A method for evaluating the ecotoxicity effects of tailwater recharge in rivers using benthic animals

Abstract

The present application relates to the technical field of river ecological risk assessment, and provides a method for evaluating the ecotoxicity effect of tailwater replenishment river channels using benthic animals. By first evaluating the assessment scope of the river, each assessment river is divided into multiple assessment river sections, a corresponding number of monitoring points are set in each assessment river section, benthic animals are used as assessment species, and field surveys are conducted at each monitoring point. Combined with environmental DNA technology, multiple biological indices of large benthic organisms in different assessment river sections are obtained, and then various biological indices of large benthic organisms in different assessment river sections are compared and analyzed. If the number of biological indices that show a downward trend from downstream to upstream among all biological indices exceeds a preset quantitative threshold, and all biological indices show a downward trend as time increases, it is determined that there is an ecotoxicity effect. Multiple, long-time interval surveys and multi-dimensional, multi-indicator analysis methods are used to accurately evaluate the ecotoxicity effect of tailwater on receiving water bodies.

Description

Technical Field

[0001] The present application relates to the technical field of water pollution treatment, and in particular to a method for evaluating the ecotoxicity effect of tailwater replenishment on a river channel using benthic animals. Background Art

[0002] At present, urban tailwater is mainly used for river and lake replenishment, ecological environmental water for sanitation and greening, and production water for industry and construction, which has achieved some economic benefits and alleviated the pressure of water shortage. As an important source of ecological or landscape water replenishment, although its nutrient content has reached the discharge standard, a large number of studies have shown that the residual toxicity of tailwater may be an important factor affecting the survival of aquatic animals. Unlike the acute toxic effects of other water pollution, tailwater has a chronic toxic effect on receiving water bodies. Therefore, how to analyze and accurately evaluate the impact of tailwater discharge on river ecology is one of the problems that the industry needs to solve.

[0003] Therefore, it is necessary to provide an improved technical solution to address the above-mentioned deficiencies in the prior art. Summary of the invention

[0004] The purpose of this application is to provide a method for evaluating the ecotoxicity effects of tailwater replenishment rivers using benthic animals to solve or alleviate the problems existing in the above-mentioned prior art. This application makes full use of environmental DNA technology and field investigation methods to comprehensively evaluate the ecological risks of tailwater replenishment rivers and provide valuable information for protecting and maintaining the good ecological status of rivers.

[0005] In order to achieve the above objectives, this application provides the following technical solutions:

[0006] This application provides a method for evaluating the ecotoxicity effect of tailwater replenishment in rivers using benthic animals, including:

[0007] Determine the assessment scope of the river to be assessed;

[0008] According to the determined assessment scope, each assessment river is divided into multiple assessment river sections;

[0009] According to the length of each assessed river section, a corresponding number of monitoring points are set up in each assessed river section;

[0010] Taking benthic animals as the evaluation species, field surveys were conducted at various monitoring points, and multiple biological indices of large benthic organisms in different evaluation sections were obtained by combining environmental DNA technology; the biological indices included large benthic diversity index, large benthic integrity index, and large benthic environmental DNA index;

[0011] A comparative analysis is conducted on various large benthic biological indices in different assessed river sections. If the number of biological indices that show a downward trend from downstream to upstream among all biological indices exceeds the preset number threshold, and all biological indices show a downward trend with time, it is determined that the tailwater replenishment has an ecotoxic effect on the river channel, and the preset number threshold is 3 or more.

[0012] Furthermore, the assessment scope of the river is determined, including:

[0013] The tailwater flow, river flow and river width are used to calculate the impact range of the tailwater through the tailwater impact assessment model;

[0014] Remove 1 / 10 of the river length from the influence range of the tailwater to obtain the assessment range of the assessed river;

[0015] The 1 / 10 river section length is measured from the tailwater discharge outlet upstream of the river;

[0016] The calculation formula of the tailwater impact assessment model is as follows:

[0017] D = (Q 尾 / Q 河 ) × L,

[0018] Where D is the horizontal impact distance of the tailwater, in meters; Q 尾 is the discharge flow of tail water, in m 3 / d;Q 河 is the flow rate of the river, in m 3 / d; L is the river width in meters.

