Tracing method for fish death caused by sudden water pollution

Abstract

The invention relates to the technical field of water environment protection, in particular to a tracing method for fish death caused by sudden water pollution. The traceability method systematically considers several possible sources of water pollution, utilizes advanced monitoring technology, covers screening of inorganic pollutants, organic pollutants and unknown organic pollutants and macro transcriptome sequencing, and performs accurate traceability from a water body to a fish body.

Description

Technical Field

[0001] The invention relates to the technical field of water environment protection, and in particular to a method for tracing the source of fish deaths caused by sudden water pollution. Background Art

[0002] According to the Diagnostic Method for Acute Poisoning and Death of Freshwater Fish, the main causes of fish death are fish disease, hypoxia, toxic algae poisoning, chemical poisoning, etc. When the 18 indicators of the Diagnostic Method for Acute Poisoning and Death of Freshwater Fish are used to determine that the fish have died due to poisoning by chemical pollutants, the chemical pollutants must be identified and their sources traced.

[0003] The existing survey methods (such as the "Survey Methods for Polluted Dead Fish (Freshwater)") focus on the behavior, morphological response and environmental characteristics of fish, and do not systematically consider the investigation of pollution sources from point sources, non-point sources, internal sources, mobile sources and external sources. The monitoring of pollutants is limited to conventional pollutants (COD, BOD, cyanide, detergents, etc.), organophosphorus pesticides, organochlorine pesticides and several heavy metals. In the past 20 years, new chemical substances have emerged in an endless stream. At the same time, monitoring technology has also been continuously improved. It is necessary to use new ideas and methods for monitoring to develop more scientific and accurate methods for tracing the source of sudden water pollution leading to fish deaths in response to the current new situation. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for tracing the source of sudden water pollution leading to fish deaths. The present invention systematically considers several possible sources of water pollution and uses advanced monitoring technology, including inorganic pollutants, organic pollutants, unknown organic pollutant screening and macrotranscriptome sequencing, from water bodies to fish bodies, so as to accurately trace the source.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for tracing the source of fish deaths caused by sudden water pollution, comprising the following steps:

[0007] 1) Collecting hydrological and rainfall information of the dead fish water body to be tested, investigating point sources, surface sources, internal sources, mobile sources and external sources around the dead fish water body and within 30 km upstream, and combining the hydrological and rainfall information and the investigation results to obtain a primary suspicious target library consisting of X and Y; X is a chemical pollutant that may be discharged into the dead fish water body, and Y is a possible source of the chemical pollutant; the cause of death of the dead fish to be tested is chemical pollution;

[0008] The point sources include: sewage treatment plants, sewage treatment plant collection enterprises and solid waste dumping; the non-point sources include: land use types and application of pesticides and fertilizers within 3km of the river; the internal sources include: dead fish water bodies and the dredging and bottom dredging of rivers 30km upstream in the past week; the mobile sources include: chemical transportation; the external sources include: human poisoning;

[0009] 2) Collect three types of water samples, namely, water samples from the dead fish water body, water samples from the sewage outlet and water samples from the control point, and detect the content of chemical pollutants in the three water samples; the sampling point of the control point water sample is a water body more than 30 km upstream of the dead fish water body; the sewage outlet water sample is the outlet of the possible source discharged into the water body in step 1); the chemical pollutants are chemical pollutants in the primary suspicious target library;

[0010] According to the detection results, the chemical pollutants in the primary suspicious target library are screened to obtain a secondary suspicious target library; the possible sources of the chemical pollutants in the secondary suspicious target library are the same as step 1);

[0011] The screening criteria are: if the content of chemical pollutants in the dead fish water sample is significantly different from that in the control point water sample, and the content of chemical pollutants in the sewage outlet water sample is greater than 4 times the content of chemical pollutants in the dead fish water sample, then the chemical pollutant is a chemical pollutant in the secondary suspicious target library;

[0012] 3) screening the three water samples in step 2) using liquid-liquid extraction gas chromatography-mass spectrometry and solid phase extraction liquid chromatography-high resolution mass spectrometry, wherein the screening is for chemical substances outside the secondary suspicious target library;

[0013] If no chemical substances other than the second-level suspected target pool are screened out in the water samples of the control points, and chemical substances other than the second-level suspected target pool are screened out in the water samples of the sewage outlet and the dead fish water, then the chemical substances are suspected chemical pollutants;

[0014] 4) Detecting and screening the suspected chemical pollutants determined in step 3) to obtain primary chemical pollutants; the detection and screening methods are the same as those in step 2);

[0015] Re-investigate using the method of step 1) to obtain possible sources of the primary chemical pollutants;

[0016] Adding the primary chemical pollutants and their possible sources to the secondary suspicious target library to obtain a tertiary suspicious target library;

[0017] 5) Re-inspecting the dead fish water and dead fish bodies, and determining the content of suspicious targets in the dead fish water and dead fish bodies; the suspicious targets are chemical pollutants in the third-level suspicious target library;

[0018] If suspicious objects are detected in both the dead fish water and the dead fish, the suspicious objects and their possible sources will form a four-level suspicious object library;

[0019] 6) The suspicious targets in the four-level suspicious target library are configured into different concentrations, and a toxicity reproduction experiment is performed on live fish. If the behavioral response and fish body odor of the experimental fish are consistent with those of the dead fish to be tested, the suspicious target and its possible source are pollutants and possible pollution sources of the dead fish.

