Basin lake endogenous phosphorus pollution quantitative calculation method

Abstract

The invention discloses a drainage basin and lake endogenous phosphorus pollution quantitative calculation method, and relates to the technical field of drainage basin and lake nutritive salt traceability, and the method comprises the steps: determining a drainage basin boundary, and collecting endogenous phosphorus output and exogenous phosphorus input near a drainage basin, and samples in a lake water body and other media; obtaining the phosphate oxygen isotope value delta < 18 > O (PO4) of each pollution source and the source-tracing water body of the lake; and substituting a phosphate oxygen isotope value delta18O (PO4) into a Bayesian model and a mixed end member model, calculating to obtain a relative contribution rate of endogenous phosphorus output and exogenous phosphorus input, combining the relative contribution rate with different types of land area data, and determining an actual relative contribution rate of the endogenous phosphorus output and the exogenous phosphorus input to the phosphorus load of the river basin lake water body. According to the method, the actual relative contribution rate of endogenous phosphorus output to the phosphorus load of the lake water body is quantitatively calculated on the basis of traditional drainage basin lake exogenous phosphorus tracing, and a supporting basis is provided for accurate quantitative calculation of drainage basin lake phosphorus.

Description

Technical Field

[0001] The present application relates to the technical field of nutrient source tracing in river basins and lakes, and more specifically, to a method for quantitatively calculating endogenous phosphorus pollution in river basins and lakes. Background Art

[0002] Lake eutrophication has become a global problem, with excessive nitrogen and phosphorus inputs being the main causes. Among them, the role of phosphorus in algal blooms is particularly prominent in shallow eutrophic lakes. The increase in phosphorus concentration in lake waters mainly comes from external inputs from point and non-point sources and internal releases from sediments. Studies have shown that when the external phosphorus load is intercepted, the continued release of phosphorus in sediments will have long-term, large-scale impacts on water bodies, exacerbating lake eutrophication and algal blooms. Therefore, quantitative tracing of the contribution of exogenous phosphorus input and endogenous phosphorus output to phosphorus pollution in basin lakes plays a vital role in pollution management, remediation and habitat restoration of lake ecosystems.

[0003] Due to the complexity of the environmental geochemical behavior of phosphorus during its transportation from land to lakes, it is difficult to identify and quantify the source of phosphorus in lakes based solely on concentration. In terms of traditional tracing of the source of phosphorus pollutants in lake waters, commonly used methods include hydrological methods, geochemical methods, mathematical modeling techniques, and phosphate oxygen isotope techniques. However, considering the large demand for data, the stability of the model, and the high cost, the use of phosphate oxygen isotope technology to identify the source of phosphorus in lake waters and quantitatively analyze the contribution rate has attracted widespread attention worldwide.

[0004] However, most of the existing studies using phosphate oxygen isotope technology for tracing are exogenous phosphorus tracing. For example, patent application publication number CN 114496108A is a method for tracing the source of phosphate in water based on phosphate oxygen isotopes and water chemical characteristics. This scheme uses phosphate oxygen isotope technology combined with water chemical characteristic content to identify and quantify the contribution ratio of various exogenous phosphorus, but the focus is on exogenous phosphorus input. There is a lack of quantitative calculation research on the contribution of endogenous phosphorus output. Based on the traditional exogenous phosphorus tracing of river basin lakes, this application can quantitatively calculate the actual relative contribution rate of endogenous phosphorus output to the phosphorus load of lake water bodies, providing a supporting basis for the accurate quantitative calculation of phosphorus in river basin lakes. Summary of the invention

[0005] 1. Technical issues to be solved

[0006] In view of the problem that the contribution of endogenous phosphorus in the source tracing of phosphorus pollution in river basins and lakes in the prior art is difficult to accurately quantify, this application provides a quantitative calculation method for endogenous phosphorus pollution in river basins and lakes by calculating the phosphate oxygen isotope value δ 18 O (PO4)The relative contribution rates of endogenous phosphorus output and exogenous phosphorus input calculated by the Bayesian model and the mixed endmember model were combined with different types of land area data to determine the actual relative contribution rates of endogenous phosphorus output and exogenous phosphorus input to the phosphorus load in the basin's lakes.

[0007] 2. Technical solution

[0008] The purpose of this application is achieved through the following technical solutions.