[0019] Furthermore, the number of the evaluated river sections is 3 or more.

[0020] Furthermore, the macrobenthic diversity index, macrobenthic integrity index and macrobenthic environmental DNA index were obtained through the following steps:

[0021] Conduct multiple and long-term field surveys at each monitoring site to obtain a macrobenthic diversity index;

[0022] Collect samples simultaneously, process and analyze the samples based on environmental DNA technology to obtain macrobenthic environmental DNA indicators;

[0023] According to preset rules, reference points and damaged points were selected within the target river area to obtain the large-scale benthic integrity index for each assessed river section.

[0024] Furthermore, the macrobenthic diversity index is the Shannon index;

[0025] The large benthic environment DNA indicators include: Observed species index, Simpson index and Chao1 richness index.

[0026] Furthermore, the length of the assessed river section is less than or equal to 50 kilometers.

[0027] Furthermore, according to the length of each assessed river section, a corresponding number of monitoring points are set in each assessed river section, including:

[0028] If the length of the assessed river section is less than 10 kilometers, only one monitoring point will be set up for the assessed river section;

[0029] If the length of the assessed river section is within the range of 10-20 km, two monitoring points shall be set up in the assessed river section;

[0030] If the length of the assessed river section is within the range of 20-30 km, three monitoring points shall be set up in the assessed river section;

[0031] If the length of the assessed river section is within the range of 30-40 km, four monitoring points shall be set up in the assessed river section;

[0032] If the length of the assessed river section is within the range of 40-50 km, five monitoring points shall be set up in the assessed river section;

[0033] A monitoring river section of 100 to 200 m is selected at each monitoring point, and the monitoring river section includes a slow flow area, a rapid flow area and a backwater area.

[0034] Furthermore, according to the length of each assessed river section, a corresponding number of monitoring points are set in each assessed river section, including:

[0035] Four monitoring points were set up in each assessed river section;

[0036] Each monitoring point selects 200m as the monitoring river section, and the monitoring river section includes a slow flow area, a rapid flow area and a backwater area.

[0037] Furthermore, the benthic fauna survey at each monitoring point needs to be conducted three or more times, with an interval of one month or more between each survey, in order to assess the chronic toxic effects of the tailwater.

[0038] Furthermore, the benthic animals at each monitoring point were surveyed four times, with the second survey being conducted one month apart from the first, the third survey being conducted two months apart from the second, and the fourth survey being conducted one month apart from the third, in order to assess the chronic toxic effects of the tailwater.

[0039] The technical solution of the embodiment of the present application has the following beneficial effects:

[0040] 1. This embodiment uses large benthic animals as the evaluation species, which makes investigation and sampling less difficult and more feasible.

[0041] 2. The combination of environmental DNA technology and field survey technology is used to obtain multiple parameters of the ecosystem, which solves the problem that environmental DNA technology is difficult to accurately identify all species in the ecosystem, and ensures the accuracy of diversity survey results to the greatest extent.

[0042] 3. Multi-dimensional and multi-indicator evaluation: Using multiple large benthic biological indices in different assessment river sections as evaluation indicators, by comparing the changing trends of evaluation indicators in different river sections and at different times, multi-parameter analysis is conducted in the time and space dimensions to systematically evaluate the ecological effects of tailwater entering the river, so as to avoid the insensitivity of a single indicator or a single dimension to the ecological effects of tailwater.

[0043] 4. Considering that the essential difference between tail water and other sewage is that tail water has chronic toxic effect on receiving water body rather than acute toxic effect, this embodiment adopts multiple, multi-river section, long time interval investigation and detection methods and multi-dimensional, multi-indicator analysis methods to accurately evaluate the eco-toxic effect of tail water on receiving water body. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings constituting part of the present application are used to provide a further understanding of the present application. The exemplary embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. Among them:

[0045] Figure 1 A schematic flow chart of a method for evaluating the ecotoxicity effects of tailwater recharge in a river channel using benthic animals according to some embodiments of the present application.

