A method and apparatus for determining the background value of chemical oxygen demand in aquatic environments

Abstract

This invention provides a method and apparatus for determining the background value of chemical oxygen demand (COD) in aquatic environments. The method includes: measuring the COD of a water sample; obtaining dissolved organic matter (DOM) and particulate organic matter (POM) samples from both the water sample and each type of end-member sample; identifying several first end-member samples that influence the DOM and POM of the water sample; calculating the background COD value of each sampling point based on the third and fourth influence coefficients corresponding to the natural source end-member samples in the first end-member samples; determining the weight of each sampling point based on the intensity of human activities within a second preset range surrounding each sampling point; and determining the background COD value of the regional and / or watershed aquatic environment based on the background COD value and weight of each sampling point. This invention quantifies the degree of influence of human activities on each sampling point and proposes a more accurate and reliable upscaling background value derivation technique.

Description

Technical Field

[0001] This invention belongs to the field of water quality protection technology, and in particular relates to a method and apparatus for determining the background value of chemical oxygen demand in aquatic environments. Background Technology

[0002] Chemical oxygen demand (COD) is the mass concentration of oxygen corresponding to the dichromate consumed by dissolved substances and suspended solids in a water sample under certain conditions after potassium dichromate oxidation treatment. Its background value mainly comes from the input of natural organic matter from plants and soil, as well as organic matter and reducing inorganic matter contained in the water body itself.

[0003] Due to my country's vast geographical span and significant differences in natural geographical environment, coupled with substantial human disturbance, the factors influencing COD concentration changes in the aquatic environment are complex, making the determination of its natural background value challenging. Currently, there is no clearly defined method for calculating the background value of COD in the aquatic environment. Studying the background value of COD in the aquatic environment helps to understand the contribution of the natural background to the concentration of organic pollutants, providing a scientific basis for setting pollutant control targets. Summary of the Invention

[0004] This invention provides a method and apparatus for determining the background value of chemical oxygen demand (COD) in aquatic environments, in order to solve the above-mentioned technical problems.

[0005] According to a first aspect of the present invention, a method for determining the background value of chemical oxygen demand (COD) in aquatic environments is provided, the method comprising the following steps:

[0006] 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.

[0007] 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.

[0008] 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.

[0009] 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.

[0010] Preferably, 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:

[0011] 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; 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;

[0012] Acquire multiple endmember samples within a first preset range surrounding the sampling point; wherein:

[0013] For the liquid end-member sample, the filter residue on the membrane was collected after filtration through a 0.45 μm filter membrane as the particulate organic matter (POM) sample of the liquid end-member sample, and the filtrate was collected as the dissolved organic matter (DOM) sample of the liquid end-member sample.

[0014] For solid end-member samples, the solid end-member samples were freeze-dried, ground, and sieved to obtain particulate organic matter (POM) samples of solid end-member samples. The particulate organic matter (POM) samples of solid end-member samples were extracted with pure water, centrifuged, and filtered through a 0.45 μm filter membrane. The filtrate was used as the soluble organic matter (DOM) samples of solid end-member samples.

[0015] Preferably, in step S2, determining several first end-member samples that affect the dissolved organic matter (DOM) and particulate organic matter (POM) of the water sample includes:

[0016] The first distribution characteristics of carbon and nitrogen isotopes were obtained from dissolved organic matter (DOM) and particulate organic matter (POM) samples of water.

[0017] The second distribution characteristics of carbon and nitrogen isotopes of dissolved organic matter (DOM) and particulate organic matter (POM) samples were obtained for each end-member sample corresponding to the water sample.

[0018] Based on the first distribution feature and the second distribution feature, endmember samples whose similarity between the second distribution feature and the first distribution feature is greater than a first preset threshold are used as first endmember samples.

[0019] Preferably, in 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:

[0020] Determine the contribution rates of carbon and nitrogen isotopes of dissolved organic matter (DOM) and particulate organic matter (POM) in the water sample;

[0021] Determine the contribution rates of carbon and nitrogen isotopes of dissolved organic matter (DOM) and particulate organic matter (POM) in each first-endmember sample.

[0022] 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; both the first and second influence coefficients are contribution rate percentages.

