洞庭湖典型水域表层沉积物中重金属空间分布特征及其潜在生态风险评价

基于2007—2012年连续对洞庭湖湘江入湖口至出湖口水域5个采样点——S1(樟树港)、S2(虞公庙)、S3(鹿角)、S4(君山)和S5(洞庭湖出口)表层沉积物中Cd、Hg、As、Cu、Pb、Cr和Zn 7种重金属质量分数分析,对该典型水域表层沉积物中重金属的空间分布特征进行了探讨,并采用潜在生态危害指数法对其生态风险进行评价. 结果表明:表层沉积物中w(Cd)、w(Hg)、w(As)、w(Cu)、w(Pb)、w(Cr)和w(Zn)分别为0.54~79.90、0.046~0.712、15.2~289.0、29.0~217.0、6.0~246.0、65.4~269.0和41.4~632.0 mg/kg,w(Cd)、w(Hg)、w(As)、w(Cu)、w(Pb)和w(Zn)沿程总体呈下降趋势,w(Cr)沿程变化较小；Cd具有很高生态风险,Hg具有中等生态风险,其余污染物具有低生态风险,不同污染物生态风险的大小顺序为Cd＞Hg＞As＞Pb＞Cu＞Cr＞Zn,各采样点的RI(潜在生态危害指数)为115.51~1 000.09,平均值为373.30,研究区域重金属总体具有高生态风险,其中S1采样点具有很高生态风险,不同采样点表层沉积物中重金属生态风险的大小顺序为S1＞S2＞S5＞S4＞S3；除Cr外,Cd、Hg、As、Cu、Pb和Zn主要来源于湘江,Cd和Hg是主要风险污染物,其中Cd为首要污染物,因此湘江重金属污染治理应以Cd为重点. 

Spatial Distribution Characteristics and Potential Ecological Risk Assessment of Heavy Metals in Typical Water Surface Sediments of Dongting Lake

Abstract: The spatial distribution characteristics of heavy metals in surface sediments of Dongting Lake from the lake entrance of Xiangjiang River to the lake exit were discussed. The ecological risk of heavy metals in the typical waters was evaluated by the potential ecological risk index based on the monitoring of seven heavy metal elements (Cd, Hg, As, Cu, Pb, Cr and Zn) in surface sediments of the study area from 2007 to 2012. The results showed that w(Cd),w(Hg),w(As),w(Cu),w(Pb),w(Cr) and w(Zn) in the surface sediments were 0.54-79.90,0.046-0.712,5.2-289.0,9.0-217.0,6.0-246.0,5.4-269.0 and 41.4-632.0 mg/kg, respectively. w(Cd),w(Hg),w(As),w(Cu),w(Pb) and w(Zn) along the study area showed a declining trend generally; the variation of w(Cr) was smaller. Cd had very high ecological risk, Hg had medium ecological risk, and the other pollutants had lower ecological risk. The ecological risk order of heavy metals was Cd>Hg>As>Pb>Cu>Cr>Zn. The RI values of various monitoring sites ranged from 115.51 to 1000.09, with an average of 373.30. The overall study area had high ecological risk, including S1 with very high ecological risk. The ecological risk order of heavy metals in surface sediments of different sites was S1>S2>S5>S4>S3. Except for Cr, the heavy metals mainly came from Xiangjiang River, in which Cd and Hg were the main risk pollutants, including Cd as primary pollutant. Therefore, the heavy metal pollution control of Xiangjiang River should focus on Cd.