[0046] Figure 2 A schematic diagram of a process for obtaining an integrity index according to some embodiments of the present application.

[0047] Figure 3 A schematic diagram of the process of obtaining environmental DNA indicators according to some embodiments of the present application. DETAILED DESCRIPTION

[0048] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present application and does not limit the present application. In fact, it will be clear to those skilled in the art that modifications and variations may be made in the present application without departing from the scope or spirit of the present application. For example, a feature shown or described as a part of an embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desired that the present application includes such modifications and variations within the scope of the appended claims and their equivalents.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present disclosure belongs. The terms used herein are only for the purpose of describing the embodiments of the present disclosure and are not intended to limit the present disclosure.

[0050] Embodiment 1:

[0051] The present application provides a method for evaluating the ecotoxicity effect of tailwater replenishment on a river channel using benthic animals. Figure 1 The process of the method is shown as Figure 1 As shown, the method includes:

[0052] Step S101: Determine the assessment scope of the assessment river.

[0053] In this embodiment, the river to be evaluated can be any tailwater replenishment river. Among them, urban tailwater refers to sewage discharged in the city, usually refers to wastewater discharged after treatment from urban sewage treatment plants. Tailwater replenishment refers to the introduction of urban tailwater into rivers, aiming to provide additional water to these rivers and improve the water quality and water volume of the rivers. It should be noted that although the tailwater has undergone certain treatment, its quality is crucial to the effect of tailwater replenishment of rivers. If the tailwater contains too many pollutants or is not properly treated, the introduction may have a negative impact on the environment. Aquatic animals are an important part of the food web and play an important role in maintaining nutrient cycles and energy flow. Therefore, a comprehensive analysis of the impact of tailwater discharge on river aquatic communities is of great significance for protecting biodiversity and maintaining ecosystem functions.

[0054] It should be noted that this embodiment does not use the entire area of ​​the selected assessment river as the assessment scope, but first defines the assessment scope of the river to select representative sampling points within the entire area of ​​the river to improve the quality of survey data and comprehensive coverage. There are many ways to define the assessment scope. For example, the assessment scope can be defined based on factors such as ecosystem characteristics and pollution source distribution, or the boundaries of the assessment scope can be determined based on the purpose of the research. This embodiment does not limit the method for determining the boundaries of the assessment scope.

[0055] Taking into account that the bottom sediment near the tailwater discharge outlet is greatly affected by scouring and it is difficult to collect samples, in some embodiments of the present application, it is preferably possible to determine the assessment range of the assessed river in the following manner: using the tailwater flow, river water flow and river width, the influence range of the tailwater is calculated through the tailwater impact assessment model; within the influence range of the tailwater, 1 / 10 of the river section length is removed to obtain the assessment range of the assessed river.

[0056] Among them, 1 / 10 of the river section length is calculated from the tailwater outfall upstream of the river. By removing the river section close to the upstream (tailwater outfall), the impact of the tailwater outfall on the sampling results can be reduced, thereby improving the accuracy of the survey data.

[0057] Specifically, the calculation formula of the above tailwater impact assessment model is as follows:

[0058] D = (Q 尾 / Q 河 ) × L,

[0059] Where D is the horizontal impact distance of the tailwater, in meters; Q 尾 is the discharge flow rate of tail water, in m 3 / d;Q 河 is the flow rate of the river, in m 3 / d; L is the river width in meters.

[0060] Through the above steps, the assessment scope of the river can be reasonably defined, so that the sampling can better represent the situation of the entire water body or water area, and then the survey results of various indicators can better reflect the real state of the water body, ensuring the accuracy and reliability of the sampling results. At the same time, the above tailwater impact assessment model is used to calculate the impact range of tailwater on the receiving water body, providing an accurate and measurable survey scope for the evaluation of the ecotoxicity effect of tailwater, making the determination of the assessment scope more operational and certain. In addition, by limiting the assessment scope, the manpower and material costs of on-site investigations and environmental DNA testing can also be reduced.