[0023] The principle of mass conservation states that the weighted average contribution rate of the first influence coefficients of carbon and nitrogen isotopes of dissolved organic matter (DOM) in each first-endmember sample is equal to the contribution rate of carbon and nitrogen isotopes of dissolved organic matter (DOM) in the water sample; and the weighted average contribution rate of the second influence coefficients of carbon and nitrogen isotopes of particulate organic matter (POM) in each first-endmember sample is equal to the contribution rate of carbon and nitrogen isotopes of particulate organic matter (POM) in the water sample.

[0024] Preferably, in step S3, the third influence coefficient of the dissolved organic matter (DOM) sample of the natural source endmember sample in the first endmember sample on the chemical oxygen demand (COD) of the water sample, and the fourth influence coefficient of the particulate organic matter (POM) sample of the natural source endmember sample in the first endmember sample on the COD of the water sample are determined, wherein:

[0025]

[0026] In the formula, α point f is the third influence coefficient of the natural source endmember sample in the first endmember sample of the sampling point numbered point; plant fsoil f algae The first influence coefficients of dissolved organic matter DOM samples in the first endmember samples are respectively plant-derived endmember samples, soil-derived endmember samples, and algal-derived endmember samples;

[0027]

[0028] In the formula, β point f' is the fourth influence coefficient of the natural source endmember sample in the first endmember sample at sampling point numbered point; plant f' soil f' algae The second influence coefficients are the particulate organic matter (POM) samples of plant-derived endmember samples, soil-derived endmember samples, and algal-derived endmember samples in the first endmember sample.

[0029] Preferably, in step S3, calculating the background chemical oxygen demand (COD) value at each sampling point based on the third and fourth influence coefficients corresponding to the natural source end-member samples in the first end-member sample includes:

[0030]

[0031] Among them, COD point,background The background value of chemical oxygen demand for the sampling point numbered "point".

[0032] Preferably, step S4: determining the weight of each sampling point based on the intensity of human activity within a second preset range surrounding each sampling point; determining 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, including:

[0033] Step S41: Determine the intensity of human activity within a second preset range around each sampling point:

[0034]

[0035]

[0036] 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"; iis 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;

[0037] 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. :

[0038]

[0039] in, This represents the number of sampling points;

[0040] 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. :

[0041]

[0042] According to a second aspect of the present invention, an apparatus for determining the background value of chemical oxygen demand (COD) in aquatic environments is provided, the apparatus comprising:

[0043] Sample acquisition module: configured to identify multiple sampling points in the aquatic environment; collect water samples from the sampling points and measure the chemical oxygen demand (COD) of the water samples; acquire 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; acquire dissolved organic matter (DOM) samples and particulate organic matter (POM) samples for both the water samples and each type of end-member sample.

[0044] Coefficient determination module: configured to 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.

[0045] The first background value determination module is configured to determine the third influence coefficient of dissolved organic matter (DOM) samples from natural source endmember samples on the chemical oxygen demand (COD) of water samples, and the fourth influence coefficient of particulate organic matter (POM) samples from natural source endmember samples on the COD of water samples; and to calculate the COD background value of each sampling point based on the third and fourth influence coefficients corresponding to the natural source endmember samples in the first endmember samples.

[0046] The second background value determination module is configured to determine the weight of each sampling point based on the intensity of human activities within a second preset range around each sampling point; and to determine the background value of chemical oxygen demand (COD) in the regional and / or watershed water environment based on the background value and weight of each sampling point.

[0047] Preferably, the step involves collecting water samples from sampling points and measuring the chemical oxygen demand (COD) of the water samples, obtaining 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; for both the water samples and each end-member sample, dissolved organic matter (DOM) samples and particulate organic matter (POM) samples are obtained, including:

[0048] 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; 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;

[0049] Acquire multiple endmember samples within a first preset range surrounding the sampling point; wherein:

[0050] For the liquid end-member sample, the filter residue on the membrane was collected after filtration through a 0.45 μm filter membrane as the particulate organic matter (POM) sample of the liquid end-member sample, and the filtrate was collected as the dissolved organic matter (DOM) sample of the liquid end-member sample.

[0051] For solid end-member samples, the solid end-member samples were freeze-dried, ground, and sieved to obtain particulate organic matter (POM) samples of solid end-member samples. The particulate organic matter (POM) samples of solid end-member samples were extracted with pure water, centrifuged, and filtered through a 0.45 μm filter membrane. The filtrate was used as the soluble organic matter (DOM) samples of solid end-member samples.

