Impact of land use on the distribution of toxic metals in surface soils in Birjand city, Iran

Accumulation of toxic metals in the soil is one of the most important issues and treats plants, animals and humans. The aim of this study was to investigate the impact of land use on the distribution of Pb, Cu, Ni, Cr, Zn and Cd in the surface soils of Birjand city (Amir Abad Area). Dairy farm, agriculture, roads, residentialroad, residential-agriculture and educational centre land use were studied. The samples were taken from depth of 0-20 cm at 16 stations, as regular grid soil sampling. After digestion with perchloric acid and nitric acid, the concentration of toxic elements was measured using atomic absorption. The results show the highest concentration of Pb (166.64 mg/kg) is found in the station number 10 in residential-road land use. The highest zinc concentration (346.50 mg/kg) is shown at the station number 1 in dairy farm land use. The maximum concentration of cadmium (8.57 mg/kg) was at station number 10 with residential-road land use. The mean concentration of cadmium element is greater than the threshold values. While mean concentrations of other elements when compared to other researches shows high values, indicating that the soil is contaminating and in the near future the concentration of toxic metal will be beyond the threshold values. So entry of toxic elements into the human food chain greatly increases. It can suggest, in order to cleanup and reduce the rate of increases toxic elements in the soil and special management and considerations may apply.