A method for determining a differentiated water pollutant emission trading ratio

Abstract

The present application relates to the differential based water pollutant emission right transaction ratio determination method, can effectively solve the problem that the transaction is not equal and the water environment quality cannot be guaranteed due to the spatial position of the pollution source, the industry pollutant type difference, the technical solution solved is, including the following steps: 1) construct the differential based water pollutant emission right transaction ratio model;2) clear water pollutant emission right transaction type and its corresponding transaction ratio type;3) establish the differential water pollutant emission right transaction ratio initial value model;4) determine the water pollutant emission right transaction ratio final value;The present application is suitable for the determination of the transaction ratio under different water pollutant emission right transaction types, makes up the current transaction conversion coefficient, so as to promote the effective development of cross-regional, cross-industry emission right transaction, has strong pertinence and use value, is a great innovation on the water pollutant emission right transaction ratio determination method.

Description

Technical Field

[0001] This invention relates to the field of environmental protection, and in particular to a method for determining the ratio of pollution discharge rights trading based on differentiated water pollutants. Background Technology

[0002] Emissions trading refers to the trading of pollutant emission quotas between pollution sources within the framework of the total pollutant emission control system, aimed at reducing emission reduction costs and efficiently utilizing environmental capacity resources. Domestic and international scholars have conducted extensive research on emissions trading from the perspectives of trading models, compensation mechanisms, and implementation progress. With in-depth research and practice, it has been found that while emissions trading can effectively improve the allocation efficiency of environmental capacity resources, water pollutants, as indicators for emissions trading, often exhibit non-uniform mixing characteristics. Pollutant migration and transformation vary depending on the spatial location of the emission source, and the properties of pollutants also differ across industries. If emissions trading is conducted at a 1:1 ratio, the receiving region may experience a rapid increase in pollutant emissions, exceeding its environmental capacity and risking a decline in local environmental quality, potentially triggering a "hotspot" issue that directly impacts the environmental quality of the receiving region. To avoid this problem, it is crucial to set appropriate trading ratios to constrain the volume of water pollutant emissions trading in each region, ensuring that water environmental quality is not sacrificed, and allowing both parties to freely trade according to a certain ratio.

[0003] In my country's pilot regions for emissions trading, many have established conversion factors to ensure the environmental quality of the recipient areas. However, these factors generally only consider spatial distance and are determined using a one-dimensional steady-state water quality model. The calculations do not account for the differences in environmental risks caused by different types of pollutants and effluent standards across industries, resulting in limited outcomes. Furthermore, emissions trading has expanded from pilot programs to include multiple industries and the entire sector, and from intra-city / county trading to province-wide trading. From a design perspective, the current emissions trading system encourages and promotes cross-industry and cross-regional transactions, indicating that conversion factors that only consider spatial distance are not suitable for the current development trend. To address the mismatch between these conversion factors and the current needs of emissions trading, this paper proposes a method for determining trading ratios under different emissions trading models in my country, taking regional total emissions, section water quality, and emission reduction costs as control targets, and comprehensively considering factors such as spatial location and pollution type. However, no publicly reported methods have been developed to date. Summary of the Invention

[0004] In view of the above situation and to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a method for determining the trading ratio of water pollutant discharge rights based on differentiation, which can effectively solve the problem of unequal trading and the inability to guarantee water environmental quality caused by differences in the spatial location of pollution sources and the types of pollutants in different industries.

[0005] The technical solution provided by this invention includes the following steps:

[0006] 1) Construct a differentiated water pollutant discharge rights trading ratio model;

[0007] 2) Obtain data on the permitted and current emissions of pollutants for the traded industrial enterprises within their respective regions, calculate the permitted and current emissions for the region, and determine whether cross-regional trading conditions are met based on the relationship between current and permitted emissions for the region; determine whether cross-industry trading conditions are met from the perspective of the biodegradability of wastewater (expressed as BOD5 / COD value) and the types of symbiotic pollutants (pollutants other than the traded pollutants) of the participating industrial enterprises; and further clarify the type of water pollutant discharge rights trading and its corresponding trading ratio type.