[0020] Preferably, the hydrological rainfall information includes:

[0021] 1) Type of water body: river, lake, pond, reservoir;

[0022] 2) Flow: water flow three days before the fish die-off;

[0023] 3) Upstream tributaries: tributaries and tributary flows 30 km upstream of the dead fish body;

[0024] 4) Rainfall: rainfall in the three days before the fish die-off;

[0025] 5) Upstream dams and dispatching conditions: whether there are dams upstream of the dead fish body, and the dispatching conditions three days before the dead fish incident;

[0026] 6) Other sudden environmental events: river bursting and bridge collapse.

[0027] Preferably, the survey contents of the point source include:

[0028] 1) Sewage treatment plant: the way of discharge into the dead fish water body and its upstream 30km main and tributary sewage treatment plants, the discharge volume, discharge rules, process flow, and whether there were abnormal discharges three days before the fish death incident; if there were abnormal discharges, the chemical pollutants discharged by the sewage treatment plant were X, and the chemical pollutants discharged by the sewage treatment plant were Y;

[0029] 2) Wastewater treatment plant receiving enterprises: the production products, raw and auxiliary materials, pollution-producing process links, sewage discharge, operation of sewage treatment facilities, and rainwater and sewage diversion of the sewage treatment plant receiving enterprises; the chemical pollutants involved in the receiving enterprises can be obtained through the analysis of the production products and raw and auxiliary materials of the receiving enterprises; if the receiving enterprise has a separate rainwater inlet, there was rainfall 3 days before the fish death incident, but the rainwater inlet was not monitored, then the chemical pollutants involved in the receiving enterprise are X, and the receiving enterprise is Y;

[0030] 3) Enterprises that directly discharge sewage into the dead fish water body: The production products, raw materials, pollution-producing process links, sewage discharge volume, operation of sewage treatment facilities, and rainwater and sewage diversion of enterprises that directly discharge sewage into the dead fish water body and its upstream 30km main and tributary rivers; by analyzing the enterprise's production products and raw materials, the chemical pollutants involved in the enterprise can be obtained; if the enterprise has a separate rainwater inlet, there was rainfall 3 days before the dead fish incident, but the rainwater inlet was not monitored, then the chemical pollutant involved in the enterprise is X, and this enterprise is Y;

[0031] 4) Solid waste: The storage of solid waste in the water body where the fish died and within 30 km upstream and 3 km from the river, including the composition of the solid waste and the rain protection conditions; determine the chemical pollutants that may be discharged into the water body based on the composition of the solid waste; if there is rainfall 3 days before the fish death incident, and there is no rain protection cover on the solid waste storage body, then the chemical pollutant of the solid waste is X and the solid waste is Y.

[0032] Preferably, the content of the surface source survey includes:

[0033] 1) Land use type: land use type of the dead fish water body and its upstream 30km and 3km from the river;

[0034] 2) Application of pesticides and fertilizers: types of pesticides and fertilizers used and the amount used in the last month;

[0035] If there is no rainfall three days before the fish die-off, the possibility of non-point source can be ruled out; if there is rainfall three days before the fish die-off, the fertilizer and pesticide applied by non-point source is X, and non-point source is the possible source of X.

[0036] Preferably, the endogenous investigation content includes:

[0037] Investigation of the dredging and sediment removal of the river channel in the dead fish water body and 30 km upstream in the past week;

[0038] If there was no scheduling of the upstream dam three days before the fish death incident, or no river dredging or sediment removal in the previous week, the possibility of internal source is ruled out; otherwise, the river sediment is tested to determine the type of toxic substance. The toxic substance in the river sediment is X, and the upstream dam or river is Y.

[0039] Preferably, the mobile source investigation includes: the transportation of mobile source chemicals in the dead fish water body and whether chemical leakage occurred 3 days before the dead fish incident; if no chemical leakage occurred 3 days before the dead fish incident, the possibility of mobile source is ruled out; otherwise, the leaked chemical is X and the mobile source chemical in the dead fish water body is Y.

[0040] Preferably, the exogenous investigation content includes:

[0041] 1) The release of snail killers and mosquito killers: whether they were released three days before the fish mortality incident;

[0042] 2) Human poisoning: whether there was human poisoning three days before the fish death incident;

[0043] If there was no release of snail killers, mosquito killers, or human poisoning three days before the fish death incident, the possibility of external release can be ruled out; otherwise, the poisoning substance is X and the person who did the poisoning is Y.

