric nitrogen deposition threshold CL(1) by the steady-state mass balance method; The total nitrogen concentration of Class III in the preset surface water environmental quality standard is 1.0 mg·L -1 As a benchmark, the total nitrogen load threshold CL(2) of surface water was determined in combination with the monitoring data of representative watersheds; The nitrate limit in the preset drinking water hygiene standard is 10 mg·L -1 Determine the groundwater nitrate threshold CL(3) as a benchmark; 3 μg·m -3 Determined as the atmospheric NH3 threshold CL(4); Based on the non-CO2 greenhouse gas emission reduction requirements corresponding to the preset 2°C temperature control target, the 30% emission reduction target for 2050 relative to 2020 is converted into an annual permissible emission cap to determine the atmospheric N2O threshold CL(5).

[0008] Preferably, the monitoring data and model simulation are used to obtain the preliminary evaluation value N of each indicator. pre (i) including: Retrieve real-time monitoring records from monitoring sites and download meteorological fields, land use, and emission inventories matching the target area; The WRF-CMAQ coupled model is called to run simulations based on the meteorological field, land use, and emission inventory to obtain grid deposition fluxes, which are then integrated according to administrative or watershed boundaries to obtain a preliminary assessment of atmospheric nitrogen deposition, N. pre (1); For rivers with monitoring sections, the amount of nitrogen entering the river is calculated by multiplying the average flow by the total nitrogen concentration; For sub-basins without monitoring sections, the emission inventory method is used to summarize agricultural, domestic and industrial source emissions and deduct the nitrogen reduction coefficient to obtain summary data; The nitrogen inflow into the river is added to the summary data to obtain the preliminary assessment value N of surface water. pre (2); The nitrate concentration data of the monitoring wells were collected, and the regional representative value was calculated using the area-weighted average method. The regional representative value was multiplied by the annual groundwater renewal volume to obtain the preliminary assessment value of groundwater nitrate N. pre (3) Due to the lack of data on annual groundwater renewal, the actual data is expressed as the relationship between agricultural nitrogen surplus and groundwater nitrate concentration.

[0009] Read the agricultural ammonia emission inventory and the livestock and poultry breeding emission inventory, sum them by cell on the GIS platform, and obtain the preliminary assessment value of atmospheric NH3 N pre (4); The EDGAR v7.0 database was used to extract the annual N2O emissions of the target area and obtain the preliminary assessment value of atmospheric N2O. pre (5).

[0010] Preferably, the preliminary evaluation value N pre (i) Perform correction to obtain the corrected evaluation value N cor (i) including: The initial assessment value Independent measured data Unify to the same time scale and space unit to form one-to-one comparison data pairs; right Perform outlier removal and use the box plot method to remove outliers; According to the formula Calculating system deviation ; According to the formula Calculate the correction factor ; when season ; According to the correction factor and preliminary assessment values Generate adjusted estimates ;in, ; Randomly select no less than 20% of all the comparison data pairs as the validation set, and repeat the cross validation ten times; if the root mean square error If the decrease is less than 1% for two consecutive iterations, stop the iteration and confirm ;in, , n is the number of data pairs in the validation set, For the The corrected evaluation value of the sample, For the Independent measured data of samples; When the RMSE of the validation set does not exceed the preset threshold, the corrected evaluation value after validation is output Otherwise, return to step " Perform outlier removal and use the box plot method to remove outliers" to re-perform quality control and iterate until the preset threshold requirements are met.

[0011] Preferably, the corrected evaluation value N cor (i) Compare with the nitrogen threshold standard CL(i) of the corresponding threshold and calculate the nitrogen load reduction E(i) of each indicator, including: According to the formula The corrected evaluation value N cor (i) is subtracted from the nitrogen threshold standard CL(i) of the corresponding threshold to obtain the difference ; According to the formula Determining nitrogen load reductions .

[0012] Preferably, it also includes: When i=3, that is, i corresponds to the index of groundwater nitrate, assuming that the decrease in groundwater nitrate concentration is proportional to the decrease in agricultural nitrogen surplus, according to the formula Calculating agricultural nitrogen surplus emission reductions ;in is the agricultural nitrogen surplus of the pth province or watershed, is the average nitrate concentration of the pth province or basin, m is the number of provinces or basins, and the calculated Used to replace E(i).

