拟协克里格法在地下水水砷空间分布特征调查研究中的应用

Using Pseudo-Cokriging to Investigate the Distribution of Groundwater Arsenic

本文以砷超标的典型地区为例,应用拟协克里格法探讨了当地潜水及两层承压水砷的空间变异特性。该方法建立于线性无偏估值理论的基础上,考虑不同变量间的相关性,引入拟协变异函数,利用已掌握的资料合理补充待研究的样本数据。应用结果表明,当地各层地下水中砷含量变异系数值分别为24.2%、26.02%、41.4%,块金值与基台值之比(C0/C0+C)分别为14.5%、3.9%、31.9%,体现了不同层位地下水砷含量的空间变异性除了受含水层结构差异的影响外,还与含水层中氧化还原条件有关。采用拟协克里格法,以潜水测试数据作为补充样本,校正两层承压水样本的估值结果,将白土山组及新近系承压水砷含量估计精度分别提高了38.1%和31.6%。该方法为大尺度、小样本情况下,开展随机变量的空间变异特征及分布规律研究提供了有效的途径。

For the lack of samples, research on arsenic distribution on a lager scale has been misled. Here, a useful method is introduced and applied. Pseudo-cokriging has improved the former cokriging method, applying the available data, by the pseudo- cross variograms, the samples are completed. Qian＇an County in western Jilin Province was selected as the research area to reveal the spatial variation characters of groundwater arsenic distribution in the phreatic aquifer, confined aquifers （Qzs, Qlb）. The ratios of nugget to sill are 14.5%, 3.9% and 31.9%, and the variation of arsenic is controlled by the differences of the aquifers. The correlations between phreatic aquifer and confined aquifers are very good, and then, based on the Pseudo-cokring method , the samples from the phreatic aquifers have been used to smooth the samples from the two aquifers , and the results are compared with those obtained by ordinary Kriging method. The preeisions of arsenic in confined aquifers have been advanced by 38.1% and 31.6%, respectively.