[0044] Preferably, the traceability method also includes: configuring the suspicious targets in the four-level suspicious target library into different concentrations, conducting experiments with live fish, and taking water after 2 to 3 days of toxicity testing to perform macrotranscriptome sequencing; based on the sequencing results, comparing the gene expression levels in the dead fish water, toxicity test water, and control water, if there is no significant difference in the gene expression levels between the dead fish water and the toxicity test water, and there is a significant difference in the gene expression levels between the dead fish water and the control water, then the suspicious target and its possible source are further determined as pollutants and possible pollution sources of dead fish.

[0045] Preferably, the detection in step 2) comprises:

[0046] Atomic absorption spectrometry, inductively coupled plasma emission spectrometry or inductively coupled plasma emission mass spectrometry is used for metals; atomic fluorescence spectrometry is used for arsenic, mercury and selenium; ion chromatography is used for inorganic anions; purge and trap / gas chromatography-cold atomic fluorescence spectrometry is used for organic mercury; purge and trap / gas chromatography-mass spectrometry is used for volatile organic pollutants; liquid-liquid extraction gas chromatography-mass spectrometry or gas chromatography is used for semi-volatile organic compounds; liquid-liquid extraction or solid phase extraction liquid chromatography-mass spectrometry or liquid chromatography is used for difficult-to-volatile organic compounds.

[0047] Preferably, the determination of the suspicious target in step 5) comprises:

[0048] If the suspected target object will be transformed in the dead fish and the transformation product is clear, the content of the transformation product shall be determined; if the suspected target object remains in the dead fish or the transformation product is unclear, the content of the suspected target object shall be determined.

[0049] Beneficial effects:

[0050] 1. Establish a suspicious target database through systematic investigation of point sources, surface sources, internal sources, mobile sources, and external sources.

[0051] 2. The monitoring of suspicious targets is expanded to metals, inorganic anions, volatile organic pollutants, semi-volatile organic compounds, and non-volatile organic compounds, which can cover most pollutants.

[0052] 3. Innovative use of non-targeted screening technology for unknown substances to provide additional monitoring for unknown pollutants.

[0053] 4. Innovative use of macrotranscriptome sequencing methods provides strong evidence.

[0054] 5. Close the chain of evidence through analysis of residual toxins in water and fish. DETAILED DESCRIPTION

[0055] The present invention provides a method for tracing the source of fish deaths caused by sudden water pollution, comprising the following steps:

[0056] 1) Collecting hydrological and rainfall information of the dead fish water body to be tested, investigating point sources, surface sources, internal sources, mobile sources and external sources around the dead fish water body and within 30 km upstream, and combining the hydrological and rainfall information and the investigation results to obtain a primary suspicious target library consisting of X and Y; X is a chemical pollutant that may be discharged into the dead fish water body, and Y is a possible source of the chemical pollutant; the cause of death of the dead fish to be tested is chemical pollution;

[0057] The point sources include: sewage treatment plants, sewage treatment plant collection enterprises and solid waste dumping; the non-point sources include: land use types and application of pesticides and fertilizers within 3km of the river; the internal sources include: dead fish water bodies and the dredging and bottom dredging of rivers 30km upstream in the past week; the mobile sources include: chemical transportation; the external sources include: human poisoning;

[0058] 2) Collect three kinds of water samples, namely, water samples from the dead fish water body, water samples from the sewage outlet and water samples from the control point, and detect the content of chemical pollutants in the three water samples; the sampling point of the control point water sample is a water body more than 30 km upstream of the dead fish water body; the water sample from the sewage outlet is the outlet of the possible source discharged into the water body in step 1); the chemical pollutants are the chemical pollutants in the primary suspicious target library; the water samples are collected as early as possible when the dead fish incident occurs;

[0059] According to the detection results, the chemical pollutants in the primary suspicious target library are screened to obtain a secondary suspicious target library; the possible sources of the chemical pollutants in the secondary suspicious target library are the same as step 1);

[0060] The screening criteria are: if the content of chemical pollutants in the dead fish water sample is significantly different from that in the control point water sample, and the content of chemical pollutants in the sewage outlet water sample is greater than 4 times the content of chemical pollutants in the dead fish water sample, then the chemical pollutant is a chemical pollutant in the secondary suspicious target library; preferably, the median lethal dose of the chemical pollutants is sorted from small to large, and the chemical pollutants ranked first are preferably detected; the method for obtaining the median lethal dose of the chemical pollutants preferably includes: querying a database or experimental detection; the database preferably includes a chemical substance toxicity database;

[0061] 3) Screening the three water samples in step 2) by liquid-liquid extraction gas chromatography-mass spectrometry and solid phase extraction liquid chromatography-high resolution mass spectrometry, wherein the screening is for chemical substances outside the secondary suspicious target library; the screening preferably includes: comparing the mass-to-charge ratio of a commercial database or characteristic substances to self-analysis, and screening chemical substances outside the secondary suspicious target library according to the comparison and analysis results; for chemical substances outside the secondary suspicious target library, if certified standard substances are available, quantitative analysis is performed using the standard substances; if certified standard substances are not available, semi-quantification is performed using other certified standard substances with similar properties;

