Ecological risk assessment method for effect of pollutants on aquatic organism population

Abstract

The invention relates to the technical field of pollutant assessment methods, in particular to an ecological risk assessment method for the effect of pollutants on aquatic organism populations. According to the ecological risk assessment method for the effect of the pollutants on the aquatic organism population, breeding and survival data of the aquatic organisms are obtained on the basis of individual multi-generation toxicity exposure experiments, the matrix model in the population ecological risk assessment model is utilized to predict the toxicity effect of the population level, and the ecological risk of the pollutants on the aquatic organism population effect is evaluated. Further predicting the toxic effect of pollutants on the individual level and population level of organisms under a long-term exposure condition, comprehensively evaluating and determining the percentage of decrease of the intrinsic growth rate of the population in combination with an individual toxic effect threshold value, deducing the toxicity threshold value of the population level, and performing risk evaluation on the population level. Meanwhile, the ecological risk of the population level is quantitatively represented by using the loss expectation of the population intrinsic growth rate. The risk evaluation method provided by the invention can provide data support for further formulating a corresponding environmental protection benchmark.

Description

Technical Field

[0001] The present invention relates to the technical field of pollutant assessment methods, and in particular to an ecological risk assessment method for the effects of pollutants on aquatic biological populations. Background Art

[0002] Triazole fungicides are the most widely used chiral fungicides. They have the advantages of high activity and fast sterilization, so they are widely used. According to statistics, the market share of triazole products in Europe exceeded 60% in 2008, and the global sales in 2018 reached 3.323 billion US dollars. There are currently 31 commercialized triazole fungicides, and the amount used in 2010 exceeded 10,000 tons. The migration, transformation and degradation of triadimefon in the environment and the metabolic process in the body are one of the determining factors that determine whether triadimefon will persist in the environment and whether it will pose a threat to the aquatic environment and organisms. Existing studies have shown that triadimefon has the characteristics of strong water solubility, stability in the water environment, difficulty in biodegradation, and easy adsorption. It is easy to accumulate in the environment, can be enriched in aquatic organisms, and has stereoselectivity in degradation and metabolism in organisms. It has been detected in Jiulong River, Taihu Lake and Baiyangdian in China, with the highest detection concentration reaching 12μg / L.

[0003] The endocrine disrupting effects of triadimefon on aquatic animals have been increasingly observed, but the toxic effects and ecological risk assessments are mainly conducted at the individual or molecular level of organisms. It is reported that changes in molecular and hormonal levels do not necessarily lead to changes in populations due to the damage repair and physiological adaptability of organisms. However, changes at the population level may lead to individual mortality, growth inhibition, and decreased fertility. In the natural environment, due to the continuous input of pollutants, there are often situations where several generations of organisms are continuously exposed to pollutants. Therefore, when assessing the risks of pollutants with potential endocrine disrupting effects, different endpoints must be considered, especially the adverse reactions caused by long-term exposure and the risks based on population dynamics. At present, when assessing the population-level response of organisms to pollutants, two key issues need to be considered: how to predict changes at the population level based on individual-level changes caused by pollutants, and how to study the multi-generational toxic effects of pollutants on organisms.

[0004] The matrix model is an effective tool for predicting population size and intrinsic growth rate based on individual life history data. The intrinsic growth rate is an endpoint that is closer to the ecosystem level than a single endpoint and can integrate multiple effects (survival, growth, reproduction, etc.) in one parameter, thereby reducing the complexity and uncertainty of ecological risk assessment. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides an ecological risk assessment method for the effects of pollutants on aquatic biological populations. The present invention explores the different levels of toxic effects of triadimefon on aquatic invertebrates under long-term exposure on the basis of multi-generation toxic effect research, studies the differences and connections between the toxic effects of triadimefon at the individual level and the population level, explores methods for extrapolating the toxic effects at the individual level to obtain the toxic effects and risks at the population level through a population model, conducts ecological risk assessments at different levels, explores systematic population-level risk assessment methods, and provides data support for further formulating corresponding environmental protection benchmarks.

