Method and device for determining background value of chemical oxygen demand of water environment

Abstract

The invention provides a method and device for determining a background value of chemical oxygen demand of a water environment, and the method comprises the following steps: measuring the chemical oxygen demand of a water sample, and obtaining a dissolved organic matter DOM sample and a particulate organic matter POM sample for the water sample and each end member sample; determining a plurality of first end member samples of dissolved organic matters DOM and particulate organic matters POM which influence the water sample; calculating a chemical oxygen demand background value of each sampling point based on a third influence coefficient and a fourth influence coefficient corresponding to a natural source end member sample in the first end member sample; determining the weight of each sampling point based on the human activity intensity within a second preset range around each sampling point; and based on the chemical oxygen demand background value and the weight of each sampling point, determining the chemical oxygen demand background value of the regional and / or watershed water environment. According to the method, the degree of influence of human activities on each sampling point is quantified, and a more accurate and reliable upscaling background value derivation technology is provided.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water quality protection, and particularly relates to a method and device for determining a background value of a chemical oxygen demand of a water environment. BACKGROUND

[0002] The chemical oxygen demand (COD) is the mass concentration of oxygen corresponding to the consumption of dichromate by the dissolved substances and suspended substances in a water sample under certain conditions. The background value of the COD is mainly derived from the input of natural organic matter from plants and soil, and the organic matter and reducing inorganic matter contained in the water body.

[0003] Due to the large span from north to south and from east to west in China, the natural geographical environment is obviously different, and is strongly disturbed by human activities. The COD concentration of the water environment is influenced by many factors, and it is difficult to determine the natural background value. At present, there is no clear method for measuring the COD background value of the water environment. Studying the COD background value of the water environment is helpful to understand the contribution of the natural background to the concentration of organic pollutants, and provides a scientific basis for formulating pollution control targets. SUMMARY

[0004] The present application provides a method and device for determining a background value of a chemical oxygen demand of a water environment, which is used to solve the above technical problems.

[0005] According to a first aspect of the present application, a method for determining a background value of a chemical oxygen demand of a water environment is provided, and the method comprises the following steps: Step S1: determining a plurality of sampling points of the water environment; collecting a water sample from the sampling points and measuring the chemical oxygen demand of the water sample; obtaining a plurality of end-member samples within a first predetermined range around the sampling points, the end-member samples being natural objects affecting the chemical oxygen demand of the water sample; obtaining a dissolved organic matter (DOM) sample and a particulate organic matter (POM) sample for the water sample and each end-member sample; Step S2: determining a plurality of first end-member samples affecting the dissolved organic matter (DOM) and the particulate organic matter (POM) of the water sample; determining a first influence coefficient of the dissolved organic matter (DOM) sample of each first end-member sample on the dissolved organic matter (DOM) sample of the water sample, and a second influence coefficient of the particulate organic matter (POM) sample of each first end-member sample on the particulate organic matter (POM) sample of the water sample; Step S3: determining a third influence coefficient of the dissolved organic matter (DOM) sample of a natural source end-member sample in the first end-member sample on the chemical oxygen demand of the water sample, and a fourth influence coefficient of the particulate organic matter (POM) sample of the natural source end-member sample in the first end-member sample on the chemical oxygen demand of the water sample; calculating the background value of the chemical oxygen demand of each sampling point based on the third influence coefficient and the fourth influence coefficient corresponding to the natural source end-member sample in the first end-member sample; Step S4: determining the weight of each sampling point based on the human activity intensity within the second preset range around each sampling point; determining the regional and / or watershed water environment chemical oxygen demand background value based on the chemical oxygen demand background value of each sampling point and the weight.

[0006] Preferably, in the step S1, the water sample is collected from the sampling point and the chemical oxygen demand of the water sample is determined, a plurality of end-member samples within the first preset range around the sampling point are obtained, and the end-member sample is a natural object affecting the chemical oxygen demand of the water sample; for the water sample and each end-member sample, the dissolved organic matter DOM sample and the particulate organic matter POM sample are obtained, including: The water sample is collected from the sampling point and the chemical oxygen demand of the water sample is determined, denoted as COD point The water sample is filtered through a 0.45 μm filter membrane, and the chemical oxygen demand of the filtered water sample is determined, denoted as COD' point point is the sampling point number; the filter residue on the filter membrane is collected as the particulate organic matter POM sample of the water sample, and the filtrate is collected as the dissolved organic matter DOM sample of the water sample; A plurality of end-member samples within the first preset range around the sampling point are obtained; wherein: For the liquid end-member sample, the filter residue on the membrane is collected as the particulate organic matter POM sample of the liquid end-member sample after filtering through a 0.45 μm filter membrane, and the filtrate is collected as the dissolved organic matter DOM sample of the liquid end-member sample; For the solid end-member sample, the solid end-member sample is freeze-dried, ground and sieved to obtain the particulate organic matter POM sample of the solid end-member sample, and after the particulate organic matter POM sample of the solid end-member sample is extracted with pure water, centrifuged and filtered through a 0.45 μm filter membrane, the filtrate is collected as the dissolved organic matter DOM sample of the solid end-member sample.

[0007] Preferably, in the step S2, a plurality of first end-member samples affecting the dissolved organic matter DOM and the particulate organic matter POM of the water sample are determined, including: The first distribution characteristics of the carbon and nitrogen isotopes of the dissolved organic matter DOM sample and the particulate organic matter POM sample of the water sample are obtained; The second distribution characteristics of the carbon and nitrogen isotopes of the dissolved organic matter DOM sample and the particulate organic matter POM sample of each end-member sample corresponding to the water sample are obtained; Based on the first distribution characteristics and the second distribution characteristics, the end-member sample with a similarity greater than a first preset threshold value between the second distribution characteristics and the first distribution characteristics is taken as the first end-member sample.