[0052] Preferably, the determination of several first end-member samples affecting dissolved organic matter (DOM) and particulate organic matter (POM) in the water sample includes:

[0053] The first distribution characteristics of carbon and nitrogen isotopes were obtained from dissolved organic matter (DOM) and particulate organic matter (POM) samples of water.

[0054] The second distribution characteristics of carbon and nitrogen isotopes of dissolved organic matter (DOM) and particulate organic matter (POM) samples were obtained for each end-member sample corresponding to the water sample.

[0055] Based on the first distribution feature and the second distribution feature, endmember samples whose similarity between the second distribution feature and the first distribution feature is greater than a first preset threshold are used as first endmember samples.

[0056] According to a third aspect of the present invention, an electronic device is provided, comprising:

[0057] A processor is used to execute multiple instructions;

[0058] Memory, used to store multiple instructions;

[0059] The plurality of instructions are to be stored in the memory and loaded and executed by the processor as described above.

[0060] According to a fourth aspect of the present invention, a computer-readable storage medium is provided, wherein a plurality of instructions are stored therein; the plurality of instructions are configured to be loaded by a processor and executed as described above.

[0061] The present invention has the following beneficial technical effects:

[0062] This invention combines a method for calculating background values ​​at sampling points based on stable isotope methods with a method for assessing the representativeness of regional / watershed background values ​​based on the intensity of human activities. For sampling points, it quantifies the impact of natural sources of DOM and POM on the DOM and POM of the collected water samples, providing a more scientifically grounded method for deriving COD background values. For regions / watersheds, it quantifies the degree of human activity impact at each sampling point, proposing a more accurate and reliable upscaling background value derivation technique. This provides new insights for deriving COD background values ​​in the water environment and serves as a reference for baseline water quality research and scientific evaluation.

[0063] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0064] 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:

[0065] 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

[0066] 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:

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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:

[0072] 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; 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;

[0073] Acquire multiple endmember samples within a first preset range surrounding the sampling point; wherein:

[0074] For the liquid end-member sample, the filter residue on the membrane was collected after filtration through a 0.45 μm filter membrane as the particulate organic matter (POM) sample of the liquid end-member sample, and the filtrate was collected as the dissolved organic matter (DOM) sample of the liquid end-member sample.

[0075] For solid end-member samples, the solid end-member samples were freeze-dried, ground, and sieved to obtain particulate organic matter (POM) samples of solid end-member samples. The particulate organic matter (POM) samples of solid end-member samples were extracted with pure water, centrifuged, and filtered through a 0.45 μm filter membrane. The filtrate was used as the soluble organic matter (DOM) samples of solid end-member samples.

[0076] In this invention, water samples and representative organic matter source (end-member) samples from the sampling point and surrounding areas are collected, including phytoplankton, aquatic plants, terrestrial plants, soil, urban domestic sewage and industrial wastewater, as well as agricultural and rural sewage, livestock and poultry manure, etc. The relevant operations are performed in accordance with documents such as HJ 91.2–2022, HJ / T 166–2004, HJ 494–2009, and HJ 495–2009. Specifically: (1) Phytoplankton were enriched in the surface water at multiple locations using a planktonic net and frozen at -20℃ for later use; (2) Among the dominant aquatic plants, emergent plants were collected at multiple locations in the water and on the shore, and submerged plants were collected at multiple locations in the water. 3-10 plants of the same species were collected at the same location and mixed as a single sample. The branches and leaves were cut, washed with deionized water, and then dried for later use; (3) Terrestrial plants were collected at multiple locations along the water body. 3-10 plants of the same species were collected at the same location and mixed as a single sample. The branches and leaves were cut, washed with deionized water, and then dried for later use; (4) Soil (including farmland soil, meadow soil, and saline-alkali soil, etc.) was collected at multiple locations within 500 m of the water body. Soil samples from the same location were collected at approximately 5 m locations. 2 (5) Mixed samples within the range and at a depth of 0-20 cm are used as samples at this location. After removing impurities, they are dried, ground, and sieved for later use; (6) Wastewater from urban domestic sewage and wastewater from typical industrial enterprises (including petrochemical, food processing, etc.) after treatment, as well as agricultural and rural sewage, are collected and frozen at -20℃ for later use; (7) Fresh manure from the main livestock and poultry species in the breeding farm is collected, freeze-dried, and stored for later use.

