Appraisal of heavy metal pollution in the water resources of Western Uttar Pradesh, India and associated risks

Abstract

The ponds are the important water resources for the developing nations including rural India. They not only supply the water during the non-monsoon period but also acts as a flood absorber during the monsoon period. However, with the increase in population, modernization, and alternate water supply schemes, the ponds are getting polluted mainly due to the discharge of wastewater from residential areas, sewage outlets, solid waste dump sites, livestock rearing sites (e.g., dairy, poultry), and fertilizers and pesticides from farmers’ fields. The sludge accumulated in these water bodies may contain an appreciable amount of toxic metals that may leach to the groundwater and long-term use of contaminated water, either directly from these water bodies or the nearby handpumps or tubewells, can cause serious threats to human health. This study investigated nine heavy metal (Pb, Cu, Ni, Zn, Cr, Cd, Fe, As, and Mn) contamination in the pond sludge, pond soil, and groundwater at twenty-one villages in Western Uttar Pradesh (India), and provides a sound case for examining the toxic metal accumulation in the terrestrial water bodies. The mean concentration of Pb, Cu, Ni, Zn, Cr, Cd, Fe, As and Mn in pond sludge was 0.64, 0.53, 0.94, 3.34, 0.62, 0.010, 151.70, 0.32, and 35.02 mg/kg sludge, respectively, and in pond soil the concentration of Pb, Cu, Ni, Zn, Cr, Cd, Fe, As and Mn were 0.13, 0.45, 1.21, 0.82, 3.22, 0.06, 2055.04, 0.16, and 457.84 mg/kg soil, respectively. The geo-accumulation index (I-geo) in the pond sludge and soil ranged from unpolluted to extremely polluted. The average I-geo values of metals in pond sludge and soil were in order Pb (4.93) > Zn (4.36) > Ni (0.70) > Cu (0.40) > As (0.32) > Cd (-0.58) > Cr (-1.96) > Fe (-4.24) > Mn (-5.28) and Cu (2.76) > Cr (2.35) > Pb (2.17) > Ni (2.01) > Zn (1.53) > Cd (-0.22) > Fe (-0.49) > As (-0.78) > Mn (-1.41), respectively. The combined ecological risk due to metal accumulation extended from low risk to very high risk. The groundwater samples were observed to non-comply the drinking water standards due to high levels of Pb, Cu, Ni, Fe, and Mn, and the human health hazard index ranged from 0.831 to 21.76. This study highlights the value of baseline monitoring and provides a sound case for examining the pond ecosystem for heavy metal toxicity before and during the rejuvenation of such water bodies in India and other sub-tropical countries.