[0006] To this end, the present invention provides the following technical solutions:

[0007] In the first aspect, the present invention provides, in an optional embodiment, a method for ecological risk assessment of the effects of pollutants on aquatic organism populations. The method is based on individual multi-generation toxicity exposure experiments to obtain reproduction and survival data of aquatic organisms, and uses a matrix model in a population ecological risk assessment model to predict toxic effects at the population level, and then predict the toxic effects of pollutants on the individual and population levels of organisms under long-term exposure conditions. At the same time, combined with individual toxic effect thresholds, a comprehensive assessment is performed to determine the percentage of decrease in the population's intrinsic growth rate, derive the population-level toxicity threshold, and conduct a population-level risk assessment. At the same time, the expected loss of the population's intrinsic growth rate is used to quantitatively characterize the ecological risk at the population level.

[0008] Preferably, the method comprises the following steps:

[0009] S1: Through multi-generation toxic exposure experiments, statistically calculate the mortality rate, survival rate, and molting times of individual organisms, analyze the multi-generational toxic effects and patterns of long-term exposure to pollutants on the individual level, and collect existing toxicity data to calculate HC using species sensitivity distribution curves. 5 , derive the predicted no-effect concentration;

[0010] S2: The survival rate and fecundity data obtained from multi-generation experiments were extrapolated to the population level through the matrix model in the biological structure population model to predict the response of aquatic organisms to triadimefon at the population level under long-term exposure conditions;

[0011] S3: Select the exposure concentration corresponding to a 5% change in the intrinsic growth rate of the population due to pollution as the safety toxicity threshold at the population level;

[0012] S4: Combine exposure assessment and effect assessment, and use the risk quotient method and population risk method in sequence to quantitatively assess the ecological risks of target pollutants in surface water.

[0013] Preferably, in step S1, the method of the multi-generation toxicity experiment is:

[0014] The invertebrate Daphnia magna was used as the research object. It had been cultured stably for more than 5 generations before the experiment. It was cultured using ElendtM4 medium and placed in a constant temperature incubator. Daphnia magna was fed with Capricornus sphenanthera every day. Triadimefon, which has potential endocrine disrupting effects, was used as the target pollutant. According to the preliminary experiment, 6 exposure groups with concentration gradients, 1 blank control group and 1 acetone control group were set. Each group had 10 parallel samples. The exposure solution was replaced every 48 hours. The number of deaths, molting, and daphnia produced in each beaker were counted every 24 hours. , and promptly suck away molting, laying and dead Daphnia; the third litter of Daphnia produced by the F0 generation with good size and vitality was selected as the F1 generation for continued exposure, and the third litter of the F1 generation was selected as the F2 generation for continued exposure. The experiment was terminated after the third generation of experimental subjects was exposed for 21 days. According to the experimental results, the multi-generation toxic effects of pollutants on the development and reproduction of large Daphnia were analyzed, the collected toxicity data were tested for log-normal distribution hypothesis, and the species SSD curves of different test endpoints were fitted, and the 5% species affected concentration was calculated. Finally, PNEC was calculated with 5 as the evaluation factor.

[0015] Preferably, in the multi-generation toxicity culture experiment, the culture conditions in the constant temperature incubator are: culture temperature of 20-22°C, 16 hours of light and 8 hours of darkness per day, and light intensity of 1110-1480 lx. When feeding Daphnia pulex with Selaginella fasciata, the feeding density is 3.0×10 5 -4×10 5 cells / mL; and / or, the culture conditions of the capillaris are: temperature of 22-24°C, 14 hours of light and 10 hours of darkness per day, and light intensity of 4440-8880lx.

[0016] Preferably, in step S2, the response of aquatic organisms to triadimefon at the population level under long-term exposure conditions is predicted from three aspects, namely, population size, population age structure, and the changing trend of population intrinsic growth rate with exposure concentration and time.