[0013] A comprehensive environmental nitrogen threshold assessment system, including: Nitrogen pollution identification unit, used to identify major nitrogen pollution problems based on the environmental characteristics and pollution status of the target area; A threshold selection unit is used to select a corresponding nitrogen threshold standard CL(i) for each of the nitrogen pollution problems, referring to preset environmental quality standards and literature research; wherein i represents the i-th indicator; The preliminary evaluation unit is used to obtain the preliminary evaluation value N of each indicator using monitoring data and model simulation pre (i); Correction processing unit, used for the preliminary evaluation value N pre (i) Perform correction to obtain the corrected evaluation value N cor (i); Emission reduction calculation unit, used to convert the corrected evaluation value N cor (i) Compare with the nitrogen threshold standard CL(i) of the corresponding threshold and calculate the nitrogen load reduction E(i) of each indicator; The result output unit is used to output the sub-item emission reduction targets and recommended measures for the corresponding indicators if E(i)>0; if E(i)=0, it is recorded as a compliance status.

[0014] The present invention discloses the following technical effects: (1) This invention introduces a correction process to correct for systematic deviations in the simulated or monitored preliminary assessment values ​​of various nitrogen pollution indicators, significantly improving the accuracy of environmental nitrogen load assessments and avoiding misjudgments of emission reductions due to factors such as model input errors and insufficient data representation. Compared to existing methods that directly use model results or inventory calculations as a basis, this invention provides a quantifiable and verifiable correction mechanism, ensuring the scientific nature and reliability of subsequent threshold comparisons and policy decisions.

[0015] (2) The present invention constructs a unified multi-indicator evaluation process, which systematically integrates nitrogen pollution problem identification, threshold selection, simulation evaluation, data correction, emission reduction calculation and governance recommendation output, solving the problems of independent evaluation and logical separation of multiple pollution indicators in existing technologies. It is particularly suitable for the integrated management needs of large-scale regions (such as provinces and river basins).

[0016] (3) The present invention uses measured values ​​aligned with national monitoring data as the basis for correction. It has strong operability and data adaptability and can be flexibly deployed at different time scales (years, seasons) and spatial units (administrative districts, sub-basins). It enhances the dynamic update capability and regional adaptability of the environmental management system and effectively responds to multi-source and variable pollution patterns.

[0017] (4) The "threshold-correction-emission reduction" coupling method proposed in this invention improves the accuracy and target decomposition capability of nitrogen pollution control strategies. In particular, it introduces a correction mechanism for the linkage between agricultural nitrogen surplus and concentration in terms of hidden pollution such as groundwater nitrate, filling the technical gap that existing methods cannot accurately correspond to the quantitative relationship between the source and the medium response, and has significant environmental benefits and promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 A flow chart of a method provided by an embodiment of the present invention; Figure 2 A schematic diagram of the system structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Figure 1 A flow chart of the method provided in the embodiment of the present invention is shown in FIG. Figure 1 As shown, the present invention provides a comprehensive environmental nitrogen threshold assessment method, comprising: Step 100: Identify the main nitrogen pollution issues based on the environmental characteristics and pollution status of the target area; Step 200: For each nitrogen pollution problem, refer to the preset environmental quality standards and literature research to select the corresponding nitrogen threshold standard CL(i); where i represents the i-th indicator; Step 300: Use monitoring data and model simulation to obtain the preliminary evaluation value N of each indicator pre (i); Step 400: Initial evaluation value N pre (i) Perform correction to obtain the corrected evaluation value N cor (i); Step 500: Correct the evaluation value N cor (i) Compare with the nitrogen threshold standard CL(i) of the corresponding threshold and calculate the nitrogen load reduction E(i) of each indicator; Step 600: If E(i)>0, output the sub-item emission reduction target and recommended measures for the corresponding indicator; if E(i)=0, record it as a compliance status.

