Evaluation of radiological risk associated with the use of nitrogenous fertilizers in Ibadan, Nigeria using gamma spectrometer

Abstract

Urea fertilizer has been considered as the most important nitrogenous fertilizer sold in Nigerian market. The use of urea fertilizers to enhance growth of vegetable crops, flowers and lawn has recently drawn public concern in the aspect of its contribution to environmental radioactivity. Potential radiological risk due to the activity concentration of ⁴⁰K, ²²⁶Ra and ²³²Th in urea fertilizer samples collected from local supplier in different locations in Ibadan, southwestern Nigeria was determined using NaI(Tl) gamma ray spectrometer detector. Results of the analyses showed that activity concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th in urea fertilizer ranged from 154.3±7.9 to 2907±18.8 Bq kg^-1; 7.5±5.2 to 23.4±10.7 Bq kg^-1 and 28.2±3.8 Bq kg^-1 respectively with total mean values of 183.6±9.6 Bq kg^-1, 13.2±5.8 Bq kg^-1and 38.3±10.0 Bq kg^-1 respectively which were lower than the corresponding maximum safety limit. Furthermore, estimation of absorbed dose rate in air and outdoor annual effective dose were below the standard safety limit 60 nGyh^-1 and 0.07 mSvy^-1 respectively. External and internal hazard indices as well as alpha index were determined with results less than unity (1.0) as the standard safety limit; an indications that there is no radiation risk associated with the use of investigated urea fertilizer samples, therefore, samples investigated were radiologically safe.