Sources, Transport and Fate of Dissolved Trace Metals in the Godavari River Mouth, India

Levels of dissolved trace metal concentrations in the Indian rivers, which are the primary sources of drinking water, are less studied because of lack of advanced instrumental facilities and the cost involved. There is an urgent need for a baseline data in the Indian rivers because studies have pointed out that certain toxic metals like lead and cadmium can affect the human body even at parts per billion level concentrations in the water. This study has attempted to fill this gap by understanding the dissolved trace metal geochemistry at the river water end member of the Godavari river, the largest in peninsular India, at Rajahmundry. Eleven bi-monthly field trips were made between September 2003 and June 2005 and 47 surface water samples were collected at Rajahmundry. This was done to study both spatial and temporal variations. These samples were analysed for trace metals (24 metals) using the facilities available at University of Southern Mississippi, USA.

Peak flow season brings in weathering products rich in rare earths and trace metals leading to an order of increase in concentrations of Cr, Fe, Mn, Cs, Co, Ni and rare earths compared to moderate and low flow seasons. Therefore, with an increase in discharge, there is an increase in the concentration of these metals.

pH, alkalinity, dissolved oxygen are uniform through out the year, and does not control the variability of dissolved trace metals in the Godavari river.

One station, PM (downstream of the site where treated paper mill effluents are discharged), had relatively higher concentrations in all the metals except rare earths, Cr, Fe, Li and Cs, compared to the rest of sampling stations, which were spaced over a distance of 6 km. Due to possible adsorption and settling with the particulates, the stations downstream do not reflect station PM concentrations.