[0077] Sample determination and DOM / POM sample preparation were carried out in accordance with GB 11892–89, GB / T 42490–2023, HJ 493–2009 and other documents. Specifically: (1) The collected water samples were filtered through a 0.45 μm filter membrane, and the COD before and after filtration was measured and recorded as COD. point and COD' point;Collect POM samples on the membrane, and use the filtrate as DOM samples; (2) Collect POM end-member samples (urban domestic sewage, industrial wastewater, agricultural and rural sewage) after filtration through a 0.45 μm filter membrane, and use the filtrate as DOM end-member samples; (3) Freeze-dry, grind and sieve solid end-member samples (algae, plants, soil and livestock and poultry manure, etc.) to obtain POM end-member samples; After pure water extraction, centrifugation and filtration through a 0.45 μm filter membrane, POM end-member samples are used to obtain DOM end-member samples.

[0078] Further, in step S2, several first-end-member samples that affect the dissolved organic matter (DOM) and particulate organic matter (POM) of the water sample are identified, including:

[0079] The first distribution characteristics of carbon and nitrogen isotopes were obtained from dissolved organic matter (DOM) and particulate organic matter (POM) samples of water.

[0080] The second distribution characteristics of carbon and nitrogen isotopes of dissolved organic matter (DOM) and particulate organic matter (POM) samples were obtained for each end-member sample corresponding to the water sample.

[0081] Based on the first distribution feature and the second distribution feature, endmember samples whose similarity between the second distribution feature and the first distribution feature is greater than a first preset threshold are used as first endmember samples.

[0082] Further, in 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:

[0083] Determine the contribution rates of carbon and nitrogen isotopes of dissolved organic matter (DOM) and particulate organic matter (POM) in the water sample;

[0084] Determine the contribution rates of carbon and nitrogen isotopes of dissolved organic matter (DOM) and particulate organic matter (POM) in each first-endmember sample.

[0085] 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; both the first and second influence coefficients are contribution rate percentages.

[0086] The principle of mass conservation states that the weighted average contribution rate of the first influence coefficients of carbon and nitrogen isotopes of dissolved organic matter (DOM) in each first-endmember sample is equal to the contribution rate of carbon and nitrogen isotopes of dissolved organic matter (DOM) in the water sample; and the weighted average contribution rate of the second influence coefficients of carbon and nitrogen isotopes of particulate organic matter (POM) in each first-endmember sample is equal to the contribution rate of carbon and nitrogen isotopes of particulate organic matter (POM) in the water sample.

[0087] In this invention, water samples and DOM and POM samples from each end-member were collected, acidified with hydrochloric acid to remove inorganic carbon, washed with ultrapure water until pH neutral, and then freeze-dried. The carbon and nitrogen isotope ratios were then determined using an isotope mass spectrometer, with analytical precisions of 0.05‰ and 0.10‰, respectively. δ 13 C and δ 15 N is calculated as follows:

[0088] (1)

[0089] (2)

[0090] In the formula, δ 13 C represents the carbon isotope ratio, ‰; δ 15 N represents the nitrogen isotope ratio, expressed in per mille (‰). 13 C / 12 C sample This indicates the carbon isotope ratio of the test sample, and is dimensionless. 13 C / 12 C standard The isotopic ratio of the standard material Vienna-PeeDee belemnites (VPDB) is 0.011180. 15 N / 14 N sample This indicates the nitrogen isotope ratio of the test sample, and is dimensionless. 15 N / 14 N standard This represents the isotope ratio of nitrogen in the atmosphere, with a value of 0.003613.

[0091] By comparing the δ values ​​of DOM and POM in collected water samples with those of DOM and POM in various endmembers, the following was observed. 13 C、δ 15 Based on the N-distribution characteristics, end metadata that is not a primary source of DOM and POM in water samples is removed, and δ is merged. 13 C、δ 15 N-distributed end-data is relatively consistent. (Using δ) 13 C and δ 15N is a parameter. Source apportionment models such as the multivariate linear mixture model IsoSource are applied to quantitatively analyze the contributions of different endmembers DOM and POM to the collected water sample DOM and POM. The total contributions of natural sources (plant source, soil source and / or algal source, etc.) are denoted as α and β, respectively.

