湘江长沙段沉积物重金属污染特征及其评价

Characteristics and assessment of heavy metal contamination in sediments from Changsha section of the Xiangjiang River, Hunan Province of China

本研究用沉积柱钻探取样法获得湘江长沙段沉积物样品,利用等离子质谱仪(ICP-MS)分析沉积物中9种重金属含量,并利用X射线衍射仪(XRD)分析沉积物的矿物组成.在此基础上,利用地累积指数和潜在生态风险指数等方法,评价沉积物重金属污染程度.结果表明,湘江长沙段沉积物中重金属含量变化较大(CV﹥0.20),分布不均一.其中Mn、Zn、Pb、Cu、Cr、Co、Ni达中等-显著富集程度,而V、Th无明显富集.地累积指数和潜在生态风险评价结果显示,长沙段沉积物中Pb、Zn、Mn、Cu达偏中度至偏重度污染,Cr、Co、Ni、Th为轻污染.重金属存在轻至中等程度的潜在生态风险,其风险程度大小排序为:Pb>Cu>Ni>Co>Zn>Mn>Cr>V.沉积物中Mn、Cu、Zn、Pb、Co、Ni、Cr、V可能与流域中上游矿石冶炼等人为活动带入有关,而Th可能来自流域岩石风化等自然过程.流域重金属污染防治中,应密切关注Mn、Cu、Zn、Pb等重金属引起的污染.

This study investigates the heavy metal contamination in sediments from Changsha section of the Xiangjiang River.Sediment samples were obtained from sedimentary cores collected by drilling into the bed sediments of the river channel,and were analyzed for concentrations of 9 heavy metals using inductively coupled plasma mass spectrometry(ICP-MS)technique and for mineral composition using X-ray diffraction(XRD)mechaine.Based on this,heavy metal contamination was assessed by geoaccumulation index(Igeo)and potential ecological risk index(RI).The results showed that the concentrations of heavy metals vary in larger variation and heterogenously distributed in the sediments(CV>0.20).Among these nine kinds of heavy metals,metals Mn,Zn,Pb,Cu,Cr,Co and Ni were enriched in moderately to significantly high degree,while metals V and Th were not obviously enriched.The results of assessment using the geoaccumulation index and potential ecological risk index suggested that heavy metals Pb,Zn,Mn and Cu had reached higher than moderate degree of contamination,metals Cr,Co,Ni and Th had reached slight degree of contamination.Also,heavy metals in bed sediments from Changsha section of the Xiangjiang River had mild to moderate degrees of potential ecological risk,with order of the ecological risk as:Pb>Cu>Ni>Co>Zn>Mn>Cr>V.The results of principal component analysis and correlation analysis indicated that the enrichment of heavy metals Mn,Cu,Zn,Pb,Co,Ni,Cr and V in bed sediments was associated with anthropogenic inputs mostly from mining and smelting for Pb-Zn ores in upper and moderate river areas of the watershed.While metal Th was mostly contributed from natural processes such as rock weathering.Therefore,the enviromental protection work in Changsha area should pay great attention to the contamination caused by metals Mn,Cu,Zn and Pb in the future.