[0062] If no chemical substances other than the second-level suspected target pool are screened out in the water samples of the control points, and chemical substances other than the second-level suspected target pool are screened out in the water samples of the sewage outlet and the dead fish water, then the chemical substances are suspected chemical pollutants;

[0063] 4) Detecting and screening the suspected chemical pollutants determined in step 3) to obtain primary chemical pollutants; the detection and screening methods are the same as those in step 2);

[0064] Re-investigate using the method of step 1) to obtain possible sources of the primary chemical pollutants;

[0065] Adding the primary chemical pollutants and their possible sources to the secondary suspicious target library to obtain a tertiary suspicious target library;

[0066] 5) Re-inspecting the dead fish water and dead fish bodies, and determining the content of suspicious targets in the dead fish water and dead fish bodies; the suspicious targets are chemical pollutants in the third-level suspicious target library;

[0067] If suspicious objects are detected in both the dead fish water and the dead fish, the suspicious objects and their possible sources will form a four-level suspicious object library;

[0068] 6) The suspicious targets in the four-level suspicious target library are configured into different concentrations, and a toxicity reproduction experiment is performed on live fish. If the behavioral response and fish body odor of the experimental fish are consistent with those of the dead fish to be tested, the suspicious target and its possible source are pollutants and possible pollution sources of the dead fish.

[0069] The present invention preferably uses the tracing method of the present invention to determine and trace the chemical pollutants after judging that the fish died due to poisoning by chemical pollutants based on the eighteen indicators of the "Diagnostic Method for Acute Poisoning and Death of Freshwater Fish".

[0070] In the present invention, the hydrological rainfall information preferably includes:

[0071] 1) Type of water body: river, lake, pond, reservoir;

[0072] 2) Flow rate: water flow rate three days before the fish die-off. Water type and flow rate are the basis for subsequent analysis of the migration and diffusion of toxic substances.

[0073] 3) Upstream tributaries: tributaries and tributary flows 30 km upstream of the dead fish water body; upstream tributaries and flows are the basis for subsequent judgment of toxic substances entering through tributaries;

[0074] 4) Rainfall: The rainfall in the three days before the fish death incident. The rainfall is a prerequisite for determining whether the toxic substances come from non-point sources or solid waste around the water body, or are discharged through stormwater outlets.

[0075] 5) Upstream dams and dispatching conditions: whether there are dams upstream of the dead fish water body, and the dispatching conditions three days before the dead fish incident. The upstream dams and dispatching conditions are the prerequisites for the subsequent judgment of whether the toxic substances are from endogenous sources;

[0076] 6) Other environmental emergencies: river breaches, bridge collapses; providing information to determine whether toxic substances are caused by environmental emergencies.

[0077] In the present invention, the content of the point source investigation preferably includes:

[0078] 1) Sewage treatment plant: the way of discharge into the dead fish water body and its 30km upstream main and tributary sewage treatment plants (pipeline, culvert, overflow, other), discharge volume, discharge pattern, process flow, and whether there was abnormal discharge three days before the outbreak of the dead fish incident (abnormal discharge means that the discharge volume is greater than the designed discharge volume or the equipment fails to discharge, etc., and whether there is abnormality is determined by checking the use of online monitoring equipment for effluent and influent and the use of accident emergency pools); if the sewage treatment plant has abnormal discharge, the chemical pollutants discharged by the sewage treatment plant are chemical pollutants that may be discharged into the dead fish water body (X), and the sewage treatment plant is the possible source of the chemical pollutants (Y);

[0079] 2) Sewage treatment plant receiving enterprises: the production products, raw and auxiliary materials, pollution-generating process links, sewage discharge volume, operation of sewage treatment facilities, and rainwater and sewage diversion of the sewage treatment plant receiving enterprises; the types and usage of toxic substances involved in the enterprise can be obtained through analysis of the production products and raw and auxiliary materials of the receiving enterprises; the amount of toxic substances discharged into the sewage treatment plant can be inferred through analysis of the pollution-generating process links, sewage discharge volume and operation of sewage treatment facilities; the possibility of the enterprise discharging sewage through the stormwater outlet can be judged through the stormwater diversion situation; if the receiving enterprise has a separate stormwater outlet, there was rainfall 3 days before the fish dead incident, but the stormwater outlet was not equipped with monitoring, then the chemical pollutants involved in the receiving enterprise are chemical pollutants that may be discharged into the water body of the dead fish, and the receiving enterprise is a possible source of the chemical pollutants;

