洞庭湖表层沉积物中重金属污染评价与分析

Analysis and Pollution Assessment of Heavy Metals in Surface Sediments of Dongting Lake

为了解综合治理后洞庭湖表层沉积物中重金属的分布及污染程度,2015年12月对洞庭湖沅江市南嘴等31个点位采集0~20 cm沉积物,测定了沉积物中Cu、Pb、Zn、Cr、Cd、As、Hg的含量,基于地积累指数法和潜在生态风险指数法对沉积物中重金属的污染状况进行了分析与评价。结果表明,洞庭湖重金属污染有所改善,但仍比较严重,以Cd最为严重,其次是Pb和As,且三大湖区重金属污染程度顺序为南洞庭湖>东洞庭湖>西洞庭湖;地积累指数法显示洞庭湖表层沉积物中7种重金属元素的污染程度顺序为Cd>Pb>As>Zn>Cu=Cr>Hg;潜在生态风险指数法显示洞庭湖表层沉积物中7种重金属元素的潜在生态风险因子的大小顺序为Cd>Hg>As>Pb>Cu>Zn=Cr。对洞庭湖沉积物中重金属的分布及来源分析发现,湘江、沅江、资江入口为重金属Cd污染最严重的3个点位,Cd主要来源于湘江、资江、沅江;Pb含量最高的点位为东洞庭湖龙口村,达到138.7 mg/kg,为工业企业集中区;Hg含量最高的点位依次为沅水入口、目平湖中与南,Hg的污染分别主要来源于沅水和周边27家污染企业;As含量最高的点位依次为澧水入口、湘江入口、资水入口和大通湖渔场内湖,说明澧水、湘江、资水给洞庭湖带来了As的污染,而大通湖渔场内湖的As来源于附近工农业污染。因此,治理湘江、沅江、资江流域重金属污染是控制洞庭湖Cd、Pb、As和Hg污染的重点途径。研究结果为洞庭湖水资源保护与有效利用、经济可持续发展及合理规划提供了指导作用。

In order to explore the distribution and pollution degree of heavy metals in surface sediments of Dongting Lake,the contents of 7 heavy metals including Cu, Pb, Zn, Cr, Cd, As, Hg in surface sediments（0-20 cm） from 31 sample sites of Dongting Lake at Nanzui Town, Yuanjiang City were investigated during Dec. 2015. The pollution of heavy metals in sedi-ments was evaluated by the methods of geo-accumulation index and potential ecological risk assessment index. The results showed that, heavy metal pollution of Dongting Lake has been improved, but still seriously, and the contents of Cd, Pb and As were much higher than other heavy metals. Moreover, the order of polluting degree of these heavy metals in Dongting Lake was South Dongting Lake East Dongting Lake West Dongting Lake. According to the analysis of geo-accumulation index and potential ecological risk assessment index, the pollution degrees of heavy metals in the surface sediments followed the sequence of CdPbAsZnCu=CrHg, and the potential ecological risk order was Cd HgAsPbCuZn=Cr. In addition, the spatial distribution and sources analysis of those heavy metals indicates that the most seriously polluted sites by Cd were the three lake entrances of Xiangjiang River, Yuanjiang River and Zijiang River, Cd pollutant mainly came from Xi-angjiang River, Yuanjiang River and Zijiang River and other inflow rivers. The highest Pb content point from Longkou Vil-lage of East Dongting Lake, reached 138.7 mg/kg, it is industrial enterprises concentrated area. The contents of Hg from thelake entrance of Yuanjiang River and Muping Lake were at the high level, the main source of Hg pollutant was from Yuanjiang River and surrounding 27 polluting enterprises. The highest concentration sites of As occurred in the lake entrances of Lishui River, Xiangjiang River, Zishui River, and the inside lake fishery of Datong Lake, and As in internal lake of Datong Lake fishing grounds were from the nearby industrial and agricultural pollution. So controlling heavy metal pollution in Xiangjiang River, Yuanjiang River And Zijiang River is the key way to control Cd, Pb, As and Hg pollution in Dongting Lake. The results would provide guidance for the protection and effective use of water resource, economic sustainable development and rational planning of Dongting Lake.