[0008] Preferably, in the step S2, a first influence coefficient of the dissolved organic matter DOM sample of each first end-member sample on the dissolved organic matter DOM sample of the water sample and a second influence coefficient of the particulate organic matter POM sample of each first end-member sample on the particulate organic matter POM sample of the water sample are determined, wherein: the contribution rates of the carbon isotopes and nitrogen isotopes of the dissolved organic matter DOM and the particulate organic matter POM of the water sample are determined; the contribution rates of the carbon isotopes and nitrogen isotopes of the dissolved organic matter DOM and the particulate organic matter POM of each first end-member sample are determined; the first influence coefficient of the dissolved organic matter DOM sample of each first end-member sample on the dissolved organic matter DOM sample of the water sample and the second influence coefficient of the particulate organic matter POM sample of each first end-member sample on the particulate organic matter POM sample of the water sample are determined based on the principle of mass conservation; the first influence coefficient and the second influence coefficient are both contribution rate ratios; the principle of mass conservation is that the weighted average contribution rate of the first influence coefficient of the carbon isotopes and nitrogen isotopes of the dissolved organic matter DOM of each first end-member sample is equal to the contribution rate of the carbon isotopes and nitrogen isotopes of the dissolved organic matter DOM of the water sample; the weighted average contribution rate of the second influence coefficient of the carbon isotopes and nitrogen isotopes of the particulate organic matter POM of each first end-member sample is equal to the contribution rate of the carbon isotopes and nitrogen isotopes of the particulate organic matter POM of the water sample.

[0009] Preferably, in the step S3, a third influence coefficient of the dissolved organic matter DOM sample of the natural source end-member sample in the first end-member sample on the chemical oxygen demand of the water sample and a fourth influence coefficient of the particulate organic matter POM sample of the natural source end-member sample in the first end-member sample on the chemical oxygen demand of the water sample are determined, wherein:

[0010] In the formula, α point is the third influence coefficient of the natural source end-member sample in the first end-member sample of the sampling point numbered as point; f plant , f soil , f algae are respectively the first influence coefficient of the dissolved organic matter DOM sample of the plant source end-member sample, the soil source end-member sample and the algae source end-member sample in the first end-member sample;

[0011] In the formula, β point is the fourth influence coefficient of the natural source end-member sample in the first end-member sample of the sampling point numbered as point; f plant , f soil , f algaeThe second influence coefficient of the particulate organic matter POM sample is respectively a plant source end member sample, a soil source end member sample, and an algae source end member sample in the first end member sample.

[0012] Preferably, in the step S3, the chemical oxygen demand background value of each sampling point is calculated based on the third influence coefficient and the fourth influence coefficient corresponding to the natural source end member sample in the first end member sample, and the step S3 comprises the following steps. COD point,background The chemical oxygen demand background value of the sampling point numbered point.

[0013] Preferably, the step S4 comprises the following steps. The step S41 comprises the following steps.

[0014]

[0015] In the formula, The human activity intensity of the sampling point numbered point; The equivalent area of the construction land in the second preset range around the sampling point numbered point; The total area of the second preset range around the sampling point numbered point; The area of the i-th land use type in the second preset range around the sampling point numbered point; CI i The equivalent conversion coefficient of the i-th land use type; n is the number of land use types in the second preset range around the sampling point numbered point; The step S42 comprises the following steps.

[0016] In the formula, The number of sampling points; The step S43 comprises the following steps.

[0017] ​​According to a second aspect of the present application, a device for determining a background value of a water environment is provided, the device comprising: a sample acquisition module configured to determine a plurality of sampling points of the water environment, collect water samples from the sampling points and determine chemical oxygen demand of the water samples, acquire a plurality of end-member samples within a first preset range around the sampling points, the end-member samples being natural objects affecting the chemical oxygen demand of the water samples, and acquire dissolved organic matter (DOM) samples and particulate organic matter (POM) samples for each of the water samples and the end-member samples; a coefficient determination module configured to determine a plurality of first end-member samples affecting the dissolved organic matter (DOM) and the particulate organic matter (POM) of the water samples, determine a first influence coefficient of the DOM sample of each of the first end-member samples on the DOM sample of the water sample and a second influence coefficient of the POM sample of each of the first end-member samples on the POM sample of the water sample; a first background value determination module configured to determine a third influence coefficient of the DOM sample of a natural source end-member sample in the first end-member samples on the chemical oxygen demand of the water sample and a fourth influence coefficient of the POM sample of the natural source end-member sample in the first end-member samples on the chemical oxygen demand of the water sample, and calculate a background value of the chemical oxygen demand of each of the sampling points based on the third influence coefficient and the fourth influence coefficient corresponding to the natural source end-member sample in the first end-member samples; a second background value determination module configured to determine a weight of each of the sampling points based on a human activity intensity within a second preset range around the sampling points, and determine a background value of the chemical oxygen demand of a water environment of a region and / or a river basin based on the background value of the chemical oxygen demand of each of the sampling points and the weight.

[0018] Preferably, the collecting water samples from the sampling points and determining the chemical oxygen demand of the water samples, acquiring a plurality of end-member samples within a first preset range around the sampling points, the end-member samples being natural objects affecting the chemical oxygen demand of the water samples, and acquiring dissolved organic matter (DOM) samples and particulate organic matter (POM) samples for each of the water samples and the end-member samples comprises: collecting water samples from the sampling points and determining the chemical oxygen demand of the water samples, denoted as CODi point , filtering the water samples through a 0.45 μm filter membrane, determining the chemical oxygen demand of the filtered water samples, denoted as CODi’ point , i is a sampling point number; collecting the filter residues on the filter membrane as particulate organic matter (POM) samples of the water samples, and collecting the filtrate as dissolved organic matter (DOM) samples of the water samples; acquiring a plurality of end-member samples within a first preset range around the sampling points; wherein: for liquid end-member samples, collecting the filter residues on the filter membrane as particulate organic matter (POM) samples of the liquid end-member samples after filtering through a 0.45 μm filter membrane, and collecting the filtrate as dissolved organic matter (DOM) samples of the liquid end-member samples. For the solid end member sample, the solid end member sample is freeze-dried, ground and sieved to obtain a particulate organic matter (POM) sample of the solid end member sample, and the particulate organic matter (POM) sample of the solid end member sample is extracted with pure water, centrifuged and filtered through a 0.45 μm filter membrane, and the filtrate is used as a dissolved organic matter (DOM) sample of the solid end member sample.

[0019] Preferably, the determining of the first end member samples affecting the dissolved organic matter (DOM) and the particulate organic matter (POM) of the water sample comprises: obtaining first distribution characteristics of carbon isotopes and nitrogen isotopes of the dissolved organic matter (DOM) sample and the particulate organic matter (POM) sample of the water sample; obtaining second distribution characteristics of carbon isotopes and nitrogen isotopes of the dissolved organic matter (DOM) sample and the particulate organic matter (POM) sample of each end member sample corresponding to the water sample; based on the first distribution characteristics and the second distribution characteristics, taking an end member sample with a similarity between the second distribution characteristics and the first distribution characteristics greater than a first preset threshold as a first end member sample.