[0009] The present application provides a quantitative calculation method for endogenous phosphorus pollution in a river basin lake, including: determining a river basin boundary as a boundary for selecting potential phosphorus sources and a clipping boundary for a land use type map; collecting solid samples and liquid samples within the river basin boundary respectively; wherein the solid samples include soil, sediments and rocks; the liquid samples include piped sewage and lake water; obtaining the phosphate oxygen isotope value of each sample; wherein the samples are divided into exogenous pollution sources and endogenous pollution sources; the exogenous pollution sources include: planting, livestock and poultry breeding, piped sewage and rock weathering; the endogenous pollution sources include: lake sediments; the phosphate oxygen isotope values ​​include P0, P1, P2, P3, P4 and P5; wherein P1, P2, P3, P4 and P5 correspond to the planting industry, respectively. , livestock and poultry farming, piped sewage, rock weathering and lake sediment; P0 corresponds to the phosphate oxygen isotope value of lake water samples; the obtained phosphate oxygen isotope values ​​P0, P1, P2, P3, P4 and P5 are used as input, and the pre-trained Bayesian model and mixed endmember model are used to calculate the relative contribution rate of exogenous pollution sources and endogenous pollution sources to phosphorus pollution in the basin; the basin boundary data and land use type data in vector format are imported into the geographic information system, and the land use type distribution map within the basin boundary is obtained by cropping; according to the calculated relative contribution rate of endogenous pollution and exogenous pollution to phosphorus pollution, and the obtained area of ​​each land use type, the actual contribution rate of endogenous pollution and exogenous pollution to phosphorus pollution is calculated.

[0010] Furthermore, the relative contribution of endogenous pollution and exogenous pollution to phosphorus pollution in the basin is calculated by the Bayesian model. The calculation formula is as follows:

[0011]

[0012] f n1 +f n2 +f n3 +f n4 +f n5 =1

[0013] in, is the phosphate oxygen isotope value P0 of the lake water sample; The phosphate oxygen isotope values ​​P1, P2, P3, P4 and P5 represent the planting industry, livestock and poultry breeding industry, pipeline sewage, rock weathering and endogenous pollution respectively; the Bayesian model is used to estimate f n1 、f n2 、f n3 、f n4 、f n5 The value is used as the relative contribution rate of crop farming, livestock and poultry farming, piped sewage, rock weathering and endogenous pollution.

[0014] Furthermore, the relative contribution of endogenous pollution and exogenous pollution to phosphorus pollution in the basin was calculated by the mixed endmember model. The calculation formula is as follows: Construct a mixed endmember model and set the isotope value j of endmember i to X ij , the isotope value j of source value k is S jk ; The fractionation coefficient of isotope j for source k is C jk , the residual is ε ij ; Set S jk Subject to the mean μ jk The normal distribution of C jk Obey λ jk is the mean and is the normal distribution of variance; according to the following formula, the relative contribution rate P of the pollution source k corresponding to each end member is estimated k :

[0015]

[0016] S jk ~N(μ jk ,ω 2 jk )

[0017] C jk ~N(λ jk ,τ 2 jk )

[0018] ε jk ~N(0,σ 2 j )

[0019] The estimated P k As the relative contribution rate of each pollution source to phosphorus pollution in the basin.

[0020] Furthermore, the basin boundary data and land use type data in vector format are imported into the geographic information system, and a land use type distribution map within the basin boundary is obtained by clipping, including: importing the vector data of the basin boundary and the land use type into the geographic information system; using the clipping function of the geographic information system, taking the basin boundary as the clipping boundary, clipping the land use type data to obtain a land use type distribution map within the basin boundary; obtaining from the land use type distribution map: cultivated land area S1, grassland area S2, urban land area S3, bare rock area S4 and lake water area S5; the cultivated land area S1 corresponds to the pollution source of the crop industry, the grassland area S2 corresponds to the pollution source of the livestock and poultry breeding industry, the urban land area S3 corresponds to the pollution source of the piped sewage, the bare rock area S4 corresponds to the pollution source of the rock weathering, and the lake water area S5 corresponds to the endogenous pollution.

[0021] Furthermore, according to the calculated relative contribution rates of endogenous pollution and exogenous pollution to phosphorus pollution, and the obtained areas of various land use types, the actual contribution rates of endogenous pollution and exogenous pollution to phosphorus pollution are calculated, including: according to the following formula, the actual contribution rates F1, F2, F3, F4, and F5 of crop farming, livestock and poultry breeding, piped sewage, rock weathering, and endogenous pollution to phosphorus pollution are calculated respectively: Among them, f ni is the actual relative contribution rate of the ith potential pollution source;

[0022] S mi is the land use type area corresponding to the ith potential pollution source, S T It is the sum of the areas of all land use types; F5 is taken as the actual contribution rate of endogenous pollution to phosphorus pollution in the basin lakes, and the sum of F1 to F4 is taken as the actual contribution rate of exogenous pollution to phosphorus pollution.

