上海市中小型河道沉积物和水生植物中重金属累积特征研究

Study on Accumulation Characteristics of Heavy Metals in Sediments and Aquatic Plants of Small and Medium-sized Rivers in Shanghai

采用野外调查和室内分析相结合的方法,以上海市8个区县25条中小型河道为研究对象,调查研究重金属在沉积物和水生植物中累积特征,采用潜在生态风险指数评价法对沉积物重金属污染进行了评价,采用生物富集系数（BCF）方法评价不同水生植物对重金属的富集特性,对水生植物与沉积物中的重金属含量进行相关性分析。分析表明,与土壤环境质量国家二级标准（GB15618-1995）相比,As、Ni和Zn平均含量是标准的6.7倍、1.5倍和1.4倍,Cd、Pb、Cu、Cr平均含量不超标。参照上海市土壤环境背景值,上海市中小型河道沉积物中7种重金属的潜在生态风险依次为：Cd〉As〉Pb〉Ni〉Cu〉Zn〉Cr,其中Cd、As生态风险严重,7种潜在生态风险Ri平均值为431.43,有强生态风险。植物体内累积最高的重金属为Cu,累积最低的重金属为Cd,沉水植物体内重金属Cd、As、Cr、Pb、Ni、Cu的含量均大于挺水植物,沉水植物苦草和水盾草对多种重金属的富集能力大于1,在重金属复合污染水体修复中具有较大潜力。根据植物体与沉积物中重金属的含量关系,发现黑藻与沉积物中重金属Cu、Ni、Pb的含量显著正相关;水盾草与沉积物中重金属Cu含量显著正相关,芦苇与沉积物中重金属Cr的含量显著正相关,上述3种植物可作为上海市河道重金属污染监测植物的选择对象。

Taking 25 small and medium-sized rivers from 8 districts in Shanghai as research objects,the study explored accumulation characteristics of heavy metals in sediments and aquatic plants by the means of field investigation and laboratory analysis.The potential ecological risk index was used to evaluate the heavy metal pollution in sediments,and bioconcentration factor（BCF） was used to assess the enrichment characteristics of heavy metals in different aquatic plants.A correlation analysis of the content of heavy metals in aquatic plants and sediments was also conducted.The results showed that,the average content of As,Ni and Zn were 6.7,1.5 and 1.4 times higher than that of the national grade II standard for the quality of soil environment（GB15618-1995）,respectively,while that of Cd,Pb,Cu and Cr did not exceed the standard.According to Shanghai soil environmental background value,the potential ecological risks of 7 heavy metals in sediments from small and medium-sized rivers in Shanghai were Cd〉As〉Pb〉Ni〉Cu〉Zn〉Cr.Cd and As had serious ecological risks.The average Ri value of potential ecological risks was 431.43,which showed strong ecological risk.The heavy metal mostly accumulated in plants was Cu,and the least was Cd.For Cd,As,Cr,Pb,Ni,Cu,there was a higher content in submerged plants than in emerged ones.Submerged plants,such as Vallisneria natans and Cabomba caroliniana,could enrich several kinds of heavy metals and the enrichment capacity was greater than 1,which showed great potential in remediation of heavy metal complex polluted water.Based on the relation of heavy metal content in plants and sediments,it was found that there was a significantly positive correlation between Hydrilla verticillata and the contents of Cu,Ni,Pb in sediments.There was a significantly positive correlation between Cabomba caroliniana and Cu content in sediments.There was a significantly positive correlation between Phragmites australis and Cr content in sediments.The above 3 speciess could be chosen as monitoring plants to detect heavy metals in polluted rivers in Shanghai.