[0020] According to a third aspect of the present application, an electronic device is provided, comprising: a processor configured to execute a plurality of instructions; a memory configured to store the plurality of instructions; wherein the plurality of instructions are stored in the memory and loaded and executed by the processor to perform the method as described above.

[0021] According to a fourth aspect of the present application, a computer readable storage medium is provided, wherein the storage medium stores a plurality of instructions; the plurality of instructions are loaded and executed by a processor to perform the method as described above.

[0022] The present application has the following beneficial technical effects: The present application combines the sampling point background value calculation based on the stable isotope method and the sampling point background value representative evaluation based on the human activity intensity of a region / river basin. For the sampling point, the influence degree of the natural source DOM and POM on the collected water sample DOM and POM is quantified, and a more scientifically based COD background value derivation method is provided; for the region / river basin, the influence degree of each sampling point affected by human activities is quantified, and a more accurate and reliable background value derivation technology is proposed, which can provide a new idea for the water environment COD background value derivation and provide a reference for the background research and scientific evaluation of water quality.

[0023] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, and to implement the content of the description, the following will describe the preferred embodiments of the present application in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention, and the invention is illustrated by the following drawings. In the drawings: Figure 1 This is a schematic flowchart illustrating a method for determining the background value of chemical oxygen demand (COD) in aquatic environments according to one embodiment of the present invention. Detailed Implementation

[0025] First, combine Figure 1 This invention describes a method for determining the background value of chemical oxygen demand (COD) in aquatic environments according to one embodiment. For example... Figure 1 As shown, the method includes the following steps: Step S1: Determine multiple sampling points in the water environment; collect water samples from the sampling points and determine the chemical oxygen demand (COD) of the water samples; obtain multiple end-member samples within a first preset range around the sampling points, where the end-member samples are natural objects that affect the COD of the water samples; obtain dissolved organic matter (DOM) samples and particulate organic matter (POM) samples for both the water samples and each type of end-member sample. Step S2: Determine several first end-member samples that affect the dissolved organic matter (DOM) and particulate organic matter (POM) of the water sample; determine the first influence coefficient of the dissolved organic matter (DOM) sample of each first end-member sample on the dissolved organic matter (DOM) sample of the water sample, and the second influence coefficient of the particulate organic matter (POM) sample of each first end-member sample on the particulate organic matter (POM) sample of the water sample. Step S3: Determine the third influence coefficient of dissolved organic matter (DOM) samples from the natural source endmember samples in the first endmember sample on the chemical oxygen demand (COD) of the water sample, and the fourth influence coefficient of particulate organic matter (POM) samples from the natural source endmember samples in the first endmember sample on the COD of the water sample; calculate the background COD value of each sampling point based on the third and fourth influence coefficients corresponding to the natural source endmember samples in the first endmember sample. Step S4: Determine the weight of each sampling point based on the intensity of human activities within the second preset range around each sampling point; determine the background value of chemical oxygen demand (COD) for the regional and / or watershed water environment based on the background value and weight of each sampling point.

[0026] Further, in step S1, water samples are collected from sampling points and the chemical oxygen demand (COD) of the water samples is measured. Multiple end-member samples are obtained within a first preset range around the sampling points. These end-member samples are natural objects that affect the COD of the water samples. For both the water samples and each end-member sample, dissolved organic matter (DOM) samples and particulate organic matter (POM) samples are obtained, including: Water samples were collected from sampling points, and the chemical oxygen demand (COD) of the water samples was measured and recorded as COD. point The water sample was filtered through a 0.45 μm filter membrane, and the chemical oxygen demand (COD) of the filtered water sample was measured and recorded as COD'.point point is the sampling point number; collect the filter residue on the collection filter as the particulate organic matter POM sample of the water sample, and the filtrate as the dissolved organic matter DOM sample of the water sample; acquire a plurality of end-member samples within a first preset range around the sampling point; wherein: for the liquid end-member sample, collect the filter residue on the 0.45 μm filter after filtration as the particulate organic matter POM sample of the liquid end-member sample, and the filtrate as the dissolved organic matter DOM sample of the liquid end-member sample; for the solid end-member sample, freeze-dry, grind and sieve the solid end-member sample to obtain the particulate organic matter POM sample of the solid end-member sample, and after the particulate organic matter POM sample of the solid end-member sample is extracted with pure water, centrifuged and filtered with a 0.45 μm filter, the filtrate is used as the dissolved organic matter DOM sample of the solid end-member sample.

[0027] In the present application, water samples at sampling points and representative organic matter source (end-member) samples are collected, including phytoplankton, aquatic plants, terrestrial plants, soil, municipal domestic sewage and industrial wastewater, as well as agricultural and rural sewage, livestock and poultry manure and other end-members, and the related operations are performed according to documents such as HJ 91.2–2022, HJ / T 166–2004, HJ 494–2009 and HJ 495–2009. Specifically: (1) phytoplankton is enriched in surface water at multiple points using a plankton net, and is stored at –20℃ for standby; (2) among dominant aquatic plants, emergent plants are collected at multiple points in water and on the shore, submerged plants are collected at multiple points in water, and 3 to 10 plants of the same species at the same point are mixed as a single sample, and the branches and leaves are washed with deionized water and dried for standby; (3) terrestrial plants are collected at multiple points along the shore of the water body, and 3 to 10 plants of the same species at the same point are mixed as a single sample, and the branches and leaves are washed with deionized water and dried for standby; (4) soil (including farmland soil, meadow soil and saline-alkali soil, etc.) is collected at multiple points within a range of 500 m along the shore of the water body, and a mixed sample of the soil samples at the same point within a range of about 5 m 2 at the same point and at a depth of 0 to 20 cm is collected as the sample at the point, and after removing impurities, the sample is dried, ground and sieved for standby; (5) municipal domestic sewage and drainage after sewage treatment of typical industrial enterprises (including petrochemical, food processing and other types), as well as agricultural and rural sewage are collected and stored at –20℃ for standby; (6) fresh manure of main livestock and poultry species in breeding plants is collected and stored after freeze-drying for standby; Sample determination and DOM, POM sample preparation are performed according to GB 11892-89, GB / T 42490-2023, HJ 493-2009 and other documents. Specifically: (1) the collected water sample is filtered through a 0.45 μm filter membrane, and the COD before and after filtration is measured, denoted as COD point and COD' point ; the POM sample on the membrane is collected, and the filtrate is used as the DOM sample; (2) for liquid end member samples (municipal domestic sewage, industrial wastewater, agricultural and rural sewage), the POM end member sample is collected on the membrane after filtration through a 0.45 μm filter membrane, and the filtrate is used as the DOM end member sample; (3) for solid end member samples (algae, plants, soil and livestock and poultry manure, etc.), freeze-drying, grinding and sieving are performed to obtain the POM end member sample; the POM end member sample is extracted with pure water, centrifuged, and filtered through a 0.45 μm filter membrane to obtain the DOM end member sample.