[0023] Further, obtaining the phosphate oxygen isotope value of the solid sample includes: adding nitric acid to a soil, sediment or rock sample that has been sieved through 100 meshes and freeze-dried to obtain an extract; adding a macroporous anion exchange resin to the extract and performing precipitation to obtain a purified phosphate solution; adding a magnesium nitrate solution to the purified phosphate solution to generate a silver phosphate precipitate; cracking the silver phosphate precipitate into carbon monoxide and silver at a preset temperature, and using a thermocouple-element analyzer and an isotope ratio mass spectrometer to determine the oxygen isotope composition of the carbon monoxide gas to obtain the phosphate oxygen isotope value of the soil, sediment and rock samples;

[0024] Furthermore, the phosphate oxygen isotope value of the liquid sample is obtained, including: filtering the pipe sewage or lake water sample through a cellulose acetate filter membrane to remove particulate matter in the water; adding sodium hydroxide solution to the filtered water sample, and then adding magnesium nitrate solution to form a phosphate-magnesium hydroxide co-precipitation; subjecting the phosphate-magnesium hydroxide co-precipitation to dissolution, precipitation and cation removal in sequence to obtain a purified phosphate solution; adding silver nitrate solution to the purified phosphate solution to generate a silver phosphate precipitate; cracking the silver phosphate precipitate into carbon monoxide and silver at a preset temperature, and using a thermocouple-element analyzer and an isotope ratio mass spectrometer to measure the oxygen isotope composition of the carbon monoxide gas to obtain the phosphate oxygen isotope value of the liquid sample.

[0025] Furthermore, the precipitation includes AMP (magnesium ammonium phosphate, NH4MgPO4) precipitation and MAP (magnesium ammonium phosphate, MgNH4PO4) precipitation. These two precipitants can selectively precipitate and separate phosphate ions from complex matrices during sample processing, thereby achieving purification and enrichment.

[0026] Furthermore, when pre-treating liquid samples (sewage, lake water), it is necessary to first use an acetate filter membrane to remove particulate matter in the water. The pore size of the filter membrane is between 0.2μm and 0.45μm. On the one hand, the filter membrane in this range can effectively remove suspended particles in the water sample and reduce the interference of solid impurities; on the other hand, the pore size of the filter membrane is not too small to avoid problems such as slow filtration speed or filter membrane clogging, taking into account the completeness of filtration and the convenience of operation.

[0027] Furthermore, in the pretreatment of solid samples (soil, sediment, rock), phosphates need to be extracted with nitric acid. The preferred range of nitric acid concentration is 1 mol / L to 1.5 mol / L. Nitric acid in this concentration range can effectively dissolve and extract inorganic phosphorus compounds in the sample to ensure the completeness of the extraction; on the other hand, the acidity is not too high to avoid corrosion of the instrument or introduction of too many impurities.

[0028] 3. Beneficial effects

[0029] Compared with the prior art, the advantages of this application are:

[0030] By obtaining the phosphate oxygen isotope values ​​δ of different pollution sources in the basin (planting, livestock and poultry farming, pipe sewage, rock weathering, lake sediments) and lake water bodies 18 O (PO4) , and substituting it into the Bayesian model and the mixed endmember model for calculation, the relative contribution rate of endogenous phosphorus output and exogenous phosphorus input to phosphorus pollution in the basin can be accurately estimated, solving the problem that traditional methods are difficult to quantitatively distinguish the contribution of endogenous and exogenous phosphorus.

[0031] GIS technology is used to clip the basin boundary and land use type data to obtain the area data of different land use types (arable land, grassland, urban land, bare rock land, and lake surface) in the basin. By combining it with the relative contribution rate of endogenous and exogenous phosphorus, the actual contribution rate of endogenous phosphorus output and exogenous phosphorus input to the phosphorus load in the basin lake water bodies can be further calculated, achieving accurate quantification of endogenous phosphorus pollution.

[0032] Advanced instruments such as thermocouple-element analyzers and isotope ratio mass spectrometers are used to extract, purify and analyze phosphates in solid samples such as soil, sediment, and rock, as well as liquid samples such as piped sewage and lake water. 18 O (PO4) Determination ensures the accuracy and reliability of sample analysis data.

