巢湖沉积物重金属污染生态风险评价及来源解析

为掌握巢湖沉积物中重金属污染现状并定量解析其来源,采用定点采样的方法获得了巢湖沉积物2015～2017年Cu、Zn、Pb、Ni、Cr、Cd、As、Hg等重金属数据,使用反距离加权插值法和风险评价编码法研究了上述重金属的空间分布特征及潜在生态风险,并应用PMF模型解析了其重金属来源,结果表明:巢湖沉积物中As三年含量均值超过了GB15618中规定的碱性水田土壤风险筛选值,而Zn生物可利用形态占比高,生态潜在风险大;巢湖沉积物中各类金属的空间分布与周边交通线位置相契合,主要表现出东西高中部低的状态,巢湖沉积物中总重金属主要来自交通源(43%)、自然源(27%)、农业源(18%)、工业源(12%),交通源贡献最大、自然源占比高于农业源和工业源,表明当前巢湖正处于城市化初始阶段,其重金属污染水平较低。但随着城市化规模的扩大及程度的加深,巢湖沉积物中重金属污染存在逐年加剧的风险。

Ecological Risk Assessment and Source Analysis of Heavy Metal Pollutions in Sediments of the Chaohu Lake

In order to elucidate the status of heavy metal pollution and quantitatively apportion sources of heavy metals in sediments of the Chaohu Lake, contents of Cu, Zn, Pb, Ni, Cr, Cd, As and Hg in sediments, which were obtained by the fixed-point sampling method from the Chaohu Lake during the period of 2015 to 2017, were analyzed. The spatial distributions and the potential ecological risks of these heavy metals were studied by Inverse Distance Weighted (IDW) and Risk Assessment Coding (RAC) methods, and the sources of heavy metals were analyzed by the Positive Matrix Factorization (PMF) model. The results showed that the average value of As in sediments of the Chaohu Lake was higher than the soil risk screening value of the alkaline paddy field specified in GB15618, Zn had a higher potential risk due to its high bioavailable form. The spatial distributions of all studied metals in sediments of the Chaohu Lake were consistent with distances of their sampling locations to the surrounding traffic lines, specifically, contents of metals were high in the east and the west regions and low in the middle of the Chaohu Lake. According to PMF results, heavy metals in sediments of the Chaohu Lake mainly came from 4 sources, that is, traffic sources (43%), natural sources (27%), agricultural sources (18%), and industrial sources (12%). The traffic source contributed the most, and the contribution of natural sources was higher than that of agricultural and industrial sources, indicating that, currently, the Chaohu Lake was in the initial stage of urbanization and its heavy metal pollution level was relatively low. However, with the expansion and the degree of the urbanization increasing, the risk of heavy metals in sediments of the Chaohu Lake will be increasing.