长江安徽段江心洲土壤重金属的分布特征及来源分析

在长江安徽段15个面积较大的江心洲采集表层(0~20 cm)和深层(150~180 cm)土壤样品,研究其重金属元素含量的分布特征和来源.表层土壤中Cd、Hg、Pb、Cu和Zn等元素平均含量分别是深层的2.33、1.67、1.35、1.48和1.43倍.以长江沉积物背景值作为基线值进行的地累积指数评价结果表明,土壤重金属富集程度依次为CdHgCuZnAsPb.不同江心洲之间以及同一江心洲内部土壤重金属含量的差异,主要与江心洲的成因及其发育演变过程有关,近期淤长的部分,土壤重金属元素含量通常比较高.因子分析结果表明,研究区土壤重金属的富集主要与细颗粒物质的粒径效应、含钙矿物对Cd等元素的固定,以及受燃煤影响的大气沉降输入有关.利用因子得分-多元回归法量化了不同来源重金属的贡献,土壤粒度端元对研究区土壤Ni、Cu、Pb、Zn、As、Cd的贡献率均超过70%.

Spatial distribution and source identification of heavy metals in soils on the alluvial islands in the Anhui section of Yangtze River

Soil samples were collected from both topsoils (0~20 cm) and subsoils (150~180 cm) from fifteen large alluvial islands in the Anhui section of Yangtze River. Spatial distribution and source identification were performed for heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn). Results of the study showed that the average contents of Cd, Hg, Pb, Cu and Zn in topsoils were 2.33, 1.67, 1.35, 1.48 and 1.43 times that in subsoils, respectively. Taking the background values of the Yangtze River sediments as baseline levels, the geo-accumulation indexes of these heavy metals were found in the order of Cd>Hg>Cu>Zn>As>Pb. The inter-and intra-island disparities of these elements were mainly associated with the formation and evolution processes of the islands. The concentrations of heavy metals in topsoils were normally high in newly formed parts of the islands. The results of factor analysis showed that three major factors, including grain size effect, fixation by calcic minerals and atmospheric deposition from coal combustion, were responsible for the enrichment of heavy metals in the study area. The contributions of various sources of heavy metals were quantified with the method of Principal Component Scores & Multipal Linear Regressions (PCS-MLR) analysis. Grain size effect was the dominant factor controlling heavy metals in study area, contributing more than 70% for Ni, Cu, Pb, Zn, As and Cd in topsoils.