珠江三角洲典型区农业土壤铬的空间结构及分布特征

通过对东莞市118处农业表层土壤和5处典型土壤纵剖面的取样调查，利用常规统计学和地统计学方法研究了土壤中铬的空间结构和分布特征。结果显示，东莞市农业土壤铬含量为2．28～94．98mg·kg^-1，平均值为44．90mg·kg^-1，略高于东莞市背景值；铬的空间结构表现为明显的几何各向异性，各向异性比约为1．8，长、短轴分别在103°和13°方向；指数模型对于实验变异函数的拟合效果较好，变异函数表现出明显的块金效应，块金值在基台值中所占的比例约为34％，表明东莞市农业土壤中铬具有较强的空间相关性；铬的空间分布具有明显西部高、东部低的地域特征，其空间分布主要受成土母质和地形的控制，铬主要来源于成土母质，另外人为活动对铬的空间分布也有显著的影响。

The Spatial Structure and Distribution of Cr Contents in Agricultural Soils in a Typical Area of the Pearl River Delta,China

Spatial variability and distribution of Cr contents in agricultural soils of Dongguan city, Guangdong Province are studied using geostatistics and geographic information system（ GIS ）techniques. 118 surface samples and 5 vertical sections of agricultural soil were collected from Dongguan city. Spatial structure is described with Variogram. The results show that Cr contents are 2.28-94.98 mg·kg^-1 in,agricultural soils of Dongguan, the mean content is 44.90 mg·kg^-1, and higher slightly than the soil background value of Dongguan. Well-defined struc- ture with nonzero nugget effect, distinct sill and range can be fitted with exponential model （R2=0.78, P〈0.01 ）, which is mostly influenced by soil parent materials and landform, the relative range is 18.3 km. Variogram analysis shows that spatial structure of Cr contents has obvious geometric anisotropy whose ratio is 1.8. The major axis is in northwestern 13° direction in which there is the longest range. The spatial distribution of Cr contents shows that Cr contents of agricultural soils are high in west and low in east, which is mostly controlled by soil parent materials and landform, is influenced strongly by anthropogenic factors.