重庆市璧山区城市人工湿地中重金属的分布特征及污染评价

On Distribution Characteristics and Pollution Evaluation of Heavy Metals in Urban Constructed Wetlands in Bishan District,Chongqing

以重庆市璧山区两个典型的城市人工湿地(观音塘湿地公园、秀湖湿地公园)为研究对象,分析水体、沉积物、优势植物样品中Cd,Cu,Zn,Pb,Cr 5种重金属的质量浓度,对水体和沉积物中的重金属进行了污染评价,并分析了植物对重金属的富集和转移能力.结果表明,两湿地水体中重金属质量浓度从大到小为:Zn,Cr,Pb,Cd,Cu,两湿地均未出现明显重金属污染情况.两湿地沉积物中5种重金属质量分数从大到小为:Zn,Pb,Cu,Cr,Cd,观音塘湿地中Cd为中等生态危害,秀湖湿地中Cd为强生态危害,其他重金属元素均为轻微生态危害,观音塘湿地的综合潜在生态风险指数(RI)为80.74,属于轻微生态危害;秀湖湿地(RI)值为99.96,属于中等生态危害.两湿地中优势植物体内重金属质量分数从大到小为:Zn,Pb,Cu,Cr,Cd,在体内的分布情况从高到低为:根、茎、叶,植物综合转移能力从大到小顺序为:梭鱼草、睡莲、再力花、黄菖蒲,梭鱼草和睡莲具有较强的重金属转移能力,在修复人工湿地沉积物中重金属污染具有较高的潜在价值.

Taking two typical urban constructed wetlands(Guanyintang Wetland Park and Xiuhu Wetland Park)in Bishan District of Chongqing as research objects,the content of Cd,Cu,Zn,Pb and Cr in water,sediment and dominant plant samples were analyzed,respectively.Using the soil background value of Chongqing as the evaluation standard,the ecological risk of heavy metals in sediments was assessed by means of potential ecological hazard index,and the transfer ability of plants to heavy metals was analyzed.The results show that the heavy metal content in the two wetlands is in the decreasing order of Zn,Cd,Cr,Cu,Pb,and there is no pollution in the two wetlands.The content of five heavy metals in the sediments of the two wetlands is in the decreasing order of Zn,Pb,Cr,Cu,Cd.Cd is a moderate ecological hazard in Guanyintang wetland,while it is a strong ecological hazard in Xiuhu wetland.And other heavy metal elements are slight ecological hazard in these two wetlands.The comprehensive potential ecological risk index(RI)of Guanyintang wetland is 80.74.It belongs to slight ecological hazard.The RI of Xiuhu wetland is 99.96,which belongs to moderate ecological hazard.The content of heavy metals in dominant plants in the two wetlands is in the decreasing order of Zn,Pb,Cu,Cr,Cd,and plant comprehensive transfer abilities are in the decreasing order of Pontederia cordata L.,Nymphaea L.,Thalia dealbata Fraser,Iris pseudacorus L.Pontederia cordata L.and Nymphaea L.have strong ability to transfer heavy metals and have high potential value in repairing heavy metal pollution in the sediments of constructed wetlands.