[0017] Preferably, the prediction formula for predicting the response of aquatic organisms to triadimefon at the population level under long-term exposure conditions from the population size is shown in formula (1):

[0018] N t+1 =AN t ...Formula (1),

[0019] In formula (1), N t+1 and N t is a population vector containing the number of organisms at each age stage (n 0 ,…n K ), A is a matrix, as shown in formula (2),

[0020]

[0021] In formula (2), S k represents the survival probability of an organism from one age group to another; f k It represents the average reproductive capacity of organisms in age group k.

[0022] Furthermore, when the aquatic organism is Daphnia magna, the population in step S2 is:

[0023] The growth of Daphnia magna was divided into three stages: 0-6d, 7-13d and 14-21d. The survival rate and growth and reproduction data of different periods were obtained from the multi-generation exposure experiment. The life history data were substituted into formula (3):

[0024]

[0025] In formula (3), F i represents the total number of offspring produced by each adult female Daphnia gracilis in stage i, S i represents the survival rate from stage i-1 to stage i;

[0026] The calculation formula for the number of female Daphnia at each stage at time t is shown in formula (4):

[0027] N t =[n 1,t ,n 2,t ,n 3,t ] T ...Formula (4),

[0028] In formula (4), n i,t is the number of organisms in stage i on day t;

[0029] The formula for calculating the population size on day t+1 is shown in formula (5):

[0030] N t+1 =AN t ...Formula (5).

[0031] Preferably, the prediction formula for predicting the response of aquatic organisms to triadimefon at the population level under long-term exposure conditions from the intrinsic growth rate of the population is shown in formula (6):

[0032] r=ln(λ)……Formula (6),

[0033] In formula (6), r is the intrinsic growth rate of the population;

[0034] The population intrinsic growth rate is the natural logarithm of the largest eigenvalue (λ) of the matrix A;

[0035] Using power function fitting, based on the intrinsic growth rate data obtained under different exposure concentrations, nonlinear least squares fitting was used to obtain formula (7):

[0036]

[0037] In formula (7), r(C) is the intrinsic growth rate of the population when the concentration is C, C is the exposure concentration of the pollutant, and r 0 , α and β are fitting parameters. α is the intrinsic growth rate of the population when there is no pollutant (C=0), α is the pollutant exposure concentration corresponding to α=0, and β is the fitting parameter.

[0038] Preferably, in step S4, when the risk quotient is greater than 10, it indicates that the pollutant presents a high risk in the area; when the risk quotient is greater than 1 and less than 10, it indicates that the pollutant presents a medium risk in the area; when the risk quotient is less than 1, it is considered a low-risk pollutant; and when the risk quotient is less than 0.1, it is considered to be no risk; and / or,

[0039] The expected loss of the intrinsic growth rate of the population is used to quantitatively characterize the risk of pollutants to biological populations. The formula used is formula (8):

[0040]

[0041] In formula (8), Δr(C) represents the loss curve of intrinsic growth rate versus concentration, and p(C) represents the probability distribution of surface water exposure concentration.

[0042] Compared with the prior art, the present invention has one of the following beneficial effects:

[0043] 1. The present invention explores the different levels of toxic effects of triadimefon on aquatic invertebrates under long-term exposure based on multi-generation toxic effect research, studies the differences and connections between the toxic effects of triadimefon at the individual level and the population level, explores methods for extrapolating the toxic effects at the individual level to obtain the toxic effects and risks at the population level through a population model, conducts ecological risk assessments at different levels, explores systematic population-level risk assessment methods, and provides data support for further formulating corresponding environmental protection benchmarks. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 This is a schematic diagram of a multi-generation toxicity experiment in Example 1 of the present invention;

[0046] Figure 2 This is a schematic diagram of the intrinsic growth rate of a population in Example 1 of the present invention;

[0047] Figure 3 This is a schematic diagram of the population age structure in Example 1 of the present invention. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0049] Using the invertebrate Daphnia gracilis as a model organism, a multi-generation toxic exposure experiment was conducted to obtain the reproduction and survival data of aquatic organisms, and the data was brought into the matrix model of the population model to derive the toxic effect index at the population level, thereby exploring the toxic effects of pollutants on the individual and population levels under long-term exposure. Combined with the toxic effect threshold at the individual level, a comprehensive assessment was conducted to determine the percentage of decline in the intrinsic growth rate of the population, derive the toxicity threshold at the population level, and conduct a risk assessment at the population level, which specifically includes the following steps:

[0050] 1) Determination and analysis of multi-generational toxic effects:

[0051] Through multi-generation toxicity exposure experiments, we statistically calculated the mortality rate, survival rate, and molting times of individual organisms, analyzed the multi-generational toxic effects and patterns of long-term exposure to pollutants at the individual level, and collected toxicity data from others' research to derive the predicted no-effect concentration (PNEC) based on the species sensitivity distribution (SSD) curve.

