洞庭湖表层沉积物重金属生态风险及其变化趋势研究

Heavy Metal Ecological Risk of Surface Sediments in Dongting Lake and Its Tread

尽管针对洞庭湖沉积物中重金属的研究工作较多,但是针对其生态风险及其变化趋势的研究工作比较少见。基于2012年2月和2013年4月对洞庭湖9个具有代表性监测点位的采样分析以及相关监测历史资料的收集,采用Hakanson生态危害指数法,研究了洞庭湖表层沉积物中重金属的生态风险及其变化趋势。结果表明,洞庭湖表层沉积物中Cd、Hg、As、Cu和Pb的含量分别为0.60~20.7 mg·kg-1、0.090~0.640 mg·kg-1、10.4~83.7 mg·kg-1、17.9~70.9 mg·kg-1和16.9~95.8 mg·kg-1,其大小顺序为Pb〉Cu〉As〉Cd〉Hg。洞庭湖表层沉积物中重金属单因子生态风险程度顺序为Cd〉Hg〉As〉Pb〉Cu,Cd和Hg为主要重金属风险污染物,其中Cd为首要污染物;全湖RI值在117.10~589.80之间,平均289.99,在空间分布上,表现为南洞庭湖区〉西洞庭湖区〉东洞庭湖区;根据Hakanson提出的分级标准,南洞庭湖区Cd具有极高的生态风险,全湖生态风险程度为中。初步分析结果表明,30年来,除Hg外,其它重金属生态风险均有一定上升,其中以Cd的上升趋势较明显,全湖重金属生态风险程度由低生态风险上升到中生态风险,提高了一个等级。因此,洞庭湖流域重金属污染治理应以湘江和资水的Cd为重点。

Although there are many studies on heavy metals in Dongting Lake sediments, the information regarding heavy metal ecological risk and its trend is little. This paper discussed the heavy metal ecological risk of surface sediments in Dongting Lake and its trend, based on sampling analysis of 9 representative monitoring sites in Febru- ary 2012 and April 2013 and some historical monitoring data. Hakanson＇s Potential Ecological Risk Index （R/） Method was employed in this paper. The results show that the contents of Cd, Hg, As, Cu and Pb in surface sedi- ments range from 0.60 mg.kg-1 to 20.7 mg. kg-1, 0.090 mg＇kg-1 to 0.640 mg·kg-1, 10.4 mg.kg-1to 83.7 mg-kg-1, 17.9 mg.kg-1 to 70.9 mg· kg-1 and 16.9 mg· kg-1 to 95.8 mg· kg-1, respectively. The descending order is as follows： Pb〉Cu〉As〉Cd〉Hg. The potential ecological risk of heavy metals in surface sediments of Dongting Lake can be arranged as Cd〉Hg〉As〉Pb〉Cu. Cd and Hg are the main heavy metal risk pollutants, and Cd is the primary pollutant： The R/values of the whole lake are between 117.10 and 589.80, with an average value of 289.99. The spa- tial distribution of R/average values has certain characteristics. South Dongting Lake is the highest area, West Dongting Lake is the middle one, and East Dongting Lake is the lowest region. According to the classification standard proposed by Hakanson, the Cd in South Dongting Lake has extremely high ecological risk. The ecological risk level of Dongting Lake is medium. In terms of the preliminary analysis, the ecological risks of other heavy metals have risen, to some extent, in the past 30 years, except Hg. And Cd＇s rising trend is obvious. The heavy metal ecological risk level in Dongting Lake has changed from low risk to medium. Therefore, heavy metal pollution con- trol in Dongting Lake basin should focus on Cd in Xiangjiang River and Zishui River.