Assessment of heavy metal contaminations in water and sediment of River Godavari, India

The Godavari is the largest river of peninsular India and receives a significant quantity of pollutants from diverse sources, including many industries, urban developments and agricultural fields. Such pollution is more prominent in the upper stretch of the river. This work aimed to assess the water and sediment contaminations of River Godavari for the presence of trace metals Cd, Cr, Cu, Mn, Pb and Zn. Samples were collected from 10 sampling stations covering the entire stretch of the river. Sediment pollution characteristics and potential ecological risks were evaluated by calculating contamination factor, degree of contamination, pollution load index, geo-accumulation, and the potential ecological risk index. Pearson's correlation analysis and principal component analysis were used to predict the probable sources of heavy metals. The concentrations of studied heavy metals in water were mostly observed below the detection limit using the flame mode of an Atomic Absorption Spectroscope and recorded safe for the biotic community. The mean concentrations of metals in the sediments were calculated and also recorded to be safe with respect to the guideline values of the United States Environmental Protection Agency (USEPA, 1999). However, the sampling site-specific calculated contamination factors indicated moderate contamination of some of the stretches as: S1 for the presence of Cu, Mn, Zn; S2 for Cu, Zn; S3 and S4 for Cu; S5 for the dominance of Mn. The rest of the sites were free from sediment metal contaminations. The degree of contamination values specified S2 as moderately contaminated. Pollution load index indicated sites S1 and S2 as contaminated. Both geo-accumulation and potential ecological risk index designated lower levels of pollution in the river owing to sediment metal contaminations. Furthermore, a comparison of the heavy metal concentrations with sediment quality guidelines signified that the heavy metal pollutions (Cu, Cr, Mn and Zn) tend to pose occasional harmful effects on the ecosystem. From Pearson's correlation analysis and principal component analysis, two main sources of metal pollution were predicted. The Cu, Cr and Zn contaminants were mainly derived from human activities and Mn from natural sources as well as human activities.