Natural radioactivity in cultivated land in the vicinity of a phosphate fertilizer plant in Nigeria

Natural radioactivity in soil and vegetable samples in cultivated land in the vicinity of an active phosphate fertilizer plant in Kaduna, Nigeria was carried out to assess the potential radiological impact of the plant on its immediate environment. The activity counting was carried out using sodium iodide gamma spectrometry. The annual committed effective dose for two vegetables in the farmlands due to uranium (238U) and thorium (232Th) was assessed. The mean activity concentration of radionuclides in the soil samples ranges from 20.5±7.3 to 31.6±4.1 Bq kg−1 for 226Ra, 19.6±1.6 to 53.2±3.7 Bq kg−1 for 232Th and 203.9±6.3 to 253.6±9.5 Bq kg−1 for 40K. The annual intake of 238U and 232Th from consumption of okra were 1.9 Bq kg−1 and 5.22 Bq kg−1 and for tomatoes 2.66 Bq kg−1 and 5.1 Bq kg−1 respectively. The committed effective doses from consumption of okra and tomatoes were 0.1 μSv y−1 and 0.12 μSv y−1 respectively.

► 238U, 232Th, and 40K in environmental samples in the vicinity of the fertilizer plant were identified.
► Soil samples range from 20.5±7.3 to 31.6±4.1, 19.6±1.6 to 53.2±3.7 and 203.9±6.3 to 253.6±9.5 Bq kg−1respectively.
► Dose rate in air due to these radionuclides range from 31.65 to 55.24 nGy h−1.
► Annual effective dose values range from 38.9 to 67.8 μSv with a mean of 44.4 μSv.
► Estimated committed effective doses from okra and tomatoes were 0.1 μSv y−1 and 0.12 μSv y−1.