Assessment of natural radioactivity and heavy metal levels in the neighborhood of mkuju uranium deposit

Abstract

The study aimed at determining the pre-mining background level of natural radioactivity and elemental composition of the samples of soil, water and foodcrops collected from Likuyu village located at about 53 Km east of the Mkuju uranium deposit. The concentration level of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Ag, Cd, Hg, Pb, Th and U in soil and foodcrop samples were determined by EDXRF technique while natural radioactivity level were determined using low level gamma spectrometry technique. The concentration levels of heavy metals in all measured samples were within the level reported in literature and below the maximum permissible concentration level of heavy metals in soil, water and foodcrops set by National and International agencies. The average radioactivity concentrations obtained in soil samples for 238U (51.7 Bq/kg), 232Th (36.4 Bq/kg) and 40K (564.3 Bq/kg) were higher than the worldwide average concentrations value of these radionuclides reported by UNSCEAR, 2000. The average activity concentration value of 238U (2.35 Bq/l) and 232Th (1.85 Bq/l) in water samples were similar and comperable to the mean concentration in the control sample collected from Nduluma River in Arusha. The concentration levels of natural radioactivity in foodcrops were within the range reported in various studied countries. The calculated total committed effective dose received by Likuyu population due to the intake of natural radioactivity from water and foodcrop consumption was found to be less than the annual dose guideline value of 1 mSv y-1 recommended by ICRP.