Radioactivity of beach sand in the south western coast of Sri Lanka.

The activity concentrations and effective dose rates due to (232)Th, (238)U and (40)K were determined for sand samples collected along the coastal strip from Crow Island to Beruwala, a part of south western coast of Sri Lanka, using a high-purity germanium detector. The ranges and the mean activity concentrations measured were (11-19 600, 2100), (7-3150, 450) and (14-1210, 220) Bq kg(-1) for (232)Th, (238)U and (40)K, respectively. The effective annual gamma dose in the area ranged from 0.004 to 16.8 mSv y(-1). For 21 % of the locations, the annual effective dose determined from the activity concentrations exceeded the average worldwide exposure of 2.4 mSv y(-1).