[0008] 3) Select influencing factors that characterize different types of water pollution discharge rights trading, determine the calculation method for the initial value of the discharge rights trading ratio for different types, and establish a differentiated model for the initial value of the water pollutant discharge rights trading ratio;

[0009] 4) Adjust the initial value of the emission rights trading ratio based on the total regional amount, cross-sectional water quality targets and emission reduction costs, and determine the final value of the emission rights trading ratio for water pollutants.

[0010] This invention is applicable to the determination of trading ratios under different types of water pollutant discharge rights trading, making up for the inapplicability of current trading conversion factors. It can effectively solve the problem of unequal trading and water environmental quality that are caused by differences in the spatial location of pollution sources and the types of pollutants in different industries. This promotes the effective development of cross-regional and cross-industry discharge rights trading, and has strong pertinence and application value. It is a major innovation in the method of determining the trading ratio of water pollutant discharge rights. Attached Figure Description

[0011] Figure 1 This is the overall flowchart of the present invention.

[0012] Figure 2 For the present invention Figure 1 The flowchart shows the types of water pollutant discharge rights trading and their corresponding trading ratio types.

[0013] Figure 3 For the present invention Figure 1 The flowchart shown is for establishing an initial value model for the differentiated water pollutant discharge rights trading ratio.

[0014] Figure 4 For the present invention Figure 1 The flowchart shown illustrates the determination of the final value of the pollution rights trading ratio for water pollutants. Detailed Implementation

[0015] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and specific examples.

[0016] Example 1

[0017] In its specific implementation, this invention includes the following steps:

[0018] 1) such as Figure 1 As shown, a differentiated water pollutant discharge rights trading ratio model is constructed using the following method:

[0019] Based on the types of pollution discharge rights trading, the factors influencing the trading ratio, and the methods for adjusting the pollution discharge rights trading ratio, pollution discharge rights trading ratio models are constructed for different types of trading, as shown in the following formulas:

[0020] λ ij =f{a ij (c,k,u,L),b ij (c,v,D),A ij (c,k,u,L,v,D)}

[0021] Where, λ ij For the emissions trading ratio; a ij b is the distance ratio; ij Industry ratio; A ij ρ is the coupling ratio; c is the pollutant emission concentration in mg / L; k is the pollutant attenuation coefficient in dg / L. -1 u represents flow velocity in m / s; L represents the distance from the discharging enterprise to the downstream section in m; v represents the volume of the discharged pollutant medium in m³. 3 D represents the pollutant equivalent value per unit mass, in kg.

[0022] 2) such as Figure 2 As shown, the types of water pollutant discharge rights trading and their corresponding trading ratio types are clearly defined by the following method:

[0023] By obtaining data on permitted and current water pollutant discharge volumes within the regions where participating industrial enterprises are located, the total permitted and current water pollutant discharge volumes within the regions are calculated. Based on the relationship between the total permitted and current water pollutant discharge volumes within the regions, the regions for water pollutant discharge rights trading are identified. If the total permitted water pollutant discharge volume of the trading target within the region is greater than the current discharge volume, cross-regional trading is permitted. If the total permitted water pollutant discharge volume of the trading target within the region is less than or equal to the current discharge volume, then discharge rights trading is only permitted within the region.

[0024] Secondly, the conditions for cross-industry trading are determined from the perspective of the biodegradability of wastewater (expressed by the BOD5 / COD ratio) and the types of symbiotic pollutants (pollutants other than the pollutants in the traded object) of the industrial enterprises participating in the transaction. If the industrial enterprises participating in the transaction have similar wastewater biodegradability (consistent BOD5 / COD ratio range) and similar types of symbiotic pollutants (similar types of pollutants other than the pollutants in the traded object and no toxic or harmful substances), then cross-industry trading can be carried out; otherwise, intra-industry trading is carried out.

[0025] The BOD5 / COD ratio range is as follows: when the BOD5 / COD value is >0.58, the wastewater is completely biodegradable; when the BOD5 / COD value is between (0.45 and 0.58), the wastewater is well biodegradable; when the BOD5 / COD value is between (0.30 and 0.45), the wastewater is biodegradable; and when the BOD5 / COD value is <0.3, the wastewater is difficult to biodegrade.

