The environment quality of metals in surface sediments 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 was 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 and pollution status and their controlling factors. The contents of metals in sediments had a low level and were not facing serious ecological risk on the whole. However, most metals exhibited higher concentrations in the central and northeastern parts of Hangzhou Bay, while Zn and Cr showed elevated contents in the adjacent area of the Qiantang River mouth, where the environmental quality assessment of metals showed low-to-moderate pollution, which was worthy of attention. 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, Pb in the northern coastal areas and Cr and Zn in the Qiantang River mouth were found to have high contents and indicated relatively serious pollution potentially caused by human activities. This study is of great scientific significance for understanding the accumulation and source-sink process of heavy metals in the sediments of the Bay of intense human activities.