The environment quality of surface sediments in relation of heavy metals in Hangzhou Bay

Hangzhou Bay is facing the environmental pressure brought by the economic development of the surrounding areas, but the comprehensive and systematic study of heavy metals in the sediments is still insufficient. In this study, heavy metals (Cu, Pb, Zn, Cr, Ni and V) in 231 surface sediments in Hangzhou Bay were analyzed to evaluate their spatial distribution, contamination status and controlling factors. The contents of metals in sediments had a low level and were not facing serious ecological risk. However, most metals exhibited higher contents in the central and northeastern parts of Hangzhou Bay, while Cr, V and Zn showed elevated contents in the adjacent area of the Qiantang River mouth, where the environmental quality assessment of metals showed low-to-moderate contamination. The heavy metals in the sediments were primarily from natural sources and their distribution was mainly dominated by the grain size of the sediments. However, most metals in the central and northern coastal areas, as well as the Qiantang River mouth were found to have high contents and indicated relatively serious contamination. This study could provide detailed background information for the future study of heavy metal geochemistry in the region, and serve as a basis for the study of modeling the heavy metals environmental behavior in sediments in coastal zones.