Preliminary investigations on dissolved uranium and silicon and major elements in the Mahanadi estuary

Uranium isotopes, Si and Na, K, Ca, Mg have been measured in the Mahanadi estuary during winter and summer seasons. U isotopes show a nearly conservative behaviour. The 234U/238U activity ratio in the freshwater end-member appears to be inversely correlated to the 238U concentration which if true, can be understood in terms of leaching of the suspended material. In the low chlorosity region (0-1 g/1) the Si concentration shows a large variation by about a factor of two irrespective of the season. Between the chlorosity range of approximately 1 to 14g/1, the winter Si values are lower (by approximately 50% to a factor of approximately 3) compared to the summer Si values. Hio.h productivity of the waters during winter as evidenced by the presence of a large number of diatoms appears to be one of the reasons. Na, K, Ca and Mg are found to behave conservatively in the Mahanadi estuary during both the winter and summer seasons. The annual suspended and dissolved cationic load from Mahanadi are estimated. (auth.)