Sumit Kumar, Pradip Kumar Maurya, Ajay Kumar Yadav, C.P. Singh and S.K. Verma
Abstract
This study evaluated heavy metal contamination in sediment, water, and macrobenthic communities of the Ganga River and assessed its ecological implications. Monthly sampling was conducted from March 2022 to February 2023 at three sites- Haridwar (Bhadrabad), Bijnor (Balawali), and Muzaffarnagar (Bairaj Ganga Bridge) - representing unique hydrological and pollution conditions. The results indicated that heavy metal concentrations were significantly higher in sediments than in water, identifying sediment as the primary sink for contamination. In sediments, the abundance of metals followed the order Zn > Cr > Pb > Cu > Cd > Hg, with site A1 exhibiting the highest concentrations for most metals. In water, the order was Pb > Cu > Zn > Cr > Cd > Hg, and concentrations of Pb and Cr exceeded World Health Organization (WHO) permissible limits at several locations. In macrobenthic communities, the dominant metals were arranged in the order Cr > Zn > Cu > Pb > Cd > Hg, providing clear evidence of bioaccumulation. Ephemeroptera and Diptera were the most abundant taxa and served as effective bioindicators of pollution stress. The results show that increasing heavy metal contamination reduces macrobenthic diversity and abundance, indicating ecological degradation of the river system. Significant spatial differences among sites were identified through analysis of variance (ANOVA), highlighting strong anthropogenic influence from sewage discharge, industrial effluents, and agricultural runoff.