A method for calculating net human life nitrogen input of a river basin

Abstract

The application provides a kind of calculation method of watershed net human life nitrogen input, belongs to the technical field of environmental management.The steps are:1) selecting calculation watershed and collecting relevant information from official channels;2) determining the proportion of administrative boundary in the watershed for data processing;3) using nitrogen intake coefficient and population to calculate the original human life nitrogen input in urban and rural areas;4) using the actual sewage treatment capacity and sewage treatment standard to calculate the sewage treatment system reduction amount of nitrogen in urban and rural areas;5) using sludge yield, processing capacity, nitrogen content and processing method to calculate the sludge nitrogen circulation amount in urban and rural areas;6) arranging the results of steps three to five to determine the net watershed human activity nitrogen input;7) identifying pollution attributes.The beneficial effects of the application are to realize the fine evaluation of watershed human life nitrogen input, reflect the objective difference of urban and rural human life nitrogen input, and the influence of sludge nitrogen, realize the identification of point source and non-point source attributes.

Description

Technical Field

[0001] This invention relates to a method for calculating net human nitrogen input in a watershed, belonging to the field of environmental management technology. It is a method for accurately assessing nitrogen input and nitrogen cycle generated by human activities within a watershed. Background Technology

[0002] Nitrogen is a crucial element in watershed material cycling, influencing ecosystem transformation processes, service functions, and biodiversity. Excessive nitrogen input leads to eutrophication and water quality degradation. With socio-economic development, human activities have intensified their impact, with human-generated nitrogen being a significant source. Compared to nitrogen inputs from agriculture, animal husbandry, and atmospheric deposition, a portion of human-generated nitrogen is directly discharged into natural water bodies, making its environmental impact more sensitive. Currently, a common method for calculating human-generated nitrogen input is to multiply the per capita nitrogen intake coefficient by the population, essentially estimating it from nitrogen sources. However, a portion of human-generated nitrogen is treated by wastewater treatment systems, meaning that not all ingested nitrogen enters the watershed; some is reduced. Some researchers have proposed calculating human-generated nitrogen in urban areas using wastewater treatment volume and rate, and in rural areas using population and nitrogen intake coefficient. While this method considers some wastewater treatment capacity, it still has the following limitations. (1) In both urban and rural areas, only a portion of the nitrogen in domestic sewage is treated, while the remainder enters the watershed directly as point or non-point sources. Treated domestic sewage enters the watershed as a point source in both urban and rural areas. Untreated domestic sewage typically enters the watershed in urban areas as a point source discharge into rivers, while in rural areas it typically enters as a non-point source through organic fertilizer recycling. Furthermore, there are significant differences in sewage treatment rates and volumes between urban and rural areas. Traditional methods struggle to objectively reflect the substantial differences in nitrogen input from urban and rural domestic sewage. (2) The nitrogen reduced by sewage treatment does not simply disappear; some enters the atmosphere through denitrification, while the rest accumulates in sludge. The nitrogen reduction from sewage treatment is directly ignored in existing methods.

[0003] In summary, existing methods for calculating net anthropogenic nitrogen input fail to reflect the objective urban-rural disparities in anthropogenic nitrogen levels within watersheds and neglect the role of wastewater in reducing nitrogen accumulation. It is necessary to study net anthropogenic nitrogen input to watersheds in accordance with nitrogen cycle processes and mass balance principles. Furthermore, a portion of anthropogenic nitrogen is emitted through point sources, while the remainder is emitted through non-point sources. Given the different environmental impacts of point and non-point source pollution, it is necessary to differentiate the nature of anthropogenic nitrogen. This will provide support for environmental management under conditions of high-intensity human activity. Summary of the Invention

[0004] The purpose of this invention is to provide a method for calculating net human-generated nitrogen input (NGI) in a watershed. This method can accurately calculate the nitrogen cycle process and net NGI input in the watershed, conforming to the mass balance principle, and can identify the point source or non-point source attributes of NGI. This invention enables refined assessment of NGI input in watersheds, reflects the objective differences in NGI input between urban and rural areas, considers the impact of sludge nitrogen, and achieves point source and non-point source attribute identification, providing technical support for watershed nitrogen management.

