Geostatistical analyses of heavy metal distribution in reclaimed mine land in Xuzhou, China

The aim of this study was to determine the ecological safety of reclaimed lands from subsided areas that had been filled with mining wastes and fly ash for agricultural purposes in the Liuxin mining area, Xuzhou, China. Both chemometric techniques and geostatistics were utilized to test the concentrations of As, Hg, Pb, Cu, Cd, Cr and Zn in reclaimed soils and in control soil at different depths. Results showed that, relative to local soil background values, the degree of variation in Hg, Cu, Cd and Pb at the majority of sampling points was large, especially for Cu in the control soil, Zn in the gangue site was also high, while As and Cr concentrations in the fly ash site and control soil were low. With reference to the China soil quality standard, besides Cd and a few samples of As, Zn and Cu, the other heavy metal concentrations were all lower than the standard. Based on this, the seriously high Cd levels were studied. To describe the regularity of the change in Cd concentration with depth, the polynomial fitting model was adopted and was found to be feasible. To achieve quantitative analysis from qualitative description, the Kriging interpolation model was applied to investigate the regular distribution of Cd. This model proved to have high precision at the fly ash site.