[0052] Multi-generation toxicity experiment: The invertebrate Daphnia magna was used as the research object. It had been cultured stably for more than 5 generations before the experiment. It was cultured using Elendt M4 medium and placed in a constant temperature incubator; the culture temperature was (20-22)℃, with 16 hours of light and 8 hours of darkness per day, and the light intensity was 1110-1480lx. Daphnia magna was fed with Luna hornii algae every day, and the feeding density was 3.0×10 5 -4×10 5 cells / mL. The culture of Lunaea hornense was carried out according to the requirements of OECD201, the incubator temperature was set at (22-24)℃, the light intensity was 4440-8880lx with 14h of light and 10h of darkness per day;

[0053] Taking triadimefon, which has potential endocrine disrupting effects, as the target pollutant, six exposure groups with concentration gradients, one blank control group and one acetone control group were set up through preliminary experiments; 10 parallel samples were set up in each group; the exposure solution was changed every 48 hours, and the number of deaths, molts, and daphnia in each beaker was counted every 24 hours, and the molted, daphnia and dead daphnia were sucked away in time; the third litter of daphnia produced by the F0 (F1) generation with good size and vitality was selected as the F1 (F2) generation for continued exposure; the experiment ended after the third generation (F2 generation) of experimental subjects was exposed for 21 days;

[0054] Based on the experimental results, the multi-generational toxic effects of pollutants on the development and reproduction of Daphnia magna were analyzed.

[0055] PNEC based on individual level: The toxicity data of triadimefon were mainly collected from the US ECOTOX database (https: / / cfpub.epa.gov / ecotox / search.cfm) and some published literature as well as previous experimental supplements; the test endpoints were divided into four categories: lethality, growth / development, reproduction, and molecular biochemistry; the collected toxicity data were tested for log-normal distribution hypothesis (Anderson-Darling, AD) using ETX2.0 software; the national ecological environment benchmark calculation software was used to select the most appropriate fitting model, fit the SSD curves of different test endpoints, and calculate the concentration at which 5% of the species were affected; PNEC was calculated using 5 as the evaluation factor.

[0056] 2) Prediction and analysis of population toxicity effects

[0057] The survival rate and fecundity data obtained from multi-generation experiments are extrapolated to the population level through a matrix model to predict the response of pollutants at the population level under long-term exposure, including the changing trend of population size with concentration and time, the change of population age structure and the changing trend of population intrinsic growth rate.

[0058] Indicator selection: Population quantity characteristics are the most basic characteristics of a population, and the dynamic changes in population quantity can reflect the fluctuation of population quantity over time;

[0059] Age structure refers to the ratio of the number of individuals of different age stages in a population to the total number of the population. The proportion of each age stage determines which age stage is dominant, which can be used to determine the stability of the population. The age structure of a population is divided into three types: growth type, stable type and decline type. A decline type population is not conducive to the reproduction and development of the population, and the population tends to decline.

[0060] The intrinsic growth rate of a population reflects its ability to continue, determines changes in population size and the average time of population extinction, and is relatively easy to operate during the estimation process, so it has been widely used in actual risk assessment.

[0061] Population model selection: The matrix model was developed by Leslie and Lewis to calculate the time-varying population size of different life stages based on survival and reproduction rates:

[0062] N t+1 =AN t ...Formula (1),

[0063] In formula (1), N t+1 and N t is a population vector containing the number of organisms at each age stage (n 0 ,…n K ), A is a matrix, as shown in formula (2),

[0064]

[0065] In formula (2), S k represents the survival probability of an organism from one age group to another; f k It represents the average reproductive capacity of organisms in age group k.

