Spectrum gamma radiation, rainfalls and radon gas measurements during 2019 and 2020 in tropical region of Brazil

Abstract

Environmental gamma radiation spectra close to the ground, rains and radon gas were monitored during the years 2019 and 2020 in the city of São Jose dos Campos, SP, tropical region of Brazil. The measurements showed the presence of Talium-238, Potassium-40, Bismuth-214 and Lead-214 in the photon energy range between (0.2-5.0) MeV with the time of one-hour measurement of sampling. The typical integrated count rate between each minute of gamma radiation in the same energy interval was 39000 counts / minutes, mean value, during all time of 110000 minutes of net measurements. The peaks observed in the gamma radiation count in this time and energy interval correspond to the presence of intense rains present in the region. With 1 hour of measurement in the region as a minimum sampling time and using a (3x3) inch sodium iodide spectrometer, it was possible to distinguish the radioactive elements in that region. Up to a height of 30 meters above the ground there was no difference in the radiation spectrum measured. The appearance of gamma ray peaks during rapid and intense rains on the site is due the presence of radon gas in these rains is increasing. It is the phenomenon of washing the radon gas in air during the rains. With weak and continuous rains in the place this phenomenon does not appear. Right in this tropical region of Brazil, the presence of radon gas ejection from the soil was the main responsible for the intensity and variation of x and gamma radiation.