Ecological risk assessment of heavy metals in sediment in the upper reach of the Yangtze River.

Heavy metal pollution in China's Yangtze River basin has been of high concern. The concentrations of heavy metals (Cr, Cd, Hg, Cu, Zn, Pb, and As) in the sediment were investigated in the upper reaches of the river, China. Sediment quality guidelines (SQGs), an enrichment factor (EF), an index of geo-accumulation (I geo), and potential ecological risk were used to evaluate the extent of contamination from the heavy metal concentrations in the sediment. Among the seven metals, a noticeable degree of pollution was seen only in the case of Cd and Cd posed a considerable ecological risk at some sample sites. The Pearson correlation analysis was implemented to determine the relationships among the heavy metals, and principal component analysis (PCA) was performed to determine the most common pollution sources. The elements As, Cd, Pb, and Zn were grouped together, and the anthropogenic sources of these heavy metals were closely related. The sites with higher Cd concentrations were mainly confined to the river's reach near industrial areas. Controlling the pollution sources will effectively reduce the pollutant concentrations in the sediment.