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 Ra-226, Ra-228, K-40 and Cs-137 in bottom sediments collected from eight locations of Mumbai Harbour Bay. The study has shown that K-40 and Ra-228 concentration is nearly uniform throughout the studied area while Ra-226 and Cs-137 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 Ra-226/Ra-228 ratio (0.72) in the sediments indicates that U-238 has relatively greater solubility and mobility than Th-232. Similarly, low activity ratio (0.18) for Cs-137/K-40 reflects the presence of very high content of K-40 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 Ra-226 and Ra-228 and Cs-137 and K-40 suggest a similar origin of their geochemical sources and identical behavior during transport in the sediment system.