Spatial Distribution of Chromium, Cobalt and Nickel in the Surface Soils of Hamadan Province

Heavy metals are very important from environmental consideration due to their toxicity and accumulative properties. The aim of this study is the evaluation of spatial distribution of Cr, Co and Ni in the surface soils of Hamadan province. For this purpose, the surface soil samples (0-20 cm) were collected using systematic random sampling method and the concentration of heavy metals and some of the soil parameters such as pH, EC, the percentage of organic matter, sand, clay and silt were analyzed. For interpolation and mapping the spatial distribution of heavy metals, the accuracy of Kriging methods and their models were compared by the Mean Absolute Error (MAE) values and Mean Bias Error (MBE), and the method with the lowest error was selected. Maps of chromium and nickel distribution were prepared by ordinary Kriging with a spherical model, and that of cobalt by disjanctive Kriging with exponential model. The western regions of Hamadan province had the highest concentration of chromium, cobalt and nickel. According to obtained maps, the regions with the highest concentrations of heavy metals corresponded to the igneous and metamorphic bedrocks. It seems that the geology is the main factor influencing the concentration of heavy metals in the soil.