[0092] Taking IsoSource as an example, the principle of end-member contribution rate calculation is as follows: According to the principle of mass conservation, after DOM (or POM) from different pollution sources enter the water body, the isotopes and their total amounts remain unchanged before and after mixing. Carbon and nitrogen isotopes can be used to quantitatively analyze the contribution ratio 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 ratio of up to three pollution sources, as shown in the following formula:

[0093] (3)

[0094] (4)

[0095] (5)

[0096] In the formula: This indicates the carbon isotope value of DOM (or POM) in the water sample, expressed in ‰. This indicates the nitrogen isotope value of DOM (or POM) in a water sample, expressed in per mille (‰); f A f B f C This indicates the proportion of different DOM (or POM) pollution sources, expressed in % (%). , , This represents the carbon isotope values ​​of different pollution sources, in per mille (‰). , , This represents the nitrogen isotope values ​​for different pollution sources, in per mille (‰).

[0097] When there are more than three pollution sources, and their number exceeds the number of isotopes plus one, the IsoSource model can be used. This model is based on a mass conservation model. By setting incremental parameters, it uses an iterative method to calculate all possible combinations of carbon and nitrogen isotope percentages from different sources (summing up to 100%). The weighted average of each combination is compared with the actual measured isotope values ​​in the mixed water body. Combinations within the tolerance parameter (generally set to 0.01‰~0.1‰) are considered feasible relative contribution percentages. Frequency analysis is performed on these feasible combinations, and combinations within the higher frequency range are considered the relative contribution proportions of pollution sources to the water environment's DOM (or POM). All possible percentage combinations of different pollution sources are calculated using the following formula:

[0098] (6)

[0099] In the formula, Q represents the number of all possible percentage combinations, in units of 1; i represents the incremental parameter, which is generally set to 1%~2%; and s represents the number of DOM (or POM) sources, in units of 1.

[0100] Further, in step S3, the third influence coefficient of the dissolved organic matter (DOM) sample of the natural source endmember sample in the first endmember sample on the chemical oxygen demand (COD) of the water sample, and the fourth influence coefficient of the particulate organic matter (POM) sample of the natural source endmember sample in the first endmember sample on the COD of the water sample are determined, wherein:

[0101] (7)

[0102] In the formula, α point f is the third influence coefficient of the natural source endmember sample in the first endmember sample of the sampling point numbered point; plant f soil f algae The first influence coefficients of dissolved organic matter DOM samples in the first endmember samples are respectively plant-derived endmember samples, soil-derived endmember samples, and algal-derived endmember samples;

[0103] (8)

[0104] In the formula, β point f' is the fourth influence coefficient of the natural source endmember sample in the first endmember sample at sampling point numbered point; plant f' soil f' algae The second influence coefficients are the particulate organic matter (POM) samples of plant-derived endmember samples, soil-derived endmember samples, and algal-derived endmember samples in the first endmember sample.

[0105] Further, in step S3, the background value of chemical oxygen demand at 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, including:

[0106] (9)

[0107] Among them, COD point,background The background value of chemical oxygen demand for the sampling point numbered "point".

[0108] In this invention, the background values ​​of water samples collected at each sampling point in different months or water seasons are calculated as the arithmetic mean of the background values ​​for that point in accordance with the requirements of documents such as the "Technical Regulations for Statistical Analysis of Surface Water Environmental Quality Monitoring Data (Trial)" issued by the Ministry of Ecology and Environment.

[0109] Further, step S4: determining the weight of each sampling point based on the intensity of human activity within a second preset range surrounding each sampling point; determining the background value of chemical oxygen demand (COD) for the regional and / or watershed aquatic environment based on the background COD value and weight of each sampling point, including:

[0110] Step S41: Determine the intensity of human activity within a second preset range around each sampling point:

[0111] (10)

[0112] (11)

[0113] 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;

[0114] 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. :

[0115]

[0116] in, This represents the number of sampling points;

[0117] 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. :

[0118]

[0119] 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.

[0120] 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:

[0121]

[0122]

[0123] 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.