[0061] Step S102: Divide each evaluation river into a plurality of evaluation river sections according to the determined evaluation scope.

[0062] Since different river sections may have different ecological environments, water quality conditions, pollution sources, biological communities, etc., this embodiment divides the assessment river into multiple assessment sections, and obtains survey data of each river section more accurately through segmented assessment, providing a data basis for subsequent multi-dimensional analysis.

[0063] At the same time, segmented assessment is also conducive to problem location, making it easier to locate ecological risk issues. If an abnormal situation occurs in a river section, targeted investigation and monitoring can be carried out to promptly identify problems and take corresponding governance measures. In addition, segmented assessment can make data management more convenient. Each assessed river section can independently collect, record and manage data to avoid data confusion and facilitate subsequent data analysis and comparison.

[0064] Preferably, in the above step S102, according to the size of the evaluation range, the number of evaluation river sections is 3 or more. By setting 3 or more evaluation river sections, the upper, middle and lower reaches of the river can be fully covered, making the spatial coverage more complete.

[0065] Furthermore, to ensure the accuracy of sampling results in different river sections, the length of the assessed river section was less than or equal to 50 km.

[0066] Step S103: According to the length of each assessment river section, a corresponding number of monitoring points are set in each assessment river section.

[0067] By matching the length of the assessed river section with the number of monitoring points, we can ensure that each monitoring point can cover different parts and characteristics of the river, thereby fully understanding the river's ecological environment, water quality, biological communities, etc.; we can also more accurately capture the changes and characteristics of different areas of the river by distributing monitoring points in a reasonable manner, thus laying the foundation for accurately assessing the eco-toxic effects of tailwater replenishment rivers.

[0068] In some embodiments, according to the length of each assessment river section, a corresponding number of monitoring points are set in each assessment river section, specifically including: if the length of the assessment river section is less than 10 kilometers, only 1 monitoring point is set for the assessment river section; if the length of the assessment river section is within the range of 10~20km, 2 monitoring points are set for the assessment river section; if the length of the assessment river section is within the range of 20~30km, 3 monitoring points are set for the assessment river section; if the length of the assessment river section is within the range of 30~40km, 4 monitoring points are set for the assessment river section; if the length of the assessment river section is within the range of 40~50km, 5 monitoring points are set for the assessment river section; at each monitoring point, a monitoring river section of 100~200m is selected, and the monitoring river section includes a slow flow area, a rapids area and a backwater area.

[0069] In the above embodiment, different numbers of monitoring points are set according to different lengths of river sections. In addition to ensuring comprehensive spatial coverage of the monitoring points, the impact of different water flow characteristics on aquatic organisms is also taken into consideration. A monitoring river section of 100 to 200 meters is selected at each monitoring point. The monitoring river section includes slow-flow areas, rapids areas and backwater areas, so that the survey data is more comprehensive and complete.

[0070] Among them, slow-flowing areas refer to areas in rivers where the water flows slowly. These areas are usually located in the upper reaches of rivers or in areas with gentle terrain, with slow water flow and relatively shallow water depth. Slow-flowing areas have important ecological functions for river ecosystems, providing suitable habitat conditions that are conducive to the growth, reproduction and habitat of many aquatic organisms. In slow-flowing areas, aquatic plants usually grow densely, and there are many species and numbers of fish and invertebrates. Rapid-flowing areas are areas in rivers where the water flows faster. These areas are usually located in the lower reaches of rivers or in areas with steeper terrain, with fast water flow and relatively deep water depth. The water flow in rapid-flowing areas is turbulent, often forming whirlpools and eddies of water flow. The ecological environment in rapid-flowing areas is relatively harsh, and the survival and reproduction of aquatic organisms are subject to certain restrictions. However, some special organisms have adapted to the rapid-flowing environment, such as some benthic organisms and stream fish. Backwater areas are areas where water flow in a river is obstructed or reversed. These areas are usually located in islands, river bays, estuaries and other places in the river. The terrain or other factors hinder the normal flow of water, causing the water to retreat or flow in the reverse direction. The water flow in the backwater area is slower and the water depth is relatively deeper, often leading to stagnation and accumulation of water bodies. The backwater area provides some special ecological environments that are suitable for the growth and habitat of some specific aquatic organisms.

