克钦湖沉积物重金属时空分布特征及风险评估

Temporal and Spatial Distribution Characteristics and Ecological Risk Assessment of Heavy Metals in Sediments of Kachin Lake

文章为探讨扎龙湿地克钦湖重金属污染是否存在风险,采集了21个表层沉积物样本和1个柱状沉积样本,结合柱状沉积年代数据,对克钦湖沉积物Cr、Cd、As、Zn、Hg和Pb共6种重金属的演化特征进行研究,分析其空间分布特征,依据潜在生态危害指数法进行生态危害评价,并探讨了重金属的污染源及主要影响因素。结果表明:沉积岩芯重金属随年代演化特征显示人类对沉积物中重金属含量的影响随着年代的增加逐渐加强;表层沉积物重金属空间分布具有一定差异性,主要表现为南湖污染重于北湖,湖周整体大于湖中心;重金属主要受有机质影响较大,各元素间相关性表明Cr、Zn与Pb具有同源性,但Pb来源相对广泛;Cd与As的来源相似,Hg与其他重金属来源不同;克钦湖沉积物重金属属于中等-较强生态危害,主要污染因子为Cd与Hg。

In order to make clear whether there exits heavy metal pollution risk in Kachin Lake of Zhalong Wetland,field experiments were conducted which involved the collection of 21 surface sediment samples and one column sediment sample.Furthermore,with the data of the sedimentary cores of Kachin Lake sediments,the evolution features of heavy metals including Cr,Cd,As,Zn,Hg and Pb were studied,and the characteristics of spatial distribution were analyzed;and on the basis of index method of potential ecological hazardousness,the ecological risk assessment was conducted.In addition,the heavy metal pollution sources and the main influence factors were discussed.The evolution of heavy metal in sedimentary cores revealed that the influence of human activities on the content of heavy metal in sediments had been gradually enhanced with the elapse of the time.Distribution of heavy metal in top-layer sediments was spatially different,indicating that water pollution of south part of the Lake was heavier than that of north part,and water pollution in the lake-shore area was more severe than that in lake’s central part;the correlation analysis showed that the existence of heavy metals was correlated to the organic matter in sediments compared with other factors;and the study regarding source of heavy metals showed that Cr,Zn and Pb were correlated and homologous,and the source of Pb was relatively extensive,while that of Cd and As were similar but Hg was exceptionally different.In conclusion,the major environmental pollution factor was Cd and Hg,and the degree of ecological harm caused by heavy metals in the sediments of Kachin Lake,in general,was between mean and strong.