Impact of paper mill effluents on the chemistry of a large tropical river, India

Bimonthly sampling was carried out from the river Godavari, the largest in peninsular India, over a period of two years to measure the major ion and heavy metal composition to elucidate the effect of paper mill effluents on the river water chemistry. Six sampling stations are spaced at a stretch of 6 km. Major ions and silica variations in the river convey their dominant sources from rock assemblages comprising of Ca and Mg rich basalts and sodic plagioclase rich granite gneiss. The magnification of major ion and heavy metal (As, Zn, Cd, Co, Ni, Cu, Mn and Pb) composition in two stations near the paper mill (station PM) and VIP ghat (station VIP) compared to the rest of the stations, clearly indicates the influence of paper mill effluents and anthropogenic activities on the river chemistry close to paper mills. Though the chemical composition is magnified in station PM, it is getting diminished downstream, because of the self-purification ability of the river. It could be due to fractionation of elements from dissolved to particulates involving processes like complexation and adsorption of metals on to the inorganic ferromagnesium oxides.