Comparative analysis of radon gas concentration in caves developed in carbonatic, quartzitic and ferruginous lithologies.

Radon gas concentrations in ferruginous, quartzitic/conglomeratic and carbonatic caves were measured and the results obtained in each lithology were compared. Three representatives of each formation (nine caves in total) were studied. The caves are located in three environmental preserved areas in the Ferriferous-Aquifer Quadrangle and in its regional surrounding, in the center-south portion of Minas Gerais State, Brazil. It was found that the average concentration in quartzitic/conglomeratic caves (4,759 Bq/m) was much higher than those obtained in carbonatic (844 Bq/m) and ferruginous (945 Bq/m) caves. This result most likely reflects differences in the uranium content of the rock types. Also, for a better understanding of the radon distribution inside the caves, concentration maps with their interpolated values were generated using geospatial analysis tools.