Spatial Heterogeneity of Soil DTPA-extractable Copper as Affected by City Pollution and Land Use in Cultivated Fields of Shenyang, China

Using the methods of soil analysis and geostatistics combined with GIS, this paper determined and mapped the spatial distribution of soil DTPA-extractable copper (Cu) in cultivated fields of Shenyang suburbs of China, aimed to assess the roles of industries and agricultural managements in affecting the spatial heterogeneity of soil Cu in this region. The results showed that the soil DTPA-extractable Cu fitted normal distribution after logarithm transformation and its semivariogram fitted a spherical model. The semivariogram indicated that the spatial dependence of soil DTPA-extractable Cu was moderate, with a spatial dependence range of 4.07 km. Stochastic factors contributed to 26.6% of the spatial variability. The spatial heterogeneity of soil DTPA-extractable Cu was deeply influenced by city pollution and land use. The common sources of soil Cu other than metalworking pollution were manure, wastewater sludge and pesticide over crops. The average concentrations of DTPA-extractable Cu in vegetable garden and in paddy soils were 2.0-2.5 and 1.2-1.8 times as much as in its originated soils , respectively. The areas with a higher concentration of soil DTPA-extractable Cu appeared in Shenyang near suburbs and in the riverside along Hunhe River and the wastewater drainage of Xihe River. The extremely high values in the near suburbs of the city’s residential area and in the vicinity of two metalworking factories and a cable manufacturer were a striking feature, indicating the key role of industrial pollution in the spatial heterogeneity of soil DTPAextractable Cu in the city.