狮牡河重金属污染及生态风险评价

Pollution and ecological risk assessment of heavy metals in Shimu River

为探明上游硫铁矿停产3年后狮牡河重金属污染状况,于2020年11月河流平水期对河水和底泥进行了一次沿河分布式采样,测定了河水和底泥中Cd、Pb、As、Hg、Cu和Zn等6种重金属的含量,对河水采用单因子污染指数法,对底泥采用地累积污染指数法和潜在生态风险指数法进行了生态风险评价。结果表明,在平水期河水中Cd污染比较严重,污染主要出现在从上游矿区河段到中游河段,其他重金属污染较轻或无污染。底泥重金属除Hg外,其他5种重金属的平均含量都显著高于农用地土壤污染风险管制值(GB 15618-2018)和铜陵土壤背景值,中游河段含量最高。底泥不同重金属地累积污染指数平均值为Cd(3.39)>Zn(2.97)>Pb (2.49)>As(2.00)>Cu(1.93)>Hg(-0.97),其中Cd达到重污染;潜在生态风险系数平均值表明Cd风险极高,As为高风险,Cu和Pb为中风险,Hg和Zn为低风险。河水和底泥重金属含量和分布及风险评价均表明狮牡河重金属污染主要受到矿区影响。

In order to investigate the heavy metal pollution status of Shimu River 3 years after the suspension of mining of a pyrite mine, which is located in the upstream part of the watershed, a distributed sampling protocol was carried out along the river for water and sediment in November 2020. The samples were analyzed for Cd, Pb,As, Hg, Cu, and Zn. The single factor pollution index was calculated to evaluate the river water. The sediments were assessed by the Geo-accumulation index(Igeo) and the potential ecological risk index(RI). The results showed that the pollution of Cd in river water was more serious among the six heavy metals, and the pollution mainly occurred from the upstream branch draining the mine to the middle reaches of the river, while the pollution of other heavy metals was less or no pollution during the normal dry season. In the sediment, the average contents of heavy metals except for Hg were significantly higher than the Risk Intervention Values for Soil Contamination of Agricultural Land(GB 15618-2018) and the soil background value of Tongling. The content of the heavy metals was the highest in the middle reaches. The average values of Igeo of the six heavy metals in the sediment were Cd(3.39)>Zn(2.97)>Pb(2.49)>As(2.00)>Cu(1.93)>Hg(-0.97),which indicated that Cd was at heavy-pollution grade. The average values of RI showed that Cd was at the very-high-risk grade, with As at high-risk, Cu and Pb at medium-risk, and Hg and Zn were at low-risk. The heavy metal content, distribution, and risk assessment of river and sediment showed that the heavy metal pollution mainly came from the mining area.