[0023] Specifically, the issues selected in step 100 of this embodiment include: atmospheric nitrogen deposition, total nitrogen load in surface water, groundwater nitrate, atmospheric NH3, and atmospheric N2O.

[0024] Optionally, step 200 of this embodiment includes: Step 201: The nitrogen deposition threshold is estimated using the steady-state mass balance method with reference to existing literature (Duan Lei. Study on the critical load zoning of acid deposition in China [D]. Beijing: Tsinghua University, 2000). The calculation formula is as follows:

[0025]

[0026]

[0027]

[0028]

[0029] Where, CL(S), CL(N), CL max (N), CL nut (N) are sulfur deposition threshold, nitrogen deposition threshold, acidification nitrogen threshold, and nutritional nitrogen threshold. * dep (BC = Ca 2+ + Mg 2+ + Na + + K + ) is the amount of basic cation precipitation after sea salt correction; BC w is the rate at which soil weathering produces base cations, Bc u (Bc = Ca 2+ + Mg 2+ + K + ) is the rate at which plants absorb basic cations; N i is the nitrogen mineralization rate; N u is the rate at which plants absorb nitrogen; N de is the denitrification rate of nitrogen; f de is the denitrification rate; N le,crit is the critical nitrogen leaching rate; ANC le,crit is the critical alkalinity leaching rate. It is an intermediate calculation parameter used to calculate the acidification nitrogen threshold.

[0030] Step 202: The nitrogen load threshold for surface water is 1.0 mg L according to the existing quality standard of my country, Environmental Quality Standard for Surface Water (GB3838-2002), Class III water standard. -1 According to the existing literature (Yu CQ, Huang X, Chen H, et al. Managing nitrogen to restore water quality in China [J]. Nature, 2019, 567(7749): 516-520.), the total nitrogen load threshold for surface water in each province was determined by empirical methods, that is, the total nitrogen concentration in the representative watershed of each province reached 1.0 mg L for the first time. -1 Total nitrogen load in the year when Step 203: The nitrate index of groundwater is based on the nitrate limit of 10 mg L specified in my country's "Healthy Standard for Drinking Water" (GB5749-2022).-1 (in N) as the threshold standard.

[0031] Step 204: Since my country currently does not have a quality standard for atmospheric NH3 concentration, the 3 μg m-3 concentration proposed by the Convention on Long-range Transboundary Air Pollution for the protection of higher plant communities and their ecological functions is selected. -3 Critical level of NH3.

[0032] Step 205: The atmospheric N2O threshold is primarily based on my country's established emission reduction strategy under the Paris Agreement's temperature control targets. Based on existing literature (Institute of Climate Change and Sustainable Development ofTsinghua University. China's long-term low-carbon development strategies and pathways [M]. Singapore: Springer, 2022.) on the current status, future emission scenarios, and outcomes of non-CO2 greenhouse gas emissions, achieving the 2°C temperature control target requires a 30% reduction in N2O emissions by 2050 compared to 2020 levels.

[0033] Optionally, step 300 of this embodiment includes: Step 301: Current atmospheric nitrogen deposition is simulated using the coupled air quality model WRF-CMAQ (Community Multiscale Air Quality Modeling System-Weather Research and Forecasting). The model parameters are set based on the actual conditions of the target area, and the source emission inventory and meteorological data are input to simulate nitrogen deposition in the target area for the target year. For example, major anthropogenic emission sources include agriculture, industry, power plants, domestic use, mobile sources, dust, biomass combustion, and solvent use.

[0034] Step 302: The current total nitrogen load to surface water is obtained using the emissions inventory method. This method uses activity data and associated emission coefficients to estimate the system's nitrogen budget and analyze the sources and destinations of nitrogen in the system. Nitrogen loads entering water bodies include agricultural runoff, grassland runoff, forest runoff, nitrogen deposition, sewage discharge, and human and livestock manure. Nitrogen inputs involved in the calculation primarily include biological fixation, chemical fertilizers, atmospheric deposition, and food and feed imports. Nitrogen outputs primarily include NH3 volatilization, output to water bodies, food and feed output, and biomass combustion emissions.

