Air-Borne Heavy Metal Contamination to River Ganga (India)

Abstract

A two year study was undertaken at Ganges basin of India to evaluate the atmospheric input of six heavy metals to river Ganga. Atmospheric bulk deposition was collected on a fortnightly basis at 8 river sites from April 2006 through March 2008 to determine atmospheric loading of heavy metals to river Ganga. The sampling protocol consisted of bulk collectors placed at 24 locations (3 at each site) selected along a 20 km long tract of river Ganga at Varanasi, India. The atmospheric fluxes of six heavy metals to river Ganga were estimated as (g ha –1 y –1 ) : Cd - 0.56 – 20.15; Cr - 0.34 – 8.87; Cu - 1.63 – 58.17; Ni - 0.21 – 7.32; Pb - 1.80 – 124.00; Zn - 124.15 – 477.18. Atmospheric deposition of all the elements was lowest at Adalpura (site 1) and highest at Rajghat downstream site (site 8) receiving maximum down — wind urban industrial emissions. Zinc alone contributed to more than 68 % of total measured heavy metal input. for season, the atmospheric fluxes were measured highest during winter followed by summer and rainy seasons. Data on heavy metal concentrations in mid — stream water showed significant correlation with their respective values received through atmospheric deposition. Corresponding to the atmospheric deposition, except for Zn, highest concentrations of Cd, Cr, Cu, Ni and Pb in mid — stream were recorded during winter followed by summer and rainy seasons. Concentrations were recorded highest for Zn followed by Ni, Cr, Pb, Cu and Cd. Concentrations of all the heavy metals were high in down — stream sampling locations. Although the concentrations of Cr, Cu and Zn remained well below their maximum admissible concentrations (MAC), more than 80 % of water samples of 7 out of 8 locations sampled, showed Cd, Ni and Pb levels above their respective MAC. Heavy metal loading to mid — stream implicates the adjoining urban agglomeration of Varanasi as the principal emission source area. The atmospheric loading to the river will continue to rise with the completion of Ganga Express highway. This may lead to serious health implications in long — run since Ganga water is also used for drinking purpose by a large population.