Determination of radon exhalation rates from soil around buildings in Lagos environments using passive measurement technique.

Abstract

In this study, measurements of radon concentrations and estimation of exhalation rates were carried out in soil around buildings within Lagos State in order to determine the contribution to indoor radon concentrations from the soil, and determine the influence of soil moisture on the exhalation rates. Fifty-four samples were collected randomly with 27 measured as wet samples and 27 dried before measurements so as to account for the moisture content. Passive measurement method, using cover cup technique with solid state nuclear track detectors, CR-39, was employed. The results showed weak correlations between the concentrations of radon emanated from the soil samples and the indoor radon concentrations. The results obtained suggested lower concentrations of radon emanated from wet soil than dry soil indicating the influence of moisture. The results further indicate that the highest and lowest values as well as the highest mean for both wet and dry soil samples were obtained from the same environment, suggesting that the soil in that environment are of anomalous petrophysical property. Concentrations of radon emanated from dry soil are higher than in wet soil, suggesting that the presence of moisture may results in reduction of radon concentrations in soil samples. The result of the surface exhalation rates and the mass exhalation rates are in congruent with results obtained for the concentrations of radon emanated from wet and dry soil samples.