[0028] Further, in the step S2, the first end member samples affecting the dissolved organic matter DOM and the particulate organic matter POM of the water sample are determined, including: obtaining the first distribution characteristics of carbon isotopes and nitrogen isotopes of the dissolved organic matter DOM sample and the particulate organic matter POM sample of the water sample; obtaining the second distribution characteristics of carbon isotopes and nitrogen isotopes of the dissolved organic matter DOM sample and the particulate organic matter POM sample of each end member sample corresponding to the water sample; based on the first distribution characteristics and the second distribution characteristics, the end member sample with a similarity greater than a first preset threshold between the second distribution characteristics and the first distribution characteristics is taken as the first end member sample.

[0029] Further, in the step S2, the first influence coefficient of the dissolved organic matter DOM sample of each first end member sample on the dissolved organic matter DOM sample of the water sample, and the second influence coefficient of the particulate organic matter POM sample of each first end member sample on the particulate organic matter POM sample of the water sample are determined, wherein: determining the contribution rates of carbon isotopes and nitrogen isotopes of the dissolved organic matter DOM and the particulate organic matter POM of the water sample; determining the contribution rates of carbon isotopes and nitrogen isotopes of the dissolved organic matter DOM and the particulate organic matter POM of each first end member sample; based on the principle of mass conservation, the first influence coefficient of the dissolved organic matter DOM sample of each first end member sample on the dissolved organic matter DOM sample of the water sample, and the second influence coefficient of the particulate organic matter POM sample of each first end member sample on the particulate organic matter POM sample of the water sample are determined; the first influence coefficient and the second influence coefficient are both contribution rate proportions; The mass conservation principle is that the weighted average contribution rate of the first influence coefficient of the carbon isotope and the nitrogen isotope of the dissolved organic matter (DOM) of each first end member sample is equal to the contribution rate of the carbon isotope and the nitrogen isotope of the dissolved organic matter (DOM) of the water sample; and the weighted average contribution rate of the second influence coefficient of the carbon isotope and the nitrogen isotope of the particulate organic matter (POM) of each first end member sample is equal to the contribution rate of the carbon isotope and the nitrogen isotope of the particulate organic matter (POM) of the water sample.

[0030] In the present application, the DOM and POM samples of the collected water sample and each end member are taken, acidified by hydrochloric acid to remove inorganic carbon, washed by ultrapure water to neutral pH, and then freeze-dried, and put into an isotope mass spectrometer to determine the carbon and nitrogen isotope ratio, and the analysis accuracy is 0.05‰ and 0.10‰ respectively. 13 C and δ 15 N are calculated as follows: (1)

[0031] (2)

[0032] In the formula, δ 13 C represents the carbon isotope ratio, ‰; δ 15 N represents the nitrogen isotope ratio, ‰; 13 C / 12 C sample represents the carbon isotope ratio of the test sample, dimensionless; 13 C / 12 C standard represents the isotope ratio of the standard substance Vienna-PeeDee belemnite (VPDB), and the value is 0.011180; 15 N / 14 N sample represents the nitrogen isotope ratio of the test sample, dimensionless; 15 N / 14 N standard represents the isotope ratio of nitrogen in the atmosphere, and the value is 0.003613; By comparing the δ 13 C, δ 15 N distribution characteristics of the collected water sample DOM, POM and the DOM, POM of each end member, the end member data which is not the main source of the water sample DOM, POM is removed, and the end member data with consistent δ 13 C, δ 15 N distribution is combined. The δ 13 C and δ 15 N are used as parameters, and the source analysis model such as the multivariate linear mixing model IsoSource is applied to quantitatively analyze the contribution of different end member DOM, POM to the collected water sample DOM, POM, wherein the total contribution of the natural source (plant source, soil source and / or algal source, etc.) is marked as α and β respectively. For example, the principle of end-member contribution rate calculation is as follows: according to the principle of mass conservation, the isotopes and total amounts of DOM (or POM) from different pollution sources remain unchanged before and after mixing. Carbon and nitrogen isotopes can be used to quantitatively analyze the contribution of different pollution sources to the DOM (or POM) of the regional / watershed water environment. The basic carbon and nitrogen isotope multivariate linear mixing model (mass conservation model) can calculate the contribution of up to three pollution sources, and the formula is as follows: (3) (4) (5) In the formula: represents the carbon isotope value of DOM (or POM) in the water sample, with units of ‰; represents the nitrogen isotope value of DOM (or POM) in the water sample, with units of ‰;f A , f B , f C represents the proportion of different DOM (or POM) pollution sources, with units of %; , , represents the carbon isotope value of different pollution sources, with units of ‰; , , represents the nitrogen isotope value of different pollution sources, with units of ‰; When the number of pollution sources exceeds three and the number of isotopes is greater than one, the IsoSource model can be used. This model is based on the mass conservation model and uses an iterative method to calculate all possible combinations of carbon and nitrogen isotopes from different sources (sum = 100%). The weighted average of each combination is compared with the actual measured isotope value of the mixed water body. Within the tolerance parameter (generally set to 0.01‰-0.1‰), the combination is considered feasible for relative contribution percentage. Frequency analysis is performed on these feasible combinations, and combinations within a higher frequency range are considered to be the relative contribution percentage of pollution sources to the water environment DOM (or POM). All possible percentage combinations of different pollution sources are calculated as follows: (6)

[0033] In the formula, Q represents the number of all possible percentage combinations, with units of pieces; i represents the incremental parameter, generally set to 1%-2%; s represents the number of DOM (or POM) sources, with units of pieces.

