重庆市两不同地貌及地质背景区土壤Cd、Se元素含量空间插值方法研究

Spatial Interpolation Method of Soil Cd and Se Element Contents in Two Different Landforms and Geological Background Areas in Chongqing City

适宜的土壤元素含量空间插值方法对不同地貌及地质背景区土地质量地球化学调查有着重要的意义。在重庆市黔江区(山地)和荣昌区(丘陵)分别以1∶5万和1∶1万工作尺度采集农田表层土壤样品,对1∶5万工作尺度的土壤Cd及Se数据,用反距离权重法(IDW)和普通克里格法(OK)进行空间插值,以1∶1万工作尺度土壤实测数据对插值结果进行交叉验证,根据验证结果对不同插值方法的准确性进行了评价。结果显示,黔江及荣昌区土壤Cd含量较高,黔江区土壤Cd及Se的空间变异性较强,元素来源受到成土母质的控制。交叉验证及栅格减法的结果显示,普通克里格法(OK)适用于山地地区元素空间插值,而反距离权重法(IDW)适用于丘陵及平原地区,两种插值方法对元素插值结果的误差主要体现在元素含量的高值区和低值区。本文给出的土壤元素适宜插值方法的选择过程及数据处理技术,可一定程度提高元素空间插值精度,为土地质量、土壤元素地球化学调查工作提供技术支撑。

The research on suitable spatial interpolation methods for soil elements in different landforms and geological background areas is of great significance for geochemical investigations of land quality. The surface soil samples of farmland were collected from Qianjiang(mountain area) and Rongchang(hill area) of Chongqing at two working scales of 1∶50000 and 1∶10000, and the contents of soil Cd and Se at the common scale of 1∶50000 were spatially interpolated with inverse distance weighting method(IDW) and ordinary kriging method(OK). Then the interpolation results were cross-validated with the measured data at 1 ∶10000 scale, and the accuracy of different interpolation methods was compared. The results showed that the contents of soil Cd in Qianjiang and Rongchang were high, and the spatial variability of soil Cd and Se in Qianjiang was strong. The source of elements was controlled by parent material. The results of cross-validation and raster subtraction showed that the OK method was suitable for spatial interpolation of elements in the mountainous areas, while the IDW method was suitable in the hilly and plain areas. The error of element content was mainly reflected in the high value area and low value area. The selection and data processing of suitable interpolation methods for soil elements given in this paper can improve the spatial interpolation accuracy of elements to a certain extent, and provide a technical support for geochemical investigations of land quality.