[0026] The types of co-existing pollutants in wastewater from various industries can be referenced to the pollutant indicators that are subject to emission limits in the corresponding industry's water pollutant discharge standards; toxic and hazardous substances refer to heavy metals and their recalcitrant organic compounds contained in industry wastewater, and cross-industry trading of these substances is not permitted.

[0027] Accordingly, four types of water pollutant discharge rights trading and corresponding four types of water pollutant discharge rights trading ratios are established. The four types of water pollutant discharge rights trading are intra-industry discharge rights trading within a region, inter-industry discharge rights trading within a region, intra-industry discharge rights trading across a region, and inter-regional inter-industry discharge rights trading. The corresponding four types of trading ratios are intra-industry discharge rights trading ratio within a region, inter-industry discharge rights trading ratio within a region, intra-industry discharge rights trading ratio across a region, and inter-regional inter-industry discharge rights trading ratio. Different types of trading ratios correspond to different influencing factors. Intra-industry discharge rights trading ratio within a region and intra-industry discharge rights trading ratio across a region are only affected by spatial distance and can be represented by distance ratio. Inter-industry discharge rights trading ratio within a region and inter-regional inter-industry discharge rights trading ratio are affected by multiple factors such as spatial distance and pollutant type and can be represented by coupling ratio composed of distance ratio and industry ratio.

[0028] 3) such as Figure 3 As shown, a model for the initial value of the differentiated water pollutant discharge rights trading ratio is established to determine the initial value of the discharge rights trading ratio. The method is as follows:

[0029] ① The distance ratio considers the characteristics of pollutant transport and transformation. Starting from the general theoretical method of the emission rights trading ratio, a water quality impact model reflecting the spatial location of pollution sources and the characteristics of pollutant transport and transformation is established. By calculating the water quality impact concentration of different industrial enterprises relative to the same control section, the initial value of the distance ratio between each trading industrial enterprise is determined.

[0030] The specific formula for calculating the distance ratio in a water quality impact model that reflects the spatial location of pollution sources and the characteristics of pollutant transport and transformation is as follows:

[0031] a ij =C j / C i =exp[k(L i -L j ) / u]

[0032] Where, a ij For each polluting enterprise, i represents the enterprise purchasing the polluting quota; j represents the number of pollutant emission quotas obtainable per unit of pollutant emission quota, i.e., the distance ratio; and k represents the pollutant attenuation coefficient, in meters (d). -1 u represents flow velocity, in m / s; L i L j The distances of polluting enterprises i and j from the downstream section are in meters.

[0033] ② The industry ratio for water pollutant discharge rights trading is based on general theoretical methods, and a model reflecting the degree of environmental damage caused by different types of pollutants is established. By calculating the degree of impact of different polluting enterprises on water bodies, the initial value of the industry ratio among the trading industrial enterprises is determined.

[0034] The specific calculation formula for industry ratios in water quality models that use pollutant equivalent values ​​to reflect the degree of pollutant damage is as follows:

[0035]

[0036] In the formula, C i C j V represents the current emission concentration of pollutants for the traded target, in mg / L. i V j The volume of the pollutant medium being discharged is expressed in meters (m). 3 ;D i D j The value represents the equivalent amount of pollutants per unit of traded goods, expressed in kg; H is the unit conversion factor.

[0037] ③ Based on a comprehensive consideration of spatial distance and industry category differences, a coupling ratio calculation formula is established to reflect the pollutant attenuation and the impact of different pollutants on water quality:

[0038]

[0039] In the formula, Aij is the coupling ratio, and C i C j V represents the current emission concentration of pollutants for the traded target, in mg / L. i V j The volume of the pollutant medium being discharged is expressed in meters (m). 3 ;D i D j The value represents the equivalent amount of pollutants per unit of traded asset, in kg; H is the unit conversion factor; k is the pollutant attenuation coefficient, in d. -1 u represents flow velocity, in m / s; L i L j The distances of polluting enterprises i and j from the downstream section are in meters.

