Environmental transport of tritium in air and seawater of Mumbai harbour bay

Tritium levels in the Mumbai Harbour Bay environment was evaluated in the main two compartments such as the air and surface seawaters. Samples were collected at 50 m away from the shore in the bay during pre and post monsoon seasons. Tritium in the condensed air moisture and in the seawater samples from 20 different locations in the vicinity of BARC was estimated by Ultra Low Level Liquid Scintillation Spectrometer. The minimum detectable limit for water samples was 1 Bq/l and it was about 0.02 Bq/m3 for air samples. Air tritium levels during pre monsoon season was in the range of 0.01 to 0.96 Bq/m3 and during post monsoon season it was in the range of 0.02-0.41 Bq/m3, while in the sea water, during pre monsoon tritium levels was observed to be in the range of 1.81 to 17.85. Bq/l and in the post monsoon it was in the range of 1.94 to 19.7 Bq/l. The post monsoon tritium in the waters shows a gradual spread of the activity on either side of the discharge point-CIRUS. Comparatively higher activity was observed near the discharge point of CIRUS, covering IRE and Mahul at the south up to 2 km distance. Post monsoon air tritium showed a gradual spread towards the south of discharge point- CIRUS and the nearby locations. The tritium levels in the bay waters at different locations indicated a good dilution and dispersion taking place in the waters. The dose due to inhalation and skin absorption to fishermen was calculated and it was in the range of 3.53E-10 to 1.69E-8Sv/y for inhalation and due to skin absorption it was 1.76E-10 to 8.47E-09Sv/y with a maximum total dose of 2.54E-08Sv/y which is several orders less than the prescribed limit. (author)