Assessing pollution risk of heavy metals in some of Varamin agricultural soils

Considering the development of industry and technology, the accumulation of environmental contaminants, especially heavy metals (HMs) in the soil lead to increasing concern about the food security. The purpose of this study was to assess the environmental risk of heavy metals using soil pollution indices. For this purpose, thirty five soil samples were taken from agricultural area in seven sites. The total and available concentration of metals extracted by Aqua Regia and DTPA were determined by an atomic absorbtion spectrometer. Geoaccumulation index (Igeo), enrichment factor (EF), pollution index (PI), contamination factor (CF), potential ecological risk (RI), and availability ratio (AR) were calculated. Mean total concentration of Cd, Pb, Zn, Ni, Co, Cu and Cr were 0.09, 52.3, 146, 25.0, 4.90, 42.1 and 73.1 mg/kg, and their available values were 0.035, 5.07, 7.10, 0.047, 0.041, 3.01 and 0.030 mg/kg of soils, respectively. The highest values of Igeo, EF, PI, RI and AR indicators were found in Cu (1.69), Cr (8.70 ), cu (5.21), Cr (43.52), and lead (10.87), respectively. Integrated pollution index (IPI) calculated using the average of total CF was 4.08 indicating the higher contamination class in the area whereas IR value was in acceptable ecological range (IR= 109). Analysis of Igeo and IR data showed that Pb, Zn and Cu vary by anthropogenic activities in the area while Cd and Co values are solely affected by lithgenic factor. Agricultural inputs and urban wastewaters can be the major factor increasing of pollutants in the agricultural soils in the area. Monitoring the pollutants concentration in the agricultural soils as well as in agricultural products is essential to conserve natural resources and obtain food security.