Natural radioactivity and geochemical processes in the marine environment of the West Coast of India

In studies related to the geochemistry of thorium and uranium, it was observed that the disequilibrium between Th232 and Th228 and between U238 and U234 exists on the surface of the labile organic layer of the sediment particles and as the surface organic matter is removed, the core of the particles show equilibrium activities. In the studies related to sedimentation and geochemistry of elements in coastal waters, it is important to recognise the physicochemical equilibrium between labile chemical species present on the particles surface and the chemical species in the ambient medium. The thickness of the labile organic layer on the sediment particles has been calculated and found to be in the range of 2.5 x 10-6cm to 10.0 x 10-6cm. The values are comparable to the values obtained by electron microscopy method. (author)