[0033] δ 18 O (PO4) As a tracer indicator, mathematical models such as the Bayesian model and the mixed endmember model are used to analyze pollution sources, combining the advantages of tracers and models, making up for the shortcomings of a single tracer or a single model that is difficult to clarify complex pollution sources, and improving the accuracy and reliability of quantitative calculations of endogenous and exogenous phosphorus contributions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A technical roadmap for a quantitative calculation method of endogenous phosphorus pollution in a watershed lake in this application;

[0035] Figure 2 This is a schematic diagram of the proportion of internal and external phosphorus sources in this application. DETAILED DESCRIPTION

[0036] The present application is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0037] Example 1

[0038] A quantitative calculation method for endogenous phosphorus pollution in a river basin lake includes the following steps: determining the boundary of the river basin, collecting samples of endogenous phosphorus output, exogenous phosphorus input, and lake water near the river basin; obtaining the phosphate oxygen isotope value δ of each pollution source and the lake traceable water body. 18 O (PO4) ; The phosphate oxygen isotope value δ 18 O (PO4) The relative contribution rates of endogenous phosphorus output and exogenous phosphorus input calculated by the Bayesian model and the mixed endmember model were combined with different types of land area data to determine the actual relative contribution rates of endogenous phosphorus output and exogenous phosphorus input to the phosphorus load in the basin's lakes.

[0039] The above technical method combines the phosphate oxygen isotope value δ 18 O(PO4) , different types of land area data, mixed endmember model and Bayesian model and other data and models, and the contribution rate of different types of land area data corresponding to the types of potential phosphorus sources can be calculated to obtain the actual contribution rate of endogenous phosphorus output and exogenous phosphorus input to the phosphorus load in the basin.

[0040] Specifically, determine the watershed boundary and sampling: First, the watershed boundary needs to be determined according to the research purpose. The determination of the watershed boundary has two main purposes: as a boundary for selecting potential phosphorus sources, that is, to collect samples of possible phosphorus pollution sources within this boundary, such as crop soil, livestock and poultry manure, pipe sewage, rocks and lake sediments, etc.; 2. It is used in the subsequent steps to use GIS to cut the land use type map to calculate the area of ​​different land use types.

[0041] After determining the boundaries of the watershed, samples of the main potential sources of phosphorus pollution need to be collected within the boundaries. These pollution sources include: planting (corresponding to the collection of soil samples), livestock and poultry farming (corresponding to the collection of feces and wastewater samples), piped sewage (corresponding to the collection of domestic wastewater and industrial wastewater samples), rock weathering (corresponding to the collection of rock samples) and endogenous pollution in lakes (corresponding to the collection of sediment samples). The selection of sampling points needs to comprehensively consider the distribution characteristics of the pollution sources and the representativeness of the samples.

[0042] In addition, water samples need to be collected in lakes to obtain the oxygen isotope value of phosphate in lake water. In order to ensure the reliability of lake water traceability, the water sample collection point must be selected downstream of the exogenous phosphorus input flow, so that the collected water samples can represent the lake water condition after the exogenous phosphorus and endogenous phosphorus are mixed.

[0043] Compared with previous basin phosphorus tracing studies, this technical solution is more comprehensive and systematic in sample collection, not only considering exogenous phosphorus input, but also emphasizing the contribution of endogenous phosphorus release. In subsequent tracing analysis, by comprehensively utilizing phosphate oxygen isotope tracing and mathematical models, the relative contributions of endogenous and exogenous phosphorus can be more accurately quantitatively analyzed, and their actual contribution rates to the phosphorus load of lake water bodies can be estimated, thereby significantly improving the accuracy of phosphorus tracing in basin lakes.

[0044] Sample analysis and data acquisition: Phosphate oxygen isotope values ​​for soil, sediment, and rock samples The acquisition steps are as follows: freeze-dry the collected soil, sediment and rock samples to remove moisture, then sieve with a 100-mesh sieve to homogenize the sample particle size for subsequent extraction. Weigh 20g of the pretreated sample into a conical flask, add 120ml of 1mol / L nitric acid (HNO3), and shake for 24h to fully dissolve the phosphate in the sample in the nitric acid solution. Add macroporous resin to the extract to remove organic matter in the solution, and then further purify the phosphate ions in the solution through a series of steps such as AMP (ammonium phosphomolybdate precipitation), MAP (magnesium phosphomolybdate precipitation) and removal of cations. Add magnesium nitrate solution to the purified solution to displace a bright yellow silver phosphate (Ag3PO4) precipitate. Collect the precipitate by centrifugation, wash it, and dry it to obtain a solid silver phosphate sample. Take an appropriate amount of silver phosphate sample, and use a high-temperature pyrolysis-stable isotope mass spectrometer (TC / EA-IRMS) to determine its δ18O value to obtain the soil, sediment and rock samples. data.

