江苏盐城大丰滨海湿地表层沉积物重金属空间分布特征及潜在生态风险评价

REGIONAL DISTRIBUTION OF HEAVY METALS IN SURFACE SEDIMENTS OF DAFENG COASTAL WETLANDS IN YANCHENG,JIANGSU AND ITS ECOLOGICAL IMPLICATIONS

对江苏盐城大丰滨海湿地表层沉积物重金属含量变化区域分布特征进行了分析,结果表明,江苏盐城大丰表层沉积物Hg、Cd、As、Cu、Pb、Cr和Zn的均值分别为0.05、0.25、7.21、25.5、20.3、67.79和68.09mg/kg,滩涂湿地均值高于人工湿地,滩涂湿地大丰港一期码头附近的JST-02的各项重金属含量最高,呈明显的点源污染的特征。重金属区域分布与粒度正相关,黏土含量对重金属的富集和分布起到一定控制作用。单因子污染指数结果表明,研究区表层沉积物7种重金属元素的单因子污染指数均值由大到小依次为Cd>Cr>Cu>Zn>Pb>As>Hg,其中Cd的均值最大为1.57,为研究区主要污染元素;综合潜在生态风险指数变化范围为15.7~184.91,均值为27.41,滩涂湿地潜在生态风险高于人工湿地;潜在生态风险参数由大到小顺序为Hg>Cd>As>Cu>Pb>Cr>Zn。Hg和Cd为主要潜在生态风险因子。整个区域具有较低的潜在生态风险,尚未达到环境污染程度,但局部区域单个污染物浓度较高。

The regional distribution patterns of seven heavy metals in the surface sediments of the Dafeng coastal wetlands in Yancheng,Jiangsu Province are carefully studied by the authors in this paper.The results show that the mean values of Hg,Cd,As,Cu,Pb,Cr and Zn in the surface sediments are 0.05,0.25,7.21,25.5,20.3,67.79 and 68.09 mg/kg respectively,and the mean values in tidal flat wetlands are obviously higher than those in man-made wetlands.The site JST-02 of the tidal flat wetland near the first-phase of Dafeng Port has the highest content of heavy metals,showing apollution pattern by a single point source.The regional distribution of heavy metals is positively correlated with particle size,suggesting that the clay content plays a critical role on the enrichment and distribution of heavy metals.The average values of single factor pollution indices show an ordered pattern from high to low in the surface sediments of the study area as CdCrCuZnPbAsHg,and the maximum value of Cd,the main pollution element of the study area is as high as 1.57.The comprehensive potential ecological risk index varies between 15.70 and 184.91,with a mean of 27.41,in an order of HgCdasCuPbCrZn,which is higher than that of man-made wetland.Hg and Cd are the main potential ecological risk factors.Our data further suggests that though the whole region has lower potential ecological risk indices and remains under the level of environmental pollution,the concentration of single pollutant may be too high already in some local areas.