天津临港滨海湿地公园重金属污染特征及风险评价

为了解天津临港滨海湿地公园重金属的污染特征及环境风险,检测了天津近海海域6种常见重金属Cu、Pb、Zn、Cd、Cr和As在湿地水体和沉积物中的浓度,并采用重金属污染指数法、物种敏感性分布法和地累积指数法与潜在生态风险指数法分别对水体和沉积物中的重金属风险进行评估。结果表明:水体中只检出Cr、Cu、Zn和As,各采样点浓度均值分别为50.93、2.56、38.21和8.67 μg/L,其中Cu、Zn、As浓度在各采样点均未超过GB 3838—2002《地表水环境质量标准》中Ⅳ类水质标准;沉积物中检出Cr、Cu、Zn、As、Cd和Pb,各采样点浓度均值分别为66.28、24.12、91.37、9.83、0.88和20.38 mg/kg,其中Cr、Cu、Zn和Cd不同程度超过我国土壤环境背景值。对水体重金属的风险评价,重金属污染指数法评价结果为低污染,主要污染重金属为Cr;物种敏感性分布法评价结果为中~高生态风险,As为导致高风险的主要重金属元素。对沉积物重金属的风险评价,地累积指数法评价结果表明Cd为中度污染,Cr、Cu、Zn、As和Pb为无污染或轻度污染;潜在生态风险指数法评价结果显示,研究区域为中、高生态风险程度。由于不同评价方法的参照状态、风险受体或保护目标不同,导致评价结果存在明显差异,建议根据风险高的评价结果采取防治措施,从而更严格地保护湿地公园生态系统。

Pollution characteristics and risk assessment of heavy metals in Tianjin Lingang Coastal Wetland Park

To understand the pollution characteristics and environmental risks of heavy metals in Tianjin Lingang Coastal Wetland Park, water and sediments were collected and the concentrations of six common heavy metals in the coastal water of Tianjin including Cu, Pb, Zn, Cd, Cr and As were detected and analyzed. The heavy metal pollution index (HPI) and the species sensitivity distribution (SSD) methods were used to assess the risk of heavy metal pollution in overlying water, the geoaccumulation index (Igeo), and the potential ecological risk index (RI) methods were used to assess the heavy metal pollution risk in sediments. The results showed that only Cr, Cu, Zn, and As were detected in water, and the mean concentration value was 50.93, 2.56, 38.21 and 8.67 μg/L, respectively. The concentrations of Cu, Zn, and As at each sampling site were within Grade Ⅳ water quality standard of Environmental Quality Standards for Surface Water(GB 3838-2002 ). All of the six heavy metals were detected in the sediments, and the mean concentration value was 66.28, 24.12, 91.37, 9.83, 0.88 and 20.38 mg/kg, respectively. The concentration of Cr, Cu, Zn and Cd exceeded the standard values of soil environmental background concentration in China in different levels. For the risk assessment of heavy metals in water, the assessment result of HPI indicated a low pollution level, and the main polluting element was Cr; the risk assessment using SSD evaluation showed a medium-high risk level and the main polluting element was As causing high risk. For sediments, the risk assessment using Igeo showed that Cd was in medium-polluting level, but Cr, Cu, Zn, As and Pb were in non or light polluting level; the risk assessment using RI showed that the ecological risk ranged from medium to high level. The risk results of different methods were different clearly due to the difference of reference state, risk acceptor or protected object. In order to protect the ecological system more strictly and effectively, the results of high risks should be accepted to take pollution prevention measures.