广州市农业表层土壤镉和铅多尺度空间结构

基于广州市2005年641个表层农业土壤样点数据,使用地统计学和多尺度嵌套模型,探讨了土壤Cd和Pb在多粒度尺度上的空间结构并进行插值估计。研究发现,随着空间粒度由粗到细,土壤Cd和Pb空间相关性依次减弱,半方差函数对重金属空间变异的代表性依次增强。多尺度嵌套模型插值效果略优于单尺度的普通克里格法,前者插值结果显示:广州农业土壤Cd和Pb含量普遍未超过国家土壤环境质量二级标准,Cd超标区主要位于中心城区的菜地,少量位于从化区、南沙区以及花都区与白云区交界。

Multi-scale Spatial Structure of Cd and Pb in Agricultural Soils in Guangzhou

Using agricultural top soil samples from 641 sites collected in 2005 in Guangzhou and methods of geo-statistics and multi-scale nested model, we characterized the scale effect of spatial structure of heavy metals with Cd and Pb in agricultural soils on three scales and projected their spatial distributions. The results showed that the spatial dependence decreased from coarser to fine grained scales, while the representation of semivariance improved increase with changing scales correspondingly. The spatial interpolation accuracy of Cd and Pb using the multi-scale nested model was in totally higher than that using the ordinary Kriging at a single scale. The multi-scale nested model estimated that the majority of agricultural soils in Guangzhou were uncontaminated compared with the Grade II national standard for heavy metal concentration in agricultural soils, of which 7.64% were polluted by Cd primarily located in vegetable fields near the most densely populated area (i.e. city center) and probably due to traffic activities, chemical fertilizer and sewage irrigation.