[0035] Step 303: Estimate the agricultural nitrogen surplus by subtracting the nitrogen absorbed by crops from the total nitrogen input to the farmland. Farmland nitrogen input includes chemical fertilizers, organic fertilizers, nitrogen deposition, biological nitrogen fixation, and straw return. Crop nitrogen absorption includes nitrogen absorbed by crop seeds and straw.

[0036] Step 304: The current atmospheric NH3 emissions are derived from the 2019 high-resolution NH3 emission inventory of my country compiled by the National Key R&D Program project "High-efficiency Control Technology of Ammonia Emission Pollution in Agriculture and Animal Husbandry" (data not published). The estimation of farmland NH3 emissions is based on existing literature (Wang C, Liu ZH, Zhang XM, et al. Managing Ammonia for Multiple Benefits Based on Verified High-Resolution Emission Inventory in China [J]. Environ. Sci. Technol. 2025, 59(10): 5131-5144). NH3 emissions from livestock and poultry farming, industrial sources, natural sources, aquaculture sources, grassland sources and other sources can be estimated using the coupled human-nature system (CHANS) developed in the existing literature (GuB J, Ju XT, Chang J, et al. Integrated reactive nitrogen budgets and futuretrends in China [J]. Proceedings of the National Academy of Sciences of theUnited States of America, 2015, 112(28): 8792-8797.).

[0037] Step 305: The current atmospheric N2O emissions are obtained from the Emissions Database for Global Atmospheric Research (EDGAR v7.0).

[0038] Furthermore, step 400 of this embodiment includes: Step 401: Perform a spatiotemporal alignment operation to unify the model simulation output and independent observation data to a consistent time scale and spatial unit. Specifically, this embodiment uses a dual-key index consisting of a geographic unit code and a timestamp to match and bind the data pairs, ensuring that each preliminary assessment value can be mapped to a unique measured data point.

[0039] Step 402: To address the potential for extreme values ​​in the measured data, an outlier removal mechanism based on the box plot method is used for quality control. Specifically, this embodiment calculates the first quartile, third quartile, and interquartile range of the measured data, automatically determining and removing outliers below the lower bound or above the upper bound. Simultaneously, this embodiment synchronously records the removed data in an outlier log for subsequent manual verification or retrospective adjustment. Compared to traditional fixed threshold methods, this method has the advantages of strong adaptability and applicability to different distribution patterns.

[0040] Step 403: After completing data cleaning, this embodiment performs system deviation estimation and correction coefficient calculation. This embodiment calculates the difference between the preliminary evaluation value and the observed value item by item and calculates their arithmetic mean as the system deviation. Subsequently, the correction coefficient for the corresponding indicator is generated by subtracting the system deviation from the preliminary evaluation value and dividing it by the preliminary evaluation value. To prevent the preliminary evaluation value from being zero, which would cause a division by zero anomaly, this embodiment implements a zero protection mechanism, in which case the correction coefficient is directly set to 1. This strategy is computationally simple and has stable convergence, making it suitable for unified correction processing of multiple nitrogen pollution indicators.

[0041] Step 404: To improve the stability and generalization of the correction coefficients, this embodiment incorporates a cross-validation and self-stopping mechanism. Specifically, this embodiment randomly selects no less than 20% of samples from all comparison data pairs to form a validation set. Ten rounds of cross-validation are repeated, and the root mean square error (RMSE) is calculated after each round. When the error decreases by less than 1% over two consecutive rounds, this embodiment automatically terminates the iteration and determines that the correction process has converged and stabilized. This strategy avoids the overfitting problem that can occur with traditional fixed-round validation.

[0042] Step 405: After the calibration is complete, this embodiment continues the result evaluation and quality backtracking process. If the root mean square error (RMS) in the validation set does not exceed a preset threshold, this embodiment confirms the calibration is effective and uses the corrected assessment value as the final result for subsequent nitrogen load reduction calculations. If the error exceeds the threshold, this embodiment returns to the outlier removal step and re-executes data cleaning and calibration calculations until the results meet the accuracy requirements. This closed-loop processing ensures that each assessment result output by this embodiment is fully credible.

