Origin, distribution, fate, and risks of potentially toxic elements in the aquatic environment of Bengaluru Metropolis, India

Abstract

This study probes the water quality, including pH, total dissolved solids (TDS), and potentially toxic elements (PTEs) concentrations, and the associated environmental and human health implications, in forty one surface water bodies in Bengaluru metropolis, southern India. The pH in 54%, TDS in 63%, Ni in 12%, and U, Mo, Pb, Cr, Co, and Cu in 5% of the forty one water bodies exceed the WHO’s permissible limits for drinking purpose. Total dissolved solids display a significant positive correlation with Pb, Cr, Co, Cu, and Ni, suggesting the association of these elements with particulate matter. Sources of metal pollution include industries in the city's west (high levels of Pb, Cr, Co, Ni, and Cu), traffic in the city Centre (Mo), and geogenic (U) sources in the city's north, east, and south. The degree of contamination is high in 25%, moderate in 10%, and low in 65% of the forty one water bodies, with the highest degree of contamination in Narasappanehalli Lake in the industrial zone, Deepanjali Nagara Lake, and Govindraj Nagar drainage systems. Uranium, Pb, and Mo display a low to medium degree of contamination, whereas Cr, Co, Ni, and Cu display a medium to high degree of contamination. The non-carcinogenic risk through ingestion of contaminated water is medium to high for adults and children and the carcinogenic risk is high in all water bodies. Channels transport contaminated water from Bengaluru water bodies to the Pinakani and Cauvery Rivers and then to the northern Indian Ocean. The states of Karnataka and Tamil Nadu rely on water from these rivers for domestic and agricultural use exposing large populations to contaminated waters. Additionally, contaminated waters can negatively impact flora and fauna of Peninsular India as well as the marine biota of the northern Indian Ocean.