广东柘林湾养殖海域沉积物中汞的分布、累积及其生态风险

Distribution,Accumulation and Ecological Risk of Mercury in the Sediment of the Mariculture Zone at Zhelin Bay of Guangdong Province

柘林湾是广东省养殖规模最大的海湾之一,为了解养殖海域沉积物中汞的分布、累积及其可能产生的生态风险,于2008年1月在柘林湾海域采集了5个站位的柱状沉积物和3个站位的表层沉积物,对其中的总汞含量进行了测定,并对其含量分布、累积特征进行了分析.结果表明,柘林湾海域表层沉积物中总汞平均含量为0.0645μg·g-1,径流输入是其空间分布特征的主要影响因素;柱状沉积物表层部分总汞含量相对较低,但不同采样区域柱样中总汞含量的垂直分布却有着显著的差异,网箱养殖区主要是由于汞近40年来来源变小导致沉积物表层部分中的总汞含量较底层低,而贝类养殖区则由于沉积后的再迁移作用使汞在氧化还原边界层富集累积;利用潜在生态危害指数法和沉积物质量基准法对此次调查的沉积物中汞的潜在生态风险进行的评价表明,汞虽对底栖生物基本无负面效应,但其潜在生态风险程度达到了中等水平,尤其是养殖区2号站位28～36cm、4号站位20～32cm和48～56cm以及6号站位36～56cm柱样中的汞甚至达到了高的潜在生态风险程度.因此,养殖区次表层沉积物中较高含量的汞应当引起足够重视.

Zhelin Bay is one of the most important mariculture bays with large-scale in Guangdong Province,China.In this study,concentrations,distributions,and accumulation characteristics of mercury from 5 sediment cores and 3 surface sediments were analyzed in Zhelin Bay in January,2008.The results showed that the mean concentration of mercury in surface sediments was 0.0645μg·g-1.The runoff input is the predominant influence in the causation of mercury distribution.The surface layer concentrations of mercury in sediment cores are relatively low,whereas the vertical distribution of mercury are exhibited obvious difference.Owing to the reduction of mercury sources in the last 40 years,the mercury concentrations in surface layer of sediment cores are lower in cage culture area than in the bottom.The subsurface enrichment of mercury in sediments of shellfish culture area is mainly controlled by the redox cycle of iron during early diagenesis near the boundary layer of redox.Based on Hakanson potential ecological risk index techniques and Sediment Quality Criterion（SQC）,the status and ecological risks of mercury pollution in sediments were assessed in this study.It was concluded that the potential ecological risks of mercury have reached a moderate level,though the mercury has few adverse effects on benthos.In the culture area,the concentrations of mercury are even at high potential ecological risks in the sediment profiles of 28～36cm in the 2nd core,20～32cm and 48～56cm in the 4th core,and 36～56cm in the 6th core.We suggested that enough attention should be paid to the higher concentrations of mercury in subsurface sediment of culture area.