V. M. Joshi

Spatial distribution and accumulation of 226Ra, 228Ra, 40K and 137Cs in bottom sediments of Mumbai Harbour Bay

The present work shows the activity levels of 226Ra, 228Ra, 40K and 137Cs in bottom sediments collected from eight locations of Mumbai Harbour Bay. The study has shown that 40K and 228Ra concentration is nearly uniform throughout the studied area while 226Ra and 137Cs are more concentrated in the southern regions of the bay. The significant variation in the activity levels of radionuclides within the study site might be due to their sorption/desorption processes onto the surface of sediment materials. The low mean value of 226Ra/228Ra ratio (0.72) in the sediments indicates that 238U has relatively greater solubility and mobility than 232Th. Similarly, low activity ratio (0.18) for 137Cs/40K reflects the presence of very high content of 40K in sediment due to presence of primary minerals in sediment. Silt and clay were reported to dominate the composition of the sediment. A significant positive correlation between 226Ra and 228Ra and 137Cs and 40K suggest a similar origin of their geochemical sources and identical behavior during transport in the sediment system.