Distribution, Ecological Risk Assessment, and Source Identification of Heavy Metals in River Sediments from Hai River and Its Tributaries, Tianjin, China

Heavy metal pollution in river sediments is one of the most serious problems in the aquatic environment. In this study, thirty-two surface sediment and overlying water samples were collected to evaluate the nutrient levels and heavy metal contents (Mo, Cu, Zn, Ni, Cd, Pb, and Cr) in the Hai River and its tributaries, which is the largest river flowing into Bohai Bay. The enrichment degree and geoaccumulation value of the studied metals decreased in the same order of Cd > Cu > Pb > Mo > Ni > Zn > Cr, and the mean contents of Cu and Cd were 2.58 and 2.93 times as high as their background values in Tianjin. Cd contributed over 50% of the ecological risk at the thirty-two sites. Moreover, according to the results of multivariate statistical analyses, Cu and Cd were mainly derived from anthropogenic sources, the quality of overlying water except COD influenced the distribution of heavy metals, and Cd had no correlations with the other heavy metals.