[0040] 4) such as Figure 4 As shown, the trading ratio is adjusted using regional total emission control targets, section water quality targets, and emission reduction costs as constraints, so that the trading ratio simultaneously meets the regional total emission control targets, section water quality targets, and emission reduction cost targets, thereby determining the final value of the water pollutant discharge rights trading ratio. The method is as follows:

[0041] Total quantity control:

[0042] Water quality targets:

[0043] Cost control: A ij ≥P j / (P i +E i )

[0044] In the formula, Q i The current total pollutant discharge in the area where polluting enterprise i is located, in t / a; A ij For the transaction ratio; Q ij C represents the amount of pollution discharge rights sold by polluting enterprise j to polluting enterprise i, in t / a; C0 represents the concentration contribution of the upstream river to the control section, in mg / L; C i The concentration of pollutant discharged by enterprise i per unit discharge volume on the control section is expressed in mg / L; C s To control the water quality target at the cross-section, the unit is mg / L; P i P j To reduce the unit pollutant cost for polluting enterprises i and j, the unit is yuan / t; Ei The GDP per unit of pollutant emissions is expressed in yuan / t.

[0045] To further understand the invention's content, features, and usage, the following examples are provided for detailed explanation.

[0046] The example exists in a river basin. Three discharge points belonging to different administrative regions were selected in this river section: A1, A2, and A3. A1 and A2 are for starch production, and A3 is for sugar production. The distances from each discharge point to the downstream section are L1, L2, and L3, respectively. The pollutant in the traded item is COD, and the influent water quality for this river section has a COD concentration of 25 mg / L. The control units are C... s1 C s2 C s3 The target COD for each cross-section is 30 mg / L, and the design flow rate of the river is 12.24 m³ / h. 3 / s, pollutant attenuation coefficient k=0.1 / d, flow velocity u=0.1m / s, as shown in Table 1.

[0047] Table 1 Comparison of parameters at three emission points in different administrative regions

[0048]

[0049] Data description: Data was obtained through statistical yearbooks, environmental statistics, environmental protection plans, and surveys.

[0050] 1) Construct a differentiated water pollutant discharge rights trading ratio model;

[0051] 2) Clarify the types of water pollutant discharge rights trading and the corresponding trading ratio types;

[0052] Data obtained through regional statistical yearbooks, environmental statistics, environmental protection plans, and surveys were used to calculate the permitted total discharge and current total discharge data of water pollutants in the regions where A1, A2, and A3 are located. It was found that the current total discharge of the three companies in the regions where they are located is less than the permitted total discharge. Therefore, A1, A2, and A3 can engage in cross-regional pollution discharge rights trading.

[0053] Secondly, A1, A2, and A3 belong to the starch industry, sugar industry, and sugar refining industry, respectively. The BOD5 / COD ratios of wastewater from the starch industry and sugar refining industry are 0.3 and 0.33, respectively, with a range between (0.30 and 0.45). The wastewater from both the starch industry and sugar refining industry has good biodegradability and is classified as biodegradable wastewater with similar wastewater properties. The wastewater discharge standards implemented by A1, A2, and A3 are the "Water Pollutant Discharge Standard for Starch Industry (GB25461-2010)", "Water Pollutant Discharge Standard for Starch Industry (GB25461-2010)", and "Water Pollutant Discharge Standard for Sugar Industry (GB21909-2008)", respectively. The types of water pollutants that are limited in the discharge standards for the starch industry and sugar refining industry are pH value, SS, BOD5, COD, NH3-N, TN, and TP. All of them show high SS concentrations and no toxic or harmful substances. In summary, the starch industry and the sugar industry have similar wastewater properties and types of symbiotic pollutants. Therefore, A1, A2, and A3 can be traded across industries for pollution discharge rights.

[0054] Accordingly, A1 and A2 can conduct cross-regional intra-industry pollution discharge rights trading, while A1 and A3, and A2 and A3 can conduct cross-regional cross-industry pollution discharge rights trading. Therefore, the trading between A1 and A2 corresponds to the cross-regional intra-industry pollution discharge rights trading ratio, i.e., the distance ratio, while the trading between A1 and A3, and A2 and A3 corresponds to the cross-regional cross-industry pollution discharge rights trading ratio, i.e., the coupling ratio.

