Geochemical studies of the river-estuarine systems of Krishna and Godavari

Abstract

During summer season, the Krishna River waters are enriched in major cations Na, K, Mg, Ca and Si by a factor of 1.2-1.9, in U by a factor of 3 and in δ D by 14.2 % compared to those of Godavari. The high δ D of Krishna River waters (+ 1.6 %) over those of Godavari (- 12.6 %) indicate relatively more evaporation of the former by 15%. The Uranium concentrations of Krishna waters at Vijayawada is 2.6 °g/l which decreases to 1.6 °g/l at Puligadda which is approximately 100 km whereas the ²³⁴U/ ²³⁸U activity ratio at both place is identical 1065 ± 0.03 suggesting authigenic removal of U does not appear to behave conservatively in the Krishna estuary as has been its behaviour in other India and some world rivers; there is removal of U from the Krishna estuarine waters. The major cations and δ D behave conservatively in both Krishna and Godavari estuaries. Si behaves almost conservatively in the Krishna Estuary whereas in the Godavari estuary there is about 15% Si removal. The fluxes of all the measured constituents from Krishna and Godavari to the Bay of Bengal during the non-monsoon period are calculated. The clay, silt and sand fractions as well as the Al, Fe, Mn, Cr and Ni concentrations of the clay fractions were determined in Krishna estuarine sediments. The non-monsoonal fluxes from Krishna River to the Bay of Bengal are also estimated.