Uranium isotopes in the Hooghly estuary, India

Abstract

Uranium isotopes are measured in the estuarine waters, bed sediments and suspended matter of the most polluted estuary of India, the Hooghly, which flows through the metropolis of Calcutta. The uranium concentrations in the freshwater-endmember of the estuary are higher (3.9-3.5 μg/l) than in any other estuary so far studied; the ²³⁴U/²³⁸U activity ratios in the river channel (Cl ≤ 7.29 g/l) are low, namely < 1.10±0.02. Uranium behaves non-conservatively in the Hooghly estuary, its concentrations are less than the values expected from the theoretical dilution curve obtained by joining the two endmember-concentrations. Based on one set of measurements, it is estimated that ~25% of the uranium entering the estuary in the dissolved form is getting removed from the estuarine waters, most likely onto sediments.