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Investigation of geological and soil influence on natural gamma radiation exposure and assessment of radiation hazards in Western Region, Peninsular Malaysia

ABSTRACT

This study was conducted to investigate the influence of geological and soil formation on natural gamma (γ) radiation exposure. The aim of this study also to obtain a baseline data of γ radiation exposure and radioactivity associated with soil in the granitic territory at Western Region of Peninsular Malaysia. From 3727 in situ measurements of γ radiation dose rates, the mean value of dose rate obtained in this study is 204 nGy h−1 with the range of between 17 and 1039 nGy h−1. The mean value obtained in this study is three times higher than the world average value of 57 nGy h−1. Based on in situ measurements, the range of annual effective dose received by the population living in the study area is 0.02–1.28 mSv y−1. The study found that the levels of γ radiation exposures are strongly influenced by the geological and soil types. From the gamma spectrometry analysis, the mean radioactivity levels of 226Ra, 232Th and 40K in soil in western region Peninsular Malaysia are slightly higher and comparable with the places of “High Natural Background Radiation Areas” (HNBRAs) in the world as reported by UNSCEAR (2000). The mean value of 226Ra was 120 Bq kg−1 and ranged from 7 to 554 Bq kg−1, whilst for 232Th was 276 Bq kg−1 with a range of 23–1806 Bq kg−1. These values indicate 3 and 9 times, respectively, higher than the world average values. However, the radium equivalent activity (Raeq) obtained in this study (277 Bq kg−1) is lower than permissible values of 370 Bq kg−1. The radiological indices of radiation hazards in this study show that the index values are higher than the permissible limit values of 1. The mean value for gamma activity index (Iγ,) external hazard index (Hex), internal hazard index (Hin) was 1.89, 1.46 and 1.78, respectively. As well as γ radiation levels, radioactivity levels of 226Ra, 232Th and 40K also were strongly influenced by the geological and soil types.