非平稳型区域土壤汞含量的各种估值方法比较

准确地描述土壤重金属含量的空间分布对于防治土壤重金属污染是十分重要的.以分布类型为对数正态分布,同时具有一阶和二阶趋势效应的土壤重金属Hg为例,分别应用普通克立格法(OK),简单克立格法(SK),对数正态克立格法(LNK),泛克立格法(UK),析取克立格法(DK)和距离反比权重法(IDW)等6种内插方法对其进行了估值,综合比较了各种内插方法的预测误差、统计特征值及插值结果分布图.结果表明一阶趋势的OK方法比0阶和二阶趋势的OK方法插值结果要好.一阶趋势的OK方法中半方差函数模型选用高斯型的比选用球状和指数型的插值效果相对要好.由于"压缩"作用,原始数据经过对数转换后的插值效果要比没有经过转换的插值方法要差.带趋势项的插值方法要比不带趋势项的插值方法要好,其中一阶趋势的UK方法插值效果最好,而IDW方法最差.

Comparison of Various Spatial Interpolation Methods for Non-stationary Regional Soil Mercury Content

Accurate delineating of the spatial distribution of soil heavy metal content is essential for pollution assessment and remediation. The objective of this paper is to evaluate various spatial interpolation methods, including ordinary Kriging (OK), simple Kriging (SK), lognormal Kriging (LNK), universal Kriging (UK), disjunctive Kriging (DK) and inverse distance weighting interpolation (IDW) for estimating soil surface Hg content with lognormal distribution, the linear and second-order polynomial trend, and to determine the optimal interpolation method. The predicted errors, statistical feature values and prediction maps obtained by different interpolation methods were compared. The result indicated that first-order trend OK method performed better than both zero and second-order OK methods. Within the method of first-order trend OK, Gaussian semi-variogram model performed better than both the spherical and exponential models. The method using transformed data performed worse than the methods without data transformation because of the 'distortion' effect arising from log transformation. Those with trend effect were better than those without trend effect. First-order trend UK method is the best method among the six methods studied, while the IDW method is the least.