Evaluation of the activity levels and the radiological hazards associated with the imported chemical and local organic fertilizers used in Ethiopia

In this study, the activity concentrations of 226 Ra, 232 Th, and 40 K in fertilizer samples obtained from farmers and suppliers utilized in Ethiopia were measured using gamma-ray spectrometry with an HPGe detector. The highest average activity concentrations of 226 Ra, 232 Th, and 40 K were found as 45.8 ± 3.1 in nitrogen phosphorous compound (NP) fertilizers, 25.7 ± 3.0 in organic fertilizers, and 799.5 ± 64.9 in organic fertilizers Bq/kg, respectively, and the corresponding lowest average values were found as 17.4 ± 2.4 in organic fertilizers, 14.3 ± 1.8 in urea, and 135.1 ± 6.6 in urea Bq/kg, respectively. The average activity concentrations of 226 Ra in NP fertilizers and 40 K in animal fertilizers were higher than the Earth's crust average values of 32 and 412 Bq/kg for 226 Ra, and 40 K respectively. Radiological hazard indicator parameters, such as the radium equivalent activity (Ra eq ), outdoor absorbed dose rates ( D out ), outdoor annual effective doses (AED out ), outdoor excess lifetime cancer risk (ELCR out ), external hazard index (H ex ), internal hazard index (H in ), alpha index ( I α ), and annual gonadal dose equivalent (AGDE), were estimated in both chemical and organic fertilizer samples. The resulting average values were within the range of the international dose safety limit of fertilizers.