Spatial Risk Assessment and Source Identification of Heavy Metals in Riverine Sediments of Lake Chaohu Basin, China

In recent decades, the rivers in Lake Chaohu Basin have been subjected to intensive anthropogenic disturbance. However, previous studies have mainly focused on Lake Chaohu, and the inflowing and outflowing rivers have not been well examined. To characterize the pollution status of heavy metals in the entire Lake Chaohu Basin, 8 heavy metals (Cu, Zn, Pb, Cr, Cd, As, Hg, and Ni) in riverine surface sediments were measured at 131 sampling sites in 7 subbasins. Spatial patterns and pollution characteristics were evaluated based on the potential ecological risk, geoaccumulation, and pollution load indexes. The results showed that Cr and Hg were the 2 main heavy metal pollutants in the surface sediments, with mean contents exceeding background values by a factor of 4.12 and 2.64, respectively. The Nanfei River (NF), which flows through Hefei city (a metropolis of the capital of Anhui Province), is characterized by large amounts of domestic and industrial waste discharged into the water body due to human activities; this waste caused serious heavy metal pollution, and NF substantially contributed to heavy metal pollution inputs to Lake Chaohu. Several subbasins in the southern part of Lake Chaohu Basin exhibited high concentrations of Cu in surface sediments, mainly from mining and agriculture. This study identified the main contamination areas, revealed the possible sources of each heavy metal, and can serve as a reference for the remediation and management of Lake Chaohu Basin to ensure the water safety of Lake Chaohu.