Evaluation of Annual Effective Dose of Radon-222 Concentrations in Ground Water from Kotorkoshi and Its Rocky Environs, Zamfara State, Nigeria

Abstract

Radon-222 Concentration of groundwater varies with the geological formation of a place or region. However, the United States Environmental Protection Agency (USEPA) stipulated a limit of 11.1 BqL^-1 for the Radon level in water. In this study, Radon activity concentrations were measured in thirty (30) samples of groundwater sources collected from three (3) rocky communities, comprising of; kotorkoshi, Kura and Sankalawa respectively, using a liquid Scintillation Analyzer. Result shows that the Radon concentrations of these region varies from 9.84 to 23.55 BqL^-1 in well samples and 10.18 to 35.59 BqL^-1 in borehole samples, with a mean value of 20.64 BqL^-1. These concentrations are higher than the maximum safety limit, above which remedial action is required. The annual effective doses due to ingestion and inhalation of the Radon were evaluated. Consequently, most of these samples had annual effective dose that are higher than the maximum permissible limit of 0.2mSvy^-1, if consumed by children, and 0.1mSvy^-1, by adults. Since granite is the major rock found in these areas, it is assumed that the geological structures of these environs, predominantly contributes to the Radon activity concentrations. However, the total annual effective doses from the entire location of the studied areas were above the safety limits, as recommended by World Health Organization (WHO) and European Union (EU) Council.