Assessment of levels of naturally occuring radioactive materials in phosphate fertilizer of nitrogen chemical of Zambia LTD

The radiological impacts of phosphate fertilizers could be significant due to the elevated radioactivity contents of naturally occurring radioactive materials (NORM) such as ²³⁸U series, ²³²Th series, and ⁴⁰K in phosphate deposits used as raw material in the production of phosphate fertilizers. The use of fertilizers in agriculture to enhance crop yield on a small planted area is becoming more common around the world. Fertilizers are mineral or organic compounds that provide the nutrients required for significant crop yield. The specific activities of ²²⁶Ra, ²³²Th, and ⁴⁰K in different types of phosphate fertilizers collected in the Nitrogen Chemicals of Zambia study area were measured using High Pure Germanium Detector (HPGe). The radionuclides concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in three different samples were analyzed, with concentrations ranging from 2±0.1 Bq/kg to 132±12 Bq/kg, 21±1.0 Bq/kg to 48.4±10 Bq/kg, and 67±4.1 Bq/kg to 6253±5 Bq/kg with the mean values of 45.93 Bq/kg, 35.3 Bq/kg and 2132.77 Bq/kg respectively. Based on the radionuclide results, the radiological hazards of radium equivalent activities (Ra_eq), external hazard index (H_ex), internal hazard index (H_in), absorbed dose (D), and annual effective dose were calculated, ranging from 37.19 Bq/kg to 689.69 Bq/kg for Ra_eq, 0.10 to 1.84 for H_ex, 0.11 to 2.20 for H_in, 16.40 nGy/h to 350.97 nGy/h for absorbed dose, and 0.02 mSv/y to 0.43 mSv/y for the annual effective dose. Based on these calculations, Sulphate of ammonia and Urea samples showed results within the world average apart from NPK 15 15 15 fertilizer sample, this implies that the use of phosphate fertilizers should be done with radiation protection precautions. The calculated annual effective doses and the mean annual effective dose for all samples were within the range of the worldwide average value of 1 mSv y^-1 according to ICRP 103. (author)