Senthilkumar B, Dhavamani V, Ramkumar S, Philominathan P
Institute for Ocean Management, Anna University Chennai, Chennai - 600 025, India.
J Med Phys. 2010 Jan;35(1):48-53. doi: 10.4103/0971-6203.55966.
This study assesses the level of terrestrial gamma radiation and associated dose rates from the naturally occurring radionuclides (232)Th, (238)U and (40)K in 10 soil samples collected from Thanjavur (Tamil Nadu, India) using gamma-ray spectrometry. The activity profile of radionuclides has clearly showed the existence of low level activity in Thanjavur. The geometric mean activity concentrations of (232)Th, (238)U and (40)K is 42.9+/-9.4 Bq.kg(-1), 14.7+/-1.7 Bq.kg(-1) and 149.5+/-3.1 Bq.kg(-1) respectively are derived from all the soil samples studied. The activity concentration of (232)Th, (238)U and (40)K in soil is due to the presence of metamorphic rocks like shale, hornblende-biotite gneiss and quartzofeldspathic gneiss in these areas. Gamma absorbed dose rates in air outdoors were calculated to be in the range between 32 nGy.h(-1) and 59.1 nGy.h(-1) with an arithmetic mean of 43.3 +/-9 nGy.h(-1). This value is lesser than the population weighted world-averaged of 60 nGy.h(-1). Inhabitants of Thanjavur are subjected to external gamma radiation exposure (effective dose) ranging between 39.2 and 72.6 muSv.y(-1) with an arithmetic mean of 53.1+/-11 muSv.y(-1). The values of the external hazard index determined from the soil radioactivity of the study area are less than the recommended safe levels.
本研究使用伽马射线能谱法评估了从坦贾武尔（印度泰米尔纳德邦）采集的10个土壤样本中天然存在的放射性核素钍-232、铀-238和钾-40的陆地伽马辐射水平及相关剂量率。放射性核素的活度分布清楚地表明坦贾武尔存在低水平活度。从所有研究的土壤样本中得出，钍-232、铀-238和钾-40的几何平均活度浓度分别为42.9±9.4贝克勒尔/千克、14.7±1.7贝克勒尔/千克和149.5±3.1贝克勒尔/千克。土壤中钍-232、铀-238和钾-40的活度浓度是由于这些地区存在页岩、角闪石-黑云母片麻岩和石英长石片麻岩等变质岩。计算得出户外空气中的伽马吸收剂量率在32纳戈瑞/小时至59.1纳戈瑞/小时之间，算术平均值为43.3±9纳戈瑞/小时。该值低于60纳戈瑞/小时的全球人口加权平均值。坦贾武尔居民受到的外部伽马辐射照射（有效剂量）在39.2至72.6微希沃特/年之间，算术平均值为53.1±11微希沃特/年。根据研究区域土壤放射性确定的外部危害指数值低于推荐的安全水平。
