A post-tsunami study on the distribution and bioaccumulation of natural radionuclides in Pichavaram mangrove environment (South East Coast of India) and dose to local human population

Abstract

The paper reports the impact of the December 26, 2004 Sumatra Tsunami on the radioactivity profile in the environment of Pichavaram Mangroves (South East Coast of India) and bioaccumulation of two toxic radionuclides 210 Po and 210 Pb in seafood organisms and possible dose transfer to local fisherman population through seafood intake. The present study (Post-Tsunami) recorded low levels in all radiological parameters analyzed with respect to primordials in sediments and 210 Po and 210 Pb in water, sediment, and seafood organisms as compared with the Pre-Tsunami data. The mean activity of 238 U and 232 Th recorded in the present study were 12.2 Bq/kg and 11.7 Bq/kg, respectively. The activity of 210 Po in water was less (1.4 mBq/l) than that of 210 Pb (2.7 mBq/l). In contrast, the activity of 210 Po in sediment was distinctly higher (3.3 Bq/kg) than that of 210 Pb (1.7 Bq/kg). The shell fishes (Prawn, Crab, Bivalves, and Squid) accumulated more 210 Po (16.4 Bq/kg) and 210 Pb (2.7 Bq/kg) than the fin fishes ( 210 Po: 6.9 Bq/kg; 210 Pb: 1.5 Bq/kg). The results indicated that fin fishes as seafood were relatively less radioactive compared with shell fishes. About 90% Committed Effective Dose Equivalent to fisherman population due to seafood intake was from 210 Po (712 μSv/y) and 10% from 210 Pb (78 μSv/y). The higher dose transfer to Pichavaram fisherman was attributed to relatively more seafood consumption. A low-level background radiation in the Post-Tsunami environment of Pichavaram Mangroves was due to the hydrodynamics of the Tsunami waves which removed the Pichavaram sediments loaded with monazites and other particles containing radionuclides.