Heavy metals in the midstream of the Ganges River: spatio-temporal trends in a seasonally dry tropical region (India)

Midstream concentrations of Cd, Cr, Cu, Fe, Ni, Pb, Mn and Zn were studied at eight sampling sites in the Ganges River at Varanasi from March 2011 to February 2013. Concentrations were lowest at Site 1 (upstream of the urban core), increased consistently downstream, and were highest at Site 8 (downstream of the urban core). The rank of concentration was Zn > Fe > Pb > Mn > Cu > Ni > Cr > Cd. Except for Zn, concentrations were highest in winter. Cr, Cu, Ni, Mn and Zn did not exceed their internationally recommended maximum admissible concentration (MAC). However, over 80% of the water samples contained Cd, over 70% Pb and about 50% Fe above their respective MACs of 3.0, 10.0 and 300 µg L-super--1. Since the river water is used for irrigation and drinking purposes, the study has relevance from a human health perspective.