Mathew S, Rajagopalan M, Abraham J P, Balakrishnan D, Umadevi A G
Research and PG Department of Physics, Mar Thoma College, Thiruvalla, Kerala, India.
Radiat Prot Dosimetry. 2012 Nov;152(1-3):80-3. doi: 10.1093/rpd/ncs193. Epub 2012 Sep 5.
Contribution of terrestrial radiation due to the presence of naturally occurring radionuclides in soil and air constitutes a significant component of the background radiation exposure to the population. The concentrations of natural radionuclides in the soil and indoor air of Chellanam were investigated with an aim of evaluating the environmental radioactivity level and radiation hazard to the population. Chellanam is in the suburbs of Cochin, with the Arabian Sea in the west and the Cochin backwaters in the east. Chellanam is situated at ∼25 km from the sites of these factories. The data obtained serve as a reference in documenting changes to the environmental radioactivity due to technical activities. Soil samples were collected from 30 locations of the study area. The activity concentrations of (232)Th, (238)U and (40)K in the samples were analysed using gamma spectrometry. The gamma dose rates were calculated using conversion factors recommended by UNSCEAR [United Nations Scientific Committee on the Effects of Atomic Radiation. Sources and effects of ionizing radiation. UNSCEAR (2000)]. The ambient radiation exposure rates measured in the area ranged from 74 to 195 nGy h(-1) with a mean value of 131 nGy h(-1). The significant radionuclides being (232)Th, (238)U and (40)K, their activities were used to arrive at the absorbed gamma dose rate with a mean value of 131 nGy h(-1) and the radium equivalent activity with a mean value of 162 Bq kg(-1). The radon progeny levels varied from 0.21 to 1.4 mWL with a mean value of 0.6 mWL. The thoron progeny varied from 0.34 to 2.9 mWL with a mean value of 0.85 mWL. The ratio between thoron and radon progenies varied from 1.4 to 2.3 with a mean of 1.6. The details of the study, analysis and results are discussed.
土壤和空气中天然存在的放射性核素所产生的陆地辐射，是人群背景辐射暴露的一个重要组成部分。对切拉纳姆土壤和室内空气中天然放射性核素的浓度进行了调查，目的是评估环境放射性水平以及对人群的辐射危害。切拉纳姆位于科钦市郊，西临阿拉伯海，东临科钦潟湖。切拉纳姆距离这些工厂所在地约25公里。所获得的数据可作为记录技术活动导致环境放射性变化的参考。从研究区域的30个地点采集了土壤样本。使用伽马能谱法分析了样本中(232)Th、(238)U和(40)K的活度浓度。伽马剂量率是根据联合国原子辐射影响科学委员会（UNSCEAR）[联合国原子辐射影响科学委员会。电离辐射的来源和影响。UNSCEAR（2000年）]推荐的转换因子计算得出的。该地区测量的环境辐射暴露率范围为74至195 nGy h(-1)，平均值为131 nGy h(-1)。主要的放射性核素为(232)Th、(238)U和(40)K，利用它们的活度得出吸收伽马剂量率的平均值为131 nGy h(-1)，镭当量活度的平均值为162 Bq kg(-1)。氡子体水平在0.21至1.4 mWL之间变化，平均值为0.6 mWL。钍射气子体在0.34至2.9 mWL之间变化，平均值为0.85 mWL。钍射气与氡子体的比值在1.4至2.3之间变化，平均值为1.6。讨论了该研究、分析和结果的详细情况。
