Heavy Metal Contamination in Ganga River Basin Sediments, India

Ganga River is one of the largest Asian rivers on which millions of livelihoods and economic growth depend. However, due to enhanced anthropogenic activities in recent times, the river is susceptible to various contaminants including heavy metals. Most heavy metals (Zn, Co, Cu, Ni, Mo, Mn) are vital components for the biological functioning of a living organism. However, short to long-term exposure to these metals can cause acute or chronic toxicity to aquatic ecosystems. These heavy metals could be sourced from natural as well as anthropogenic agents. Anthropogenic activities like agricultural runoff, sewage, and industrial runoff can potentially be sources of these metals. In this study, we have addressed the Spatio-temporal heavy metal pollution distribution along with its contributing sources in the Ganga River basin (26-bed sediment samples from Rishikesh to Bansberia). The post-monsoon concentrations are found to be low as compared to the monsoon season for Zn, Ni, and Co probably due to lesser erosional and accumulation activity in the riverbeds. Cr concentrations are high possibly due to agricultural activities and input coming from Yamuna and Chambal River confluence. However, Cu is possibly due to the confluence of the Yamuna and Ganga Rivers and human influence. The order of metals in the monsoon and the post-monsoon season is found similar i.e. Zn>Cr>Cu>Ni>Co. A positive correlation is found between Ni-Co, Ni-Cu, Ni-Cr, Cr-Co, Cr-Cu, and Co-Cu in monsoon season and between Ni-Co, Ni-Cr, Cr-Co, and Zn-Cu in post-monsoon season possibly due to their elution from common sources. Such a pattern is not uniform for each metal along the entire stretch of the study area in both seasons due to site-specific weathering and anthropogenic activities. Average concentrations of Ni, Cu, and Cr for both seasons are found to be exceeding the WHO/USEPA recommended values, showing the pollution of these heavy metals in the sediments.