[0005] To achieve the above objectives, the present invention can be implemented through the following technical solution:

[0006] A method for calculating net human nitrogen input to a watershed, the specific steps of which are as follows:

[0007] Step 1: Select the watershed for calculation and obtain information such as total population, urban population, rural population, nitrogen intake coefficient, sewage discharge, sewage treatment capacity, sewage treatment volume, sludge production, sludge treatment volume, administrative boundaries, and DEM elevation from official channels such as statistical yearbooks, World Bank data, urban and rural construction statistical yearbooks, and geospatial cloud.

[0008] Step 2: Extract the watershed boundary using GIS and DEM elevation data, overlay the watershed boundary with the administrative boundary to determine the proportion of the administrative boundary within the watershed, and process the raw data based on this proportion to obtain data on the total population, urban population, rural population, sewage discharge, sewage treatment capacity, sewage treatment volume, sludge production, and sludge treatment volume within the watershed.

[0009] Step 3: Calculate the nitrogen input from early human life. Using population and nitrogen intake coefficients at different times, calculate the nitrogen input from early human life in urban and rural areas respectively. To unify the nitrogen input, reduction, and recycling amounts in subsequent processes, divide by the watershed area and perform dimensional conversion. The converted units are kg / N / km². -2 yr -1 Since the nitrogen cycle processes in urban and rural areas are not entirely the same, the nitrogen input from primitive human life in urban and rural areas should be calculated separately based on the corresponding urban or rural population, and the sum of the two should be taken as the nitrogen input from primitive human life in the watershed. In areas where conditions permit, different nitrogen intake coefficients can be used for field investigation.

[0010] YSDSR=RK×DXS / A

[0011] In the formula, YSDSR represents the nitrogen input from the original human life in the watershed, expressed as kg N km. -2 yr -1 RK represents urban or rural population (persons); DXS represents urban or rural nitrogen intake coefficient (kg N / person / year); A represents area (km²). 2 ;

[0012] Step 4: Calculate the nitrogen reduction of the wastewater treatment system. The nitrogen reduction for urban and rural areas is determined by multiplying the wastewater treatment volume by the difference between the wastewater inlet concentration and the outlet concentration. For areas without wastewater treatment capacity, the smaller of the wastewater discharge volume and the wastewater treatment capacity is used as the treatment capacity. The wastewater inlet and outlet concentrations are determined with reference to the Water Supply and Drainage Design Manual and the Pollutant Discharge Standard for Urban Wastewater Treatment Plants (GB 18918-2002). Different standards should be adopted for different periods based on the watershed conditions. Similarly, the sum of the two concentrations for rural and urban areas represents the nitrogen reduction of the watershed's wastewater treatment system.

[0013] NXJL=WSCLL×(C0-C S ) / A

[0014] In the formula, NXJL represents the nitrogen reduction amount of the watershed wastewater treatment system, expressed in kg N km. -2 yr -1 WSCLL refers to the volume of urban or rural wastewater treated, 10 3 m 3 C0 is the inlet concentration of urban or rural wastewater treatment systems, in mg / L; C s A represents the concentration at the outlet of urban or rural wastewater treatment systems, in mg / L; A represents the area, in km². 2 ;

[0015] Step 5: Calculate the nitrogen cycle volume of the sludge. The nitrogen reduced during wastewater treatment does not disappear from the watershed. Part of it is converted into nitrogen-containing gases during biochemical processes and enters the atmosphere; this part is usually calculated in the nitrogen settling section and is no longer used as nitrogen input for human life. The other part accumulates in the sludge, resulting in treated and untreated sludge. The untreated portion essentially re-enters the watershed and participates in the nitrogen cycle. The treatment of sludge is more complex. Common sludge treatments include sanitary landfill, incineration, production of building materials, and land application. According to the "Technical Specifications for Sludge Treatment and Disposal of Urban Wastewater Treatment Plants," the residue from sanitary landfill and incineration is covered with a layer of sludge on top of the landfill. Impermeable materials and natural soil theoretically limit the entry of sludge nitrogen into the watershed cycle. Sludge nitrogen from the production of building materials is also considered to have left the watershed nitrogen cycle system. Therefore, only sludge nitrogen treated through land application is considered to have entered the watershed nitrogen cycle. In summary, the amount of sludge nitrogen in the cycle is the sum of untreated sludge nitrogen and sludge nitrogen treated through land application. Similarly, for rural and urban areas, calculations should be made separately using the amount of untreated sludge, the amount of treated sludge, the nitrogen content of the sludge, and the proportion of sludge treated through land application to the total amount of sludge treated. The sum of these two calculations is the nitrogen reduction amount of the watershed wastewater treatment system. In areas where conditions permit, different sludge nitrogen contents can be used for on-site investigation.

