长江三角洲地区土壤重金属污染的空间变异特征——以江苏省太仓市为例

SPATIAL VARIABILITY OF SOIL HEAVY METALS CONTAMINATION IN THE YANGTZE RIVER DELTA——A CASE STUDY OF TAICANG CITY IN JIANGSU PROVINCE

城市化、工业化和农业集约化的发展影响着土壤环境和健康质量。本研究以位于长江三角洲地区的江苏省太仓市为典型区,采用地统计学方法对其耕层土壤中Cd、Cr、Cu、Ni、Hg、Pb、Zn和As等8种重金属结构特征和空间分布格局进行了分析,并用模糊数学法综合评价了土壤重金属的污染程度,结果表明:太仓市表层土壤Zn、Cu属强变异强度,呈对数正态分布;Cd、Ni、Hg、As、Cr和Pb属中等变异强度,呈正态分布。除Cd、Cr和Pb略低于背景值外,其他重金属均高于其背景值,其中以As污染指数和超标率最高。土壤重金属复合污染严重,模糊综合评价污染结果为一级。通过半方差函数模型拟合发现Hg、Cd符合球状模型,其他重金属均符合指数模型,8种重金属元素在一定范围内均存在空间相关性。采用Kriging最优内插法得到了耕层土壤重金属含量的空间分布图,发现土壤重金属含量与母质、土壤质地、有机质含量以及工业化、城市化和农业集约化程度密切相关。

Environment and health of the soil are closely linked with the developments of urbanization, industrialization and agricultural intensivism. In this article, spatial distributions of 8 heavy metals （Cd, Cr, Cu, Ni, Hg, Pb, Zn and As） in the topsoil （0 - 20 cm） in Taicang city, a typical region of the Yangtze River Delta, were analyzed by mean of the geostatistical method, and heavy metal contamination of the soil evaluated comprehensively by means of Fuzzy Mathematical Models. Zn and Cu were distributed lognomally, strong in variability, while Cd, Ni, Hg, As, Cr and Pb distributed nomally, medium in variability. Apart from Cd, Cr and Pb, all the other soil heavy metals exceeded their background levels in concentration, and As ranked first in contamination index and over limit rate. Compound heavy metals contamination of the soil in Taicang was quite severe, and evaluated as Grade One. The results of semivariance analysis showed that Hg and Cd were fit for the spherical model, and the others fitted for exponential model, and the distributions of the 8 heavy metals were correlated in a given spatial range. The Kriging interpolation method was applied to work out heavy metal concentration distribution maps, which indicate that heavy metal concentrations in the soils are closely related to their parent material, soil texture, and organic matter contents and the degree of industrialization, urbanization and agricultural intensivism of a city.