Levels of 232Th activity in the South Adriatic Sea marine environment of Montenegro

Th-232 activities in the South Adriatic Sea-water, surface sediment, mud with detritus, seagrass (Posidonia oceanica) samples, and the mullet (Mugilidae) species Mugil cephalus, as well as soil and sand from the Montenegrin Coast, were measured using the six-crystal spectrometer PRIPYAT-2M, which has relatively high detection efficiency and a good sensitivity, and allows a short acquisition time, and measuring samples of any shape, without preliminary preparation and calibration measurements for different sample geometries. An average Th-232 activity concentration in surface soil layer is found to be 40.33 Bq kg(-1), while in sand-4.7 Bq kg(-1). The absorbed dose rate in air due to Th-232 gamma radiation from surface soil layer ranged from 11.76 to 63.39 nGy h(-1), with a mean of 24.06 nGy h(-1). Corresponding average annual effective dose rate has been found to be 0.03 mSv y(-1). The absorbed dose rates due to the thorium gamma radiation in air at 1 m above sand surface on the Montenegrin beaches have been found to be from 0.41 to 9.08 nGy h(-1), while annual effective dose rates ranged from 0.0005 to 0.011 mSv y(-1). Th-232 activity concentration in seawater ranged from 0.06 to 0.22 Bq L-1, as in the mullet (Mugil cephalus) whole individuals from 0.63 to 1.67 Bq kg(-1). Annual intake of Th-232 by human consumers of this fish species has been estimated to provide an effective dose of about 0.003 mSv y(-1).