[0034] Further, in the step S3, a third influence coefficient of the dissolved organic matter DOM sample of the natural source end member sample in the first end member sample on the chemical oxygen demand of the water sample and a fourth influence coefficient of the particulate organic matter POM sample of the natural source end member sample in the first end member sample on the chemical oxygen demand of the water sample are determined, wherein: (7)

[0035] In the formula, α point is the third influence coefficient of the natural source end member sample in the first end member sample of the sampling point numbered as point; f plant , f soil , and f algae are respectively the first influence coefficients of the dissolved organic matter DOM sample of the plant source end member sample, the soil source end member sample, and the algae source end member sample in the first end member sample. (8)

[0036] In the formula, β point is the fourth influence coefficient of the natural source end member sample in the first end member sample of the sampling point numbered as point; f' plant , f' soil , and f' algae are respectively the second influence coefficients of the particulate organic matter POM sample of the plant source end member sample, the soil source end member sample, and the algae source end member sample in the first end member sample.

[0037] Further, in the step S3, the chemical oxygen demand background value of each sampling point is calculated based on the corresponding third influence coefficient and fourth influence coefficient of the natural source end member sample in the first end member sample, and the calculation comprises: (9) In the formula, COD point,background is the chemical oxygen demand background value of the sampling point numbered as point.

[0038] In the present application, the background value of the water sample collected at each sampling point in different months or water periods is calculated as the arithmetic mean value according to the requirements of the documents such as the Technical Regulation for Statistical Data of Monitoring of Surface Water Environmental Quality (Trial) issued by the Ministry of Ecology and Environment.

[0039] Further, the step S4 comprises: determining the weight of each sampling point based on the intensity of human activities within the second preset range around each sampling point; and determining the regional and / or basin water environment chemical oxygen demand background value based on the chemical oxygen demand background value and the weight of each sampling point, and the calculation comprises: Step S41: determining the intensity of human activities within the second preset range around each sampling point: (10)

[0040] (11)

[0041] In the formula, The intensity of human activity at the sampling point numbered "point"; The equivalent area of ​​construction land within the second preset range surrounding the sampling point numbered "point"; The total area of ​​the second preset range surrounding the sampling point numbered "point"; CI represents the area of ​​the i-th land use type within the second preset range surrounding the sampling point numbered "point"; i is the construction land equivalent conversion factor for the i-th land use type; n is the number of land use types within the second preset range surrounding the sampling point numbered point; Step S42: Determine the weight of each sampling point based on the intensity of human activity within a second preset range around each sampling point. :

[0042] in, This represents the number of sampling points; Step S43: Based on the background values ​​and weights of chemical oxygen demand (COD) at each sampling point, determine the background values ​​of COD in the regional and / or watershed water environment. :

[0043] In this invention, based on existing land use data products, the area (or proportion) of various land uses within a certain radius of a sampling point is analyzed. The land use status within this spatial range should significantly influence the water quality at the sampling point; the size of the range should be adjusted according to the actual situation of the region / watershed. In this invention, the surrounding second preset range should be as similar as possible to the first preset range.

[0044] The human activity intensity at sampling points was quantified using the Land Surface Human Activity Intensity (HAI) proposed by Xu Yong et al. This index uses construction land equivalent as the basic unit of measurement. It determines the construction land equivalent conversion factor for different land use types based on the presence of artificial barriers and the normal exchange of moisture, nutrients, air, and heat between the surface and the surrounding land. The ratio of the total construction land equivalent to the total area of ​​the region is calculated as the human activity intensity. The calculation formula is as follows:

[0045]

[0046] The conversion factors for cultivated land, forest land, shrubland, grassland, urban and rural land and industrial and mining land, and water bodies are 0.2, 0, 0, 0, 1.0, and 0, respectively. The human activity intensity of each sampling point is converted into the weight of the point background value to the regional / river basin background value (the total is 1). The human activity intensity of each sampling point is HAI1, HAI2, …, HAI n , and the weight of each sampling point is :

[0047] If there is a case where HAI is 0, a small number such as 1e -6 may be appropriately added. Based on the weight, the sampling point background values are weighted and averaged to calculate the regional / river basin COD background value, and the formula is:

[0048] By adopting the technical scheme, compared with the prior art, the technical progress mainly obtained by the present application is that the sampling point background value calculation based on the stable isotope method and the sampling point background value based on the human activity intensity are combined to evaluate the method of the regional / river basin background. For the sampling point, the influence degree of the natural source DOM and POM on the collected water sample DOM and POM is quantified, and a more scientific and basis COD background value derivation method is provided; for the region / river basin, the degree of influence of each sampling point by human activities is quantified, and a more accurate and reliable background value derivation technology is provided, which can provide a new idea for the water environment COD background value derivation and provide a reference for the background research and scientific evaluation of water quality.

[0049] The present application provides a specific embodiment of a method for determining the chemical oxygen demand background value of a water environment.

[0050] Taking the water environment COD background value derivation of the Fenhe River Basin (Yellow River Basin) as an example, the human activity intensity of the basin is large, the sediment content is high, the COD is affected by both artificial sources and natural sources, and the background value derivation steps include: S1, collecting water samples, measuring COD, and collecting COD possible source (end member) samples around the sampling point, completing the preparation of DOM and POM samples of water samples and end member samples.

[0051] In this embodiment, according to the requirements of the relevant standard documents, 29 points are set in the Fenhe River Basin, and the water body and the surrounding possible organic matter sources (including plant sources, algae sources, soil sources, domestic sewage sources, industrial sources, agricultural sources, etc.) are sampled in August (flood season) and December (dry season) of 2023. According to the requirements of the relevant standard documents, the sampling point water sample, the liquid end member sample and the solid end member sample are respectively treated, measured and analyzed: the sampling point water sample and the water sample filtered by 0.45 μm filter membrane are measured by acid titration method to measure COD (denoted as COD point and COD'.point ), the water sample after filtration was used as the DOM sample, and the POM sample on the membrane was collected; each type of liquid end member (pollutant source; including domestic sewage source, industrial source and agricultural source) was filtered through a 0.45 μm filter membrane, and the POM end member sample on the membrane was collected, and the filtrate was used as the DOM end member sample; each type of solid end member (including plant source, algal source, soil source, etc.) was freeze-dried, ground and sieved to obtain the POM end member sample, which was extracted with pure water, centrifuged, and the supernatant was filtered through a 0.45 μm filter membrane to obtain the DOM end member sample.