[0055] 3) Establish a differentiated initial value model for the pollution discharge rights trading ratio and determine the initial value of the pollution discharge rights trading ratio;

[0056] ①The wastewater discharge rights of enterprises A1, A2, and A3 are traded among themselves. The initial values ​​of the distance ratio are shown in Table 2.

[0057] Table 2 Initial values ​​of the distance ratio of three emission points in different administrative regions

[0058]

[0059] ② Referring to the "Table of Equivalent Values ​​of Water Pollutants", the equivalent values ​​of COD, SS, BOD, TP, and NH3-N per unit mass (1 kg) can be expressed as: 1 kg COD = 4 kg SS = 0.5 kg BOD5 = 0.25 kg TP = 0.8 kg NH3-N. Therefore, based on the premise that wastewater from the starch and sugar industries meets discharge standards, and considering the trading of wastewater discharge rights per unit volume, the initial calculation result of the cross-industry ratio when the starch industry (belonging to A1 and A2) trades wastewater discharge rights with the sugar industry (belonging to A3) is as follows:

[0060] The initial value of the ratio of the starch industry purchasing COD emission rights per unit mass from the sugar industry is as follows:

[0061]

[0062] The initial value of the ratio of the sugar industry purchasing COD emission rights per unit mass from the starch industry is:

[0063]

[0064] ③ Cross-regional and cross-industry pollution discharge rights trading between A1 and A3, and between A2 and A3, needs to take into account spatial distance and differences in industry categories. Therefore, the initial settlement results of the coupling ratio are shown in Table 3.

[0065] Table 3. Calculation results of the initial values ​​of the coupling ratio of the three emission points in different administrative regions.

[0066]

[0067] In summary, the initial values ​​of the water pollutant discharge rights trading ratios among A1, A2, and A3 are shown in Table 4.

[0068] Table 4. Preliminary values ​​of pollutant discharge rights trading ratios at three discharge points in different administrative regions.

[0069]

[0070] 4) Adjust the trading ratio using regional total emissions, cross-sectional water quality targets, and emission reduction costs as constraints to determine the final value of the emissions trading ratio;

[0071] When no pollutants enter the river along its course, and only a pollutant concentration of 25 mg / L enters at the source, the pollutant concentrations at the outlet sections of each water function zone are 15.61 mg / L, 9.3 mg / L, and 5.76 mg / L, respectively. After removing the influence of the initial inflow concentration, the water quality targets for each control section are 14.39 mg / L, 20.70 mg / L, and 24.24 mg / L, respectively, i.e., Cs = (14.39, 20.70, 24.24).

[0072] Taking a water pollutant discharge rights trading volume of 3860 t / a and a corresponding concentration of 10 mg / L as an example, the trading ratio is analyzed as follows:

[0073] When A1 purchases pollutant emission quotas for A2, C s1 C s2 C s3 The water quality at the control section was C = (16.25, 9.69, 12.18), which is consistent with C s In comparison, C s1 The water quality at one section did not meet the standards, but the water quality at the other sections met the standards.

[0074] When A1 purchases pollutant emission quotas for A3, C s1 C s2 Cs3 The water quality at the control section was C = (20.37, 18.10, 11.2), which is consistent with C s In comparison, C s1 The water quality at one section did not meet the standards, but the water quality at the other sections met the standards.

[0075] When A2 purchases pollutant emission quotas from A1, C s1 C s2 C s3 The water quality at the control section was C = (0, 9.66, 12.17). Compared with Cs, the water quality at all sections met the standards.

[0076] When A2 purchases pollutant emission quotas for A3, C s1 C s2 C s3 The water quality at the control section was C = (6.25, 18.09, 11.19). Compared with Cs, the water quality at all sections met the standards.

[0077] When A3 purchases pollutant emission quotas from A1, C s1 C s2 C s3 The water quality at the control section was set at C = (0, 5.96, 12.6), which is consistent with C s In comparison, the water quality at all cross-sections met the standards;

[0078] When A3 purchases A2's pollutant emission quota, C s1 C s2 C s3 The water quality at the control section was C = (6.25, 3.69, 12.87), which is consistent with C s In comparison, the water quality at all cross-sections met the standards;

[0079] In summary, when the pollutant discharge rights trading ratio is calculated using theoretical methods, it will inevitably lead to water quality exceeding standards in some administrative sections. Therefore, it is necessary to adjust the trading ratio to protect water quality.

