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).

Natural radioactivity and gamma dose from Sri Lankan clay bricks used in building construction.

The specific radioactivity concentrations of 226Ra, 232Th and 40K have been determined by gamma ray spectrometry with an HPGe detector in clay brick samples from kiln sites located in 17 towns. The average values of the measured activities are 35, 72, and 585 Bq kg(-1), respectively, for the above radionuclides. The average estimated radium equivalent concentration is 183 Bq kg(-1) and is comparable with reported values for many countries in the world. This value and the value obtained from the criteria formula suggest that the use of local clay bricks do not pose a radiological hazard. The calculated average absorbed dose rate in air within buildings was found to be 102 nGy h(-1) while the population weighted indoor annual effective dose was 0.20 mSv.

A study of air particulate pollution in Colombo using a nuclear-related analytical technique.

Air particulate matter of two size fractions (coarse [2.5-10 microns] and fine [less than 2.5 microns]) were collected at an urban residential site (Colombo University ground) over a period of 12 mo during 1996 using a Gent PM10 stacked filter unit. Seventy-five sets of samples collected during this period were analyzed for 10 elements: Al, Si, K, S, Ca, Ti, Fe, Zn, Br, and Pb by energy-dispersive X-ray fluorescence, which is a multielement analysis. This is a highly sensitive technique enabling quantitative analysis of very low masses. The average concentrations of lead, sulfur, and bromine, which are generally associated with combustion products of automotive exhausts, dominate the fine fraction in this study. The minimum and maximum concentration of lead resulting in an annual average of 0.09 microgram/m3 was found to be 0.0042 and 0.441 microgram/m3 in particulate matter with less than 10 microns equivalent aerodynamic diameter. The maximum concentration determined is well below the limits set by the World Health Organization (0.5-1.0 microgram/m3). The recommended value for Pb in Sri Lanka is 0.5 microgram/m3. Al, Si, Ca, Ti, and Fe exhibited enhanced concentrations in the coarse fraction, which probably originate from disturbed soil as a result of wind and traffic.