京杭大运河江南城镇段表层沉积物重金属富集水平及潜在生态风险评价

ENRICHMENT AND POTENTIAL ECOLOGICAL RISK ASSESSMENT OF HEAVY METALS IN SURFACE SEDIMENT FROM URBAN SECTIONS ALONG THE GRAND CANAL OF CHINA

以京杭大运河9个江南城镇段表层沉积物为研究对象,研究具城镇源特征的重金属(Cu、Pb、Zn、Cd和Cr)在表层沉积物中的富集水平及其潜在生态风险.结果表明,Cu、Pb、Zn和Cd在大运河城镇段表层沉积物中显著富集,分别为所属长江沉积物相应背景值的1.2—6.4、1.8—5.8、2.6—18.7和7.1—22.7倍,Cr与背景值接近,属轻微富集.潜在生态风险评价进一步表明,城镇段大运河表层沉积物重金属(Cu、Pb、Zn、Cd和Cr)含量已达到"强"富集水平,属污染水平,其中Cd的生态风险指数最高.根据国家土壤环境质量标准(GB15618—1995),城镇段大运河表层沉积物的传统农田堆肥可能存在生态风险.表层沉积物重金属富集水平对大运河水环境质量、农业生产和生态环境健康已构成威胁,必要的环境保护和管理措施迫在眉睫,尤其是对Cd污染的修复.

Enrichment levels of urban derived heavy metals（Cu,Pb,Zn,Cd,and Cr） and their potential ecological risks were investigated in surface sediments from 9 urban sections along the Grand Canal.Results indicated that Cu,Cd,Pb,and Zn were heavily enriched in the urban section sediments.Their concentrations were 1.2—6.4（Cu）,1.8—5.8（Pb）,2.6—18.7（Zn） and 7.1—22.7（Cd） times the background values of the surface sediment in the Yangtze River Delta,respectively.The potential ecological risk assessment pointed out that the enrichment levels of selected heavy metals reached the＂highly polluted＂level in the urban surface sediments,and Cd had the greatest potential ecological risk.Following the National Soil Environmental Quality Guidelines（GB15618—1995）,the traditional agricultural use of surface sediments as manure would cause secondary pollution risk by heavy metals.In short,the enrichment of heavy metals in urban sediments resulted in threats to water quality,agricultural production,and ecosystem health in the regions of the Grand Canal.Environmental protection measures and proper management should be taken for the Grand Canal.