[0080] Regional aggregate constraints:

[0081] Based on the existing trading ratio, the trading volume for pollution discharge rights is 3860t / a. After calculation, it was found that the total pollution discharge after the trading is within the total amount of regional pollution discharge permits.

[0082] Water quality target constraints:

[0083] When water functional zone A1 purchases pollutant discharge quotas from A2, the water environmental quality of A1 should be guaranteed, that is:

[0084] (α 11 +α 12 C1exp[-kL1 / u]≤CS1

[0085] (1+α 12 10×exp[-0.1×40.7×1000 / 24×3600×0.1]≤14.39

[0086] α 12 =1.31

[0087] When water function zone A1 purchases pollutant discharge quotas from A3, the water environmental quality of A1 should be guaranteed, that is:

[0088] (α 11 +α 13 C1exp[-kL1 / u]≤C S1

[0089] (1+α 13 10×exp[-0.1×40.7×1000 / 24×3600×0.1]≤14.39

[0090] α 13 =1.31

[0091] Emissions reduction cost constraints:

[0092] Survey data shows that the average cost of treating chemical oxygen demand (COD) per unit is similar between the starch and sugar industries, both at 2000 yuan / t. According to environmental statistics, the output value per unit of wastewater from the starch industry is 3041 yuan / t, while that from the sugar industry is 2252 yuan / t. After verification with transaction ratios, both meet the requirements.

[0093] Based on the above constraints, the results of adjusting the pollutant discharge rights trading ratios among different administrative regions are shown in Table 5.

[0094] Table 5 Final values ​​of pollutant discharge rights trading ratios at three discharge points in different administrative regions.

[0095]

[0096] The above results indicate that the distance ratio and coupling ratio do not differ significantly in intra-industry transactions. However, when conducting cross-industry transactions, the coupling ratio is more equitable than the distance ratio alone, as shown in this example, A. 23 The starch industry purchased pollution discharge rights from the sugar industry. The single distance ratio was 1.68. After coupling the distance ratio with the industry ratio, the transaction ratio was adjusted to 1.41, a decrease of 16.1%. 31The sugar industry purchases pollution discharge rights from the starch industry. The single distance ratio is 0.37. After coupling the distance ratio with the industry ratio, the transaction ratio is adjusted to 0.44, an increase of 18.9%. From the perspective of the wastewater properties and discharge standards of the starch and sugar industries, the wastewater discharge standards of the sugar industry are higher than those of the starch industry, resulting in relatively higher pollution control costs. Therefore, in terms of the industry ratio, when the starch industry purchases pollution discharge rights from the sugar industry, the actual amount of pollution discharge obtained from purchasing one unit of discharge is less than one unit; while when the sugar industry purchases pollution discharge rights from the starch industry, the actual amount of pollution discharge obtained from purchasing one unit of discharge is greater than one unit. Therefore, in cross-industry transactions, coupling the distance ratio with the industry ratio to determine the ratio result is more equitable. Secondly, adjusting the pollution discharge rights transaction ratio based on regional total amount, cross-sectional water quality, and emission reduction costs can better activate the pollution discharge rights trading market. In this example, under the constraints of regional total amount and cross-sectional water quality, A 12 A 13 The emissions trading ratios have all decreased to some extent, and the adjusted ratios are designed to ensure that both parties in the transaction benefit. Therefore, they have a certain stimulating effect on both parties participating in the transaction.

[0097] The method of this invention is scientific and reasonable. By clarifying the determination method of different types of trading ratios, it effectively solves the problem that water quality cannot be guaranteed in the current cross-regional and cross-industry pollution discharge rights trading. It can promote the development of pollution discharge rights trading, help activate the pollution discharge rights trading market, provide technical support for the effective operation of pollution discharge rights trading and the protection of regional water environment quality, and provide theoretical support for improving the pollution discharge rights trading mechanism. It has practical promotion and application value.

