天津市平原土壤微量元素含量的空间自相关研究

SPATIAL AUTOCORRELATION ANALYSIS OF TRACE ELEMENT CONTENTS OF SOIL IN TIANJIN PLAIN AREA

空间自相关是区域化变量的基本属性之一，而空间自相关统计可用于检测研究区域内变量的分布是否具有空间结构。本研究以天津市平原区土壤微量元素为例，采用Ｍｏｒａｎ’ｓＩ统计量，研究了土壤微量元素含量的空间自相关关系、空间自相关的方向性、空间自相关与距离的关系以及不同方向的自相关与距离的关系。结果证实在本研究的采样密度下（平均约３００平方公里一点），天津市平原区多数土壤微量元素含量表现出显著的正空间自相关；土壤微量元素含量的空间自相关关系在受表生与人为作用影响较大的Ａ层最为强烈；人为活动改变了部分微量元素含量（汞、镉、铅、锌、砷）在研究区土壤中，尤其是表土中原有的空间分布结构特征。

Spatial autocorrelation is one of the basic characteristics of regionalized variable,and statistics based on spatial autocorrelation can be used to test if the distributionof a variable in a two-dilnentional space follows a certain pattern or at random.Values of Moran’s I of trace element contents in soil of Tianjin plain area werecalculated. The spatial autocorreiation characteristics, the directional characteristicsof spatial autocorrelation, the relationship between spatial autocorrelation and lag ofsapmling and the relationship between spatial autocorrelation in different directionsand lag of sampling were investigated.Under the sampling density of 300 km￣2 per sample,significant by positivespatial autocorrelations were detected for most trace elements studied.The most si-gnificant spatial autocorrelation was found in horizon A where the original distribu-tion of the elements had been modified remarkably by natural forces and humanactivities. The spatial structure characteristics of Hg, Cd, Pb, Zn, and As contentsin surface soil were further altered by pollution and agricultural practice.