[Impact of coastal exploitation on the heavy metal contents in the sediment of Bohai Bay].

To explore the trend of the changes in ecological environment caused by reclamation and the situation of heavy metal pollution in Bohai Bay, the contents and spatial distribution of Cd, Pb, Cu and Zn in the surface sediments of Bohai Bay were collected in 2003 and 2011 and studied. The BCR three-stage sequential extraction procedure was applied to investigate the speciation and contents of four heavy metals (Cd, Pb, Cu and Zn) in the surface sediments of Bohai Bay in 2011. The bioavailability of these four heavy metals was also determined preliminarily. Besides, the pollution level and potential ecological risk of these elements were evaluated using the potential ecological risk index and sediment enrichment factors. The results indicated that the contents of Cu, Cd and Pb in the surface sediments of Bohai Bay in 2011 were higher than those in 2003, indicating an increased level of heavy metal pollution. The distribution of Cu, Zn and Cd showed essentially the same pattern, all with higher content in the central area of Bohai Bay. High content of Pb was found in the estuarine, the central and southern area of Bohai Bay. There were significant positive correlations among these four elements. The results indicated that these four elements probably had the same pollution source. Cu, Zn and Cd were mainly found in the residual fractions, whereas Pb was mainly found in the reducible fractions. The bioavailability of these four metals is listed here in descending order: Cd > Pb > Cu > Zn. The comprehensive assessment results showed that Cd was the primary element with high ecological risk while Cu, Zn, Pb were the minor ones with relatively low risk.