Research On Assessment Of Water Sources Safety On Urban Surface Water

With the rapid development of urbanization and industrialization,the shortage of urban surface water is becoming more and more serious.At present,the state and local governments have issued relevant policies and programs,emphasizing the protection of water source safety.The premise of ensuring water source safety is to conduct a comprehensive assessment of water source safety.However,the existing urban surface drinking water source safety assessment system is not perfect,and the way of emphasizing water quality safety is not direct enough.Therefore,according to the characteristics of urban surface drinking water sources,combined with the previous research,this study constructed a safety evaluation system of urban surface drinking water sources covering water quality safety and comprehensive safety of water sources.Water quality safety assessment considers the pollution and potential risk of water quality,which is composed of water quality category,eutrophication,water health risk and water pollution risk.The index weight is determined by the combination of G1 weighting method and entropy weighting method;The eutrophication was evaluated by comprehensive nutrition index method,and the evaluation index was determined according to the main nutritional factors of the water source;The health risk assessment of water quality adopts the health risk model of the United States Environmental Protection Agency,and the carcinogens are hexavalent chromium,cadmium and arsenic;The non carcinogens were evaluated by 8 indexes including lead,mercury,volatile phenol,cyanide and fluoride;The risk of water pollution is evaluated by New Zealand qualitative method according to the investigation of water source.The driving force pressure state impact response model(DPSIR)is used to evaluate the comprehensive safety of water sources,which covers the socio-economic,water quality,water quantity,ecology,management and other factors affecting the safety of urban surface drinking water sources.The G1 weighting method is used for the index weight,and the index evaluation method is used for the evaluation method.Finally,the comprehensive safety index value of urban surface drinking water sources is obtained,And determine its safety status.According to the above model,the safety of drinking water sources in Changsha section of Xiangjiang River is evaluated,and some water quality indexes of Changsha section of Xiangjiang River are predicted by using the water quality monitoring data over the years,and the results are analyzed,so as to construct the water source safety guarantee mechanism.The specific conclusions are as follows:(1)Results of water quality safety assessmentFrom 2015 to 2018,the overall water quality safety level of the drinking water source area in Changsha section of Xiangjiang River was medium safety,and the water quality safety situation showed a good trend year by year.The water quality in the whole year,dry season and wet season meets the class III standard of surface water environmental quality,the total health risk level of water body is low,and the water pollution risk in the downstream drinking water source area is high,so it is necessary to prevent the total phosphorus.(2)Comprehensive safety evaluation results of water sourceCombined with the basic situation of Changsha section of Xiangjiang River and considering the rainfall factor,the comprehensive safety evaluation indexes of 26 urban surface drinking water sources were constructed.The results show that the average safety index of drinking water sources in Changsha section of Xiangjiang River from 2015 to 2018 is 0.787,which is in a relatively safe state.By analyzing the variation characteristics of the safety index values of each system,it shows that the improvement of the comprehensive safety level of the drinking water source areas in Changsha section of Xiangjiang River mainly depends on the treatment and response of human beings to the water source areas and their surrounding environment.Therefore,the optimization of some indexes under each system should be strengthened in Changsha section of Xiangjiang River.(3)Water quality prediction results and safeguard measuresIn the next five years,the content of total phosphorus in the drinking water source of the Changsha section of Xiangjiang River will increase year by year.Combined with the evaluation results of the drinking water source area in Changsha section of Xiangjiang River,the water source safety guarantee work is strengthened from four aspects of policy measures,management measures,system construction and engineering measures,so as to provide theoretical support and decision-making basis for the water source guarantee work of relevant departments.