渤海湾海岸带开发对近岸沉积物重金属的影响

为了解渤海湾围填海造成的生境变化趋势及重金属污染状况,对2003年和2011年渤海湾表层沉积物4种重金属(Cd、Pb、Cu、Zn)的含量及空间分布分别进行了研究,并采用BCR三步分级提取法分析了2011年渤海湾表层沉积物中这4种重金属不同赋存形态的含量,评估了这4种重金属的生物有效性,最后分别采用富集系数法和潜在生态危害指数法对2011年重金属污染程度及潜在生态危害进行了评价.结果表明,2011年渤海湾沉积物中Cu、Cd、Pb的含量均比2003年偏高,重金属污染形势趋于严峻.Cu、Zn、Cd的空间分布趋势基本相似,其高值区均集中在渤海湾的中部海域.Pb的高值区主要集中在近岸河口和渤海湾中部及南部.4种重金属相互之间相关性显著,说明它们之间可能具有一定的同源性.形态分析表明Cu、Zn、Cd主要以残渣态存在,Pb主要以可还原态存在,各元素生物有效性排序为:Cd>Pb>Cu>Zn.Cd为渤海湾表层沉积物中最主要的污染元素,且具有较强的生态危害.Cu、Zn、Pb污染程度较低,生态危害轻微.

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.