Risk Assessment and Uncertainty Analysis of Radon-222 Concentrations in Groundwater Within Abuja, Nigeria, Using Liquid Scintillation Counting

Abstract

Radon-222 (222Rn) in groundwater is a potential source of internal radiation exposure through ingestion, particularly in regions where groundwater constitutes a major source of drinking water. This study presents an assessment of 222Rn concentrations, radiological risks, and measurement uncertainties in groundwater within Kubwa, Abuja, Nigeria, using liquid scintillation counting. Thirty groundwater samples collected during the peak dry season were analysed using a calibrated Tri-Carb 1000 TR liquid scintillation analyser, with corrections for radioactive decay and partitioning effects. The 222Rn concentrations ranged from below the detection limit to 2.30 Bq L⁻¹, with a mean of 0.29 ± 0.43 Bq L⁻¹. Estimated annual effective doses were of the order of 10⁻³ mSv y⁻¹, well below the recommended reference level of 0.1 mSv y⁻¹. Expanded relative uncertainties (k = 2) ranged from approximately 6% for higheractivity samples to over 20% for samples near the detection limit. The results indicate a very low radiological risk from 222Rn ingestion through groundwater and provide baseline data for the study area. The findings also demonstrate the importance of considering detection limits and measurement uncertainty in environmental radioactivity assessments.