[0052] S2, stable isotope determination of DOM and POM of the water sample and the end member sample and calculation of end member contribution rate were performed.

[0053] In this embodiment, the DOM and POM samples of the water sample at the sampling point and each end member were completely wetted by dropwise addition of hydrochloric acid, placed in a desiccator containing concentrated hydrochloric acid for fumigation for 48 hours to remove inorganic carbon by acidification, repeatedly washed with ultrapure water until the pH value was about 7, freeze-dried, and placed in an elemental analyzer (Flash EA 2000HT) and an isotope mass spectrometer (Thermo Fisher Scientific Inc., USA) for combined use, and the carbon and nitrogen isotope ratios δ 13 C and δ 15 N were determined during the process. The average analysis error of δ 13 C and δ 15 N was about 0.13 ‰ and 0.1 ‰. As seen from the results, the average δ 13 C of the DOM of the water sample in the wet season was –23.31 ‰, and the average δ 13 C of the POM of the water sample in the wet season was –23.44 ‰, and the average δ 15 N was 9.71 ‰; the δ 13 C in the dry season was similar to that in the wet season, but the δ 15 N was lower than that in the wet season, and the average δ

[0054] In this embodiment, the carbon and nitrogen isotope determination of the end member samples of soil, plant, agriculture, industry, etc. in the Fenhe River Basin showed that the δ 13 C and δ 15 N of the aquatic organism DOM were –26.02 ‰ and 17.34 ‰ on average, the δ 13 C and δ 15 N of the agricultural source were –23.53 ‰ and 0.52 ‰ on average, the δ 13 C and δ 15 N of the industrial source were –26.26 ‰ and 13.30 ‰ on average, the δ 13 C and δ 15 N of the domestic source were –19.10 ‰ and 12.79 ‰ on average, and the δ 13 C and δ15 N average –28.31‰ and 7.74‰, terrestrial C4 plant δ 13 C and δ 15 N average –20.29‰ and 4.22‰, riparian soil δ 13 C and δ 15 N average –24.71‰ and 5.02‰; POM, water δ 13 C, δ 15 N –29.96‰ and 7.07‰, respectively, terrestrial C3 and C4 plant δ 13 C, δ 15 N –28.31‰, 7.74‰ and –20.29‰, 4.22‰, respectively, riparian soil δ 13 C, δ 15 N –24.71‰ and 5.02‰, respectively.

[0055] In this embodiment, based on the characteristics of stable isotopes (δ 13 C, δ 15 N) of each end member DOM, POM, the contribution of different end members to the DOM, POM of the sampling point water sample is quantified by IsoSource model (the average of each interval solution; the sum is 1), and the DOM, POM input by agricultural source, industrial source, and resident life source are taken as artificial sources, and the plant source and soil source are taken as natural sources (the basin is seriously affected by human activities, and the algal source is taken as an artificial source). The contribution of natural sources and artificial sources to water body DOM, POM is obtained, and the contribution of natural sources and artificial sources to DOM in the Fenhe River Basin is 10.9% and 89.1% respectively, and the contribution of natural sources and artificial sources to POM is 58.9% and 41.1% respectively. Specifically, the natural source contribution of each sampling point DOM in the wet season ranges from 1.7% to 9.3%, and the natural source contribution in the dry season ranges from 8.8% to 35.1%; the natural source contribution of POM in the wet season ranges from 43.2% to 63.8%, and the natural source contribution in the dry season ranges from 35.1% to 62.9%.

[0056] S3, develop the background value of the sampling point.

[0057] In this embodiment, for each water sample, the total contribution rate of natural sources in DOM, POM , is multiplied by the measured COD to obtain the background value; the background values of the water samples collected in August and December at each sampling point are averaged to obtain the background value of the point. In terms of results, the background value of the 29 sampling points ranges from 8.62 to 58.89 mg L –1 .

[0058] S4, human activity intensity assessment and weight determination of the sampling point, and regional / river basin COD background value derivation.

[0059] In this embodiment, based on the 30 m resolution land use data in 2023 in the existing land use data product (CLCD; https: / / zenodo.org / records / 12779975), the proportion of each type of land use in the 1 km radius range of each sampling point is analyzed; studies have shown that the land use in this spatial range can greatly affect the water quality of the sampling point. The human activity intensity is calculated, and the human activity intensity of the 29 sampling points ranges from 4.76% to 82.12%. The human activity intensity of each sampling point is converted into the weight of the background value of the point to the background value of the basin, and the highest weight is 0.22.

[0060] In this embodiment, based on the weight, the background values of the sampling points are weighted and averaged, and the COD background value of the Fenhe River Basin is calculated to be 21.90 mg / L –1 .

[0061] The device for determining the chemical oxygen demand background value of the water environment disclosed in the embodiment of the application can include: The sample acquisition module is configured to determine a plurality of sampling points of the water environment, collect water samples from the sampling points and determine the chemical oxygen demand of the water samples, obtain a plurality of end-member samples within a first predetermined range around the sampling points, the end-member samples being natural objects affecting the chemical oxygen demand of the water samples, and obtain dissolved organic matter (DOM) samples and particulate organic matter (POM) samples for the water samples and each end-member sample; The coefficient determination module is configured to determine a plurality of first end-member samples affecting the dissolved organic matter (DOM) and the particulate organic matter (POM) of the water samples, determine a first influence coefficient of the DOM sample of each first end-member sample on the DOM sample of the water sample, and a second influence coefficient of the POM sample of each first end-member sample on the POM sample of the water sample; The first background value determination module is configured to determine a third influence coefficient of the DOM sample of the natural source end-member sample in the first end-member sample on the chemical oxygen demand of the water sample, and a fourth influence coefficient of the POM sample of the natural source end-member sample in the first end-member sample on the chemical oxygen demand of the water sample, and calculate the chemical oxygen demand background value of each sampling point based on the third influence coefficient and the fourth influence coefficient corresponding to the natural source end-member sample in the first end-member sample; The second background value determination module is configured to determine the weight of each sampling point based on the human activity intensity within a second predetermined range around each sampling point, and determine the chemical oxygen demand background value of the regional and / or basin water environment based on the chemical oxygen demand background value and the weight of each sampling point.

