Environmental assessment of contaminated soils in Dostbaiglou mine (north of Meshginshahr - Iran)

Contamination of soil with pathological and carcinogenic toxic elements presents a vitally important challenge for the environment. The dispersed contamination source is one of the important pollution sources, which different elements originate from weathering of rock and alterations zones and diffuse in the environment. The mine lands are considered as one of the dispersed contamination sources. In these locations, excavation, concentration and uncovering of some elements cause contamination of soil, which leads to contamination of the environment. This paper presents the pollution load of toxic elements in 236 soil samples collected around mining zone in north of Meshginshahr, northwest of Iran. Pollution intensity of the soils was calculated based on the pollution index and enrichment factor. Classification of the soils was done by using the factorial and cluster analysis. Soil samples collected in this study contain higher concentrations of harmful elements compared to the target and intervention limits set by international regulatory standards. Concentration of elements such as As (3-3430mg/kg), Mo (0.5-160mg/kg), Sb (0.21-97.6mg/kg), Pb (3.7-518mg/kg), Cu (10-748mg/kg) and Sn (0.5-11.4mg/kg) was found to be very high in the region soils. Some of the soil samples also have a worrying levels of Cr (3-267mg/kg), Mn (27-4120mg/kg) and Co (0.5-211mg/kg) concentrations. As per the pollution index, 19.4-66.7% of the soils on the mineralized and altered zones in the region are considered as contaminated with toxic elements. There is a high variation of concentration of elements in the soil samples. Distribution of the elements have been influenced heavily by both chemical (pH, organic carbon content (%), concentration of Fe + Mn, Al and S) and physical (grain size < 63µm) factors. Emphasis need to be put on control measures of pollution and remediation techniques in the study area.