Heavy-metal concentration of sewage-contaminated water and its impact on underground water, soil, and crop plants in alluvial soils of northwestern India

Heavy-metal concentration in underground and surface water, soil, and crop plants growing in farmers' fields near the industrial city of Ludhiana, Punjab, India, that receive irrigation with water contaminated with sewer and untreated industrial effluents was studied. The concentrations of lead (Pb), chromium (Cr), cadmium (Cd), and nickel (Ni) in sewage-contaminated water were 18, 80, 88, and 210 times higher than in shallow handpump water, and 21, 133, 700, and 2200 times higher than in deep tube-well water, respectively. The concentrations of Cd and Ni in shallow handpump underground water were significantly higher than in deep tube-well underground water. The concentrations of Pb, Cr, Cd, and Ni in deep tube-well water were 0.017, 0.003, 0.0002, and 0.0002 mg L-1, respectively. Soils irrigated with sewage-contaminated water had higher electrical conductivity, cation exchange capacity, organic carbon (C), and clay content but had lower pH and calcium carbonate content compared to soils irrigated with deep underground water. The concentrations of diethylenetriamine pentaacetic acid (DTPA)-extractable Pb, Cr, Cd, and Ni in soils irrigated with sewage-contaminated water were 1.8, 35.5, 3.6, and 14.3 times higher, and total concentrations of these heavy metals were 1.5, 3.0, 3.7, and 2.2 times higher than that in soils irrigated with deep underground water. The mean concentrations of Pb, Cr, Cd, and Ni in crop plants growing on soils irrigated with sewage-contaminated water were 4.88, 4.20, 0.29, and 3.99 mg kg-1, which were 1.2, 2.1, 8.7, and 1.9 times higher than in plants irrigated with deep tube-well water, respectively. The amounts of potentially toxic metals were significantly and positively correlated with cation exchange capacity and organic C content and negatively correlated with soil pH. In conclusion, long-term accumulation of toxic metals in soils and their uptake by crop plants has a high potential for phytotoxicity as well as for entering into the food chain. The findings also suggest contamination of underground shallow drinking water through leaching of some highly mobile metals. Copyright © Taylor & Francis Group, LLC.