[0062] The embodiment of the application further provides an electronic device, which includes: A processor is configured to execute a plurality of instructions. a memory for storing a plurality of instructions; The plurality of instructions are stored in the memory and loaded and executed by the processor to perform the method as described above.

[0063] The embodiment of the present application further provides a computer readable storage medium, wherein the storage medium stores a plurality of instructions; the plurality of instructions are loaded and executed by a processor to perform the method as described above.

[0064] It should be noted that the embodiments and features of the present application can be combined if there is no conflict.

[0065] In several embodiments provided by the present application, it should be understood that the disclosed system, device and method can be implemented by other ways. For example, the device embodiments described above are only schematic; the division of the units is only a logical function division; there can be another division manner in actual implementation; for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections can be indirect couplings or communication connections through some interfaces, devices or units, and can be electrical, mechanical or other forms.

[0066] The units described as separated components can or can not be physically separated, and the components displayed as units can or can not be physical units, i.e. can be located in one place, or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0067] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can be a physically independent unit, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware, or in the form of hardware plus software function unit.

[0068] The integrated unit in the form of the software function unit can be stored in a computer readable storage medium. The software function unit is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a physical machine server, or a network cloud server, etc., which needs to be installed with an Ubuntu operating system) to execute part of steps of the method described in various embodiments of the present application. The foregoing storage medium includes a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0069] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present application still belongs to the scope of the technical solution of the present application.

Claims

1. A method for determining a background value of chemical oxygen demand in an aqueous environment, characterized by, The method comprises: Step S1: determining a plurality of sampling points of a water environment; collecting water samples from the sampling points and determining the chemical oxygen demand of the water samples, obtaining a plurality of end-member samples within a first preset range around the sampling points, the end-member samples being natural objects affecting the chemical oxygen demand of the water samples; for the water samples and each end-member sample, obtaining a dissolved organic matter (DOM) sample and a particulate organic matter (POM) sample; Step S2: determining a plurality of first end-member samples affecting the dissolved organic matter (DOM) and the particulate organic matter (POM) of the water samples; determining a first influence coefficient of the dissolved organic matter (DOM) sample of each first end-member sample on the dissolved organic matter (DOM) sample of the water sample, and a second influence coefficient of the particulate organic matter (POM) sample of each first end-member sample on the particulate organic matter (POM) sample of the water sample; Step S3: determining a third influence coefficient of the dissolved organic matter (DOM) sample of a natural source end-member sample in the first end-member samples on the chemical oxygen demand of the water sample, and a fourth influence coefficient of the particulate organic matter (POM) sample of the natural source end-member sample in the first end-member samples on the chemical oxygen demand of the water sample; calculating the chemical oxygen demand background value of each sampling point based on the third influence coefficient and the fourth influence coefficient corresponding to the natural source end-member sample in the first end-member samples; Step S4: determining the weight of each sampling point based on the intensity of human activities within a second preset range around each sampling point; determining the regional and / or basin water environment chemical oxygen demand background value based on the chemical oxygen demand background value and the weight of each sampling point.

2. The method of claim 1, wherein, In the step S1, the water samples are collected from the sampling points and the chemical oxygen demand of the water samples is determined, and a plurality of end-member samples within a first preset range around the sampling points are obtained, the end-member samples being natural objects affecting the chemical oxygen demand of the water samples; For the water samples and each end-member sample, a dissolved organic matter (DOM) sample and a particulate organic matter (POM) sample are obtained, comprising: Water samples were collected from sampling points and the chemical oxygen demand of the water samples was determined, denoted as COD point The water samples were filtered through 0.45 μm filter membranes, and the chemical oxygen demand of the filtered water samples was determined, denoted as COD' point point is the sampling point number; the filter residues on the filter membranes were collected as particulate organic matter POM samples of the water samples, and the filtrates were dissolved organic matter DOM samples of the water samples; a plurality of end-member samples within a first preset range around the sampling points are obtained; wherein: for liquid end-member samples, the filter residue on the membrane is collected as the particulate organic matter (POM) sample of the liquid end-member sample after filtration through a 0.45 μm filter membrane, and the filtrate is the dissolved organic matter (DOM) sample of the liquid end-member sample; for solid end-member samples, the particulate organic matter (POM) sample of the solid end-member sample is obtained by freeze-drying, grinding and sieving the solid end-member sample, and the dissolved organic matter (DOM) sample of the solid end-member sample is obtained by leaching, centrifuging and filtering the particulate organic matter (POM) sample of the solid end-member sample through a 0.45 μm filter membrane.

3. The method of claim 2, wherein, In the step S2, a plurality of first end-member samples affecting the dissolved organic matter (DOM) and the particulate organic matter (POM) of the water samples are determined, comprising: obtaining the first distribution characteristics of carbon isotopes and nitrogen isotopes of the dissolved organic matter (DOM) sample and the particulate organic matter (POM) sample of the water sample; obtaining the second distribution characteristics of carbon isotopes and nitrogen isotopes of the dissolved organic matter (DOM) sample and the particulate organic matter (POM) sample of each end-member sample corresponding to the water sample; based on the first distribution characteristics and the second distribution characteristics, the end-member sample with a second distribution characteristic similar to the first distribution characteristic by more than a first preset threshold is taken as a first end-member sample.

4. The method of claim 3, wherein, The step S2 determines a first influence coefficient of the dissolved organic matter DOM sample of each first end member sample on the dissolved organic matter DOM sample of the water sample, and a second influence coefficient of the particulate organic matter POM sample of each first end member sample on the particulate organic matter POM sample of the water sample, wherein: The contribution rates of the carbon isotopes and nitrogen isotopes of the dissolved organic matter DOM and the particulate organic matter POM of the water sample are determined; The contribution rates of the carbon isotopes and nitrogen isotopes of the dissolved organic matter DOM and the particulate organic matter POM of each first end member sample are determined; The first influence coefficient of the dissolved organic matter DOM sample of each first end member sample on the dissolved organic matter DOM sample of the water sample and the second influence coefficient of the particulate organic matter POM sample of each first end member sample on the particulate organic matter POM sample of the water sample are determined based on the mass conservation principle; the first influence coefficient and the second influence coefficient are both contribution rate proportions; The mass conservation principle is that the weighted average contribution rate of the first influence coefficient of the carbon isotopes and nitrogen isotopes of the dissolved organic matter DOM of each first end member sample is equal to the contribution rate of the carbon isotopes and nitrogen isotopes of the dissolved organic matter DOM of the water sample; and the weighted average contribution rate of the second influence coefficient of the carbon isotopes and nitrogen isotopes of the particulate organic matter POM of each first end member sample is equal to the contribution rate of the carbon isotopes and nitrogen isotopes of the particulate organic matter POM of the water sample.