[0045] Phosphate oxygen isotope values ​​of water samples The acquisition steps are as follows: Filter the collected water sample with a 0.45μm filter membrane to remove suspended particles in the water. Add 1mol / L sodium hydroxide and 0.5mol / L magnesium nitrate solution to the filtered water sample at a volume ratio of 1% to form a phosphate-magnesium hydroxide coprecipitate. After standing for several hours, centrifuge and collect the precipitate. Purify the coprecipitate sample and precipitate silver phosphate with reference to the soil sediment sample. Take an appropriate amount of silver phosphate sample and determine its δ 18 O value, obtain the water sample data.

[0046] Specifically, combined with the phosphate oxygen isotope value Using the mixed endmember model and the Bayesian model, we can calculate the relative contribution rate f of different potential phosphorus pollution sources. ni The formula used is as follows:

[0047]

[0048] f n1 +f n2 +f n3 +f n4 +f n5 =1

[0049]

[0050] S jk ~N(μ jk ,ω 2 jk )

[0051] C jk ~N(λjk ,τ 2 jk )

[0052] ε jk ~N(0,σ 2 j )

[0053] Among them, δ 18 O (PO4-river) is the lake water body δ 18 O (PO4) Value; δ 18 O (PO4-n1) , δ 18 O (PO4-n1) , δ 18 O (PO4-n1) , δ 18 O (PO4-n1) , δ 18 O (PO4-n1) The δ represents the potential pollution sources such as planting, livestock and poultry breeding, pipe sewage, rock weathering and endogenous pollution. 18 O (PO4) value; where f n1 、f n2 、f n3 、f n4 、f n5 Respectively represent the relative contribution rates of potential pollution sources such as planting, livestock and poultry breeding, pipe sewage, rock weathering and endogenous pollution; X ij is the isotope value j of end member i; P k Estimated by the model; S jk represents the isotope value j of source value k, which obeys the mean μ jk Normal distribution; C jk represents the fractionation coefficient of isotope j to source k, expressed as λ jk and Normal distribution with mean; ε ij is the residual, describing the additional inter-observation variance not described by the model. Since only phosphate oxygen isotopes are used, the value of j in the formula is 1.

[0054] Specifically, land use type area calculation: collect land use type vector data and basin boundary vector data in the study basin area to ensure that the coordinate systems of the two types of data are consistent. Import the basin boundary data and land use type data into ArcGIS software and display them as two layers respectively. Use ArcGIS's "Clip" tool to clip the land use type layer with the basin boundary layer as the clipping range. The land use type layer obtained after clipping is the current land use distribution map within the study basin. Open the attribute table of the clipped land use type layer, add a new field "Area", and use ArcGIS's "Calculate Geometry" function to calculate the area of ​​each land use type polygon in square kilometers (km2). Export the attribute table as an Excel file to summarize the area data of different land use types.

[0055] When calculating the area of ​​land use types, different land use types correspond to different phosphorus pollution sources. Among them, the cultivated land area represents the pollution source of the planting industry, the grassland area represents the pollution source of the livestock and poultry breeding industry, the urban construction land area represents the pipeline sewage pollution source (including domestic sewage and industrial wastewater), the unused land (such as bare rock land) area represents the rock weathering pollution source, and the lake water area represents endogenous pollution. Because forest land has good soil and water conservation functions and has a significant effect on phosphorus interception, it is usually not considered as a phosphorus pollution source. Therefore, when the area is counted, the forest area can be excluded from the pollution source area. To facilitate the subsequent pollution source analysis, the area data of different land use types can be classified in the Excel summary table, such as classifying cultivated land, grassland, urban construction land, unused land, lake water bodies, etc. into categories such as planting industry, livestock and poultry breeding industry, pipeline sewage, rock weathering and endogenous pollution. Through the above GIS analysis and data collation steps, the area data of different land use types in the study basin can be accurately obtained and linked with the corresponding pollution source types, providing important area parameters for subsequent pollution source analysis and calculation of lake phosphorus load contribution rate.