[0080] 3) Enterprises that directly discharge sewage into the dead fish water body: The production products, raw materials, pollution-generating process links, sewage discharge volume, sewage treatment facility operation, and rainwater and sewage diversion of enterprises that directly discharge sewage into the dead fish water body and its upstream 30km main and tributary rivers; by analyzing the production products and raw materials of the enterprise, the types and usage of toxic substances involved in the enterprise can be obtained; by analyzing the pollution-generating process links, sewage discharge volume and sewage treatment facility operation, the amount of toxic substances discharged into the water body can be inferred; the possibility of the enterprise discharging sewage through the stormwater outlet can be judged by the stormwater and sewage diversion situation; if the enterprise has a separate stormwater outlet, there was rainfall 3 days before the outbreak of the dead fish incident, but the stormwater outlet was not equipped with monitoring, then the chemical pollutants involved in the enterprise are chemical pollutants that may be discharged into the dead fish water body, and the enterprise is a possible source of the chemical pollutants;

[0081] 4) Solid waste: The solid waste dumping situation in the water body where fish died and within 30km upstream and 3km from the river, including the composition, dumping quantity and rain protection conditions of the solid waste; solid waste is a potential point source risk source. If there is rainfall 3 days before the fish die incident, the potential point source risk source will become a point source pollution source; the type and quantity of toxic substances involved will be analyzed based on the composition and dumping quantity of the solid waste; the possibility of toxic substances involved entering the water body through rainwater will be judged based on the rain protection conditions of the outer layer of the solid waste dump; if there is rainfall 3 days before the fish die incident and the solid waste dump has no rain protection cover, the chemical pollutants involved in the solid waste are chemical pollutants that may be discharged into the water body where fish died, and the solid waste is a possible source of the chemical pollutants.

[0082] In the present invention, the content of the surface source survey preferably includes:

[0083] 1) Land use type: land use type (cultivated land, forest land, grassland, construction land) within the dead fish water body and 30 km upstream and 3 km from the river;

[0084] 2) Application of pesticides and fertilizers: types of pesticides and fertilizers used and the amount used in the last month;

[0085] If there was no rainfall three days before the fish die-off, the possibility of non-point source can be ruled out; otherwise, the application of fertilizers in the surrounding land should be analyzed to determine the possibility of toxic substances entering the water body through non-point source; if there was rainfall three days before the fish die-off, the fertilizers and pesticides applied from non-point sources are chemical pollutants that may be discharged into the water body where the fish died, and the applied pesticides or fertilizers are possible sources of chemical pollutants.

[0086] In the present invention, the content of the endogenous investigation preferably includes:

[0087] Investigation of the dredging and sediment removal of the river channel in the dead fish water body and 30 km upstream in the past week;

[0088] If there was no scheduling of the upstream dam three days before the fish death incident, or no river dredging or sediment removal in the previous week, the possibility of endogenous source is ruled out; otherwise, the river sediment is tested, and the possibility and type of endogenous source of toxic substances are determined in combination with the sediment monitoring results; the detection method preferably includes the screening described in the above technical solution.

[0089] In the present invention, the content of the mobile source investigation preferably includes: the transportation situation of mobile source chemicals in the dead fish water body and whether chemical leakage occurred in the previous 3 days; if no chemical leakage occurred in the 3 days before the outbreak of the dead fish incident, the possibility of mobile source is ruled out; otherwise, by analyzing the type and quantity of the leaked chemical, the leaked chemical is X and the mobile source chemical in the dead fish water body is Y.

[0090] In the present invention, the content of the exogenous investigation preferably includes:

[0091] 1) The release of snail killers and mosquito killers: whether they were released three days before the fish death incident;

[0092] 2) Human poisoning: whether there was human poisoning three days before the fish death incident;

[0093] If there was no release of snail killers, mosquito killers, or human poisoning three days before the outbreak of the fish death incident, the possibility of external release can be ruled out; otherwise, the possibility of external release of toxic substances can be determined by analyzing the type and amount of snail killers and mosquito killers, and the type and amount of human poisoning, where the poisoning substance is X and the person who poisoned is Y.

[0094] In the present invention, the traceability method preferably also includes: configuring the suspicious targets in the four-level suspicious target library into different concentrations, conducting experiments with live fish, and taking water after 2 to 3 days of toxicity testing for macrotranscriptome sequencing; based on the sequencing results, comparing the gene expression levels in the dead fish water, toxicity test water and control water. If there is no significant difference in the gene expression levels between the dead fish water and the toxicity test water, and there is a significant difference in the gene expression levels between the dead fish water and the control water, then the suspicious target and its possible source are further determined as pollutants and possible pollution sources of the dead fish; the genes for the gene expression level detection are preferably determined based on the symptoms of the dead fish combined with common knowledge in the field, such as if the liver has lesions, the expression levels of liver-related genes are detected.

