Geo-accumulation index and enrichment factor of trace metals in urban soils irrigated by a highly contaminated wastewater drain in Chandigarh and adjacent areas, India

Urban wastewater and soil samples from agricultural fields irrigated with wastewater from the storm water drain (commonly known as N-choe) were analyzed for heavy metals. Results reveal that the wastewater contained concentration of Fe, Ni, Mn and Cd which was higher than the permissible limits for irrigation prescribed by FAO, (1985). In this study, geoaccumulation index (I_geo), enrichment factor (ER), contamination factor (CF) and pollution load index (PLI) have been applied to assess heavy metal distribution in the soils of the study area. Based on geoaccumulation index, soil in the study area is moderately to strongly contaminated with Cd and Ni. According to enrichment factor, samples showed very severe enrichment of Cd and Ni, minor enrichment of Cr, Mn, Pb, Zn. CF values of Cd and Ni were greater than 6 and PLI at 1.75 were observed indicating serious anthropogenic pollution in the study area. Elevated concentrations of Ni and Cd in the soil samples may be attributed to application of wastewater in the agricultural fields as the concentration of these heavy metals were found to be high in the wastewater. Data highlight that long-term practice of wastewater irrigation has resulted in significant buildup of heavy metals in the soil and that such elevated amounts may be transferredto the food chain causing potential health hazard to consumers.