[0056] Specifically, the actual contribution rate F of multiple potential pollution sources i The calculation formula is as follows:

[0057]

[0058] Among them, F N1 、F N2 、F N3 、F N4 、F N5represents the actual contribution rate of crop farming, livestock and poultry breeding, pipe sewage, rock weathering and endogenous pollution combined with land use data; F1, F2, F3, F4 and F5 represent the actual relative contribution rate of potential pollution sources such as crop farming, livestock and poultry breeding, pipe sewage, rock weathering and endogenous pollution combined with land use data; S m1 , S m2 , S m3 , S m4 , S m5 They represent the land use areas of cultivated land, grassland, urban construction land, unused land and lake water bodies; S T It is the sum of the areas of all land use types.

[0059] Specifically, F5 represents the actual relative contribution rate of endogenous phosphorus output (i.e., lake sediment release) to the phosphorus load of lakes in the basin, and the sum of F1+F2+F3+F4 represents the actual relative contribution rate of exogenous phosphorus input (including agriculture, livestock and poultry farming, piped sewage and rock weathering) to the phosphorus load of lakes in the basin.

[0060] Compared with previous basin phosphorus tracing studies, this application comprehensively considers endogenous and exogenous phosphorus pollution, and quantitatively calculates their respective actual contribution rates to the lake phosphorus load, making up for the shortcomings of traditional studies that only focus on exogenous phosphorus input or qualitatively describe endogenous phosphorus release. The pollution source analysis is combined with land use analysis. By weighted average method, the relative contribution rate of the pollution source is multiplied by the area data of its corresponding land use type and divided by the total area to obtain the actual contribution rate of each pollution source. This method not only considers the relative importance of different pollution sources, but also considers their spatial distribution characteristics in the basin, making the calculation results more accurate and reliable. The calculation results quantitatively give the actual relative contribution rate of endogenous phosphorus output and exogenous phosphorus input to the phosphorus load of the basin lakes, which can intuitively compare the relative importance of endogenous and exogenous phosphorus pollution, and provide an important basis for the accurate tracing and control of phosphorus pollution in the basin. Relevant departments can formulate targeted measures such as endogenous sediment dredging and exogenous pollution control to improve the accuracy and effectiveness of eutrophication prevention and control of basin lakes.

[0061] Example 2

[0062] Taking the Poyang Lake Basin as an example, the Poyang Lake Basin is the general name for the five river basins of Ganjiang River, Fuhe River, Xinjiang River, Raohe River, and Xiuhe River, as well as the Poyang Lake area, with a basin area of ​​166,835.74 square kilometers. A precise quantitative calculation method for the contribution of endogenous phosphorus pollution to basin lakes, specifically including the following steps: the main potential sources of phosphorus pollution collected include planting, livestock and poultry farming, piped sewage (domestic wastewater and industrial wastewater), rock weathering, and lake sediments, corresponding to the collection of soil, water, rock, and sediment samples. Obtain the phosphate oxygen isotope values ​​(δ 18O (PO4) ), as shown in Table 1; different types of land area data can be obtained from globeland30.org or the Resources and Environment Science and Data Platform (https: / / www.resdc.cn). 18 O (PO4) )The relative contribution rates of endogenous phosphorus output and exogenous phosphorus input calculated by substituting them into the Bayesian model and the mixed endmember model were combined with different types of land area data to determine the actual relative contribution rates of endogenous phosphorus output and exogenous phosphorus input, thereby quantitatively analyzing the effects of endogenous phosphorus output and exogenous phosphorus input on the phosphorus load of lakes in the basin. Figure 2 This is a schematic diagram of the proportion of internal and external phosphorus sources in this application, as shown in Table 2 and Table 3.

[0063] Table 1

[0064]

[0065] Table 2

[0066]

[0067]

[0068] Table 3

[0069]

[0070] In Table 1, the average phosphorus and oxygen isotope value of Poyang Lake is 14.44±1.63‰, and the average phosphorus and oxygen isotope values ​​of crop production, livestock and poultry farming, piped sewage (domestic wastewater and industrial wastewater), rock weathering and lake sediments are 15.58±0.17‰, 18.03±2.21‰, 12.4±0.8‰, 8.2±1.05‰ and 13.7±0.46‰, respectively.