[0066] Calculation of population size and intrinsic growth rate:

[0067] The present invention divides the growth of Daphnia magna into three stages: 0-6d, 7-13d and 14-21d, and obtains the survival rate and growth and reproduction data of different periods from multi-generation experiments. In the Leslie matrix analysis, the life history data is substituted into the matrix A:

[0068]

[0069] In formula (3), F i represents the total number of offspring produced by each adult female Daphnia gracilis in stage i, S i represents the survival rate from stage i-1 to stage i;

[0070] The number of female Daphnia at each stage at time t is calculated as follows:

[0071] N t =[n 1,t ,n 2,t ,n 3,t ] T ...Formula (4),

[0072] In formula (4), n i,t is the number of organisms in stage i on day t;

[0073] The population size on day t+1 is calculated as follows:

[0074] N t+1 =ANt ...Formula (5).

[0075] The intrinsic growth rate (r) of a population is an important comprehensive indicator for measuring the instantaneous population growth rate. It is the natural logarithm of the maximum eigenvalue (λ) of the matrix A:

[0076] r=ln(λ)……Formula (6),

[0077] In order to establish the dose-effect curve of the intrinsic growth rate of the population under different exposure concentrations, a power function was used to fit the data of the intrinsic growth rate obtained under different exposure concentrations, and the nonlinear least squares method was used to fit the following formula:

[0078]

[0079] In formula (7), r(C) is the intrinsic growth rate of the population when the concentration is C, C is the exposure concentration of the pollutant, and r 0 , α and β are fitting parameters. α is the intrinsic growth rate of the population when there is no pollutant (C=0), α is the pollutant exposure concentration corresponding to α=0, and β is the fitting parameter.

[0080] 3) Derivation of population-level toxicity thresholds

[0081] When r = 0, the population has no growth potential due to pollution, and when r < 0, the population begins to decline. Calculations show that the concentration at r = 0 is greater than the predicted no-effect concentration derived from acute toxicity. If other factors are taken into account, at this concentration, the population must be on the verge of extinction. In order to obtain a more realistic threshold, the exposure concentration corresponding to the change of the population's intrinsic growth rate by 5% due to pollution is selected as the population-level safety toxicity threshold.

[0082] 4) Population-level ecological risk assessment: Combining exposure assessment and effect assessment, the risk quotient (RQ) method and population risk quantitative assessment are used to assess the ecological risk of target pollutants at surface water concentration levels.

[0083] RQ: RQ is the ratio of the environmental exposure concentration to the toxicity threshold of the pollutant. When the RQ value is greater than 10, it means that the pollutant presents a high risk in the area. When the RQ value is greater than 1 and less than 10, it means that the pollutant has a medium risk to the area. If it is less than 1, it is considered a low-risk pollutant. If the RQ value is less than 0.1, it is considered to be risk-free.

[0084] Population risk: The risk of pollutants to biological populations is quantitatively characterized using the loss expectation of the population's intrinsic growth rate:

[0085]

[0086] In formula (8), Δr(C) represents the loss curve of intrinsic growth rate versus concentration, and p(C) represents the probability distribution of surface water exposure concentration.

[0087] Example

[0088] Specific implementation process of multi-generation toxicity experiment:

