Determination of Radon-222 Concentration in Soil Samples from VI, Shaffa and Garta Sama Communities of Michika Local Government Area, Adamawa State, Nigeria

Abstract

Radon-222 and its progeny contributed greatly to natural background radiation. Long time exposure to radiation increases the high probability of cancer to persons, radiological hazard associated with inhalation of radon-22 gas from 25 soil samples were collected and analysed for radon usig RAD7 electronic detector. The research measured soil-gas radon-222 activity concentration, absorbed dose rate, annual effective dose equivalent and excess lifetime cancer risk at five sampling points (VI-East, VI-West, VI-South, Garta sama-South, and Shaffa- South) at 50m, 100m, 200m, 500m and 2km from artisanal mining pit. Radon-222 concentrations ranged from 257 – 6,438 Bq/m3 across all sampling points and distance. Four out five points exceeded the ICRP reference level (300 Bq/m3) and WHO screening limit (100 Bq/m3) at every distance sampled, including the 2km control zone. AEDE ranged from 0.006 – 0.162mSv/y and ELCR 0.29 ×10-3) at most sampling points. Radon concentration did not decline monotonically with distance, VI- East reached its survey maximum at 500m, and elevated readings persisted 2km from the pit. This results showed that exposure is driven primarily by geogenic/structural control from basement lithology, with a secondary genuine anthropogenic amplification from fracture enhanced radon emanation near the mining disturbance. Relative to comparable Nigerian and West African NORM studies, the exposure recorded is real and exceeds international guidance but is intermediate in severity. These research findings support an area-based, rather than excavation confined, approach to radiological risk mitigation around artisanal mining sites.