[0016] WNDXH=WCLWN+YCLWN

[0017] WCLWN=WCLW×K / A

[0018] YCLWN=YCLW×K×R / A

[0019] In the formula, WNDXH is the nitrogen cycling rate of the watershed sludge, expressed in kg N km. -2 yr -1 WCLWN represents the nitrogen recycling rate of untreated sludge, expressed in kg N / km². -2 yr -1 YCLWN represents the nitrogen recycling rate of treated sludge, expressed in kg N / km². -2 yr -1 WCLW represents the amount of untreated sludge in urban or rural areas, in kg; K represents the nitrogen content of urban or rural sludge, in %; YCLW represents the amount of treated sludge in urban or rural areas, in kg; R represents the proportion of sludge treated by urban or rural land use to the total sludge treated, in %; A represents the area, in km². 2 ;

[0020] Step 6: Calculate the net human nitrogen input to the watershed. Subtract the nitrogen reduction of the wastewater treatment system NXJL from the original human nitrogen input YSDSR and add the nitrogen recycling amount of sludge WNDXH to obtain the net human nitrogen input JDSR. Similarly, rural and urban areas are calculated separately, and the sum of the two is the nitrogen reduction amount of the wastewater treatment system in the watershed.

[0021] JDSR = YSDSR - NXJL + WNDXH

[0022] In the formula, JDSR is the net anthropogenic nitrogen input to the watershed, expressed as kg N / km². -2 yr -1 YSDSR is the nitrogen input from the original human life in the watershed, expressed in kg N / km². -2 yr -1 NXJL represents the nitrogen reduction rate (kg N km) of a watershed wastewater treatment system. -2 yr -1 WNDXH represents the nitrogen recycling rate of sludge, expressed in kg N / km². -2 yr -1 ;

[0023] Step 7: Identify the point and non-point source attributes of nitrogen input from human life. For urban areas, the nitrogen output from human life is either collected through sewage pipes and treated by sewage treatment systems or enters water bodies through rainwater pipes and combined sewers. Regardless of the route, except for nitrogen reduced by sewage treatment plants and nitrogen from sludge recycling, it is a point source. Therefore, the point source portion of nitrogen input from human life in urban areas is the original nitrogen input from human life in urban areas (YSDSRCS) minus the nitrogen reduced by sewage treatment systems (NXJLCS). The non-point source portion in urban areas is (WNDXHCS). Nitrogen from rural areas is different from that in urban areas. In addition to being collected by sewage treatment systems, most of the remaining nitrogen enters the watershed in the form of organic fertilizer. Therefore, the point source portion of nitrogen from rural areas is the nitrogen discharged from the effluent of sewage treatment systems (NXJLNCWS), and the rest is non-point source discharge.

[0024] JDSR = JDSRRP + JDSRNP

[0025] JDSRP=YSDSRCS-NXJLCS+NXJLNCWS

[0026] NXJLNCWS=NCWSCLL×C s / A

[0027] JDSRNP=JDSR-JDSRP=WNDXHCS+(JDSRNC-NXJLNCWS)

[0028] In the formula, JDSR is the net human living nitrogen input, expressed in kg N / km². -2 yr -1 JDSRP is the point source component of net human living nitrogen input, measured in kg N / km². -2 yr -1 The non-point source portion of net human living nitrogen input (JDSRNP), kg N km -2 yr -1 YSDSRCS is the nitrogen input for primitive human life in urban areas, expressed in kg N / km². -2 yr -1 NXJLCS is the nitrogen reduction measure for urban wastewater treatment systems, expressed in kg N / km². -2 yr -1 The calculation method is shown in step five; NXJLNCWS represents the nitrogen discharge of wastewater from rural sewage treatment systems, expressed in kg N km. -2 yr -1 NCWSCLL represents the rural domestic sewage treatment capacity, 10 3 m 3 C s The concentration at the wastewater treatment system outlet is mg / L; WNDXHCS represents the nitrogen circulation rate of sludge in urban areas, kg N / km².-2 yr -1 JDSRNC represents net human nitrogen input in rural areas, expressed in kg N / km². -2 yr -1 A represents the area, in km². 2 .