[0095] The investigation of pollution sources around sudden water pollution incidents and the establishment of a suspicious target library are the basis of tracing the source. Quantitative monitoring of suspicious objects is the core means of tracing the source. Non-targeted screening is a powerful supplement. Fish residual toxin and sediment monitoring are targeted reviews. eDNA analysis and toxicity reproduction tests or computational toxicology are supporting evidence. If the above aspects cannot be fully implemented due to objective reasons, the necessary processes can be carried out according to the actual situation, and the pollutants and sources that caused the fish deaths can be obtained through comprehensive analysis.

[0096] In order to further illustrate the present invention, a method for tracing the source of fish deaths caused by sudden water pollution provided by the present invention is described in detail below in combination with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0097] Example 1

[0098] According to public feedback, a large number of dead fish were found floating in a river. Based on the 18 diagnostic indicators of the "Diagnostic Methods for Acute Poisoning and Death of Freshwater Fish", the fishery department combined the behavioral characteristics, physiological characteristics, autopsy results and the metal content of the fish sent for inspection during the investigation, ruled out fish disease outbreaks, hypoxia, toxic algae poisoning and other factors that caused the fish deaths, and comprehensively determined that the fish deaths were caused by chemical pollutant poisoning.

[0099] Collecting hydrological and rainfall information of the dead fish water body, it was determined that three days before the dead fish incident, a sudden rainstorm hit the area. The next day, the river surface rose rapidly, and the river flow increased from 280m 3 / s increased to 1240m 3 / s. An investigation was conducted on point sources, non-point sources, internal sources, mobile sources, and external sources around the dead fish water body and about 30 km upstream. There is a small amount of cultivated land in the surrounding area, mainly woodland and grassland, and the amount of pesticide used is negligible, which excludes the possibility of non-point sources. There was no transportation and leakage of mobile source chemicals 3 days before the outbreak of the dead fish incident, so the possibility of mobile sources can be ruled out. There was no release of snail killers, mosquito killers, etc. 3 days before the outbreak of the dead fish incident, and there was no artificial poisoning, so the possibility of external sources can be ruled out. Therefore, point sources and internal sources are more likely.

[0100] The main stream of the dead fish water body 30 km upstream has tailwater from a chemical park sewage treatment plant, and several other companies also discharge into the river. Through investigation, it was found that the chemical park sewage treatment plant had no abnormal discharge of sewage three days before the fish death incident, and it is unlikely that toxic substances entered the river through the sewage treatment plant's sewage outlet.

[0101] By analyzing the products and raw materials of enterprises that receive sewage treatment plants and enterprises whose sewage directly enters the river, three enterprises involved in toxic substances were found, namely a fluorine chemical enterprise, a mineral processing agent production enterprise, and a certain type of pesticide production enterprise. Among them, the sewage of a fluorine chemical enterprise is directly discharged into the river, and the sewage of a mineral processing agent production enterprise and a certain type of pesticide production enterprise is discharged into the sewage treatment plant. Through further investigation of the enterprises' production products, raw materials, pollution-producing process links, sewage discharge, sewage treatment facility operation, and rainwater and sewage diversion, a preliminary suspicious target library was established, including four types of substances: yellow phosphorus, a certain bionic insecticide, turpentine, and fluoride.

[0102] The effluent from the sewage treatment plant, the rainwater outlet and outlet of the enterprise, and the water samples retained on the day of the fish death incident were monitored, with the parameters of turpentine, fluoride and yellow phosphorus. Yellow phosphorus was not detected, so the possibility of yellow phosphorus can be ruled out. Turpentine was 2.9μg / L in the water body of the dead fish and 11.5μg / L at the outlet of a mineral processing enterprise, with a concentration difference of less than 4 times, and it was also removed from the suspicious target library.

[0103] The water samples retained on the day of the fish death incident and the company's rainwater outlets and outlets were screened by gas chromatography-mass spectrometry. Bionic pesticides were screened out at the rainwater outlets and outlets of a chemical company that produces bionic pesticides. Further quantitative monitoring was performed using a standard solution of bionic pesticides, where the bionic pesticides in the rainwater outlets were 978μg / L; the bionic pesticides in the outlets were 42μg / L; and the bionic pesticides in the water samples retained on the day of the fish death incident were 0.3μg / L. The concentration of this substance in the rainwater outlet was significantly higher than that in the outlet, and the suspected substance was initially identified as a bionic pesticide.

[0104] The bionic insecticide is a new type of organic synthetic bionic insecticide developed in the 1960s and is widely used to control pests on various crops such as rice, vegetables and fruit trees. The bionic insecticide has a blocking effect on the synaptosomes of the central nervous system of insects, and ultimately has an insecticidal effect. In order to further find out the cause, the residual poison in the landfilled dead fish and the fish samples left by the dead fish were monitored. In view of the characteristics of the bionic insecticide that it will be metabolized in the organism, its metabolites are generally detected in the organism. Therefore, gas chromatography-tandem mass spectrometry was used to monitor the metabolites of the bionic insecticide in the fish body. The monitoring results showed that 15.8μg / kg of bionic insecticide metabolites were detected in the landfilled dead fish, and 13.1μg / kg of bionic insecticide metabolites were detected in the dead fish samples. However, since the fish sample detection time was more than 10 days after the dead fish incident, the fish samples had passed the optimal detection time, and there would be a certain error in the fish body residue.