[0124] The intensity of human activity at each sampling point is converted into a weight (summed to 1) of the background value at that point relative to the background value of the region / basin. Let the intensity of human activity at each sampling point be HAI1, HAI2, …, HAI n Then the weight of each sampling point for:

[0125]

[0126] If HAI is 0, a smaller number can be added, such as 1e. -6 ;

[0127] Based on the weights, a weighted average is calculated on the background values ​​of the sampling points to obtain the regional / basin COD background value. The formula is as follows:

[0128]

[0129] By adopting the above technical solution, the main technological advancements of this invention compared to existing technologies are as follows: It combines a method for calculating background values ​​at sampling points based on the stable isotope method with a method for assessing the representativeness of regional / watershed background values ​​based on the intensity of human activities. For sampling points, it quantifies the impact of natural sources of DOM and POM on the DOM and POM of the collected water samples, providing a more scientifically grounded method for deriving COD background values. For regions / watersheds, it quantifies the degree of human activity impact at each sampling point, proposing a more accurate and reliable upscaling background value derivation technique. This provides new insights for deriving COD background values ​​in the water environment and serves as a reference for baseline water quality research and scientific evaluation.

[0130] This invention provides a specific embodiment of a method for determining the background value of chemical oxygen demand (COD) in aquatic environments.

[0131] Taking the derivation of the background COD value in the Fenhe River Basin (Yellow River Basin) as an example, this basin has high intensity of human activities and high sediment content. COD is affected by both anthropogenic and natural sources. The steps for deriving the background value include:

[0132] S1. Carry out water sample collection, COD determination, and collection of COD potential sources (endmembers) around the sampling point, and complete the preparation of DOM and POM samples of water samples and endmember samples.

[0133] In this embodiment, in accordance with relevant standard documents, 29 sampling points were set up in the Fenhe River Basin. Sampling of the water bodies at these points and surrounding potential sources of organic matter (including plant sources, algae sources, soil sources, domestic sewage sources, industrial sources, and agricultural sources) was conducted in August (high water season) and December (low water season) of 2023. According to relevant standard documents, the water samples, liquid end-member samples, and solid end-member samples from the sampling points were processed, measured, and analyzed respectively. The COD (denoted as COD) of the water samples from the sampling points and the water samples filtered through a 0.45 μm filter membrane was determined using acid titration. point With COD point After filtration, the water sample was used as the DOM sample, and the POM sample on the membrane was collected. Various liquid end-members (pollutant sources, including domestic sewage, industrial and agricultural sources) were filtered through a 0.45 μm filter membrane, and the POM end-member samples on the membrane were collected. The filtrate was used as the DOM end-member sample. Various solid end-members (including plant sources, algae sources, soil sources, etc.) were freeze-dried, ground and sieved to obtain POM end-member samples. The POM end-member samples were extracted with pure water, centrifuged, and the supernatant was filtered through a 0.45 μm filter membrane to obtain the DOM end-member sample.

[0134] S2. Perform stable isotope determination of DOM and POM in water samples and end-member samples, and calculate the end-member contribution rate.

[0135] In this embodiment, water samples from sampling points and DOM and POM samples from each endmember were taken, completely wetted with hydrochloric acid, and placed in a desiccator containing concentrated hydrochloric acid for 48 hours to remove inorganic carbon through acidification. The samples were repeatedly washed with ultrapure water until the pH reached approximately 7, then freeze-dried. The samples were then placed in an elemental analyzer (Flash EA 2000HT) and an isotope mass spectrometer (Thermo Fisher Scientific Inc., USA) coupled to determine the carbon and nitrogen isotope δ¹⁸O. 13 C and δ 15 N ratio, δ 13 C and δ 15 The average analytical errors for N were approximately 0.13‰ and 0.1‰. The results showed that the δ¹⁴ Ω of the DOM in the water samples during the high-water season... 13 The average concentration of C was -23.31‰ during the dry season and -25.26‰ during the wet season. The δ¹⁴P of water samples from the POM (particulate matter) during the wet season... 13The average value of C is -23.44‰, and the average value of δ is... 15 The average nitrogen (N) was 9.71‰; the average δ during the dry season was... 13 C is close to the high-water season, but δ 15 N is lower than during the high-water season, averaging 3.9‰.