Claims

1. A method for determining a differentiated water pollutant emission trading ratio, characterized in that, It comprises the following steps: 1) constructing a differentiated water pollutant emission trading ratio model; 2) obtaining the transaction target pollutant permit emission and current emission data of the industrial enterprises in the region participating in the transaction, calculating the regional permit emission and current emission, determining whether the cross-regional transaction condition is met according to the relationship between the regional current emission and the permit emission, determining whether the cross-industry transaction condition is met from the perspectives of the wastewater biodegradability and symbiotic pollutant types of the industrial enterprises participating in the transaction, and then determining the water pollutant emission trading type and the corresponding trading ratio type; 3) selecting the influencing factors representing different water pollutant emission trading types, determining the calculation method of the initial value of the different types of emission trading ratio, and establishing a differentiated water pollutant emission trading ratio initial value model; 4) adjusting the initial value of the emission trading ratio according to the regional total amount, the section water quality target and the emission reduction cost, and determining the final value of the water pollutant emission trading ratio; In the step 3), the differentiated water pollutant emission trading ratio initial value model is established, and the initial value of the emission trading ratio is determined by: ① The distance ratio considers the characteristics of pollutant transport and transformation, and the water pollutant emission trading ratio is determined by starting from the general theoretical method of the water pollutant emission trading ratio, establishing a water quality influence model reflecting the spatial position of the pollution source and the characteristics of pollutant transport and transformation, and calculating the water quality influence concentration of the unit emission of the water pollutant of different industrial enterprises relative to the same control section to determine the initial value of the distance ratio between the trading industrial enterprises; The distance ratio of the water quality influence model reflecting the spatial position of the pollution source and the characteristics of pollutant transport and transformation is specifically calculated by the formula: a ij = C j / C i = exp[k(L i - L j ) / u] wherein, in the formula, a ij is the pollution discharge enterprise, i is the purchase of the pollution discharge enterprise, j is the number of pollution discharge indexes that a unit pollution discharge index can obtain, i.e., the distance ratio; k is the pollution attenuation coefficient, unit d -1 ; u is the flow rate, unit m / s; L i , L j is the distance between the pollution discharge enterprises i and j and the downstream section, unit m; ② The industry ratio considers the characteristics of pollutants, and the initial value of the industry ratio between the trading industrial enterprises is determined by starting from the general theoretical method of the water pollutant emission trading ratio, establishing a model reflecting the damage degree of different types of pollutants to the environment, and calculating the influence degree of different emission enterprises on the water body; The industry ratio of the water quality model reflecting the damage degree of pollutants is specifically calculated by the formula: In the formula, C i , C j is the current emission concentration of the pollutant of the transaction target, with units of mg / L; V i , V j is the volume of the pollutant medium, with units of m 3 ; D i , D j is the equivalent value of the unit transaction target pollutant, with units of kg; and H is the unit conversion coefficient. ③ The coupling ratio comprehensively considers the differences in spatial distance and industry category, and the coupling ratio calculation formula of the water quality influence model reflecting the attenuation of pollutants and different pollutants is established by: In the formula, Aij is the coupling ratio, and C i C j V represents the current emission concentration of pollutants for the traded target, in mg / L. i V j The volume of the pollutant medium being discharged is expressed in meters (m). 3 ;D i D j The value represents the equivalent amount of pollutants per unit of traded asset, in kg; H is the unit conversion factor; k is the pollutant attenuation coefficient, in d. -1 u represents flow velocity, in m / s; L i L j The distances from polluting enterprises i and j to the downstream cross-section are in meters.

