迁安市农田重金属含量空间变异性

Spatial variability of farmland heavy metals contents in Qianan City.

利用地统计学和GIS相结合的方法，对河北省迁安市农田土壤耕层（0～20cm）8种重金属含量的空间变异性进行了研究．结果表明，农田中8种重金属含量均值未超过土壤环境质量（GB15618—1995）二级标准，属于中等变异．Cu、Zn、Ni、Cr和As含量的变异函数理论模型符合指数模型，空间相关程度强；Hg和Cd含量的变异函数理论模型符合球状模型，空间相关程度中等；Pb含量具有纯块金效应，空间相关程度弱．在整个研究尺度上，Pb含量具有恒定的变异，其余7种重金属含量由空间自相关部分引起的空间变异性起主要作用，空间相关距离为11—20km．用普通Kriging方法对Cu、Zn、Ni、Cr、Hg、As和Cd含量空间局部插值表明，北部山地重金属含量较高，而中部盆地重金属含量较低．

By the methods of geostatistics and GIS, this paper studied the spatial variability of Cu, Zn, Ni, Cr As, Hg, Cd and Pb contents in the farmland topsoil （0 -20 cm） of Qianan City, Heboi Province. The results showed that the average contents of test metals were under the secondary standard of environmental quality standard for soil （ GB 15618-1995） , and belonged to moderate variability. The theoretical models of semi-variance of Cu, Zn, Ni, Cr and As contents fitted exponential models, and their spatial correlations were strongly spatial dependence; while the theoretical models of Hg and Cd contents fitted spherical models, and their spatial correlations were moderately spatial dependence. The Pb content had pure nugget effect, and was weakly spatial dependence. In whole research scale, Pb content had lasting variability, while the other seven heavy metals contents had the spatial variability mainly caused by their spatial correlation parts. The ranges of heavy metals spatial correlations were about 11 krn to 20 km. The Krlging＇ s interpolation of Cu, Zn, Ni, Cr, Hg, As and Cd contents showed that their contents were higher in northern mountainous area, but lower in mid basin.