[0071] In another optional embodiment, according to the length of each evaluation river section, a corresponding number of monitoring points are set in each evaluation river section, specifically including: 4 monitoring points are set in each evaluation river section; 200m of each monitoring point is selected as the monitoring river section, and the monitoring river section includes a slow flow area, a rapids area and a backwater area.

[0072] In the above embodiment, the same number of monitoring points are uniformly set in each evaluated river section, and the same length of monitoring river section is set at each monitoring point to ensure the integrity of data investigation, simplify the selection and setting process of sampling monitoring points, and improve sampling efficiency.

[0073] Step S104: Taking benthic animals as evaluation species, conducting on-site surveys at various monitoring points, and combining environmental DNA technology to obtain multiple biological indices of large benthic organisms in different evaluation river sections; the biological indices include large benthic diversity index, large benthic integrity index and large benthic environmental DNA index.

[0074] Among them, benthic animals are highly sensitive to water quality and the health of river ecosystems, and the response of benthic animal communities to environmental changes is usually relatively stable and lasting, which can be used as an indicator for long-term monitoring. By continuously monitoring the dynamic changes of benthic animal communities, potential ecological risks can be identified. Therefore, this embodiment uses benthic animals as evaluation species, combines large benthic animal diversity index, integrity index and environmental DNA indicators, and utilizes multi-river section, multiple, and long-time interval field survey methods, while integrating environmental DNA technology. Through multi-dimensional and multi-indicator comprehensive assessment of the ecological risks of tailwater replenishment rivers, the analysis can accurately and effectively assess the impact of tailwater discharge on river ecology.

[0075] Step S105: Compare and analyze various large benthic biological indices of different assessment river sections. If the number of biological indices that show a downward trend from downstream to upstream among all biological indices exceeds the preset number threshold, and all biological indices show a downward trend over time, it is determined that the tailwater replenishment has an ecotoxic effect on the river channel.

[0076] After obtaining multiple evaluation indicators, during the implementation phase of the evaluation, the changing trends of all biological indices from downstream to upstream are compared as spatial dimension objects, and the changing trends of all biological indices over time are compared as time dimension objects. The analysis results of multiple parameters in the spatiotemporal dimension are combined to determine the eco-toxic effects of tailwater replenishment on the river channel. This multi-dimensional, multi-indicator analysis method can avoid the insensitivity of a single indicator or a single dimension to the ecological effects of tailwater, and improve the accuracy of the evaluation of the eco-toxic effects of tailwater replenishment on rivers.

[0077] Based on the foregoing embodiments, in some embodiments, the large benthic diversity index, the large benthic integrity index and the large benthic environmental DNA index are obtained by the following steps: multiple and long-term field surveys are conducted at each monitoring point to obtain the large benthic diversity index; samples are collected simultaneously, and the samples are processed and analyzed based on environmental DNA technology to obtain the large benthic environmental DNA index; according to preset rules, reference points and damaged points are selected in the target river area to obtain the large benthic integrity index of each evaluated river section.

[0078] Among them, multiple and long-term on-site investigations of each monitoring point may specifically include: the investigation of benthic animals at each monitoring point needs to be conducted 3 or more times, with the interval between each investigation being greater than or equal to 1 month, in order to evaluate the chronic toxic effects of the tail water.

[0079] In other embodiments, multiple and long-term on-site surveys are conducted at each monitoring point, specifically including: the benthic animals at each monitoring point are surveyed 4 times, with the second survey being 1 month apart from the first, the third survey being 2 months apart from the second, and the fourth survey being 1 month apart from the third, to evaluate the chronic toxic effects of the tail water.

