Evaluation of Heavy Metals Contamination in Agricultural Soils

Abstract The present study was conducted to assess heavy metals contamination in agricultural soils in the National Capital Region, Delhi. A total of 84 soil samples were collected from selected agricultural areas located near industries, national highways, state highways, Yamuna floodplain, residential complexes, and wastewater irrigated soils. Heavy metal concentrations (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn), pH, and organic carbon (%) were analyzed in the collected soil samples. The average value of pH and organic carbon in the soil samples collected were 7.79±0.49 and 0.53±0.17 percent. Average concentrations of heavy metals in soils were found to be in the order of Fe> Al>Mn> Zn> Ni>Cr> Cu>Pb> Co> Cd with value as 14916.92 mg kg -1 , 13538.87 mg kg -1 , 277.16 mg kg -1 , 74.53 mg kg -1 , 35.34 mg kg -1 , 33.68 mg kg -1 , 22.94 mg kg -1 , 18.45 mg kg -1 , 1.88 mg kg -1 , and 0.92 mg kg -1 . A very high concentration of Fe (6640.09-32650.23 mg kg -1 ), Al (5631-27209.99 mg kg -1 ), Mn (73.8-735.72 mg kg -1 ), Zn (16.45-221.88 mg kg -1 ), Ni (7.63-192.63 mg kg -1 ), and Cr (9.65-127.21 mg kg -1 ) were recorded in agricultural soil samples. The average concentrations of Mn, Ni, and Zn in the soil samples were several times higher than their concentration in Indian natural background soils. A significant potential ecological risk has been noticed in nearly all the agricultural soil samples except for the samples collected nearby residential areas. The contamination factor has shown that most of the soil samples were moderately contaminated with Mn, Ni, Fe, and Cr and some soil samples were considerably to strongly contaminated with Cd, Zn, Pb, and Ni. Wastewater irrigated soils showed a moderate to a strong degree of accumulation of heavy metals (Cd, Ni, and Zn).