[0136] In this embodiment, considering both wet and dry seasons, carbon and nitrogen isotope measurements of end-member samples from soil, plants, agriculture, and industry in the Fenhe River basin indicate that the δ¹² values ​​of aquatic organisms (DOMs) are... 13 C and δ 15 The average N was -26.02‰ and 17.34‰, and the agricultural source δ 13 C and δ 15 The average N values ​​were -23.53‰ and 0.52‰, and the industrial source δ 13 C and δ 15 The average N was -26.26‰ and 13.30‰, and the δ of the residents' living sources 13 C and δ 15 The average N values ​​were -19.10‰ and 12.79‰, and the δ values ​​of terrestrial C3 plants were... 13 C and δ 15 The average N values ​​were -28.31‰ and 7.74‰, and the δ values ​​of terrestrial C4 plants were... 13 C and δ 15 The average nitrogen (N) was -20.29‰ and 4.22‰, and the δ¹⁰ of the riverbank soil was... 13 C and δ 15 The average nitrogen (N) was -24.71‰ and 5.02‰; regarding phosphorus (POM), the water body δ... 13 C、δ 15 N was -29.96‰ and 7.07‰, respectively, and the δ of terrestrial C3 and C4 plants was... 13 C、δ 15 N values ​​were -28.31‰, 7.74‰ and -20.29‰, 4.22‰, respectively, and the δ¹⁸O values ​​for the riverbank soil were also observed. 13 C、δ 15 N were -24.71‰ and 5.02‰, respectively.

[0137] In this embodiment, the stable isotopes (δ¹²) of each endmember DOM and POM are used. 13 C、δ 15The contribution of different endmembers to the DOM and POM of water samples at sampling points was quantified using the IsoSource model (mean of solutions in each interval; summed to 1). DOM and POM inputs from agricultural, industrial, and residential sources were considered anthropogenic sources, while plant and soil sources were considered natural sources (algae sources were considered anthropogenic sources due to severe human impact on the watershed). The contributions of natural and anthropogenic sources to the DOM and POM of water bodies were distinguished. The results showed that the contributions of natural and anthropogenic sources to the DOM in the Fenhe River basin were 10.9% and 89.1%, respectively, and to the POM, respectively, were 58.9% and 41.1%. Specifically, the contribution of natural sources to the DOM at each sampling point ranged from 1.7% to 9.3% during the high-water season and from 8.8% to 35.1% during the low-water season; the contribution of natural sources to the POM ranged from 43.2% to 63.8% during the high-water season and from 35.1% to 62.9% during the low-water season.

[0138] S3. Derive the background values ​​of the sampling points.

[0139] In this embodiment, for each water sample, the total contribution rate of natural sources in DOM and POM is used. , The background value was obtained by multiplying the measured COD by the background value; the average background value of water samples collected in August and December at each sampling point was the background value for that point. The results showed that the background values ​​at the 29 sampling points ranged from 8.62 to 58.89 mg / L. –1 .

[0140] S4. Conduct an assessment of the intensity of human activities at sampling points and determine their weights, and derive the background COD values ​​for the region / basin.

[0141] In this embodiment, based on 2023 30 m resolution land use data from existing land use data products (CLCD; https: / / zenodo.org / records / 12779975), the proportion of various land uses within a 1 km radius of each sampling point was analyzed. Studies have shown that land use within this spatial range can significantly influence water quality at the sampling points. Human activity intensity was calculated accordingly, yielding a range of 4.76% to 82.12% for the 29 sampling points. The human activity intensity at each sampling point was then converted into a weight of the background value at that point relative to the watershed background value, resulting in a maximum weight of 0.22.

[0142] In this embodiment, a weighted average of the background values ​​at each sampling point was calculated based on the weights, yielding a COD background value of 21.90 mg / L for the Fenhe River Basin. –1 .

[0143] This invention discloses an apparatus for determining the background value of chemical oxygen demand (COD) in aquatic environments. The apparatus may include:

[0144] Sample acquisition module: configured to identify multiple sampling points in the aquatic environment; collect water samples from the sampling points and measure the chemical oxygen demand (COD) of the water samples; acquire 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; acquire dissolved organic matter (DOM) samples and particulate organic matter (POM) samples for both the water samples and each type of end-member sample.

[0145] Coefficient determination module: configured to 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.

[0146] The first background value determination module is configured to determine the third influence coefficient of dissolved organic matter (DOM) samples from natural source endmember samples on the chemical oxygen demand (COD) of water samples, and the fourth influence coefficient of particulate organic matter (POM) samples from natural source endmember samples on the COD of water samples; and to calculate the COD background value of each sampling point based on the third and fourth influence coefficients corresponding to the natural source endmember samples in the first endmember samples.