[0043] Furthermore, step 500 of this embodiment includes: Step 501: First, read the corrected assessment value obtained in the previous stage and retrieve the corresponding nitrogen threshold standard. Comparing the two, a differential calculation ("current value minus threshold") is performed for each indicator to determine whether it exceeds the standard. This differential operation is a rigid judgment, directly reflecting the absolute difference between the actual corrected nitrogen load and the target threshold, and is a prerequisite for subsequent quantification of emission reductions.

[0044] Step 502: After the difference result is generated, this embodiment immediately performs a positive / negative determination: If the difference is positive, it indicates that the indicator has exceeded the threshold and emission reduction measures are required; if the difference is zero or negative, it is considered to be in compliance. In the event of an exceeding threshold, this embodiment directly determines the difference value as the nitrogen load emission reduction requirement for that indicator, retaining its original unit without conversion to ensure traceability and consistency with the threshold standard.

[0045] Step 503: To prevent negative numbers from interfering with subsequent summary analysis, this embodiment incorporates a "negative" logic when recording emission reductions: Differences in on-target indicators are automatically reset to zero, retaining only positive differences in exceeded indicators. This allows decision makers to intuitively identify the pollution items that require priority treatment and reduces the repetition of redundant data in subsequent reports.

[0046] Step 504: When the indicator number is three, corresponding to groundwater nitrate concentration, this embodiment uses an agricultural source-driven replacement algorithm. This embodiment assumes that the reduction in groundwater nitrate concentration is linearly related to the reduction in agricultural nitrogen surplus in each province or river basin: the agricultural nitrogen surplus of the previous year is first calculated for each province, and then the annual average concentration of groundwater nitrate in the same province is combined to calculate the potential surplus reduction contribution of each province; then, the sum of all provinces is calculated to obtain the total amount of surplus that can be reduced. This total amount directly replaces the original difference and serves as the final reduction target for the groundwater nitrate indicator, thereby realizing a precise governance strategy of source-medium linkage.

[0047] Step 505: After completing the above processing, this embodiment writes the emission reduction amount, compliance status, and (if applicable) agricultural surplus replacement value for each indicator into the result buffer for subsequent use by the result output and control measure matching unit. By combining differential judgment, non-negative processing, and a source-side replacement mechanism, this embodiment achieves differentiated emission reduction accounting for specific media while ensuring simple and efficient calculations. This fully addresses the shortcomings of existing technologies that make it difficult to accurately trace the source of groundwater nitrate and quantify control needs.

[0048] As an optional implementation manner, step 600 of this embodiment includes: Step 601: Based on the emission reduction results calculated in the previous stage, the system first determines whether the emission reduction for each indicator is greater than zero. This determination serves as the entry condition for a logical branch, distinguishing between treatment paths for indicators exceeding standards and those meeting standards, thereby enabling targeted management of different pollution control states. This branch determination is direct and actionable, serving as a prerequisite for the subsequent generation of control recommendations and the creation of a compliance profile.

[0049] Step 602: For indicators determined to be exceeding the standard (i.e., emission reductions greater than zero), this embodiment uses this emission reduction as a sub-target for that pollution indicator. A list of corresponding treatment measures is then matched to the pre-set nitrogen pollution control knowledge base. This list automatically selects a number of recommended measures based on pollution type (e.g., ammonia volatilization, runoff into rivers, nitrate leaching, etc.) and regional attributes (e.g., farmland type, fertilization intensity, groundwater vulnerability, etc.). These measures are then output in a structured "indicator-target-recommendation" triple format, enabling quick reference by policymakers and implementers.

[0050] Step 603: For indicators that have met the target (i.e., where the emission reduction is zero), this embodiment records the corrected assessment value, the corresponding threshold, the determination result of the difference being zero, and the processing timestamp in the target compliance database. This database, as part of the regional target compliance archive management module, is used to generate annual environmental quality reports, support governance effectiveness evaluation, and track indicators dynamically. These records do not generate emission reduction targets or include governance recommendations to avoid wasting resources.

