扎龙湿地沉积物重金属空间分布特征及其潜在生态风险评价

采用电感耦合等离子体质谱仪法(ICP-MS)测定了扎龙湿地表层沉积物重金属的含量,分析了其空间分布特征,评价了其潜在生态风险,并在此基础上探讨了重金属污染来源及环境影响因子.结果表明:①扎龙湿地沉积物Hg、Cd、As、Cu、Pb、Zn和Cr的平均值分别0.065、0.155、10.26、18.20、21.35、52.08和46.47 mg.kg-1,均超过松嫩平原土壤背景值,含量分布存在明显的差异性.从空间分布上看,重金属含量北部高于南部,东部高于西部,核心区含量低,其中东部重金属含量最高,尤其是Hg和Cd分别为整个区域最小值的20.8、32.4倍,存在明显的累积性.②潜在生态风险评价结果显示:单个重金属潜在生态风险顺序为Hg>Cd>As>Pb>Cu>Cr>Zn;整个研究区综合潜在生态风险指数(RI)介于76.9～473.5,平均值171.9,属于中等生态危害,并以东部潜在危害程度最大,将作为今后重金属污染防治的重点区域.③除Hg和Pb之外,各重金属含量间呈极显著正相关,表明这些元素污染具有同源性.④有机质是扎龙湿地表层沉积物中重金属的主要环境影响因子,但目前扎龙湿地盐碱化加剧,沉积物中重金属释放风险加大,应该引起当地政府及有关部门的高度重视.

Distribution and Potential Ecological Risk Assessment of Heavy Metals in Sediments of Zhalong Wetland

This study investigated the concentrations of heavy metals in the sediments of the Zhalong Wetland using ICP-MS, analyzed their spatial distributions, evaluated the potential ecological risk, and explored the pollution sources and environmental influencing factors. The results can be summarized as the followings: 1The concentrations of Hg, Cd, As, Cu, Pb, Zn and Cr were 0.065, 0.155, 10.26, 18.20, 21.35, 52.08 and 46.47 mg·kg^-1, respectively, which were all above the soil background values of the Songnen Plain. Their spatial distributions were distinctly different. The concentration of heavy metals in the north was higher than that in the south, and the east was higher than the west. Particularly in the eastern region, the concentrations of Hg and Cd were 20.8 and 32.4 times the minimum values of the whole area. And in the core zone, the concentration was relatively low. 2The sequence of the potential ecological risk posed by the metals was Hg>Cd>As>Pb>Cu>Cr>Zn. The average potential ecological risk index (RI) of the Zhalong Wetland was 171.9 (ranged from 76.9-473.5), suggesting a moderate ecological risk. However, the potential ecological risk was extremely high in the east which should be treated as the major heavy metal pollution prevention site in the future. 3Except for Hg and Pb, the concentrations of all heavy metals were significantly correlated to each other, indicating that those heavy metals had homology. 4Organic matter was the major environmental influencing factor. However, the trend of land salinization in the Zhalong Wetland has been intensified, indicating a higher risk of heavy metal releasing from the sediments, to which the local authorities should pay enough attention.