[Pollution Characteristics and Potential Risks of Heavy Metals in Reservoir Basin Sediments of the Hilly Areas in the...

The upper Yangtze River is an important water conservation area， and its hilly terrain is prone to soil erosion， which causes pollutants such as heavy metals to migrate into the water and then accumulate in the reservoir sediments. It may pose a potential threat to drinking water safety and water ecological health. In this study， the Quanmin Reservoir Basin of Sichuan Province located in the upper reaches of the Yangtze River was selected， and the basic sediment physicochemical properties as well as the spatial distributions and occurrence characteristics of heavy metals （including Cr， Mn， Ni， Cu， Zn， Cd， and Pb） in the main inflowing rivers and reservoir areas were investigated. The sources， correlations with environmental factors， and potential risks of heavy metals were analyzed using multivariate statistical methods. The results showed that： ① The average content of each heavy metal in sediments was higher in the downstream reservoir than that in the upstream rivers. Both in the river and the reservoir sediments， Mn and Cd mainly existed in the acid-soluble state in both the river and the reservoir， while the other five heavy metals mainly existed in the residual state. ② Combined with the results of the correlation analysis， principal component analysis， and the positive matrix factorization， the natural sources of Cr， Ni， Cu， Zn， Cd， and Pb contrabuted more than 60%， while the agricultural sources of Mn contrabuted more than 70%. ③ Organic matter， nitrogen， phosphorus， and redox potential in the sediments significantly affected the distribution and occurrence fractions of the studied heavy metals. ④ The pollution degrees and comprehensive potential ecological risks of heavy metals in the sediments were at the low level， but the average risk coding indexes of Mn and Cd reached 56.0% and 51.2%， respectively. Considering the different sources and the higher release potential of Mn when compared with those of the other metals， further attention should be paid to the potential impacts of Mn on the water environment and aquatic ecosystem.