[0105] Based on the above investigation and monitoring results, it is comprehensively judged that the substance that caused the death of fish in this river section is mainly the bionic pesticide, and the possible source is the enterprise's rainwater outlet.

[0106] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for tracing the source of fish deaths caused by sudden water pollution, characterized in that: The following steps are involved: 1) Collecting hydrological and rainfall information of the dead fish water body to be tested, investigating point sources, surface sources, internal sources, mobile sources and external sources around the dead fish water body and within 30 km upstream, and combining the hydrological and rainfall information and the investigation results to obtain a primary suspicious target library consisting of X and Y; X is a chemical pollutant that may be discharged into the dead fish water body, and Y is a possible source of the chemical pollutant; the cause of death of the dead fish to be tested is chemical pollution; The point sources include: sewage treatment plants, sewage treatment plant collection enterprises and solid waste dumping; the non-point sources include: land use types and application of pesticides and fertilizers within 3km of the river; the internal sources include: dead fish water bodies and the dredging and bottom dredging of rivers 30km upstream in the past week; the mobile sources include: chemical transportation; the external sources include: human poisoning; 2) Collect three types of water samples, namely, water samples from the dead fish water body, water samples from the sewage outlet and water samples from the control point, and detect the content of chemical pollutants in the three water samples; the sampling point of the control point water sample is a water body more than 30 km upstream of the dead fish water body; the sewage outlet water sample is the outlet of the possible source discharged into the water body in step 1); the chemical pollutants are chemical pollutants in the primary suspicious target library; According to the detection results, the chemical pollutants in the primary suspicious target library are screened to obtain a secondary suspicious target library; the possible sources of the chemical pollutants in the secondary suspicious target library are the same as step 1); The screening criteria are: if the content of chemical pollutants in the dead fish water sample is significantly different from that in the control point water sample, and the content of chemical pollutants in the sewage outlet water sample is greater than 4 times the content of chemical pollutants in the dead fish water sample, then the chemical pollutant is a chemical pollutant in the secondary suspicious target library; 3) screening the three water samples in step 2) using liquid-liquid extraction gas chromatography-mass spectrometry and solid phase extraction liquid chromatography-high resolution mass spectrometry, wherein the screening is for chemical substances outside the secondary suspicious target library; If no chemical substances other than the second-level suspected target pool are screened out in the water samples of the control points, and chemical substances other than the second-level suspected target pool are screened out in the water samples of the sewage outlet and the dead fish water, then the chemical substances are suspected chemical pollutants; 4) Detecting and screening the suspected chemical pollutants determined in step 3) to obtain primary chemical pollutants; the detection and screening methods are the same as those in step 2); Re-investigate using the method of step 1) to obtain possible sources of the primary chemical pollutants; Adding the primary chemical pollutants and their possible sources to the secondary suspicious target library to obtain a tertiary suspicious target library; 5) Re-inspecting the dead fish water and dead fish bodies, and determining the content of suspicious targets in the dead fish water and dead fish bodies; the suspicious targets are chemical pollutants in the third-level suspicious target library; If suspicious objects are detected in both the dead fish water and the dead fish, the suspicious objects and their possible sources will form a four-level suspicious object library; 6) The suspicious targets in the four-level suspicious target library are configured into different concentrations, and a toxicity reproduction experiment is performed on live fish. If the behavioral response and fish body odor of the experimental fish are consistent with those of the dead fish to be tested, the suspicious target and its possible source are pollutants and possible pollution sources of the dead fish.

2. The traceability method according to claim 1, characterized in that: The hydrological rainfall information includes: 1) Type of water body: river, lake, pond, reservoir; 2) Flow: water flow three days before the fish die-off; 3) Upstream tributaries: tributaries and tributary flows 30 km upstream of the dead fish body; 4) Rainfall: rainfall in the three days before the fish die-off; 5) Upstream dams and dispatching conditions: whether there are dams upstream of the dead fish body, and the dispatching conditions three days before the dead fish incident; 6) Other sudden environmental events: river bursting and bridge collapse.

