Evaluation of environmental natural radioactivity levels in soil and ground water of Barkin Ladi, Plateau state, Nigeria

Gamma spectrometry was used to measure gamma dose rate in air and to determine the activity concentration of naturally occurring radionuclides viz. Ra-226 Th-232 and K-40 in soil samples collected across the geological formations of Barkin Ladi. Dose rates measured in-situ ranged from 5 nGy h(-1) to 1265 nGy h(-1) with a mean value of 325 nGy h(-1). The activity concentrations of Ra-226 ranged from 27 to 327 Bq kg(-1), 34 to 457 Bq kg(-1) for Th-232 and 43 to 1055 Bq kg(-1) for K-40. Their mean values are significantly higher than their corresponding global average values. Annual effective dose due to exposure to gamma dose is calculated at 0.34 mSv y(-1). Mass concentrations of uranium (U-238) and thorium (Th-232) determined in groundwater samples using Inductive Coupled Plasma Mass Spectrometry (ICP-MS) ranged from 2.5 to 35 mu g l(-1) for U-238 and 0.5 to 15 mu g l(-1) for Th-232. Ingestion effective dose varies between 10.5 and 142 mSv y(-1) for U-238 and between 0.34 and 10.2 mSv y(-1) for Th-232. Mass concentration of three water samples exceed the toxicity limit of U in groundwater provided by WHO. The result revealed that human risk due to ingestion of groundwater is from chemical toxicity rather than radiological effects. The results of this work will be useful for radio-geochemical investigation and groundwater resources management.