西笤溪流域重金属污染磁学研究及多元分析

 对西苕溪流域的土壤样品及部分太湖近岸表层底泥样品,进行了环境磁学测试与化学分析.采用指标聚类分析,抽取磁化率、S比值和Cr、Fe、Pb、Sr、Ti、Zn含量等8个典型指标.再应用模糊C均值聚类分析,分辨出了4种不同的样品类型和两种不同的人类活动响应.取自丘陵山地的第一类样品,以强的磁化率、高的S比值和低的Sr、Ni和Zn含量为特征,代表了流域的自然背景.分布在河谷平原农耕区的第二类样品,磁化率、S比值以及重金属含量都很低,反映了农业活动对环境的影响.而分布在滨湖平原和东苕溪流域的第三类样品,Sr、Ni和Zn含量最高,反映了工业活动对环境的影响.代表丘陵与平原过渡带的第四类样品,其磁参数和重金属含量介于丘陵山地与平原之间.由于流域的磁背景场很高,且人类活动多元化,磁与重金属的相关性差,因此单一的磁化率不能直接指示污染状况.

Magnetic studies on heavy metal pollution and multivariate analysis in West Tiaoxi Basin

Soil samples in the Tiaoxi Catchment, mostly in West Tiaoxi Catchment, as well as some sediments in Taihu Lake, were collected and analyzed with magnetic properties and heavy metal concentrations. Finally,four sample clusters and two anthropogenic impacts were discerned by fuzzy c-means cluster. The first cluster possibly represents the geologic background of hilly area where the concentrations of Ni, Sr and Zn are very weak, but magnetic susceptibility and S ratio are very strong. The second cluster, with weak magnetic susceptibility and heavy metal concentration, reveals the agricultural effect on field of the western basin. In contrast, the third cluster, with high concentration of Ni, Sr and Zn, relatively high magnetic susceptibility and S ratio,shows the industrial impact on the east. Samples of the last cluster, with middle value of all proxies, are the intermediates of hilly area and basin. The correlation between magnetic proxies and heavy metal is not easy to find,because of high background and multiple anthropogenic impacts.