2. The method of claim 1, wherein the method is a method of determining a differentiated water pollutant emission trading ratio based on differences. Specifically, the following steps are included: 1) constructing a differentiated water pollutant emission trading ratio model, which is: According to the water pollutant emission trading type, the determination of the trading ratio influencing factor, and the determination of the emission trading ratio adjustment method, the emission trading ratio model under different types is constructed, and the formula is as follows: λ ij = f(a ij (c, k, u, L), b ij (c, v, D), A ij (c, k, u, L, v, D) Wherein, λ ij is the ratio of pollution discharge trading; a ij is the distance ratio; b ij is the industry ratio; A ij is the coupling ratio; c is the pollutant emission concentration, unit mg / L; k is the pollutant attenuation coefficient, unit d -1 ; u is the flow rate, unit m / s; L is the distance from the downstream section of the pollution discharge enterprise, unit m; v is the volume of the emitted pollutant medium, unit m 3 ; D is the equivalent value of unit mass of pollutants, unit kg; 2) determining the water pollutant emission trading type and the corresponding trading ratio type, which is: The total amount of water pollutant emission license and the total amount of water pollutant emission status in the region where the industrial enterprises participating in the transaction are located are calculated by obtaining the data of the total amount of water pollutant emission license and the total amount of water pollutant emission status in the region where the industrial enterprises participating in the transaction are located, and the water pollutant emission trading region is identified according to the relationship between the total amount of water pollutant emission license and the total amount of water pollutant emission status in the region; if the total amount of water pollutant emission license in the region is greater than the total amount of water pollutant emission status, cross-regional transaction can be carried out, and if the total amount of water pollutant emission license in the region is less than or equal to the total amount of water pollutant emission status, only the emission trading within the region is allowed; Secondly, from the angles of the biodegradability of the wastewater of the industrial enterprises participating in the transaction and the types of symbiotic pollutants, it is determined whether the cross-industry transaction condition is met; if the biodegradability of the wastewater of the industrial enterprises participating in the transaction is similar and the types of symbiotic pollutants are similar, the cross-industry transaction can be carried out, otherwise, the intra-industry transaction is carried out; The BOD5 / COD ratio ranges from 0.3 to 0.58, when the BOD5 / COD value is greater than 0.58, the wastewater is completely biodegradable; when the BOD5 / COD value ranges from 0.45 to 0.58, the wastewater is well biodegradable; when the BOD5 / COD value ranges from 0.30 to 0.45, the wastewater is biodegradable; and when the BOD5 / COD value is less than 0.3, the wastewater is difficult to biodegrade; The types of wastewater symbiotic pollutants in each industry can refer to the index pollutants required to be discharged in the water pollutant emission standard of the corresponding industry; toxic and harmful substances refer to heavy metals and non-biodegradable organic matter contained in industrial wastewater, which are not allowed to carry out cross-industry transaction; Accordingly, four types of water pollutant emission trading and corresponding four types of water pollutant emission trading ratio are formed, the four types of water pollutant emission trading are intra-industry emission trading within the region, cross-industry emission trading within the region, intra-industry emission trading across regions, and cross-industry emission trading across regions; the corresponding four types of trading ratio are intra-industry emission trading ratio within the region, cross-industry emission trading ratio within the region, intra-industry emission trading ratio across regions, and cross-industry emission trading ratio across regions, different types of trading ratio correspond to different influencing factors, the intra-industry emission trading ratio within the region and the intra-industry emission trading ratio across regions are only affected by the spatial distance factor, that is, the distance ratio can be used to represent; the cross-industry emission trading ratio within the region and the cross-industry emission trading ratio across regions are affected by multiple factors such as spatial distance and pollutant type, that is, the coupling ratio composed of distance ratio and industry ratio can be used to represent; 3) A differentiated water pollutant emission trading ratio initial value model is established to determine the initial value of the emission trading ratio; 4) The total amount of the region, the water quality target of the section, and the emission reduction cost are used as constraint conditions to adjust the trading ratio, so that the trading ratio meets the regional total amount control target, the section water quality target, and the emission reduction cost target at the same time, thereby determining the final value of the water pollutant emission trading ratio, the method is: Total amount control: Water quality targets: Cost control: A ij ≥ P j / (P i +E i ) In the formula, Q i is the total amount of pollutant emissions in the area where the pollution enterprise i is located, in units of t / a; A ij is the transaction ratio; Q ij is the amount of pollution rights sold by the pollution enterprise j to the pollution enterprise i, in units of t / a; C0is the concentration contribution value of the upstream of the river to the control section, in units of mg / L; C i is the impact concentration of the pollution enterprise i on the control section for unit pollution emission, in units of mg / L; C s is the water quality target of the control section, in units of mg / L; P i , P j is the cost of the pollution enterprises i and j for reducing unit pollutant amount, in units of yuan / t; E i is the total value of production per unit of pollutant emission, in units of yuan / t.

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