[0089] Take the young Daphnia gracilis (N3) produced by the same batch of well-grown mother Daphnia for the third time and with good vitality in a 50ml beaker for a multi-generation exposure experiment (such as Figure 1 As shown in the figure, one female Daphnia was placed in each beaker, recorded as F0. According to the toxic effect concentration of triadimefon in the ECOTOX database (https: / / cfpub.epa.gov / ecotox / search.cfm) and previous research basis, six concentrations were set, namely 0.1, 0.2, 0.4, 0.8, 1.6, and 3.2 mg / L (the concentrations were marked as 3-8 from low to high), and 10 replicates were set for each concentration. The experimental blank controls were M4 medium and M4 medium containing 0.1 mL / L acetone (marked as 1 and 2, respectively). The third litter of Daphnia produced by the F0 (F1) generation with good size and vitality was randomly selected as the F1 (F2) generation for continued exposure, with 10 replicates for each concentration, and each replicate used a 50 ml beaker with a Daphnia. According to the OECD211 standard, the exposure time for each generation was set to 21 days, the exposure solution was replaced every two days, and the concentration of the exposure solution was kept constant. The number of dead, molted, and produced daphnia in each beaker was counted every day, and the molted, produced, and dead daphnia were sucked out in time. Be careful when sucking out the daphnia to avoid scratching the daphnia. The data obtained were used for the analysis of the toxic effects of triadimefon at the individual level and as the data source for the model used for the population-level toxic effect analysis. After the experiment, the exposure solution was taken to determine the actual concentration.

[0090] The data statistical analysis software involved was Origin 2021 (Origin Lab Corporation, Northampton, MA, USA) and SPSS Statistics 26 (BM Corporation, Armonk, NY, USA). One-way analysis of variance and multi-way analysis of variance were used for significance test and variance homogeneity test, and the arithmetic mean of the repeated groups was taken and expressed as mean ± standard deviation (SD). P < 0.05 indicated that there was a significant difference between the two samples.

[0091] PNEC derivation based on SSD curve: Following the principles of accuracy, relevance and reliability, toxicity data of triadimefon for different toxic effect endpoints (lethality, growth and development, reproduction and molecular biology) were collected according to the ECOTOX database and previous studies, and the Anderson-Darling of the ETX2.0 package was used to perform a log-normal distribution hypothesis test on each data set. The species SSD curves of different test endpoints were fitted using the National Ecological Environment Benchmark Calculation Software, and the 5% species affected concentration was calculated and divided by the evaluation factor 5 (which depends on the number of toxicity data) to obtain the PNEC of different effect endpoints, which depends on the number of supporting toxicity data.

[0092] Prediction of population toxicity effects: In order to more intuitively observe the long-term effects of different concentrations of triadimefon exposure on the population level of Daphnia magna, a population statistical analysis model was constructed based on the multi-generation toxicity data of Daphnia magna (including reproduction rate and survival rate) using the Leslie matrix. The initial population size was set to 1, thereby simulating the dynamic changes of the population over time, predicting the age structure of the population after 1, 2, and 3 years, calculating the population intrinsic growth rate, and drawing the concentration-intrinsic growth rate fitting curve (see Figure 2 ) and establish a dose-response relationship between population effect index and triadimefon concentration.

[0093] Matlab2014 (USA) was used for matrix operations, population size calculations, and the population intrinsic growth rate-concentration curve was fitted using the nonlinear least squares method. Origin2021 (OriginLab Corporation, Northampton, MA, USA) was used to plot the population age structure (see Figure 3 ). SPSS Statistics 26 (BM Corporation, Armonk, NY, USA) was used for significance analysis.

[0094] Taking into account the toxic effects at the individual level, multi-generational toxic effects, PNE C based on the SSD curve, and the predicted population-level toxic effects, in order to obtain a more realistic threshold, the pollutant concentration when the population intrinsic growth rate decreases by 5% was selected as the population-level toxic threshold concentration.

[0095] The RQ method was used to evaluate the risks of different regions based on individual toxicity thresholds and population toxicity thresholds. Considering that the loss of population intrinsic growth rate is more suitable than the population intrinsic growth rate to characterize the harm of pollutants to the population, the loss of population intrinsic growth rate was used to quantitatively predict population risk.

[0096] Conclusion: Taking the pollutant concentration when the intrinsic growth rate of the population decreases by 5% as the toxicity threshold concentration at the population level, the toxicity threshold of triadimefon is 0.089 mg / L; using the population risk assessment method, it was found that without considering other factors, the predicted value of the loss of the intrinsic growth rate of the large Daphnia magna population due to triadimefon in surface water was 0.0018-0.0039.

