Soil-to-organic Sangyod rice grain transfer factors (TF values) of natural and anthropogenic radionuclides in Phatthalung province, Thailand

Abstract

The specific activities of natural (40K 226Ra and 232Th) and anthropogenic (137Cs) radionuclides in paddy soil and organic Sangyod rice grain were measured and analyzed in this study with an aim to determine the soil-to-organic Sangyod rice grain transfer factors (TF values) of all required radionuclides in Don Pradu sub-district, Pak Phayun district in Phatthalung province in the south of Thailand. The high purity germanium (HPGe) detector and gamma-ray spectrometry analysis system which were installed and used in advanced laboratory at TINT were used to conduct experiments to measure and analyze of all required radionuclides in this research. The average concentrations of 40K 226Ra, 232Th, and 137Cs in paddy soil were found to have a value of 657.30 ± 23.03, 180.01 ± 4.39, 162.02 ± 3.84 and < 1.81 Bq/kg respectively while in organic Sangyod rice grain, their values were 24.11 ± 2.01, 0.28 ± 0.07, 0.17 ± 0.06 and 0.10 ± 0.03 Bq/kg respectively. For TF values were calculated and found to be 0.037, 0.002, 0.001, and 0.055 for 40K, 226Ra, 232Th, and 137Cs, respectively. Furthermore, four important radiological hazard indices which are gamma-absorbed dose rate (D), radium equivalent activity (Raeq), external hazard index (Hex) and annual external effective dose rate (AEDout) were also evaluated by using the average values of 40K, 226Ra and 232Th. In addition, by using the AEDout value, the excess lifetime cancer risk (ELCR (outdoor)) in paddy soil in the study area would be also studied, evaluated and presented. Moreover, the evaluated TF values of required radionuclides were higher than that reported by the International Atomic Energy Agency (IAEA) in 2010 but the values were much lower than those in the study in Malaysia.