[0051] Step 604: After the above branch outputs are complete, this embodiment packages and organizes the processed results for all indicators and pushes them to output interfaces, including reporting modules, decision support terminals, or remote management platforms. Through this output mechanism, this embodiment implements an integrated closed loop of pollutant identification, assessment, judgment, and response, ensuring that each emission reduction or compliance status has clear quantitative evidence and supporting technical pathways, thereby enhancing the scientific nature, pertinence, and enforceability of environmental governance.

[0052] Corresponding to the above method, such as Figure 2 As shown, this embodiment also provides a comprehensive environmental nitrogen threshold assessment system, including: Nitrogen pollution identification unit, used to identify major nitrogen pollution problems based on the environmental characteristics and pollution status of the target area; A threshold selection unit is used to select a corresponding nitrogen threshold standard CL(i) for each of the nitrogen pollution problems, referring to preset environmental quality standards and literature research; wherein i represents the i-th indicator; The preliminary evaluation unit is used to obtain the preliminary evaluation value N of each indicator using monitoring data and model simulation pre (i); Correction processing unit, used for the preliminary evaluation value N pre (i) Perform correction to obtain the corrected evaluation value N cor (i); Emission reduction calculation unit, used to convert the corrected evaluation value N cor (i) Compare with the nitrogen threshold standard CL(i) of the corresponding threshold and calculate the nitrogen load reduction E(i) of each indicator; The result output unit is used to output the sub-item emission reduction targets and recommended measures for the corresponding indicators if E(i)>0; if E(i)=0, it is recorded as a compliance status.

[0053] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0054] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A comprehensive environmental nitrogen threshold assessment method, characterized in that: include: Identify major nitrogen pollution issues based on the environmental characteristics and pollution status of the target area; For each of the nitrogen pollution problems, the corresponding nitrogen threshold standard CL(i) is selected with reference to the preset environmental quality standards and literature research; where i represents the i-th indicator; The preliminary evaluation value N of each indicator is obtained by using monitoring data and model simulation pre (i); For the initial evaluation value N pre (i) Perform correction to obtain the corrected evaluation value N cor (i); The corrected evaluation value N cor (i) Compare with the nitrogen threshold standard CL(i) of the corresponding threshold and calculate the nitrogen load reduction E(i) of each indicator; If E(i)>0, the sub-item emission reduction targets and recommended measures for the corresponding indicators are output; if E(i)=0, it is recorded as a compliance status.

2. The comprehensive environmental nitrogen threshold assessment method according to claim 1, characterized in that: The main nitrogen pollution problems include: atmospheric nitrogen deposition, total nitrogen load to surface water, groundwater nitrate, atmospheric ammonia emissions and nitrous oxide emissions.

3. The comprehensive environmental nitrogen threshold assessment method according to claim 1, characterized in that: For each of the nitrogen pollution issues, the corresponding nitrogen threshold standards CL(i) were selected with reference to the preset environmental quality standards and literature research, including: Calculate the atmospheric nitrogen deposition threshold CL(1) by the steady-state mass balance method; The total nitrogen concentration of Class III in the preset surface water environmental quality standard is 1.0 mg·L -1 As a benchmark, the total nitrogen load threshold CL(2) of surface water was determined in combination with the monitoring data of representative watersheds; The nitrate limit in the preset drinking water hygiene standard is 10 mg·L -1 Determine the groundwater nitrate threshold CL(3) as a benchmark; 3 μg·m -3 Determined as the atmospheric NH3 threshold CL(4); Based on the non-CO2 greenhouse gas emission reduction requirements corresponding to the preset 2°C temperature control target, the 30% emission reduction target for 2050 relative to 2020 is converted into an annual permissible emission cap to determine the atmospheric N2O threshold CL(5).

