洞庭湖区重金属分布特征及潜在生态风险评价

为研究和评价洞庭湖重金属污染现状,选取洞庭湖区及不同入湖水系共24个采样点分别研究表层水及底泥中重金属的浓度水平,采样点的布设覆盖了整个湖区及湖区的入水、出水水系,在空间上保证了监测数据的代表性和完整性。采用地累积指数法和潜在生态风险指数法对底泥中的重金属污染现状进行评价,同时对湖区重金属进行了Pearson相关关系分析,能较全面客观地反映洞庭湖区的重金属污染现状。结果表明:湖区内监测点位Cr,Cd,Pb,Cu,As,Hg的平均值分别为地球化学背景值的2. 0,10,2. 2,2. 3,6. 6倍;洞庭湖底泥中不同种类的重金属Igeo表现为Cd Hg Pb Cu Cr As,湖区内Itot(综合地累积指数)值表现为东洞庭(君山)南洞庭(万子湖)西洞庭(目平湖);各重金属潜在风险程度表现为Cd Hg As Cu Pb Cr,Cd和Hg的生态风险贡献率之和为87. 78%;湖区内的RI值在25. 32～222. 40之间,平均值128. 49,与2013年相比RI值显著降低,处于低生态风险水平。

Distribution characteristics and potential ecological risk assessment of heavy metals in Dongting

For studying and evaluating the status quo of heavy metal pollution in Dongting Lake, we have studied the concentration levels of heavy metal in surface water and sludge respectively with the data selected from 24 sampling points in entire Dongting Lake and the rivers entering and leaving the lake which ensured the representativeness and integrity of the monitoring data in the space. The present pollution status of heavy metal in sludge was evaluated by ground accumulation index method and potential ecological risk index method, and the Pearson correlation analysis of heavy metals in lake area was carried out, which could reflect the pollution status of heavy metal in Dongting Lake region comprehensively and objectively. The results indicated that the average values of Cr, Cd, Pb, Cu, As and Hg at the lake area′s monitoring points were 2.0, 10, 2.2, 2.3 and 6.6 times of geochemical background values respectively. The heavy metal′s Igeo in Dongting Lake′s sediment were characterized by Cd>Hg>Pb>Cu>Cr> As, and the value of Itot (integrated accumulation index) in the lake area was represented as East Dongting Lake (Junshan Lake) >South Dongting Lake (Wanzi Lake) > West Dongting Lake (Muping Lake). The potential risk level of individual heavy metal was Cd>Hg>As>Cu>Pb>Cr, and the total ecological risk contribution rate of Cd and Hg was 87.78%; the RI values in the lake area were between 25.32~ 222.40, with average of 128.49, which was at a low level of ecological risk and significantly reduced compared with 2013.