[0071] In Table 2, the Poyang Lake basin area is 166,835.74 km 2 Among them, the cultivated land area is 48416.42km 2 , accounting for 29.02%; the grassland area is 2266.94km 2 , accounting for 1.36; the urban construction land area is 10282.07km 2 , accounting for 6.16%; the forest area is 95239.5km 2 , accounting for 57.09%; the water area is 9392.46km 2 , accounting for 5.63%; the unused land area is 1238.35km 2 , accounting for 0.74%.

[0073] In Table 3, the actual relative contribution rates of exogenous phosphorus inputs including crop farming, livestock and poultry farming, piped sewage (domestic wastewater and industrial wastewater), and rock weathering to the phosphorus load of Poyang Lake were 69.03%, 4.25%, 13.09%, and 1.09%, respectively. The contribution rate of exogenous phosphorus input was 87.46%, and the contribution rate of endogenous phosphorus output was 12.54%.

[0074] The invention of the present application and its implementation methods are described schematically above. The description is not restrictive. Without departing from the spirit or basic features of the present application, the present application can be implemented in other specific forms. What is shown in the accompanying drawings is only one of the implementation methods of the invention of the present application. The actual structure is not limited to this. Any figure mark in the claims should not limit the claims involved. Therefore, if a person of ordinary skill in the art is inspired by it, without departing from the purpose of the present invention, a structural method and an embodiment similar to the technical solution are designed without creativity, which should all fall within the scope of protection of this patent. In addition, the word "including" does not exclude other elements or steps, and the word "one" before the element does not exclude the inclusion of "multiple" elements. The multiple elements stated in the product claim can also be implemented by one element through software or hardware. The words first, second, etc. are used to indicate names, and do not indicate any specific order.

Claims

1. A quantitative calculation method for endogenous phosphorus pollution in a river basin lake, comprising: Determine watershed boundaries to serve as boundaries for potential phosphorus source selection and as clipping boundaries for land use type maps; Collect solid and liquid samples within the watershed boundary separately; Solid samples include soil, sediment and rock; liquid samples include piped sewage and lake water; Obtain the phosphate oxygen isotope value of each sample; wherein, the samples are divided into exogenous pollution sources and endogenous pollution sources; exogenous pollution sources include: crop pollution sources, livestock and poultry breeding pollution sources, pipe sewage pollution sources and rock weathering pollution sources; endogenous pollution sources include: lake sediment pollution sources; phosphate oxygen isotope values ​​include P0, P1, P2, P3, P4 and P5; wherein, P1, P2, P3, P4 and P5 correspond to crop, livestock and poultry breeding, pipe sewage, rock weathering and lake sediment respectively; P0 corresponds to the phosphate oxygen isotope value of lake water samples; The obtained phosphate oxygen isotope values ​​P0, P1, P2, P3, P4 and P5 were used as inputs to calculate the relative contribution of exogenous and endogenous pollution sources to phosphorus pollution in the watershed using the pre-trained Bayesian model and mixed endmember model, respectively; Import the watershed boundary data and land use type data in vector format into the geographic information system, and obtain the land use type distribution map within the watershed boundary by clipping; Based on the calculated relative contribution rates of endogenous and exogenous pollution to phosphorus pollution and the obtained areas of various land use types, the actual contribution rates of endogenous and exogenous pollution to phosphorus pollution are calculated.

2. The method for quantitatively calculating endogenous phosphorus pollution in a river basin lake according to claim 1, characterized in that: The relative contribution of endogenous pollution and exogenous pollution to phosphorus pollution in the basin is calculated by the Bayesian model. The calculation formula is as follows: f n1 +f n2 +f n3 +f n4 +f n5 =1 in, is the phosphate oxygen isotope value P0 of the lake water sample; Phosphate oxygen isotope values ​​P1, P2, P3, P4 and P5 represent the crop industry, livestock and poultry breeding industry, pipe sewage, rock weathering and endogenous pollution respectively; Use the Bayesian model to estimate f n1 、f n2 、f n3 、f n4 、f n5 The value is used as the relative contribution rate of crop farming, livestock and poultry farming, piped sewage, rock weathering and endogenous pollution.

3. The quantitative calculation method for endogenous phosphorus pollution in a river basin lake according to claim 2 is characterized in that: The relative contribution of endogenous pollution and exogenous pollution to phosphorus pollution in the basin was calculated using the mixed endmember model. The calculation formula is as follows: Construct a mixed end member model and set the isotope value j of end member i to X ij , the isotope value j of source value k is S jk ; The fractionation coefficient of isotope j for source k is C jk , the residual is ε ij ; Setting S jk Subject to the mean μ jk The normal distribution, C jk Obey λ jk is the mean and is a normal distribution with variance; According to the following formula, the relative contribution rate P of the pollution source k corresponding to each end member is estimated k : S jk ~N(μ jk ,oh 2 jk ) C jk ~N(λ jk ,t 2 jk ) e jk ~N(0,σ 2 j ) The estimated P k As the relative contribution rate of each pollution source to phosphorus pollution in the basin.

