Distribution Pattern of Some Heavy Metals in Topsoils of Golestan Province

In order to better understand the extent of soil pollution by heavy metals and its effect on ecosystem, spatial information on ecological impacts of heavy metals would be necessary. Therefore, in the present study, the spatial pattern of ecological risk of heavy metals (cadmium, lead, copper, nickel and zinc) have been identified in surface soils of Golestan province. To this end, over 346 surface soil samples (0-30 cm) were collected all over the province. After the initial preparations, soil samples were digested using mixtures of different acids, and heavy metals concentrations were then detected. The accumulative risk of the elements were then determined for each sampling point on the basis of the background concentrations as well as available equations; then, the spatial pattern of ecological risks of the elements were identified using ordinary kriging technique. The results showed that the average total concentrations of cadmium, lead, copper, nickel and zinc in the study area, were 0.12, 15.42, 23.9, 34.88 and 82.08 mg/kg, respectively, and the concentration levels (mg/kg) of Cd, Cu, Pb, Ni and Zn ranged from 0.35 for cadmium to 37.2, 84.4, 75.85 and 392.4, for the other metals, respectively. Interpolation results also indicated that there were three main areas with very high ecological vulnerability in the province: a) a region in the center of the southern part of the province located in the mountainous area, b) a region where stretched as a tape from south to north in the east of the province, and c) a region in the northwest of the province, which covers the plain areas and Soofikam wetland and its adjacent regions.