[0147] The second background value determination module is configured to determine the weight of each sampling point based on the intensity of human activities within a second preset range around each sampling point; and to determine the background value of chemical oxygen demand (COD) in the regional and / or watershed water environment based on the background value and weight of each sampling point.

[0148] The present invention further provides an electronic device, comprising:

[0149] A processor is used to execute multiple instructions;

[0150] Memory, used to store multiple instructions;

[0151] The plurality of instructions are to be stored in the memory and loaded and executed by the processor as described above.

[0152] The present invention further provides a computer-readable storage medium storing a plurality of instructions; the plurality of instructions are used by a processor to load and execute the method as described above.

[0153] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0154] In the embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between devices or units through some interfaces, and may be electrical, mechanical, or other forms.

[0155] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0156] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in the form of hardware plus software functional units.

[0157] The integrated unit, implemented as a software functional unit, can be stored in a computer-readable storage medium. This software functional unit, stored in a storage medium, includes several instructions to cause a computer device (which may be a personal computer, a physical server, or a cloud server, etc., requiring the Ubuntu operating system to be installed) to execute some steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0158] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

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; obtaining a dissolved organic matter DOM sample and a particulate organic matter POM sample for each end-member sample and the water 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; In the step S3: , wherein a point is the third influence coefficient of the natural end-member sample in the first end-member 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 end-member sample, the soil end-member sample, and the algal end-member sample in the first end-member 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.

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 each end-member sample and the water 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 The water samples were filtered through a 0.45 μm filter membrane, and the chemical oxygen demand of the filtered water samples was determined, denoted as point is the sampling point number; the filter residue on the filter membrane was collected as a particulate organic matter POM sample of the water sample, and the filtrate was a dissolved organic matter DOM sample of the water sample; 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, the 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, 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 includes the following steps. where CODbackground is the background value of chemical oxygen demand for the sampling point numbered point. point,background is the background value of chemical oxygen demand for the sampling point numbered point.

6. The method of claim 5, wherein, In the step S4, the weight of each sampling point is determined based on the human activity intensity within a second preset range around each sampling point. In the step S5, the regional and / or basin water environment chemical oxygen demand background value is determined based on the chemical oxygen demand background value and the weight of each sampling point, and the step S5 includes the following steps. Step S41: determining human activity intensity in the second preset range around each sampling point; , , wherein, is the human activity intensity of the sampling point numbered as point; is the construction land equivalent area in the second preset range around the sampling point numbered as point; is the total area of the second preset range around the sampling point numbered as point; is the area of the i-th land use type in the second preset range around the sampling point numbered as 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 as 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 : .

7. A device for determining the background value of chemical oxygen demand (COD) in aquatic environments, characterized in that, The device includes: 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 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. The third influence coefficient and the fourth influence coefficient corresponding to the natural source end member sample in the first end member sample are used to calculate the chemical oxygen demand background value of each sampling point; The second background value determination module is configured to determine the weight of each sampling point based on the human activity intensity in the second preset range around each sampling point; The chemical oxygen demand background value of each sampling point and the weight are used to determine the regional and / or watershed water environment chemical oxygen demand background value; The first background value determination module, wherein: , wherein α point is the third influence coefficient of the natural end-member sample in the first end-member sample of the sampling point numbered point; f plant , f soil , f algae are the first influence coefficients of the plant end-member sample, the soil end-member sample and the dissolved organic matter DOM sample of the algal end-member sample in the first end-member sample, respectively; , wherein β point is the fourth influence coefficient of the natural end-member sample in the first end-member sample of the sampling point numbered point; f plant , f soil , f algae are the second influence coefficients of the plant end-member sample, the soil end-member sample and the particulate organic matter POM sample of the algal end-member sample in the first end-member sample, respectively.

8. The apparatus of claim 7, wherein, The water sample is collected from the sampling point, and the chemical oxygen demand of the water sample is determined to obtain a plurality of end member samples in the first preset range around the sampling point, 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, a dissolved organic matter DOM sample and a particulate organic matter POM 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; A plurality of end member samples in 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 used 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 the filtrate is used as the dissolved organic matter DOM sample of the solid end member sample 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.

9. The apparatus of claim 7, wherein, The determination of the first end member sample affecting the dissolved organic matter DOM and the particulate organic matter POM of the water sample includes: 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; 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 used as the first end member sample.

Images