Natural Radioactivity and Radon Exhalation in Phosphate Fertilizers

Abstract

238U, 232Th, 226Ra, 222Rn and 40K activity concentrations in fertilizer samples collected from a local market were determined. Radon activity concentrations ranged from 0.04–252 Bq kg−1 and were comparable with low activity concentrations ranges reported previously. Radon exhalation rates and effective 226Ra concentration were determined using CR-39 solid-state nuclear track detectors. Effective 226Ra concentrations ranged from 4.27–33.93 Bq kg−1. Two different 222Rn exhalation rates were determined; area dependent exhalation rates (0.044–0.351 Bq m−2 h−1) and mass dependent exhalation rates (0.023–0.180) Bq kg−1 h−1). Even without secular equilibrium, strong correlations were generally apparent among uranium concentrations, effective 226Ra concentrations and 222Rn exhalation rates in samples with high concentrations of uranium. 232Th and 40K concentrations ranged from 0–44.6 and 0.08–127 μg/g, respectively.