[0080] Samples were obtained by conducting on-site surveys of benthic animals at each monitoring point, species identification was performed on each sample, the number of different species present in the samples at each monitoring point was counted, and the large benthic diversity index was calculated based on this.

[0081] It should be noted that the biodiversity index is a comprehensive indicator for measuring the diversity of biological species in an ecosystem. The biodiversity index of this embodiment can be, for example, an indicator reflecting species richness and species uniformity. Among them, the Shannon index comprehensively considers the indicators of species richness and species uniformity. It not only considers the number of species, but also considers the relative abundance between different species. Therefore, as a preferred embodiment, the large benthic diversity index is the Shannon index, and its calculation formula is as follows:

[0082] ,

[0083] In the formula, H is the Shannon index, P i It is a species i The ratio of the number of individuals to the total number of individuals of all species in the community. P i = N i / N , N i For species i The number of individuals, N is the total number of individuals of all species in the community, S is the number of species.

[0084] Furthermore, the large-scale benthic integrity index of each assessed river section can be selected according to preset rules, and reference points and damaged points can be selected in the target river area, and the following Figure 2 Follow the steps shown to get:

[0085] Step S121, selection of reference points: conduct on-site inspections in the study area to identify areas that are less affected by human activities, and select 5 to 10 reference sections within these areas for investigation.

[0086] Step S122, selection of damaged points: determine the areas with more intense human activities through on-site investigation, and select 5-10 damaged sections for investigation.

[0087] Step S123, calculation of integrity index score: BIBIS = (BIBIO / BIBIE)×100, where BIBIS is the score for evaluating the biological integrity index of large benthic invertebrates in rivers; BIBIO is the monitoring value of the biological integrity index of large benthic invertebrates in rivers; BIBIE is the optimal expected value of the biological integrity index of large benthic invertebrates in the water ecological zone where the river, lake or reservoir is located.

[0088] In a preferred embodiment, the macrobenthic environmental DNA indicators include: Observed species index, Simpson index and Chao1 richness index. These environmental DNA indicators can be obtained by synchronously collecting samples and processing and analyzing the samples based on environmental DNA technology, such as Figure 3 As shown, the specific steps include:

[0089] Step S131, sample collection: Determine the river section, monitoring point, and monitoring section to be evaluated according to the previous steps, and then collect 10 L of water (10-50 cm below the water surface) at each sampling point using a sterile bottle and immediately transfer it to a low-temperature incubator below 4°C for eDNA macrobarcode analysis.

[0090] Step S132, DNA extraction, PCR amplification and high-throughput sequencing: The water sample was filtered through a 0.22 μm polycarbonate membrane, and then the DNA was extracted and PCR amplified using the universal primers LCO1490 (5′-GGTCAACAAATCATAAAGATATTGG-3′) and HCO2198 (5′-TAAACTTCAGGGTGACCAAAAAATCA-3′) for large invertebrate benthic animals, followed by high-throughput sequencing.

[0091] Step S133, processing of sequencing data: Sequencing data were processed using QIIME v 1.9.1, with a minimum sequence length of 300 bp and a minimum threshold quality score of 20. Secondly, the maximum mismatch of primer matching was set to 2, and reads with ambiguous characters were discarded. After that, paired end sequences with overlaps >10 bp were merged into a single sequence. Sequences were detected using VSEARCH v 1.9.6, and chimeric sequences were removed. Operational taxonomic units (OTUs) with a similarity of 97% were clustered using the clustering program VSEARCH v 1.9.6. All OTUs were assigned taxonomic categories using the Ribosomal Database Project classifier, and taxonomic categories at the species level were predicted based on the NCBI Nucleotide Sequence Database (NT). The BLACKS pipeline was used to assign taxonomic annotations to each OTU in macroinvertebrates with a similarity cutoff of ≥98%. Non-target taxa were manually removed before subsequent statistical analysis.

[0092] Step S134, environmental DNA technical analysis: Through environmental DNA analysis, the observed species index (Sobs), Simpson index (D), and Chao1 richness index are obtained.