[0029] The beneficial effects of this invention are as follows:

[0030] The present invention discloses a method for calculating net human living nitrogen input in a watershed, which is based on the principle of mass balance and follows the cycle of human living nitrogen in urban and rural areas. It systematically considers the nitrogen intake, treatment, and recycling process, and can accurately calculate human living nitrogen input. In addition, based on the human living nitrogen cycle, it identifies point source and non-point source components, which can provide support for the study of the environmental impact of human living nitrogen input and the high-quality management of watershed nitrogen. Attached Figure Description

[0031] Figure 1 This is a calculation structure diagram of a watershed net human living nitrogen input method;

[0032] In the figure: JDSR is the net human life nitrogen input to the watershed; NXJL is the nitrogen reduction of the watershed wastewater treatment system; NXJLCS is the nitrogen reduction of the urban wastewater treatment system; NXJLNC is the nitrogen reduction of the rural wastewater treatment system; WNDXH is the nitrogen circulation of sludge in the watershed; WNDXHCS is the nitrogen circulation of sludge in urban areas; WNDXHNC is the nitrogen circulation of sludge in rural areas; YSDSR is the nitrogen input from the original human life in the watershed; YSDSRCS is the nitrogen input from the original human life in urban areas; YSDSRNC is the nitrogen input from the original human life in rural areas; WSCLL is the wastewater treatment volume; C0 is the inlet concentration of the wastewater treatment system; C s YCLWN is the nitrogen circulation volume of untreated sludge in the watershed; YCLWNCS is the nitrogen circulation volume of untreated sludge in urban areas; YCLWNNC is the nitrogen circulation volume of untreated sludge in rural areas; YCLWN is the nitrogen circulation volume of treated sludge in the watershed; YCLWNCS is the nitrogen circulation volume of treated sludge in urban areas; YCLWNNC is the nitrogen circulation volume of treated sludge in rural areas; WCLW is the amount of untreated sludge in the watershed, kg; K is the nitrogen content of sludge; YCLW is the amount of treated sludge in the watershed; R is the proportion of land-use treated sludge to the total sludge treated; NXJLNCWS is the nitrogen discharge of wastewater treatment system effluent in rural areas; JDSRNP is the non-point source portion of net human life nitrogen input; JDSRRP is the point source portion of net human life nitrogen input; JDSRNC is the net human life nitrogen input in rural areas; JDSRCS is the net human life nitrogen input in urban areas.

[0033] Figure 2 This is a graph showing the calculated net human nitrogen input in the Liaohe River Basin (Shenyang) in an embodiment of the present invention. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments.

[0035] This invention proposes a method for calculating net human-generated nitrogen input in a watershed. Based on the nitrogen cycle and mass balance principles, this method accurately calculates the nitrogen input for human-generated nitrogen input and quickly identifies point and non-point source attributes. The specific steps of this method are as follows:

[0036] Step 1: Select the calculation domain and collect relevant information.

[0037] This case study selects the Shenyang area in the Liaohe River Basin as the case analysis. Information such as total population, urban population, rural population, nitrogen intake coefficient, wastewater discharge, wastewater treatment capacity, wastewater treatment volume, sludge production, sludge treatment volume, administrative boundaries, and DEM elevation were obtained from official channels such as statistical yearbooks, World Bank data, urban and rural construction statistical yearbooks, and geospatial cloud.

[0038] Step 2: Use GIS and DEM elevation data to extract the watershed boundary, overlay the watershed boundary with the administrative boundary, and calculate that 71.15% of the administrative area of ​​Shenyang City belongs to the Liaohe River Basin. When only one city is calculated, since this invention uses the unit area method, no proportional conversion is required. However, considering that large watersheds usually involve multiple cities and the watershed proportion of each city is different, conversion must be performed in this case.

