NATURAL RADIOACTIVITY MEASUREMENT IN SELECTED DOMINANT SOIL TYPES OF EASTERN HARARGHE, OROMIA, ETHIOPIA

Abstract

Exposure to radiations beyond acceptable limits induces unintended and undesirable effects on human health. The dominant fraction of terrestrial radiation comes from soils and rocks. Soils are encountered on regular bases by those who work on farms or constructions. In this study, the activity concentrations of 226Ra, 232Th and 40Kwere determined using high resolution gamma spectrometry (HPGe detector) and their radiological hazards are presented for dominant soil types of eastern Hararghe, Ethiopia. For the study, a total of twenty soils samples were gathered from four Kebeles of Haramaya and two kebeles of Kombolcha districts. The specific geographical locations of each soil sample were identified by using GPS. Each sample passed all the lab protocols of ERPA. The samples were sealed for about a month to achieve secular equilibrium among the decay series of natural radionuclides. Each sample was mounted for an average of 34,200 seconds in the detection geometry to carry out the identification and the analysis of the activity concentrations. The results showed the activity concentration of 226Ra in all soil types to be lower than the allowable limits. The activity concentrations of 232Th and 40K were higher than the recommended values except 40K, in Cambisol soil type. All the radiological hazard assessment variables were made by using standard formulas which are applicable for soil environmental samples. The radiological hazard values obtained in this study were compared with world acceptable limits and it was found the average values of absorbed dose rates exceeded the world acceptable limits except in Cambisol soil type. But the average values of radium equivalent activity, indoor and outdoor annual effective dose rates, and external and internal hazard indices were below the world allowable limits. Implementation of safety rules are based on radium equivalent activity. The obtained data from those soil samples in the study area showed no much significant radiological health risk to the local population.