Simultaneous Observations of the Gamma Background from Soil Radionuclides and the Electrical Conductivity of the Near-Surface Atmosphere

Abstract—The paper presents the results of simultaneous ground-based observations of the gamma-ray spectra from soil radionuclides, the volumetric activity of radon, and the electrical conductivity of the air in the near-surface atmosphere. Based on an analysis of gamma radiation spectra, estimates were obtained for the 238U, 232Th and 40K concentrations in the upper soil layer and the dose rate of terrestrial gamma radiation for 43 sites of 8 observation points, the distance between which ranges from 1 m to 25 km. The range of recorded concentrations was 1.28–2.64 mg/kg for 40K, 0.7–1.41 mg/kg for 238U and 4.4–8.88 mg/kg for 232Th. The average ratios between the volumetric activities of these soil radionuclides and the statistics of deviations from the average values were determined. During the observation period, the range of variations in the gamma dose rate from soil radionuclides at a height of 1 m above the Earth’s surface was 26–52 nGy/h. During rain, an increase in the number of gamma quanta is recorded in peaks 214Bi, reaching 1200% for photon energies near 1765 keV and 300% for photon energies near 2204 keV. The autocorrelation function of the time series of the gamma dose rate from soil radionuclides in fair-weather conditions decreases with a characteristic time scale of several days, which decreases to several hours if precipitation occured during the analyzed time interval, accompanied by an intensification in the 214Bi lines in the gamma-ray spectrum. The electrical conductivity of the air in the near-surface atmosphere shows diurnal variation with a minimum during the daytime and two maxima—in the morning and evening. Height-separated observations showed that the electrical conductivity at a height of 0.5 m is, on average, greater than at a height of 1.5 m, and during the daytime, the difference in conductivity values at these heights is expressed more distinctly.