[0093] The ecological risk of the tailwater replenishment river was evaluated by comparing the Shannon index, integrity index, observed species index (Sobs), Simpson index (D) and Chao1 richness index in different river sections from upstream to downstream.

[0094] The following judgment is made based on the results of comparative analysis: if 3 or more indexes in the monitoring points from downstream to upstream (the upstream is the tailwater discharge point) show a gradient decrease, and all indexes show a downward trend with time, it proves that the tailwater replenishment has an eco-toxic effect on the river channel. The greater the degree of decline, the greater the toxic effect, which is used to evaluate the eco-toxic effect of the tailwater discharge from the sewage treatment plant on the receiving water body.

[0095] Example Experiment:

[0096] Different rivers are selected below, and experiments are conducted using different settings, and the experimental data are compared and analyzed to illustrate that the method provided in this embodiment can be applied to the assessment of the ecotoxicity effects of tailwater on different river channels and to obtain accurate assessment results.

[0097] (1) Experiment 1 was conducted on River 1 with the following settings:

[0098] Survey time settings:

[0099] The benthic animal survey was conducted four times, with the second survey being conducted one month apart from the first, the third survey being conducted two months apart from the second, and the fourth survey being conducted one month apart from the third, in order to assess the chronic toxic effects of the tailwater.

[0100] Obtaining diversity index:

[0101] Three monitoring points were set up in each assessed river section;

[0102] At each monitoring point, 100m of the river section was selected as the monitoring section, including the slow flow area, rapids area and backwater area. Then the field investigation was started and the Shannon index was calculated based on the investigation results.

[0103] Obtaining the completeness index:

[0104] In areas less affected by human activities, five reference sections were selected as reference points, and in areas with stronger human activities, five damaged sections were selected as damaged points. On-site investigations were carried out at the reference points and damaged points, and the integrity index was calculated.

[0105] (2) Experiment 2 was conducted on River 2, with the following specific settings:

[0106] Survey time setting: The benthic animal survey was conducted three times, with the second survey separated by 1 month and the third survey separated by 2 months, in order to evaluate the chronic toxic effects of tailwater.

[0107] Obtaining diversity index:

[0108] Four monitoring points were set up in each assessed river section;

[0109] At each monitoring point, 200m of the river section was selected as the monitoring section, including the slow flow area, rapids area and backwater area. Then the field investigation was started and the Shannon index was calculated based on the investigation results.

[0110] Obtaining the completeness index:

[0111] In areas less affected by human activities, 10 reference sections were selected as reference points, and in areas with stronger human activities, 10 damaged sections were selected as damaged points. On-site investigations were carried out at the reference points and damaged points, and the integrity index was calculated.

[0112] The results of the two rivers in Experiment 1 and Experiment 2 in each evaluation section were compared and analyzed, and the results are shown in Table 1 and Table 2:

[0113] Table 1 Monitoring results of Experiment 1

[0114]

[0115] Table 2 Monitoring results of Experiment 2

[0116]

[0117] From the results in Tables 1 and 2, it can be seen that the sensitivity of the biological indexes of the two rivers is different under the influence of tailwater. The integrity index and Chao1 richness index in Experiment 1 are not sensitive to the influence of tailwater, and the Shannon index in Experiment 2 is also not sensitive to the influence of tailwater. The other three indexes in Experiment 1 and the other four indexes in Experiment 2 all show a strong sensitivity, and all show a significant gradient decline from downstream to upstream. Therefore, the ecological effect of tailwater discharge on the receiving water body can be evaluated based on the changes of three or more indices. In addition, according to the results of multiple surveys in Experiments 1 and 2, it can be seen that with the increase of tailwater discharge time, all indices show different degrees of decline, showing the chronic toxicity effect of tailwater on the receiving water body rather than the acute toxicity effect. Therefore, this method is suitable for the evaluation of the ecological toxicity effect of tailwater on different rivers.

