Pollution characteristics and ecological risk assessment of heavy metals in surface sediments of lakes along the east route of South-to-North Water Diversion Project

Nansi Lake, Luoma Lake, Hongze Lake and Gaoyou Lake along the east route of South-to-North Water Diversion Project were taken as the research objects, the spatial distribution characteristics and ecological risks of seven heavy metals (Cr, Cu, Ni, Zn, Pb, Cd, As) in the surface sediments of the four lakes were analyzed by the multi-index comprehensive evaluation model (TOPSIS method) and the potential ecological risk index method, and were compared and analyzed with other lakes in the five geographic regions of China. The results showed that the concentration of heavy metals in the surface sediments of the four lakes was lower than that of Taihu Lake, Chaohu Lake, Dongting Lake and Poyang Lake in the Eastern Plain Lake Area, but higher than that of the lakes in Mengxin, Qinghai-Tibet, Northeast Mountain and Plain Lake areas, and the distribution of heavy metals in lake sediments in different regions had obvious differences. In addition to geological structural characteristics, human activities such as industrial and agricultural production were the main factors that led to differences in heavy metals in lake sediments. The comprehensive potential ecological risk level of heavy metals in the surface sediments of the four lakes was low, but the individual heavy metal of Cd had moderate to high potential ecological risks. It was recommended to strengthen the supervision of industrial and agricultural production discharge around the lakes along the east route of South-to-North Water Diversion Project, further adjust and optimize the industrial structure along each lake, and strictly control the input of heavy metal pollution, especially the control of heavy metal Cd and other human activities, to ensure the water environment safety of the lakes along the east route of South-to-North Water Diversion Project.