Natural Radioactivity and Radon Exhalation in Phosphate Fertilizers

U-238, Th-232, Ra-226, Rn-222 and K-40 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 Ra-226 concentration were determined using CR-39 solid-state nuclear track detectors. Effective Ra-226 concentrations ranged from 4.27-33.93 Bq kg(-1). Two different Rn-222 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 Ra-226 concentrations and Rn-222 exhalation rates in samples with high concentrations of uranium. Th-232 and K-40 concentrations ranged from 0-44.6 and 0.08-127 mu g/g, respectively.