Natural Radiation from Soil using Gamma‐Ray Spectrometry

We have studied the distribution of natural radioactivity in the soil of Interlagos, in São Paulo city and Billings Reservoir, in São Bernardo do Campo, São Paulo, Brazil. The main contribution of the effective radiation dose is due to the elements of the $238Th$ decay series, with smaller contributions from $40K$ and the elements of the series of $238U.$ The results indicate the dose in all of the studied areas is around the average international dose due to external exposure to gamma rays (0.48 mSv/yr) proceeding from natural terrestrial elements.