Comprehensive Evaluation Of Water Environment Status And Analysis Of Water Pollution Sources Based On Fuzzy Theory

As the process of urbanization continues to accelerate,the problem of water pollution in China is becoming more and more significant,and the current situation of the water environment is not optimistic.The Liao River Basin is relatively densely populated,with a high level of economic development.Thus,various pollution problems in the basin have existed for a long time,and now Liao River Basin has become one of the most seriously polluted rivers in China.The Liao River Basin is located on the axis of Liaoning Province,running through the central area of Liaoning Province,and the water pollution in the region is also not optimistic.At present,comprehensive water quality assessment and human health risk assessment of heavy metals based on measured data from monitoring sections are widely used in the study of water pollution in river basins,and have obtained good evaluation results,with popularization and application in major river basins.In order to improve the water environment quality of the Liao River basin in Liaoning Province,this study comprehensively evaluated the water environment quality of the two major river systems,assessed the human health risks caused by heavy metals discharge,and analyzed the sources of pollutants in study rivers.In this study,we selected 22 water quality sampling sections in the Liao River Basin in2019（including two types of rivers:surface rivers and rivers entering the sea）to monthly monitor regular water quality indicators(DO,BOD₅,COD_Cr,COD_Mn,NH₃-N,and TP)and heavy metal pollution indicators（Cu,Zn,Pb,Cd and Cr）,and a total of 227 samples were obtained.Based on the fuzzy mathematics theory,the comprehensive index Z_k was applied to further calculate the results of the traditional fuzzy evaluation method,taking an objective and reasonable assessment of the water quality of each monitoring section in study area.At the same time,based on the monitoring data of heavy metal pollutants,first the heavy metal pollution index（HPI）method was used to evaluate the of heavy metal pollution status,then the US Environmental Protection Agency（US EPA）health risk assessment method was applied to calculate the non-carcinogenic（Rn）and carcinogenic（Rc）health risks of adults and children caused by drinking water respectively,and the evaluation levels of different metals in different rivers and heavy metals were determined to make sure the magnitude of human health risks caused by heavy metals.In addition,with 11 indicators,correlation analysis and spatial cluster analysis of monitoring sections were carried out.Then based on multivariate statistical method,we did research on the identification and analysis of pollution sources of different water systems and rivers.Finally,based on the results of the evaluation,opinions and appropriate measures are proposed on the overall management of the quality of water environment in Liao River Basin.The main conclusions are as follows:（1）The overall water quality of the Huntai River system in the study area in 2019 was better than that of the Liao River system,and the upstream water quality was better than downstream.Specifically,the main stream of the Liao River was generally at a good level.The proportion of sections in the comprehensive evaluation of water quality at grades I-III was71.4%,and 80%sections of the three major rivers in the Huntai River System were at grades I-III,showing the overall water quality was in excellent and good condition.The five monitoring sections of Zhaoquan River,Shuguang Bridge,Yujiafang,Yutai and Puheyan in the study area were seriously polluted,and their water quality was not optimistic.At the same time,the evaluation result of Liaohe Park at the sampling section of rivers entering the sea was at grade III,and Zhaoquan river was at grade IV.The comprehensive water quality index（Z_k）made the evaluation results further refined,which showed that the water quality of the Juliu River Bridge in the Liao River System was the best（Z_k=2.350）,and the Shuguang Bridge was the worst（Z_k=3.521）.In the Huntai River System,the Dahuofang Reservoir was the best（Z_k=1.116）,and Yujiafang section was the worst（Z_k=3.911）.（2）The HPI index of the 22 water quality monitoring sections was far less than 10,indicating that in the study area,heavy metal pollution was lower than the standard limit of national level III which means acceptable.The results of the health risk assessment of heavy metal showed that the overall non-carcinogenic and carcinogenic health risks of children were significantly higher than adults,and the health risks of heavy metals in the Liao River system were lower than those in the Huntai River system.For different types of heavy metals,the carcinogenic risk of Cr was much higher than that of Cd,and none of non-carcinogenic heavy metals exceeded the maximum recommended by the US EPA.Simultaneously,Cd in the Hunhe River and Cr in the Daliao River had significantly higher human health risks than other rivers,and the evaluation results of the Xiaojiemiao and Puheyan sections of the Taizi River and the Sancha River sections of the Daliao River were significantly higher than other sections.（3）The result of spatial cluster analysis was that when Squared Euclidean Distance（SED）was 5,the 7 stations of the Liao River System were clustered into 3 groups,and the 15 stations of the Huntai River System were clustered into 4 groups.Combined with factor analysis method,and based on the results of spatial clustering,further analysis of water pollutants and their sources were studied.The results showed that the main pollution sources of the Liao River system were domestic,industrial and agricultural pollution,while domestic pollution and industrial were the main pollution sources of the Huntai River system.For the source analysis of heavy metals,industry,traffic and domestic garbage dump constituted the main sources in the Liao River system,and the Huntai River system were mainly from industrial actions and traffic.Corresponding opinions and suggestions for the overall management of the water environment in the Liao River Basin were proposed.Comprehensive treatment measures for the environment quality of water in the Liao River Basin include engineering works,management and supporting measures.The comprehensive prevention and control of water pollution in the Liao River Basin include prevention and control measures on industrial pollution,agricultural pollution,and heavy metal pollution.The above conclusions and suggestions can provide practical suggestions for further implementation of the comprehensive management of the Liao River Basin,and can also provide relevant references for river basin governance in China.