湘江流域衡阳段沉积物重金属污染特征及风险评价

2015-2019年连续5年采集了衡阳市湘江流域河流沉积物，测定了沉积物中9种重金属含量。采用地累积指数法及潜在生态危害指数法对沉积物中9种重金属的污染特征及生态风险进行了评价。地累积指数法评价结果表明：湘江干流及四条主要支流沉积物普遍存在Cd污染，部分河流As、Hg、Pb、Cu、Zn、Mn有一定程度的污染，V、Cr多为无污染或无污染到中度污染。潜在生态危害指数法评价结果表明：As、Cd、Hg、Cu呈现出中等生态危害至极强生态危害程度，9种重金属总潜在生态危害指数表明舂陵水、耒水、湘江干流均为很强生态危害程度，蒸水、洣水为强生态危害程度。两种评价方法均表明衡阳市湘江流域各河流沉积物重金属以舂陵水污染最为严重，其次为耒水、湘江干流，蒸水、洣水污染相对较轻；舂陵水、耒水、湘江干流3条河流沉积物重金属2017-2019年污染较2015-2016年有所减轻。

Pollution Characteristics and Risk Assessment of Heavy Metals in Sediments from the Hengyang Section of the Xiangjiang River Basin

From 2015 to 2019, nine kinds of heavy metals in the sediments of Xiangjiang River Basin of Hengyang City were measured. The pollution characteristics and ecological risks of 9 heavy metals in sediments were evaluated by the methods of land accumulation index and potential ecological hazard index. The results show that cadmium pollution is common in the main stream and four main tributaries of Xiangjiang River, arsenic, mercury, lead, copper, zinc and manganese pollution to some extent in some rivers, and vanadium and total chromium pollution is mostly non pollution or non pollution to moderate pollution. The evaluation results of potential ecological harm index method show that arsenic, cadmium, mercury and copper present moderate to extremely strong ecological harm degree, the total potential ecological harm index of nine heavy metals shows that Chongling water, Leishui and Xiangjiang River main stream are all of very strong ecological harm degree, and Zhengshui and Mishui are of strong ecological harm degree. The two evaluation methods showed that the heavy metal pollution of Chongling water was the most serious, followed by Leishui and main stream of Xiangjiang River, and the pollution of Zhengshui and Mishui was relatively light; the pollution of Chongling water, Leishui and main stream of Xiangjiang River in 2017-2019 was less than that in 2015-2016.