上海宝山和青浦区表土磁性特征的差异及环境指示意义

分别在上海宝山区和青浦区设置49和36个监测点,对表土磁化率(χl)f和主要重金属污染元素含量进行比较研究。结果表明:宝山表土Cu、Zn、Pb、Cd、Cr、Mn和Ni的平均含量分别为31.2、194.1、140.8、0.55、85.5、805.7和36.5 mg kg-1;青浦区表土平均含量分别为39.7、128.8、38.5、0.36、62.4、567.2和34.7 mg kg-1。宝山表土重金属污染程度普遍高于青浦,尤其是Pb、Cd、Zn含量显著高于青浦。宝山表土χlf显著增强,平均为180.1×10-8 m3 kg-1,且区域分异性较大,变异系数达110.4%;青浦表土χlf平均为32.7×10-8 m3 kg-1,变幅为10.4×10-8~117.5×10-8 m3 kg-1,变异系数为75.5%。宝山表土χlf与Cu、Zn、Pb、Cr、Mn、Ni、Fe含量存在极显著正相关关系(P<0.01);但青浦表土χlf仅与Zn、Mn(P<0.01)、Cu(P<0.05)显著相关。两区表土磁性特征、重金属累积以及两者相关性的差异,与不同的土地利用方式有关。尤其是青浦稻田土壤磁性弱,是该区χlf与重金属含量相关程度较低的重要原因。

Difference in Magnetic Susceptibility of the Topsoils and its Environmental Implication in Baoshan and Qingpu Districts,Shanghai

Magnetic susceptibility(χlf) and heavy metal contents in 49 and 36 topsoil(0-5 cm) samples,spatially distributed in Baoshan and Qingpu Districts,Shanghai,respectively,were studied.Results show that the contents of Cu,Zn,Pb,Cd,Cr,Mn and Ni in the topsoils in Baoshan District are 31.2,194.1,140.8,0.55,85.5,805.7,36.5 mg kg-1,respectively;those in Qingpu District,are 39.7,128.8,38.5,0.36,62.4,567.2 and 34.7 mg kg-1,respectively.The topsoils in Baoshan District are commonly more severely polluted by heavy metals than those in Qingpu District.Especially,Pb,Cd and Zn in the Baoshan topsoils are significantly higher than those in Qingpu.χlf of the topsoils in Baoshan District is significantly enhanced,with a mean of 180.1×10-8 m3 kg-1,moreover,varies greatly from site to site,with CV of 110.4%.In contrast,χlf values of the topsoils in Qingpu District range from 10.4×10-8-117.5× 10-8 m3 kg-1,with a mean of 32.7×10-8 m3 kg-1 and CV of 75.5%.χlf values in Baoshan topsoils are positively significantly correlated with the contents of Cu,Zn,Pb,Cr,Mn,Ni and Fe(P<0.01);those in Qingpu,however,are only significantly with Zn,Mn(P<0.01) and Cu(P<0.05).The differences in magnetic properties and heavy metal contents as well as their correlations between the Baoshan and Qingpu topsoils are attributed to different landuse patterns.Especially,weak χlf values in paddy soil may be responsible for the low-level correlations betweenχlf and heavy metal contents in the Qingpu topsoils.