Abstract

The Jos – Bukuru crystalline rocks have high radioactivity, but not much is known about the concentration of radon in waters of its aquifers. In this work, the activity concentrations of Radon-222 (222 Rn) were investigated from twenty (20) water samples collected at different locations within the Jos – Bukuru area. The analysis of radon was done using Liquid Scintillation counter. A total of fifteen (15) out of the twenty water samples were analysed for anions and cations. The anions (SO4-2 and Cl-) were analysed using a multiparameter and HCO3- by titration. The cations (major ions, trace elements and rare earth elements were analysed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Radon concentration in groundwater of the study area ranges from 1.62Bq/L to 24.55Bq/L with a mean value of 15.62Bq/L. only twenty five percent (25%) of the water sources had radon above the 10 Bq/L recommended by the WHO. These values were obtained within the Jos and Bukuru Boitite Younger Granite Aquifers. The variation in radon content in water are the results of: (1) the actual use of the wells in the area such as extraction of groundwater which increases the groundwater circulation thereby decreasing the radon content and (2) Bad well constructions with inflow of surface water and (3) bedrock geology. Radon behaved independently with regards to the major ions and some of the trace elements, but showed positive but not significant relationship with uranium and some of the rare earth elements indicating possible contribution of these elements to concentration of radon in the waters. The Annual Effective Doses due to ingestion of 222Rn in water for the three (3) categories of people varies from 0.038 mSv/y, 0.077 mSv/y and 0.271 mSv/y for adults, children and infants respectively. These are within the recommended limits of 0.1 mSv/y for adults and children but high for infants. The composition of the groundwaters in the area is dominated by natural water–rock interactions while other areas were highly impacted by anthropogenic sources. On the basis of TDS, all the samples are within the range of desirable to permissible for drinking.

Key words: Bukuru, Crystalline rocks, Radioactivity, Radon-222 (222 Rn)