Assessments for Heavy Metals Pollution of Groundwater at Lakeside of the Dongting Lake Based on Identification Index and Sensitivity Analysis

The west embankment of Xiangyin county in the lakeside of Dongting Lake was taken to study the pollution level of heavy metals in the groundwater.The pollution status of various heavy metals in the groundwater was studied with the comprehensive identification index based on entropy weight model system and the sensitivity analysis of the comprehensive evaluation results to each evaluation factor.A comparative study was carried out according to the results from different evaluation methods.According to class Ⅲ level of GBT 14848-1993 Water Environment Quality Standards of Groundwater,the contamination rate of the heavy metals in this area reached 67%,and the worst levels of water quality were class Ⅴ,class Ⅳ and inferior class Ⅴ,respectively.The pollution levels of heavy metals showed a remarkable spatial heterogeneity.The west tributary was the most seriously contaminated(pollution index was 4.126,belonging to class Ⅳ),followed by the Dongting lake district,and the east tributary lightest(pollution index was 3.515).In addition,polluted conditions gradually aggravated from the upstream to the downstream in the two tributaries.Sensitivity analysis suggested that comprehensive evaluation was sensitive to Pb and Mn,and their sensitive coefficients were 0.0539 and 0.0479 respectively.This result indicated that Pb and Mn are the major metal pollutants to influence the groundwater quality of the west embankment.