[0039] Step 3: Calculate the original human nitrogen input for urban, rural, and watershed areas. In 2001, China's per capita nitrogen intake coefficient was taken as 4.58 kg N / person / year. This coefficient was multiplied by the population of the urban and rural areas within the Liaohe River Basin (Shenyang) in 2001 and divided by the area, yielding the original human nitrogen input for urban and rural areas as 1482.81 kg N / km². -2 yr -1 and 955.40 kg Nkm -2 yr -1 The nitrogen input from the original human life in the basin was 2484.21 kg N / km². -2 yr -1 .

[0040] Step 4: Calculate the nitrogen reduction of urban, rural, and watershed wastewater treatment systems. The wastewater inlet and outlet concentrations are 40 mg / L and 20 mg / L, respectively (Class B standard adopted in 2001). According to the Urban and Rural Construction Statistical Yearbook, the urban wastewater discharge is 420.28 million tons, and the urban wastewater treatment capacity is 182.5 million tons. Taking 182.5 million tons as the urban domestic wastewater treatment volume, substituting it into the formula in Step 4, we can obtain the nitrogen reduction of the urban wastewater treatment system as 281.90 kg N·m³ / s. -2 yr -1 The wastewater treatment volume in rural areas is 0.16 million tons, and the calculated nitrogen reduction from the rural wastewater treatment system is 0.003 kgN / km². -2 yr -1 The total nitrogen reduction achieved by the watershed's wastewater treatment system was 281.903 kg N·m³. -2 yr -1 .

[0041] Step 5: Calculate the nitrogen cycle of sludge in urban areas, rural areas, and watersheds. The sludge production, treatment, and untreated amounts in urban areas are 40,150 tons, 35,308 tons, and 4,842 tons, respectively. The nitrogen content of the sludge is 4%. Sludge treated through land application accounts for 60.72% of the total wastewater treatment. Substituting these values ​​into the formula in Step 5, the nitrogen cycle of sludge in urban areas can be calculated as 81.184 kg N / km². - 2 yr -1 The amount of sludge discharged, treated, and untreated in rural areas was 0.36 tons, 0.32 tons, and 0.04 tons, respectively, with a nitrogen content of 4%. Sludge treated through land application accounted for 60.72% of the total wastewater treatment. Similarly, the nitrogen cycle of sludge in rural areas was calculated to be 0.001 kg N·m·K. -2 yr -1 The total nitrogen cycling volume of sludge in the watershed was 81.185 kg N·m³. -2 yr -1 .

[0042] Step 6: Calculate the net nitrogen input from human life in the watershed. Subtract the nitrogen reduction from the wastewater treatment system (NXJL) from the original nitrogen input from human life in the watershed (YSDSR), and add the nitrogen recycling volume from the sludge (WNDXH) to obtain the net nitrogen input from human life in the watershed (JDSR). The calculated net nitrogen input from human life in the urban area is 1282.094 kg N / km². -2 yr -1 The net nitrogen input for human life in rural areas is 955.398 kg N / km². -2 yr -1 The net nitrogen input from human activities in the basin was 2237.492 kg N / km². -2 yr-1 .

[0043] Step 7: Identify the point source and non-point source attributes of nitrogen input from human life. For rural areas, point source nitrogen is calculated by multiplying the treated wastewater volume by the wastewater discharge concentration. Substituting this into the formula from Step 7, the nitrogen discharge from the wastewater treatment system in rural areas is calculated to be 0.03 kg N / km². -2 yr -1 Point source nitrogen in urban areas is calculated by subtracting nitrogen reduction from wastewater treatment systems from primary human living nitrogen. Adding urban and rural point source nitrogen together yields a total watershed point source nitrogen of 1200.913 kg N / km². -2 yr -1 Subtracting the point source nitrogen from the total net anthropogenic nitrogen in the basin yields the non-point source nitrogen from anthropogenic sources, which is 1036.579 kg N / km². -2 yr -1 Further calculations based on the composition of non-point source nitrogen from human activities in the watershed show that the non-point source nitrogen in urban areas, i.e., the nitrogen cycle in urban sludge, is 81.184 kg N·m³ / km². -2 yr -1 Non-point source nitrogen in rural areas represents a net human nitrogen input of 955.398 kg Nkm. -2 yr -1 Subtract 0.003 kg N / km from the nitrogen discharge in the effluent from rural wastewater treatment systems. -2 yr -1 The calculation showed that the non-point source nitrogen input from human activities in the watershed was 1036.579 kg N / km². -2 yr -1 .

