External and Internal Radiation Doses from Chemical Fertilisers Used in Ibadan, Oyo State, Nigeria
The knowledge of external and internal doses of radiation emitted from radionuclides contained in different chemical fertilizers sold in Ibadan, Nigeria is very important. Therefore, activity concentrations of 40K, 226Ra and 232Th radionuclides in Urea, NPK (15 – 15 – 15), NPK (16 – 16 – 16) and Single Super Phosphate (SSP) fertilizer brands sold in the area for agricultural purposes were determined using gamma– ray spectroscopy. Radium equivalent activity (Raeq), gamma radiation or representative index (𝑰𝑰𝜸𝜸), alpha index (𝑰𝑰𝜶𝜶), annual gonadal dose equivalent (AGDE), external exposure (Dext) to gamma radiation as well as internal exposure (Dint) to doses of radiation to the marketers and users of the products were calculated. The calculated Raeq for the four brands of chemical fertilizers were 80.90 𝑩𝑩𝑩𝑩 𝒌𝒌𝒌𝒌−𝟏𝟏, 295.95 𝑩𝑩𝑩𝑩 𝒌𝒌𝒌𝒌−𝟏𝟏, 293.93 𝑩𝑩𝑩𝑩 𝒌𝒌𝒌𝒌−𝟏𝟏 and 706.17 𝑩𝑩𝑩𝑩 𝒌𝒌𝒌𝒌−𝟏𝟏 respectively. External gamma doses were 0.60 𝒎𝒎𝒎𝒎𝒎𝒎 𝒚𝒚−𝟏𝟏, 6.73 𝒎𝒎𝒎𝒎𝒎𝒎 𝒚𝒚−𝟏𝟏, 6.65 𝒎𝒎𝒎𝒎𝒎𝒎 𝒚𝒚−𝟏𝟏 and 13.00 𝒎𝒎𝒎𝒎𝒎𝒎 𝒚𝒚−𝟏𝟏 while the sum of the internal doses due to inhalation and ingestion were found as 3.93 𝝁𝝁𝝁𝝁𝝁𝝁 𝒚𝒚−𝟏𝟏, 4.51 𝝁𝝁𝝁𝝁𝝁𝝁 𝒚𝒚−𝟏𝟏, 3.61 𝝁𝝁𝝁𝝁𝝁𝝁 𝒚𝒚−𝟏𝟏 and 8.97 𝝁𝝁𝝁𝝁𝝁𝝁 𝒚𝒚−𝟏𝟏 respectively. More external and internal doses of radiation were calculated for marketers of the products than farmers. The order of SSP > NPKs > Urea fertilizers was observed for external exposure to gamma radiation. The results could serve as important radiometric data and information upon which future environmental monitoring of external and internal exposure to gamma radiation and alpha parti
