Monitoring of heavy metal contamination in Netravati river basin: overview of pollution indices and risk assessment

The continuum fluctuations of river water quality and the metal contamination within the sediments of Netravati river basin were analysed using multivariate techniques and environmental indices. Water and sediment samples were collected from ten locations along the flow path of river in the basin and the hydrogeochemical features were investigated. The results were compared with maximum permissible limit values recommended by World Health Organization. A comprehensive Water Quality Index methodology was applied to come up with transparent understanding of overall excellence in water quality status. The dominant water cations and anions were within the order of Na + > Mg 2+ > Ca 2+ > K + and HCO 3 − > Cl − > SO 4 2− > NO 3 − . The average abundance of sediment heavy metals was in the order of Pb > Mn > Ni > Zn > Cr > Cu > Co. An approach of exploiting environmental indices: enrichment factor, geoaccumulation index, contamination factor, degree of contamination, modified degree of contamination and Pollution Load Index were accustomed to assess the pollutant level. Geochemical investigation and spatial distribution of heavy metals were represented by geographic information system based maps. The results indicate that lead contamination of surficial sediments might pose a significant threat to aquatic biota and the persistent exposure of pollutants even in low concentration causes changes in metabolic activities and alterations in the community structure of river biota.