Monitoring and assessment of contamination and ecological risk of heavy metals in Hezarpich surface soils

This study aimed to investigate the contamination of heavy metals including cadmium (Cd), copper (Cu), zinc (Zn), and lead (Pb), and monitor the spatial distribution of soil contamination around the municipal landfill site in Gorgan, Iran. Samples were taken from the surface and deep soil to investigate changes in heavy metals from 110 spots all around the landfill site. The highest concentrations of heavy metals in the collected surface samples were related to zinc, lead, copper, and cadmium, respectively. The values of Cd, Pb, Cu, and Zn in the collected surface samples varied between 0.11-0.51, 18.2-53.9, 21.2-44.9, and 71.2-103 mg, respectively. The mean concentrations of cadmium, lead, copper, and zinc increased by 2.25, 1.08, 0.99, and 0.63 times compared to the initial values, respectively. The highest concentrations of heavy metals in the collected deep samples were related to zinc, lead, copper, and cadmium, respectively. The values of Cd, Pb, Cu and Zn in the collected deep samples varied between 0.09-0.41, 12.2-43.9, 14.0-37.9, and 43.1-72.9 mg respectively. The mean concentrations of cadmium, lead, copper and zinc increased by 1.57, 0.87, 0.61, and 0.56 times compared to the initial values, respectively. The spatial distribution maps show a high concentration of heavy metals located at the central and northwestern parts of the landfill site. The results showed a moderate contamination factor for all heavy metals in the surface soil of the landfill area. The geo-accumulation index ranged from un-contaminated to moderate pollution for zinc, lead, and copper and moderate pollution for cadmium.