Natural radiological studies of Kelantan and Terengganu States, Malaysia

Abstract

Natural environmental radioactivity arises mainly from primordial radionuclides such as 40K and also from 238U and 232Th decay series and have always been present in a variety of concentrations in every part of the earth’s mantle and in the tissue of every living being. Natural radioactivity can be found almost everywhere; in soil, public water supplies, oil and atmosphere. It poses a measurable exposure to human beings. The present study was aimed of providing the base line data of Terrestrial Gamma Radiation Dose rates (TGRD), natural radioactivity concentrations and the corresponding radiological health hazards in the environments of Kelantan and Terengganu states. TGRD were measured using a micro roentgen survey meter model 19 manufactured by Ludlum, from 150 and 145 locations at Kelantan and Terengganu states, respectively. A total of sixty (60) soil samples and ten (10) water samples from major rivers were collected with thirty six (36) soil and five (5) water samples collected from Kelantan and twenty four (24) soil and five (5) water samples collected from Terengganu, respectively. The soil samples were analyzed using a high purity germanium detector (HPGe) and Genie 2000 software, while the water samples were analyzed at Malaysian Nuclear Agency using atomic absorption spectrometry (AAS) for 40K and inductively coupled plasma mass spectrometer (ICP-MS) for U and Th concentrations. The measured TGRD mean values of 209 nGy h-1 and 150 nGy h-1 which are about three times the world and two times Malaysian averages of 59 nGy h-1 and 92 nGy h-1 respectively. The mean activity concentrations of 226Ra, 232Th, and 40K in the soil samples were found to be 82 Bq kg-1, 123 Bq kg-1 and 643 Bq kg-1 for Kelantan, and 79 Bq kg-1, 84 Bq kg-1, and 545 Bq kg-1 for Terengganu. 226Ra and 232Th in Kelantan are three times and in Terengganu twice the world average values of 32 Bq kg-1 and 45 Bq kg-1, while 40K is slightly higher than the world average value of 420 Bq kg-1. For water samples, the mean concentrations of U and Th and activity concentration of 40K was found to be 13 mBq L-1, 4 mBq L-1 and 1119 mBq L-1 for Kelantan and 0.71 mBq L-1, 0.23 mBq L-1 and 56 mBq L-1 for Terengganu, respectively. The health hazard impact of radium equivalent (Raeq), annual effective dose (AED), and external radiation hazard index (Hex) which are indicators of radiological health hazards were computed as 307 Bq kg-1, 1.28 mSv y-1 and 0.83 for Kelantan and 242 Bq kg-1, 0.92 mSv y-1 and 0.65 for Terengganu, respectively. Statistical relationships between TGRD with underlying geological formations and soil types were obtained. Isodose contour maps which shows the distribution pattern of TGRD for both states were produced. Radiological health due to TGRD and natural radioactivity are on the average higher than both the world average and Malaysian average but were still within the recommended values of 370 Bq kg-1, 0.48 mSv y-1 and unity, thus should not pose any significant danger to the populations.