东洞庭湖湿地土壤重金属污染特征及潜在生态风险评价

选择东洞庭湖3个典型洲滩(小西湖、六门闸和麻塘)进行土壤取样,分析其土壤重金属含量,并应用单项污染指数法、内梅罗综合污染指数法以及Hakanson潜在生态危害指数法对土壤中重金属污染特征和潜在生态危害进行了评价。结果表明,东洞庭三个洲滩区域(小西湖、六门闸和麻塘)土壤重金属Cd、Cr、Ni、Pb、Hg、As的含量分别为0.59-2.40 mg/kg,114.52-119.94 mg/kg,53.49-66.59 mg/kg,42.88-83.46 mg/kg,0.09-0.21 mg/kg and 11.65-24.04 mg/kg,麻塘洲滩中的6种土壤重金属指标均高于小西湖和六门闸两个洲滩,其中Cd问题突出,Cd含量是背景值的7倍,是小西湖和六门闸的3.8和4.1倍。单项污染分级评价表明,研究区重金属污染程度依次为CdNiHgAsPbCr,以麻塘最为严重,小西湖次之,六门闸基本不存在污染。潜在生态危害系数和污染分级评价表明,麻塘达到中度生态危害,小西湖和六门闸则为低度生态危害。因此,东洞庭湖洲滩湿地土壤,尤其是与湘江航道相连的地区,土壤重金属污染问题值得高度关注,需采取合理措施进行治理。

Characteristics and potential ecological risk of heavy metals in wetland soils around East Dongting Lake

Soils in three typical bottomlands (Xiaoxihu, Liumenzha and Matang) around East Dongting were sampled and the contents of heavy metals in the soils were analyzed. The characteristics of heavy metal pollution and potential ecological risks were evaluated using the single factor pollution index method, Nemerow composite index method and Hakanson potential ecological risks index method. The results showed that the contents of Cd, Cr, Ni, Pb, Hg, and As in soils from the three bottomlands were 0.59-2.40 mg/kg, 114.52-119.94 mg/kg, 53.49-66.59 mg/kg, 42.88-83.46 mg/kg, 0.09-0.21 mg/kg and 11.65-24.04 mg/kg respectively. And the values of six indexes of heavy metals in the Matang bottomlands were higher than those in the Xiaoxihu and Liumenzha bottomlands. Of the six kinds of heavy metals, Cd pollution was the most severe one, as the content of Cd in Matang was 7 times more than the background value, and 3.8 times and 4.1 times more than the contents of Xiaoxihu and Liumenzha respectively. The single factor pollution index of different heavy metals were as follows, Cd > Ni > Hg > As > Pb > Cr, which also showed that the heaviest polluted bottomlands was in Matang, and then in Xiaoxihu, and the lightest polluted bottomlands was in Liumenzha. The potential ecological risks index of heavy metals and pollution grading evaluation showed that the soils in Liumenzha and Xiaoxihu were at low ecological risk, while the soils in Matang was at moderate ecological risk. Therefore, the heavy metal pollution in the bottomlands around Dongting Lake, especially in the area which connected to Xiangjiang River, should be attracted more and more attention and effective measures should be take to handle the heavy metal pollution in this district.