Assessment and Insights into Heavy Metal Contamination in Sediments of the Ganga River, India: Sources, Trends and Ecological Implications

This study presents the comprehensive synthesis of four decades (1980–2025) of research on heavy metal contamination in the sediments of the Ganga River, India, focusing on spatial and temporal trends, ecological risks, and pollution sources. By integrating various qualitative and quantitative studies, we identify cadmium, lead, and chromium as the most persistent and ecologically hazardous metals, with cadmium’s ecological risk increasing by 230% post 2015. Pollution hotspots are concentrated downstream of major urban – industrial hubs such as Kanpur, Varanasi, and Patna. The analysis reveals that river sediments function as both sinks and secondary sources of contamination, with metal mobility and bioavailability strongly linked to sediment fractionation and organic matter content. Comparative assessment with global rivers shows moderate-to-high enrichment for Mn and Pb but relatively lower Zn, Ni, and Cu levels, indicating mixed natural and anthropogenic inputs. The findings underscore that despite decades of mitigation programmes; ineffective wastewater treatment and weak regulatory enforcement have allowed heavy metal loads to persist or intensify. These insights provide a robust evidence base for targeted pollution control, advanced remediation strategies, and strengthened monitoring frameworks to safeguard the Ganga’s ecological integrity and public health value.