四川泸县农业土壤Cd含量空间变异性研究

采用统计和地统计分析技术对四川泸县及附近水稻产区土壤Cd含量的空间变异性进行了研究。研究区土壤Cd监测数据呈正态分布，其经验半变异函数表现为各向同性，应用指数模型拟合经验半变异函数，采用普通克里格法预测土壤Cd的空间分布。交叉验证结果表明监测值与估计值呈显著的线性相关性，相关系数为0.365，没有系统估计误差的存在。研究结果表明，本区域农业土壤Cd含量存在明显的空间异质性，面源污染、大气沉降和污水灌溉是引起土壤Cd空间变异性的主要原因。

Spatial Variability of Soil Cadmium in Luxian Agricultural Area, Sichuan Province

The problem of soil contamination by heavy metals has received much attention in recent years in China. Cadmium, as a seriously concerned environmental heavy metal, is easily accumulated by rice. This article analyzed the cadmium content in land soil using 303 soil samples distributed throughout the rice producing area in Luxian, Sichan. Spatial variability and distribution character of soil Cd were discussed through statistics and geostatistical analysis. Normal distribution of Cd in study area was observed. The analysis of exploratory spatial data showed that the autocorrelation of soil Cd existed and the experimental semivariogram was isotropic. Spherical model and exponential model were used to match the experimental semivariogram. The results of cross-validation showed that the exponential model with sill could best simulate the experimental semivariogram. Ordinary kriging was used to estimate the Cd distribution in study area. The significant correlation between the estimated values and the monitored values was found. No system errors could he tested. Soil areas with high concentration of Cd presented strip belt-shaped. Patches with high concentration of soil Cd and those with low concentration of soil Cd showed relatively decentralized distribution, which suggested there was clear spatial heterogeneity in soil Cd. Non-point pollution and wastewater irrigation may he the main reasons affected the spatial variability.