[0044] The case analysis in this embodiment shows that the method of the present invention not only has a clear structure that considers the entire process of input, treatment, and recycling, reflecting the objective differences in nitrogen from urban and rural human life and the impact of sludge nitrogen, but also conforms to quality balance. It can quickly and accurately calculate watershed nitrogen input from human life and identify point source and non-point source attributes, providing support for watershed nitrogen environment management.

[0045] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for calculating net human-generated nitrogen input in a watershed, characterized in that, Includes the following steps: Step 1: Select the calculation basin and obtain total population, urban population, rural population, nitrogen intake coefficient, wastewater discharge, wastewater treatment capacity, wastewater treatment volume, sludge production, sludge treatment volume, administrative boundaries, and DEM elevation information from official channels; Step 2: Extract the watershed boundary using GIS and DEM elevation data, overlay the watershed boundary with the administrative boundary to determine the proportion of the administrative boundary within the watershed, and process the raw data based on this proportion to obtain data on the total population, urban population, rural population, sewage discharge, sewage treatment capacity, sewage treatment volume, sludge production, and sludge treatment volume within the watershed. Step 3: Calculate the nitrogen input for primitive human life. Using population and nitrogen intake coefficients at different times, calculate the nitrogen input for primitive human life in urban and rural areas respectively. For dimensionality conversion, the units are kg, N, and km. -2 yr -1 Nitrogen input from primary human life in urban and rural areas is calculated separately based on the corresponding urban or rural population, and the sum of the two is taken as the nitrogen input from primary human life in the watershed. In areas where conditions permit, different nitrogen intake coefficients can be used for field investigation. Step 4: Calculate the nitrogen reduction of the wastewater treatment system. The nitrogen reduction for urban and rural areas is determined by multiplying the wastewater treatment volume by the difference between the wastewater inlet concentration and the outlet concentration. For areas without wastewater treatment capacity, the smaller of the wastewater discharge volume and the wastewater treatment capacity is used as the treatment capacity. The wastewater inlet and outlet concentrations are determined with reference to the water supply and drainage design manual and the pollutant discharge standards for urban wastewater treatment plants. Different standards should be adopted for different periods based on the watershed conditions. Similarly, the sum of the two values ​​for rural and urban areas represents the nitrogen reduction of the watershed's wastewater treatment system. Step 5: Calculate the nitrogen recycling amount of sludge. The nitrogen reduced during the wastewater treatment process does not disappear from the watershed. The nitrogen recycling amount of sludge is the nitrogen of untreated sludge plus the nitrogen of sludge treated by land application. Similarly, for rural and urban areas, the nitrogen recycling amount of sludge is calculated separately based on the amount of untreated sludge, the amount of treated sludge, the nitrogen content of sludge, and the proportion of sludge treated by land application to the total amount of sludge treated. The sum of the two is the nitrogen reduction amount of the wastewater treatment system in the watershed. In areas where conditions permit, different sludge nitrogen contents can be used for on-site investigation. Step 6: Calculate the net human nitrogen input to the watershed. Subtract the nitrogen reduction of the wastewater treatment system NXJL from the original human nitrogen input YSDSR and add the nitrogen recycling amount of sludge WNDXH to obtain the net human nitrogen input JDSR. Similarly, rural and urban areas are calculated separately, and the sum of the two is the nitrogen reduction amount of the wastewater treatment system in the watershed. JDSR = YSDSR - NXJL + WNDXH In the formula, JDSR is the net anthropogenic nitrogen input to the watershed, expressed in kg N / km². -2 yr -1 YSDSR is the nitrogen input from the original human life in the watershed, expressed in kg N / km². -2 yr -1 NXJL represents the nitrogen reduction rate (kg N km) of a watershed wastewater treatment system. -2 yr -1 WNDXH is the nitrogen recycling rate of sludge, expressed in kg N km. -2 yr -1 ; Step 7: Identify the point source and non-point source attributes of nitrogen input from human life. For urban areas, the point source portion of nitrogen input from human life is the original nitrogen input from human life in the urban area (YSDSRCS) minus the nitrogen reduction from the wastewater treatment system (NXJLCS). The non-point source portion in urban areas is (WNDXHCS). For rural areas, the point source portion of nitrogen input from human life is the nitrogen discharged from the effluent of the wastewater treatment system (NXJLNCWS), and the rest is non-point source discharge. JDSR = JDSRRP + JDSRNP JDSRP=YSDSRCS-NXJLCS+NXJLNCWS NXJLNCWS=NCWSCLL×C s / A JDSRNP= JDSR- JDSRP=WNDXHCS+ (JDSRNC- NXJLNCWS) In the formula, JDSR is the net anthropogenic nitrogen input to the watershed, expressed in kg N / km². -2 yr -1 JDSRP is the point source component of net anthropogenic nitrogen input to the watershed, measured in kg N / km². -2 yr -1 JDSRNP is the non-point source portion of net anthropogenic nitrogen input to the watershed, expressed as kg N / km². -2 yr -1 YSDSRCS is the nitrogen input for primitive human life in urban areas, expressed in kg N / km². -2 yr -1 NXJLCS is the nitrogen reduction measure for urban wastewater treatment systems, expressed in kg N / km². -2 yr -1 The calculation method is shown in step four; NXJLNCWS represents the nitrogen discharge of wastewater from rural sewage treatment systems, expressed in kg N / km². -2 yr -1 NCWSCLL represents the rural domestic sewage treatment capacity, 10 3 m 3 ; C s This refers to the effluent concentration at the wastewater treatment system outlet, in mg / L; WNDXHCS represents the nitrogen circulation rate of sludge in urban areas, in kg N / km². -2 yr -1 JDSRNC represents net human nitrogen input in rural areas, expressed in kg N / km². -2 yr -1 A represents the area, in km². 2 .

