Due to accumulation of heavy metals in soil and its risk to human health, their recognition, origin and distribution have attracted considerable interest in recent years. No information is currently available on the distribution pattern of heavy metals concentration in soils of Hamadan province. The purpose of this research was to determine the spatial variability of selected heavy metals in some surface soils of the Hamadan Province . A total of 263 surface (0-10 cm) soil samples were collected to determine their total and plant bioavailable copper (Cu), nickel (Ni), lead (Pb) cadmium (Cd) and zinc (Zn) contents. Also, parent rock samples were collected to investigate the effect of parent material on the enrichment of selected elements in the soils studied. Selected soil properties including pH, electrical conductivity, organic matter, cation exchange capacity and texture were also determined to understand the relationships between heavy metal contents and soil properties. The spatial variability of these variables was examined by variogram models and kriging. The results of geostatistical analysis showed that the spherical model was the best model for describing the spatial variability of Pb, Zn, Ni and Cu. The major factor controlling the total concentration of Cu, Pb, Zn and the plant bioavailable concentration of Pb in the area appears to be land use. Parent material analysis shows that the concentration of Ni and Cu in shale is much higher than that in any other parent rocks. Therefore, the content of Cu in the soils studied seems to be mainly controlled by soil parent material and land use. The major factor controlling the total and bioavailable concentration of Ni in the area appears to be parent material. Multivariate geostatistical analysis was performed to identify the source of heavy metals. Co, Cr and Ni are associated with parent rocks and correspond to the first factor termed the lithologenic component. The second factor was mainly attributed to Cu. This element was also included in the first and third factors, indicating a mixed source from both lithologic and anthropogenic inputs. Zn and Pb seem to be related to the anthropogenic activities and comprised the third factors. A significant correlation was found between metals from the lithogenic sources and selected soil properties such as soil organic matter, clay and CEC indicating an interaction among them. Keyword : Heavy metals, spatial variability, kriging, multivariate analysis, anthropogenic activities, lithogenic, Hamadan
