杭州湾及邻近海域表层沉积物重金属的分布、来源及评价

根据1996—2012年期间杭州湾及其邻近海域春季调查资料,研究了表层沉积物中Cu、Pb、Zn、Cd、Hg、As 6种重金属含量的时空分布特征,探讨了其影响机理,并对其来源及潜在生态风险进行了分析.结果表明:杭州湾及其邻近海域表层沉积物中Cu、Pb、Zn、Cd、As 5种重金属主体上呈现出以南汇嘴附近海域为高值区,向东北部和西南部海域逐渐递减的趋势;Hg在长江口南支入海口和杭州湾口北岸未呈现出明显的高值区,在舟山东南海域出现了明显的高值区.历史变化趋势表明,自1996年以来,杭州湾及其邻近海域表层沉积物中Pb含量总体呈上升趋势;Cu、Zn、As含量在2001—2009年期间均表现出了上升趋势,2009年以来总体呈下降趋势;Cd、Hg含量有一定波动但总体保持稳定.基于历史数据统计法确定的Cu、Pb、Zn、Cd、Hg、As的环境背景值分别为20.6、21.0、80.5、0.102、0.039、9.99 mg·kg~(-1).各金属元素两两之间基本呈显著正相关(p0.05或p0.01),来源具有相似性.主成分分析表明,陆源碎屑颗粒的输送对研究区域表层沉积物中重金属的组成和分布具有决定性的意义,同时,重金属在不同介质间转换机制及海水养殖污染对沉积物重金属来源也有一定贡献.表层沉积物总体潜在风险为中等,Hg和Cd是主要生态风险贡献因子,其中,Hg的潜在生态风险程度为强.RI相对高值区分布在舟山东南海域、长江南支入海口及杭州湾口北岸.

Distribution,sources and assessment of heavy metals in surface sediments of the Hangzhou Bay and its adjacent areas

The spatial and temporal distribution characteristics and mechanisms,as well as the sources and potential ecological risks of heavy metals (Cu,Zn,Pb,Cd,Hg,and As) in surface sediments were analyzed based on the data obtained from Hangzhou Bay and its adjacent waters in spring from 1996 to 2012.The results show that:1Cu,Pb,Zn,Cd,and As presented similar overall spatial distribution patterns though differed in smaller scales,with concentrations peaked around Nanhuizui waters and decreased along north-east and south-west directions,while Hg concentrated in southeast waters of Zhoushan,instead of the southern branch of Yangtze River Estuary or northern Hangzhou Bay waters.2 The temporal variation of heavy metals displays different patterns,i.e.,Pb concentration kept rising on the whole scale,and overall concentrations of Cu,Zn,and As increased during 2001-2009 and then decreased since 2009,whereas Cd and Hg remained relatively stable with slight fluctuations during the studied period.3The environmental background values were 20.6,21.0,80.5,0.102,0.039,and 9.99 mg·kg^-1 for Cu,Pb,Zn,Cd,Hg,and As concentrations,respectively,which were assumed based on mathematical statistics methods according to the historical records.4The heavy metal elements were significantly correlated (p < 0.05 or even 0.01),suggesting possibly similar sources.And transport of terrigenous clastic particles was a decisive determinant of composition and distribution,while transition mechanisms of heavy metals in different substrates and pollution of marine aquaculture were also important contributors to the sources of heavy metals in this area,based on the principal components analysis.5The overall potential ecological risk level was moderate,with Hg and Cd being the prominent proportions of which Hg showed the level of potential risk as strong.The relatively high values of potential ecological risk index were determined in the surface sediments of Zhoushan southeast waters,southern branch of Yangtze River Estuary,and northern waters of Hangzhou Bay.