2. The method for calculating net human living nitrogen input in a watershed according to claim 1, characterized in that, In step three, the formula for calculating the nitrogen input for primitive human life is as follows: YSDSR=RK×DXS / A In the formula, YSDSR represents the nitrogen input from the original human life in the watershed, expressed as kg N km. -2 yr -1 RK represents urban or rural population (in people); DXS represents urban or rural nitrogen intake coefficient (kg N / person / year); A represents area (km²). 2 .

3. The method for calculating net human living nitrogen input in a watershed according to claim 1, characterized in that, Step four, the formula for calculating the nitrogen reduction of the wastewater treatment system, is as follows: NXJL=WSCLL×(C0-C S ) / A In the formula, NXJL represents the nitrogen reduction amount of the watershed wastewater treatment system, expressed in kg N km. -2 yr -1 WSCLL refers to the volume of urban or rural wastewater treated, 10 3 m 3 C0 is the inlet concentration of urban or rural wastewater treatment systems, in mg / L; C s A represents the concentration at the outlet of urban or rural wastewater treatment systems, in mg / L; A represents the area, in km². 2 .

4. The method for calculating net human living nitrogen input in a watershed according to claim 1, characterized in that, Step five: The formula for calculating the nitrogen circulation rate of sludge is as follows: WNDXH=WCLWN+YCLWN WCLWN=WCLW×K / A YCLWN = YCLW × K × R / A In the formula, WNDXH is the nitrogen cycling rate of the watershed sludge, expressed in kg N km. -2 yr -1 WCLWN represents the nitrogen recycling rate of untreated sludge, expressed in kg N / km². -2 yr -1 YCLWN represents the nitrogen recycling rate of treated sludge, expressed in kg N / km². -2 yr -1 WCLW represents the amount of untreated sludge in urban or rural areas, in kg; K represents the nitrogen content of urban or rural sludge, in %; YCLW represents the amount of treated sludge in urban or rural areas, in kg; R represents the proportion of sludge treated by urban or rural land use to the total sludge treated, in %; and A represents the area, in km². 2 .

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