3. The traceability method according to claim 1, characterized in that: The investigation contents of the point sources include: 1) Sewage treatment plant: the way of discharge into the dead fish water body and its upstream 30km main and tributary sewage treatment plants, the discharge volume, discharge rules, process flow, and whether there were abnormal discharges three days before the fish death incident; if there were abnormal discharges, the chemical pollutants discharged by the sewage treatment plant were X, and the chemical pollutants discharged by the sewage treatment plant were Y; 2) Wastewater treatment plant receiving enterprises: the production products, raw and auxiliary materials, pollution-producing process links, sewage discharge, operation of sewage treatment facilities, and rainwater and sewage diversion of the sewage treatment plant receiving enterprises; the chemical pollutants involved in the receiving enterprises can be obtained through the analysis of the production products and raw and auxiliary materials of the receiving enterprises; if the receiving enterprise has a separate rainwater inlet, there was rainfall 3 days before the fish death incident, but the rainwater inlet was not monitored, then the chemical pollutants involved in the receiving enterprise are X, and the receiving enterprise is Y; 3) Enterprises that directly discharge sewage into the dead fish water body: The production products, raw materials, pollution-producing process links, sewage discharge volume, operation of sewage treatment facilities, and rainwater and sewage diversion of enterprises that directly discharge sewage into the dead fish water body and its upstream 30km main and tributary rivers; by analyzing the enterprise's production products and raw materials, the chemical pollutants involved in the enterprise can be obtained; if the enterprise has a separate rainwater inlet, there was rainfall 3 days before the dead fish incident, but the rainwater inlet was not monitored, then the chemical pollutant involved in the enterprise is X, and this enterprise is Y; 4) Solid waste: The storage of solid waste in the water body where the fish died and within 30 km upstream and 3 km from the river, including the composition of the solid waste and the rain protection conditions; determine the chemical pollutants that may be discharged into the water body based on the composition of the solid waste; if there is rainfall 3 days before the fish death incident, and there is no rain protection cover on the solid waste storage body, then the chemical pollutant of the solid waste is X and the solid waste is Y.

4. The traceability method according to claim 1, characterized in that: The contents of the surface source survey include: 1) Land use type: land use type of the dead fish water body and its upstream 30km and 3km from the river; 2) Application of pesticides and fertilizers: types of pesticides and fertilizers used and the amount used in the last month; If there is no rainfall three days before the fish die-off, the possibility of non-point source can be ruled out; if there is rainfall three days before the fish die-off, the fertilizer and pesticide applied by non-point source is X, and non-point source is the possible source of X.

5. The traceability method according to claim 1, characterized in that: The internal source investigation includes: Investigation of the dredging and sediment removal of the river channel in the dead fish water body and 30 km upstream in the past week; If there was no scheduling of the upstream dam three days before the fish death incident, or no river dredging or sediment removal in the previous week, the possibility of internal source is ruled out; otherwise, the river sediment is tested to determine the type of toxic substance. The toxic substance in the river sediment is X, and the upstream dam or river is Y.

6. The traceability method according to claim 1, characterized in that: The mobile source investigation includes: the transportation of mobile source chemicals in the dead fish water body and whether there was a chemical leakage three days before the dead fish incident; if there was no chemical leakage three days before the dead fish incident, the possibility of mobile source is ruled out; otherwise, the leaked chemical is X and the mobile source chemical in the dead fish water body is Y.

7. The traceability method according to claim 1, characterized in that: The external source investigation includes: 1) The release of snail killers and mosquito killers: whether they were released three days before the fish mortality incident; 2) Human poisoning: whether there was human poisoning three days before the fish death incident; If there was no release of snail killers, mosquito killers, or human poisoning three days before the fish death incident, the possibility of external release can be ruled out; otherwise, the poisoning substance is X and the person who did the poisoning is Y.

8. The traceability method according to claim 1, characterized in that: The traceability method also includes: configuring the suspicious targets in the four-level suspicious target library into different concentrations, conducting experiments with live fish, and taking water after 2 to 3 days of toxicity testing to perform macrotranscriptome sequencing; based on the sequencing results, comparing the gene expression levels in the dead fish water, the toxicity test water, and the control water. If there is no significant difference in the gene expression levels between the dead fish water and the toxicity test water, and there is a significant difference in the gene expression levels between the dead fish water and the control water, then the suspicious target and its possible source are further determined to be a pollutant and a possible source of pollution of the dead fish.

9. The traceability method according to claim 1, characterized in that: The detection in step 2) includes: Atomic absorption spectrometry, inductively coupled plasma emission spectrometry or inductively coupled plasma emission mass spectrometry is used for metals; atomic fluorescence spectrometry is used for arsenic, mercury and selenium; ion chromatography is used for inorganic anions; purge and trap / gas chromatography-cold atomic fluorescence spectrometry is used for organic mercury; purge and trap / gas chromatography-mass spectrometry is used for volatile organic pollutants; liquid-liquid extraction gas chromatography-mass spectrometry or gas chromatography is used for semi-volatile organic compounds; liquid-liquid extraction or solid phase extraction liquid chromatography-mass spectrometry or liquid chromatography is used for difficult-to-volatile organic compounds.

10. The traceability method according to claim 1, characterized in that: The determination of the suspicious target in step 5) includes: If the suspected target object will be transformed in the dead fish and the transformation product is clear, the content of the transformation product shall be determined; if the suspected target object remains in the dead fish or the transformation product is unclear, the content of the suspected target object shall be determined.