渤海湾各形态重金属的地球化学特征及其环境意义

根据2008年对渤海湾的调查,重点研究了渤海湾湾内和湾口柱状沉积物重金属的生物地球化学特征,通过剖析不同形态重金属的特征,结合渤海湾生态环境信息的综合分析,系统探讨了渤海湾沉积物重金属的演变趋势、影响控制因素以及潜在生态风险。结果表明,湾内海河口附近沉积柱重金属含量有几次突变,20～22cm段极小值可对应1939年海河北系的洪水,10～12cm段极小值可对应1963年海河南系的洪水,1963年至今重金属含量有逐渐增加的趋势。不同形态重金属百分含量从大到小为：残渣态〉铁锰氧化物结合态〉碳酸盐结合态〉有机结合态〉可交换态,且重金属在海河口附近都表现出较高的可浸取态百分含量。风险评价结果表明,重金属总量富集因子由大到小为：Pb〉Cd〉Zn〉Cr〉V〉Co〉Cu〉Ni,其中Pb、Cd和Zn的富集因子均大于1,说明其有污染,但渤海湾沉积物总体质量良好,潜在生态风险较低。从重金属形态角度评价,V和Cr无污染,Zn、Co、Cu、Ni和Pb在湾内及湾外均有不同程度的污染,而Pb的污染最为严重。

Geochemical Characteristics of Heavy Metals in Different Fraction and Their Environmental Significance in Bohai Bay Sediment Cores,China

The geochemical characteristics of eight heavy metals（Cd,Co,Cr,Cu,Ni,Pb,V and Zn） in two sediment cores from Bohai bay,North China,were studied.The samples were collected in 2008.A sequential extraction procedure was used to gain their fractionation information.Five operationally defined fractions were obtained by this protocol,i.e.exchangeable（L1）,bound to carbonates（L2）,bound to Fe/Mn-oxides（L3）,bound to organic matter and sulphides（L4）,and residual fraction（R5）.According to sedimentary data and vertical distribution of heavy metal in the core from the relatively nearshore site,there were several breaks which could be corresponding to the following：the lowest concentration level which occurred in 1939 could be ascribed to the flood of Haihe basin;another flood event in 1963 might be the reason for the other concentration decline in the layer of 10~12 cm depth;the contents of heavy metals kept increasing after 1963.The relative metal concentrations in different fractions took on the order of R5L3L2L4L1.The heavy metals in extractable fractions were rich near the estuary of Haihe River.The order of enrichment factors（EFs） for studied heavy metals was PbCdZnCrVCoCuNi.Although the EFs for Pb,Cd and Zn above 1 suggested that they could be polluted by exterior input,but the whole ecological risk of Bohai Bay was low and indicated that the sediment quality was relatively good in general.The ratios of heavy metals in total extractable and residual fractions showed that V and Cr were clean,while Zn,Co,Cu,Ni and Pb were polluted in different levels at different cores,among which Pb was the most polluted one.