[0097] The method of the present invention is applied, based on the experimental data of multi-generational toxic effects of Daphnia magna, combined with the population model to predict the ecotoxic effects and threshold concentrations of pollutants at the population level, and to conduct ecological risk assessment at the population level. Risk assessment at the population level may be more in line with the actual situation of protecting the ecosystem. The research results can provide data support for further formulating corresponding environmental protection benchmarks, and provide a certain reference for carrying out risk assessment at the population level of this type of pollutants with similar structures, similar properties, and multi-generational toxic effects.

[0098] Although the principles of the present invention are described in detail above in conjunction with the preferred embodiments of the present invention, those skilled in the art should understand that the above embodiments are merely explanations of the exemplary implementations of the present invention, and are not intended to limit the scope of the present invention. The details in the embodiments do not constitute limitations on the scope of the present invention, and any obvious changes such as equivalent transformations, simple replacements, etc. based on the technical solution of the present invention, without departing from the spirit and scope of the present invention, fall within the protection scope of the present invention.

Claims

1. A method for ecological risk assessment of the effects of pollutants on aquatic organism populations, characterized in that: The method is based on individual multi-generation toxicity exposure experiments to obtain reproduction and survival data of aquatic organisms, and uses the matrix model in the population ecological risk assessment model to predict the toxic effects at the population level, and then predicts the toxic effects of pollutants on the individual and population levels of organisms under long-term exposure conditions. At the same time, combined with the individual toxicity effect threshold, a comprehensive assessment is made to determine the percentage of decrease in the population's intrinsic growth rate, derive the population-level toxicity threshold, and conduct a population-level risk assessment. At the same time, the expected loss of the population's intrinsic growth rate is used to quantitatively characterize the ecological risk at the population level.

2. The method for ecological risk assessment of the effects of pollutants on aquatic organism populations according to claim 1, characterized in that: The method comprises the following steps: S1: Through multi-generation toxic exposure experiments, the mortality rate, survival rate, and molting times of individual organisms are statistically calculated to analyze the multi-generational toxic effects and patterns of long-term exposure to pollutants at the individual level. At the same time, existing toxicity data are collected, and HC5 is calculated using the species sensitivity distribution curve to derive and predict the no-effect concentration; S2: The survival rate and fecundity data obtained from multi-generation experiments were extrapolated to the population level through the matrix model in the biological structure population model to predict the response of aquatic organisms to triadimefon at the population level under long-term exposure conditions; S3: Select the exposure concentration corresponding to a 5% change in the intrinsic growth rate of the population due to pollution as the safety toxicity threshold at the population level; S4: Combine exposure assessment and effect assessment, and use the risk quotient method and population risk method in sequence to quantitatively assess the ecological risks of target pollutants in surface water.

3. The method for ecological risk assessment of the effects of pollutants on aquatic organism populations according to claim 2, characterized in that: In step S1, the method of the multi-generation toxicity experiment is: The invertebrate Daphnia magna was used as the research object. It had been cultured stably for more than 5 generations before the experiment. It was cultured using Elendt M4 medium and placed in a constant temperature incubator. Daphnia magna was fed with Lunaea hornense every day. Triadimefon, which has a potential endocrine disrupting effect, was used as the target pollutant. According to the preliminary experiment, 6 exposure groups with concentration gradients, 1 blank control group and 1 acetone control group were set. Each group had 10 parallel samples. The exposure solution was replaced every 48 hours. The number of deaths, molts, and daphnia produced in each beaker was counted every 24 hours, and the molted, daphnia produced and dead daphnia were sucked away in time. The third litter of Daphnia magna produced by the F0 generation with good size and vitality was selected as the F1 generation for continued exposure, and the third litter of the F1 generation was selected as the F2 generation for continued exposure. The experiment was terminated after the third generation of experimental subjects was exposed for 21 days. The multi-generation toxic effects of pollutants on the development and reproduction of Daphnia magna were analyzed based on the experimental results. The collected toxicity data were tested for log-normal distribution hypothesis, and the species SSD curves of different test endpoints were fitted. The affected concentration of 5% of the species was calculated, and finally PNEC was calculated with 5 as the evaluation factor.

