The environment quality of heavy metals in sediments from the central Bohai Sea.

The heavy metals (Cu, Co, Ni, Zn, Cr, Pb, Cd) in surface and core sediments from the central Bohai Sea were analyzed to evaluate the temporal/spatial distribution and pollution status. Cd exhibited gradual increase vertically, while others were stable or declined slightly in core sediments. In surface sediments, metals showed higher values in 'central mud area of the Bohai Sea' and the coastal area of the Bohai Bay. Cd and Pb also had high levels in the northeastern part of Bohai Sea. Both the contamination factors (CFs) and the geo-accumulation index (Igeo) indicated that Cu, Co, Ni, and Cr were not at pollution levels, while Pb, Zn, and Cd indicated moderate contamination. Compared with sediment quality guidelines (SQGs), Cu, Zn, Cr, Pb, and Cd were likely to produce occasional adverse biological effects, while Ni showed possible ecotoxicological risks. The combined levels of the metals have a 21% probability of being toxic.