[0118] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for evaluating the ecotoxicity effect of tailwater replenishment in a river channel using benthic animals, characterized in that: include: Determine the assessment scope of the river to be assessed; According to the determined assessment scope, each assessment river is divided into multiple assessment river sections; According to the length of each assessed river section, a corresponding number of monitoring points are set in each assessed river section; a monitoring river section of 100-200m is selected at each monitoring point, and the monitoring river section includes a slow flow area, a rapid flow area and a backwater area; Taking benthic animals as the evaluation species, field surveys were conducted at various monitoring points, and multiple biological indices of large benthic organisms in different evaluation sections were obtained by combining environmental DNA technology; the biological indices included large benthic diversity index, large benthic integrity index, and large benthic environmental DNA index; Compare and analyze various bio-indices of large benthic organisms in different assessment sections. If the number of bio-indices showing a decreasing trend from downstream to upstream among all bio-indices exceeds a preset number threshold, and all bio-indices show a decreasing trend over time, it is determined that the tailwater replenishment has an ecotoxic effect on the river channel, and the preset number threshold is more than 3; Determine the scope of the river assessment, including: The tailwater flow, river flow and river width are used to calculate the impact range of the tailwater through the tailwater impact assessment model; Remove 1 / 10 of the river length from the influence range of the tailwater to obtain the assessment range of the assessed river; The 1 / 10 river section length is measured from the tailwater discharge outlet upstream of the river; The calculation formula of the tailwater impact assessment model is as follows: D =(Q 尾 / Q 河 )×L, Where, D is the horizontal impact distance of tailwater, in meters; Q 尾 is the discharge flow of tail water, in m 3 / d;Q 河 is the flow rate of the river, in m 3 / d; L is the river width in meters.

2. The method according to claim 1, characterized in that The number of the assessed river sections is more than 3.

3. The method according to claim 1, characterized in that: The macrobenthic diversity index, macrobenthic integrity index and macrobenthic environmental DNA index were obtained by the following steps: Conduct multiple field surveys at each monitoring site to obtain a macrobenthic diversity index; Collect samples simultaneously, process and analyze the samples based on environmental DNA technology to obtain macrobenthic environmental DNA indicators; According to preset rules, reference points and damaged points were selected within the target river area to obtain the large-scale benthic integrity index for each assessed river section.

4. The method according to claim 3, characterized in that: The macrobenthic diversity index is the Shannon index; The macrobenthic environment DNA indicators include: Observed species index, Simpson index and Chao1 richness index.

5. The method according to claim 1, characterized in that The length of the assessed river section is less than or equal to 50 kilometers.

6. The method according to any one of claims 1 to 5, characterized in that According to the length of each assessed river section, a corresponding number of monitoring points are set in each assessed river section, including: If the length of the assessed river section is less than 10 kilometers, only one monitoring point will be set up for the assessed river section; If the length of the assessed river section is within the range of 10-20 km, two monitoring points shall be set up in the assessed river section; If the length of the assessed river section is within the range of 20-30 km, three monitoring points shall be set up in the assessed river section; If the length of the assessed river section is within the range of 30-40 km, four monitoring points shall be set up in the assessed river section; If the length of the assessed river section is within the range of 40-50 km, 5 monitoring points will be set up in the assessed river section.

7. The method according to any one of claims 1 to 5, characterized in that According to the length of each assessed river section, a corresponding number of monitoring points are set in each assessed river section, including: Four monitoring points were set up in each assessed river section; Each monitoring point selects 200m as the monitoring river section, and the monitoring river section includes a slow flow area, a rapid flow area and a backwater area.

8. The method according to any one of claims 6 or 7, characterized in that: The benthic animal surveys at each monitoring point must be conducted more than three times, with the interval between each survey being greater than or equal to one month, in order to assess the chronic toxic effects of the tailwater.

9. The method according to any one of claims 6 or 7, characterized in that: The benthic animals were surveyed four times at each monitoring point, with one month between the second survey and the first, two months between the third survey and the second, and one month between the fourth survey and the third, in order to evaluate the chronic toxic effects of the tailwater.

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