5. The method of claim 4, wherein, The step S3 determines a third influence coefficient of the dissolved organic matter DOM sample of the natural source end member sample in the first end member sample on the chemical oxygen demand of the water sample, and a fourth influence coefficient of the particulate organic matter POM sample of the natural source end member sample in the first end member sample on the chemical oxygen demand of the water sample, wherein: , wherein a point is the third influence coefficient of the natural endmember sample in the first endmember sample of the sampling point numbered point; f plant , f soil , f algae are the first influence coefficients of the dissolved organic matter DOM sample of the plant endmember sample, the soil endmember sample, and the algal endmember sample in the first endmember sample, respectively; , wherein β point is the fourth influence coefficient of the natural endmember sample in the first endmember sample of the sampling point numbered point; f plant , f soil , f algae are the second influence coefficients of the POM sample of the plant endmember sample, the soil endmember sample, and the algal endmember sample in the first endmember sample, respectively.

6. The method of claim 5, wherein, The step S3 calculates the chemical oxygen demand background value of each sampling point based on the third influence coefficient and the fourth influence coefficient corresponding to the natural source end member sample in the first end member sample, including: where COD point,background is the chemical oxygen demand background value for the sampling point numbered point.

7. The method of claim 6, wherein, The step S4 determines the weight of each sampling point based on the human activity intensity in the second preset range around each sampling point; The step S41 determines the human activity intensity in the second preset range around each sampling point: The device includes: , , wherein, is the human activity intensity of the sampling point numbered point; is the construction land equivalent area in the second preset range around the sampling point numbered point; is the total area of the second preset range around the sampling point numbered point; is the area of the i-th land use type in the second preset range around the sampling point numbered point; CI i is the construction land equivalent conversion coefficient of the i-th land use type; n is the number of land use types in the second preset range around the sampling point numbered point; Step S42: determining the weight of each sampling point based on the human activity intensity within the second preset range around each sampling point : wherein, is the number of sampling points; Step S43: determining the regional and / or basin water environment chemical oxygen demand background value based on the chemical oxygen demand background value and the weight of each sampling point : 。 8. An apparatus for determining a background value of a chemical oxygen demand in an aquatic environment, characterized by The sample acquisition module is configured to determine a plurality of sampling points of the water environment; The sample acquisition module is configured to determine a plurality of sampling points of the water environment; The coefficient determination module is configured to determine a plurality of first end member samples that affect the dissolved organic matter DOM and the particulate organic matter POM of the water sample; determine a first influence coefficient of the dissolved organic matter DOM sample of each first end member sample on the dissolved organic matter DOM sample of the water sample, and a second influence coefficient of the particulate organic matter POM sample of each first end member sample on the particulate organic matter POM sample of the water sample; ​ The first background value determination module is configured to determine a third influence coefficient of a dissolved organic matter (DOM) sample of a natural source end member sample in the first end member sample on the chemical oxygen demand of the water sample and a fourth influence coefficient of a particulate organic matter (POM) sample of the natural source end member sample in the first end member sample on the chemical oxygen demand of the water sample; The chemical oxygen demand background values of the sampling points are calculated based on the third influence coefficients and the fourth influence coefficients of the natural source end member samples in the first end member samples; The second background value determination module is configured to determine the weights of the sampling points based on the human activity intensities in the second preset range around the sampling points. The regional and / or basin water environment chemical oxygen demand background values are determined based on the chemical oxygen demand background values and the weights of the sampling points.

9. The apparatus of claim 8, wherein, The water samples are collected from the sampling points, and the chemical oxygen demand of the water samples is determined to obtain a plurality of end member samples in a first preset range around the sampling points, the end member samples being natural objects affecting the chemical oxygen demand of the water samples. The dissolved organic matter (DOM) samples and the particulate organic matter (POM) samples of the water samples and each end member sample are obtained, including: Water samples were collected from sampling points and the chemical oxygen demand of the water samples was determined, denoted as COD point The water samples were filtered through 0.45 μm filter membranes, and the chemical oxygen demand of the filtered water samples was determined, denoted as COD' point point is the sampling point number; the filter residues on the filter membranes were collected as particulate organic matter POM samples of the water samples, and the filtrates were dissolved organic matter DOM samples of the water samples; The plurality of end member samples in the first preset range around the sampling points are obtained, and wherein: For the liquid end member sample, the filter residue on the membrane is collected as the particulate organic matter (POM) sample of the liquid end member sample after the liquid end member sample is filtered through a 0.45 μm filter membrane, and the filtrate is used as the dissolved organic matter (DOM) sample of the liquid end member sample; For the solid end member sample, the particulate organic matter (POM) sample of the solid end member sample is obtained by freeze-drying, grinding and sieving the solid end member sample, and the dissolved organic matter (DOM) sample of the solid end member sample is obtained by extracting the particulate organic matter (POM) sample of the solid end member sample with pure water, centrifuging and filtering the particulate organic matter (POM) sample of the solid end member sample through a 0.45 μm filter membrane.

10. The apparatus of claim 8, wherein, The first end member samples affecting the dissolved organic matter (DOM) and the particulate organic matter (POM) of the water sample are determined, including: The first distribution characteristics of carbon isotopes and nitrogen isotopes of the dissolved organic matter (DOM) sample and the particulate organic matter (POM) sample of the water sample are obtained; The second distribution characteristics of carbon isotopes and nitrogen isotopes of the dissolved organic matter (DOM) sample and the particulate organic matter (POM) sample of each end member sample corresponding to the water sample are obtained; The end member samples with the second distribution characteristics similar to the first distribution characteristics and with a similarity greater than a first preset threshold are used as the first end member samples based on the first distribution characteristics and the second distribution characteristics.

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