上海宝山区农用土壤重金属分布与来源分析

Analysis on Heavy Metal Concentrations in Agricultural Soils of Baoshan,Shanghai

以上海宝山区为典型区域,在获取216个农用表层土壤样品重金属实测数据的基础上,运用多元统计和地统计相结合的方法,对上海宝山区农用土壤重金属的含量水平、分布特征和来源进行系统分析.结果表明,上海市宝山区农用土壤重金属Cd、Hg、As、Cr、Pb、Cu、Zn的平均含量值分别为0.195、0.148、7.44、82.5、29.1、33.2、124.5 mg.kg-1,均没有超过国家土壤环境质量二级标准,但Cd、Zn、Cr、Pb、Cu、Hg元素平均含量值超过上海市土壤背景值,其中Cd、Hg、Zn最为显著,分别是对应背景值的1.50、1.48、1.45倍,呈现出明显的累积趋势.相关分析和因子分析结果显示,各元素的来源可分为三类,Zn、Cd、Hg和Pb为一类,Cr和Cu为一类,As单独为一类;前两类元素含量远高于对应元素背景值,来源主要受各种人为活动影响,As元素含量与背景值相当,各样品含量的变异程度最低,来源主要与成土母质有关.空间结构分析表明,As元素以土壤母质、地形等结构性变异为主,其它元素主要受人为活动等随机因子影响;通过对临界值概率等值线的分布分析发现,Cd、Zn、Cr、Cu、Hg来源以点源为主,来源较为集中,Pb来源相对较为分散.

Based on the acquisition of heavy metal data from 216 topsoil samples of the agricultural land in Baoshan District,a typical region of Shanghai City,the content,distribution characteristics and sources of the heavy metals in agricultural soil of Shanghai Baoshan District were analyzed with the methods of combining multivariate statistics and geo-statistical.The results show that the average concentrations of the Cd,Hg,As,Cr,Pb,Cu and Zn in agricultural soil of Baoshan District are 0.195,0.148,7.44,82.5,29.1,33.2 and 124.5 mg·kg^-1,they are lower than the secondary standards of the national soil environment;but the average concentrations of the Cd,Hg,Cr,Pb,Cu and Zn are more than background values of soil in Shanghai.Especially the Cd,Hg,Zn,they are 1.50,1.48,1.45 times higher than the background values,showing a net cumulative trend.The results of correlation analysis and factor analysis show that the sources of these elements can be divided into three categories;the Zn,Cd,Hg and Pb as one class;the Cr and Cu as another class;the As in a separate category.The concentrations of the former two classes are much higher than the background value,implying mainly from various human activities;the content of the As is almost the same as the background value of soil,it has the lowest degree of variation.Spatial structure analysis shows that the distribution of the As is influenced by the soil structural variations,such as soil parent material,topography,and other elements are mainly affected by random factors of human activities.Through the probability distribution of contour lines of the critical value,it can be found that the Cd,Zn,Cr,Cu,Hg come mainly from the point sources of pollution,but the source of Pb is relatively dispersed.