百年来东海内陆架沉积物中重金属的累积过程及生态风险变化

ACCUMULATIVE PROCESS AND ECOLOGICAL RISK HISTORY OF SEDIMENTARY HEAVY METALS IN THE INNER SHELF OF THE EAST CHINA SEA OVER THE LAST 100 YEARS

研究了东海内陆架两个沉积岩芯DH33和KP04中重金属的含量,分析了重金属的累积过程及影响因素,并对不同重金属间的相关性进行了比较,最后利用潜在生态危害指数表征了百年来的生态风险变化。结果表明:东海内陆架沉积物中重金属主要来源于长江的入海携带,因地理位置差异,两岩芯重金属含量变化与长江径流量变化响应程度不同,DH33靠近长江口,响应较好,径流量大的年份重金属含量高;KP04远离长江口,响应较差,浙闽沿岸流和台湾暖流均会对KP04有物源供应。重金属V与Cr、Cr与Ni间相关性良好;As、Hg、Cd 3者与其它金属相关性较差,KP04重金属的含量总体大于DH33,与"粒度律"相矛盾,初步推测KP04站位重金属含量的变化受物源供应和沉积速率共同作用的影响,台湾暖流可能是重要的物源供应途径。生态风险评价结果显示,仅岩芯KP04在1990s和1930s处于"中度污染"级别,且主要是由Hg、Cd、As引起。

The re-construction of heavy metals′ record in coastal sediment core can improve the acknowledgement on the history of their usage/emissions in the coastal areas and the related river basins.In recent years,more and more reports have indicated the gradually increased emissions of various heavy metals into the shelf seas in China.However,the emission and accumulation history of multiple heavy metals have been less referred.In the present work,the contents of heavy metals （such as V,Cr,Zn,Ni,Cu,Co,As,Pb,Hg and Cd） from two sedimentary cores of DH33 and KP04 in the inner shelf of the East China Sea have been measured for studying their history records and then evaluating their ecological risks in the past.The Pearson correlations between these heavy metals have been used for evaluating their accumulation process and the influencing factors.Also the ecological risks have been performed by using potential ecological risk index during the last 100 years.Our results showed that the contents of V,Cr,Zn,Ni,Cu,Co,As,Pb,Hg and Cd in DH33 were 66.69＆#177;5.82,48.72＆#177;3.69,56.88＆#177;3.72,26.82＆#177; 1.34,7.80＆#177;0.76,12.65＆#177;0.63,3.99＆#177;0.25,12.77＆#177;0.91,0.042＆#177;0.008 and 0.069＆#177;0.005 mg/kg respectively,while they were 66.58 ＆#177; 1.60,49.37 ＆#177; 3.45,85.62 ＆#177; 6.36,29.90 ＆#177; 1.60,11.71 ＆#177; 0.76,13.45＆#177;1.03,7.67＆#177;1.02,19.04＆#177;1.10,0.044＆#177;0.004 and 0.007＆#177;0.004 mg/kg respectively in KP04.By comparing with the inter-annual runoff variation of the Yangtze River,it was found that the accumulative process was strongly correlated with the annual runoff of the Yangtze River.The contents of these heavy metals except Cd in core KP04,which is farther away from the Yangtze Delta and the coastline,were higher than those in DH33.The results were in conflict with the geological locations and the ＆quot;granularity law＆quot;.This could be attributed to the different accumulation process or controlling factors in the two sea regions.The contents of heavy metals in core DH33 were mainly controlled by the Yangtze River runoff,with higher accumulations in larger runoff years.In core KP04,their accumulations of these heavy metals were controlled by the provenance supply and the sedimentation rate,with Taiwan Warm Current as another important provenance source.Significant correlations between V,Cr and Ni have been observed,suggested their possible origin and accumulation mechanism.The poor correlations of As,Hg and Cd with other metals suggested their different origins and accumulation process in marine settings.The evaluation on the ecological risk showed that there was only ＆quot;moderately polluted＆quot; by Hg,Cd and As in KP04 and it happened in 1990s and 1930s.Comparing with the deltas and coastal areas,the overall ecological risks of heavy metals were at lower levels in the inner shelf.The potential risks of Hg,Cd and As still needed to be concerned because of their bio-accumulations along the food chain.