4. The comprehensive environmental nitrogen threshold assessment method according to claim 1, characterized in that: Using monitoring data and model simulation, we can get the preliminary evaluation value N of each indicator. pre (i) including: Retrieve real-time monitoring records from monitoring sites and download meteorological fields, land use, and emission inventories matching the target area; The WRF-CMAQ coupled model is called to run simulations based on the meteorological field, land use, and emission inventory to obtain grid deposition fluxes, which are then integrated according to administrative or watershed boundaries to obtain a preliminary assessment of atmospheric nitrogen deposition, N. pre (1); For rivers with monitoring sections, the amount of nitrogen entering the river is calculated by multiplying the average flow by the total nitrogen concentration; For sub-basins without monitoring sections, the emission inventory method is used to summarize agricultural, domestic and industrial source emissions and deduct the nitrogen reduction coefficient to obtain summary data; The nitrogen inflow into the river is added to the summary data to obtain the preliminary assessment value N of surface water. pre (2); The nitrate concentration data of the monitoring wells were collected, and the regional representative value was calculated using the area-weighted average method. The regional representative value was multiplied by the annual groundwater renewal volume to obtain the preliminary assessment value of groundwater nitrate N. pre (3); Read the agricultural ammonia emission inventory and the livestock and poultry breeding emission inventory, sum them by cell on the GIS platform, and obtain the preliminary assessment value of atmospheric NH3 N pre (4); The EDGAR v7.0 database was used to extract the annual N2O emissions of the target area and obtain the preliminary assessment value of atmospheric N2O. pre (5).

5. The comprehensive environmental nitrogen threshold assessment method according to claim 1, characterized in that: For the initial evaluation value N pre (i) Perform correction to obtain the corrected evaluation value N cor (i) including: The initial assessment value Independent measured data Unify to the same time scale and space unit to form one-to-one comparison data pairs; right Perform outlier removal and use the box plot method to remove outliers; According to the formula Calculating system deviation ; According to the formula Calculate the correction factor ; when season ; According to the correction factor and preliminary assessment values Generate adjusted estimates ;in, ; Randomly select no less than 20% of all the comparison data pairs as the validation set, and repeat the cross validation ten times; if the root mean square error If the decrease is less than 1% for two consecutive iterations, stop the iteration and confirm ;in, , n is the number of data pairs in the validation set, For the The corrected evaluation value of the sample, For the Independent measured data of samples; When the RMSE of the validation set does not exceed the preset threshold, the corrected evaluation value after validation is output Otherwise, return to step " Perform outlier removal and use the box plot method to remove outliers" to re-perform quality control and iterate until the preset threshold requirements are met.

6. The comprehensive environmental nitrogen threshold assessment method according to claim 1, characterized in that: The corrected evaluation value N cor (i) Compare with the nitrogen threshold standard CL(i) of the corresponding threshold and calculate the nitrogen load reduction E(i) of each indicator, including: According to the formula The corrected evaluation value N cor (i) is subtracted from the nitrogen threshold standard CL(i) of the corresponding threshold to obtain the difference ; According to the formula Determining nitrogen load reductions .

7. The comprehensive environmental nitrogen threshold assessment method according to claim 6, characterized in that: Also includes: When i=3, that is, i corresponds to the index of groundwater nitrate, assuming that the decrease in groundwater nitrate concentration is proportional to the decrease in agricultural nitrogen surplus, according to the formula Calculating agricultural nitrogen surplus emission reductions ;in is the agricultural nitrogen surplus of the pth province or watershed, is the average nitrate concentration of the pth province or basin, m is the number of provinces or basins, and the calculated Used to replace E(i).

8. A comprehensive environmental nitrogen threshold assessment system, characterized in that: include: Nitrogen pollution identification unit, used to identify major nitrogen pollution problems based on the environmental characteristics and pollution status of the target area; A threshold selection unit is used to select a corresponding nitrogen threshold standard CL(i) for each of the nitrogen pollution problems, referring to preset environmental quality standards and literature research; wherein i represents the i-th indicator; The preliminary evaluation unit is used to obtain the preliminary evaluation value N of each indicator using monitoring data and model simulation pre (i); Correction processing unit, used for the preliminary evaluation value N pre (i) Perform correction to obtain the corrected evaluation value N cor (i); Emission reduction calculation unit, used to convert the corrected evaluation value N cor (i) Compare with the nitrogen threshold standard CL(i) of the corresponding threshold and calculate the nitrogen load reduction E(i) of each indicator; The result output unit is used to output the sub-item emission reduction targets and recommended measures for the corresponding indicators if E(i)>0; if E(i)=0, it is recorded as a compliance status.

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