Risk Assessment Of Heavy Metals In Sediments Of Drinking Water Source

With the development of social economy, the increasing discharge of pollutants into the environment during production causes more and more serious environmental pollution problems. Human activities severely disrupt the structure of the aquatic ecosystem, of particular is the increasing problem of heavy metal pollution in sediments. Water is the source of human life. The heavy metal pollution in sediments of drinking water source area could lead to a deterioration of the water environment, lower the water quality, and thus directly threaten human health. Therefore, it's of great significance to accurately analyze and evaluate the heavy metal contamination in sediments of drinking water source area, and take effective preventive measures.From the perspectives of current situation and future risks of heavy metal pollution, an evaluation method was established in this study considering 3 aspects:the characteristic analysis, pollution assessment, and risk prediction. The characteristic analysis includes a total characteristic analysis and a parsing of pollution source:to be specific, the total characteristic analysis consists of a characteristic analysis of heavy metals in sediments in space and time, and the parsing of pollution source illustrates the pollution source using the correlation analysis and principal components analysis (PC A). In the method of the pollution assessment, the geo-accumulation index and potential ecological risk index were used respectively to evaluate the pollution of the single metal and the multiple metals considering different values of the environmental background:both parts contributed to assessing the current situation of heavy metal pollution. In the method of the future risk prediction, to identify the types of environmental factors was necessary. The grey forecasting model-GM (1,1) was used in this study to calculate the concentration of environmental factors in the forecast year, the results of which were taken into the RBF neural network model to calculate the concentration of heavy metals in the forecast year. The geo-accumulation index and potential ecological risk index were used to assess the risk of the heavy metal pollution.The Biliuhe reservoir, which is one of the most important water sources in Dalian, is the "source of life" of Dalian. A risk assessment method was used in this study taking the Biliuhe reservoir as an example. To explore the characteristics of the heavy metal pollution in the Biliuhe reservoir, sediment samples were collected from the plentiful water period, common water period, and dry period to analyze the Cr, Cu, Ni, Pb, Zn, As, Cd and Hg in this study. The results showed that the mean values were below the first level of the "Soil Environment Quality Standard" of China (GB 15618-1995). The characteristic analysis showed that the contents of some heavy metals in the middle of the reservoir were higher than others, and there was no significant regularity in the time distribution. The results of the correlation analysis showed that there was a good correlation between some heavy metals, inferring that some gold concentrators and tailings reservoirs in the upstream and the unreasonable use of fertilizers were the pollution sources based on the PCA. The comprehensive assessment results showed that the pollution level in the reservoir was slight, with Hg and Cd the primary elements with higher ecological risks. The forecasting results indicated that the predicted risk values of Hg and Cd were higher than others in the forecasting year, posing some ecological risks.According to the evaluation results of the Biliuhe reservoir, this study put forward some suggestions to the prevention of heavy metals in sediments from the perspectives of internal control methods and exogenous control methods, in order to provide evaluation results of the present and predicted situation and target management measures for administrative departments.