4. The method for ecological risk assessment of the effects of pollutants on aquatic organism populations according to claim 3, characterized in that: In the multi-generation toxicity culture experiment, the culture conditions in the constant temperature incubator are: culture temperature of 20-22°C, 16 hours of light and 8 hours of darkness per day, and light intensity of 1110-1480lx.

5. The method for ecological risk assessment of the effects of pollutants on aquatic organism populations according to claim 3, characterized in that: When feeding large Daphnia pulex with Algae, the feeding density was 3.0×10 5 -4×10 5 cells / mL; and / or, The culture conditions of the capillaris are: temperature of 22-24°C, 14 hours of light and 10 hours of darkness per day, and light intensity of 4440-8880lx.

6. The ecological risk assessment method for the effects of pollutants on aquatic organism populations according to claim 2 is characterized in that: In step S2, the response of aquatic organisms to triadimefon at the population level under long-term exposure conditions is predicted from three aspects, namely, population size, population age structure, and the changing trend of population intrinsic growth rate with exposure concentration and time.

7. The method for ecological risk assessment of the effects of pollutants on aquatic organism populations according to claim 6, characterized in that: The prediction formula for predicting the response of aquatic organisms to triadimefon at the population level under long-term exposure conditions from population size is shown in formula (1): N t+1 = AN t …… Equation (1), In formula (1), N t+1 and N t is a population vector containing the number of organisms at each age stage (n0, ...n K ), A is a matrix, as shown in formula (2), In formula (2), S k represents the survival probability of an organism from one age group to another; f k It represents the average reproductive capacity of organisms in age group k.

8. The method for ecological risk assessment of the effects of pollutants on aquatic organism populations according to claim 7, characterized in that: When the aquatic organism is Daphnia magna, the population in step S2 is: The growth of Daphnia magna was divided into three stages: 0-6d, 7-13d and 14-21d. The survival rate and growth and reproduction data of different periods were obtained from the multi-generation exposure experiment. The life history data were substituted into formula (3): In formula (3), F i represents the total number of offspring produced by each adult female Daphnia gracilis in stage i, S i represents the survival rate from stage i-1 to stage i; The calculation formula for the number of female Daphnia at each stage at time t is shown in formula (4): N t = [n 1,t , n 2,t , n 3,t T …… Equation (4),​ In formula (4), n i,t is the number of organisms in stage i on day t; The formula for calculating the population size on day t+1 is shown in formula (5): N t+1 = AN t ……Equation (5).

9. The method for ecological risk assessment of the effects of pollutants on aquatic organism populations according to claim 6, characterized in that: The prediction formula for predicting the response of aquatic organisms to triadimefon at the population level under long-term exposure conditions based on the intrinsic growth rate of the population is shown in formula (6): r=ln(λ)……Formula (6), In formula (6), r is the intrinsic growth rate of the population; The population intrinsic growth rate is the natural logarithm of the largest eigenvalue (λ) of the matrix A; Using power function fitting, based on the intrinsic growth rate data obtained under different exposure concentrations, nonlinear least squares fitting was used to obtain formula (7): In formula (7), r(C) is the intrinsic growth rate of the population when the concentration is C, C is the exposure concentration of the pollutant, r0, α and β are fitting parameters, r0 is the intrinsic growth rate of the population when there is no pollutant (C = 0), α is the pollutant exposure concentration corresponding to = 0, and β is the fitting parameter.

10. The ecological risk assessment method for the effects of pollutants on aquatic organism populations according to claim 2, characterized in that: In step S4, when the risk quotient is greater than 10, it indicates that the pollutant presents a high risk in the area; when the risk quotient is greater than 1 and less than 10, it indicates that the pollutant presents a medium risk in the area; when the risk quotient is less than 1, it is considered a low-risk pollutant; and when the risk quotient is less than 0.1, it is considered to be no risk; and / or, The expected loss of the intrinsic growth rate of the population is used to quantitatively characterize the risk of pollutants to biological populations. The formula used is formula (8): In formula (8), Δr(C) represents the loss curve of intrinsic growth rate versus concentration, and p(C) represents the probability distribution of surface water exposure concentration.

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