4. The quantitative calculation method for endogenous phosphorus pollution in a river basin lake according to claim 3 is characterized in that: Import the basin boundary data and land use type data in vector format into the geographic information system, and obtain the land use type distribution map within the basin boundary by clipping, including: Importing vector data of watershed boundaries and land use types into GIS; Using the clipping function of the geographic information system, the land use type data is clipped with the watershed boundary as the clipping boundary to obtain the land use type distribution map within the watershed boundary; From the land use type distribution map, we can obtain: cultivated land area S1, grassland area S2, urban land area S3, bare rock land area S4 and lake water area S5; The cultivated land area S1 corresponds to the pollution source of the planting industry, the grassland area S2 corresponds to the pollution source of the livestock and poultry breeding industry, the urban land area S3 corresponds to the pollution source of piped sewage, the bare rock area S4 corresponds to the pollution source of rock weathering, and the lake water area S5 corresponds to endogenous pollution.

5. The method for quantitatively calculating endogenous phosphorus pollution in a river basin lake according to claim 4, characterized in that: Based on the calculated relative contribution rates of endogenous pollution and exogenous pollution to phosphorus pollution, and the obtained area of ​​each land use type, the actual contribution rates of endogenous pollution and exogenous pollution to phosphorus pollution are calculated, including: According to the following formula, the actual contribution rates of crop farming, livestock and poultry farming, piped sewage, rock weathering and endogenous pollution to phosphorus pollution are calculated respectively: Among them, f ni is the actual relative contribution rate of the ith potential pollution source; S mi is the land use type area corresponding to the ith potential pollution source, S T It is the sum of the areas of all land use types; F5 is taken as the actual contribution rate of endogenous pollution to phosphorus pollution in the basin lakes, and the sum of F1 to F4 is taken as the actual contribution rate of exogenous pollution to phosphorus pollution.

6. The method for quantitatively calculating endogenous phosphorus pollution in a river basin lake according to claim 5, characterized in that: Obtain phosphate oxygen isotope values ​​for solid samples, including: Add nitric acid to the sieved and freeze-dried soil, sediment or rock sample to obtain an extract; performing precipitation treatment on the extract to obtain a purified phosphate solution; adding magnesium nitrate solution to the purified phosphate solution to generate silver phosphate precipitate; The silver phosphate precipitate is cracked into carbon monoxide and silver at a preset temperature, and the phosphate oxygen isotope values ​​of soil, sediment and rock samples are obtained by measuring the oxygen isotope composition of carbon monoxide gas using a thermocouple-element analyzer and an isotope ratio mass spectrometer.

7. The method for quantitatively calculating endogenous phosphorus pollution in a river basin lake according to claim 6, characterized in that: Obtain phosphate oxygen isotope values ​​for liquid samples, including: Filter pipe sewage or lake water samples through cellulose acetate filter membranes to remove particulate matter in the water; After adding sodium hydroxide solution to the filtered water sample, magnesium nitrate solution is added to form phosphate-magnesium hydroxide coprecipitation; Purifying the phosphate-magnesium hydroxide coprecipitate to obtain a purified phosphate solution; adding a silver nitrate solution to the purified phosphate solution to generate a silver phosphate precipitate; The silver phosphate precipitate is cracked into carbon monoxide and silver at a preset temperature, and the phosphate oxygen isotope value of the liquid sample is obtained by measuring the oxygen isotope composition of the carbon monoxide gas using a thermocouple-element analyzer and an isotope ratio mass spectrometer.

8. The method for quantitatively calculating endogenous phosphorus pollution in a river basin lake according to claim 6 or 7, characterized in that: The precipitation includes AMP precipitation and MAP precipitation.

9. The method for quantitatively calculating endogenous phosphorus pollution in a river basin lake according to claim 8, characterized in that: Acetate fibers with a diameter of 0.2 μm to 0.45 μm are used.

10. The quantitative calculation method for endogenous phosphorus pollution in a river basin lake according to claim 9, characterized in that: The concentration of nitric acid ranges from 1 mol / L to 1.5 mol / L.

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