Variability of thoron distribution in the surface atmosphere at Borok Geophysical Observatory

Abstract

The variability of radon-220 (thoron) distribution in the surface atmosphere is investigated by mathematical modeling of thoron turbulent transport, based on the data of continuous field natural observations at Borok Geophysical Observatory (Central Russia). The thoron flux from the surface was set according to the observations. Variations of turbulent diffusion coefficient altitude profiles were calculated by the observations of wind velocity pulsations at two altitudes made synchronously on the same location. The altitude profiles of thoron volumetric activity typical for the atmospheric surface layer are estimated. It is shown that the thoron volumetric activities at any altitudes vary concurrently, but the largest thoron volumetric activity, as well as its gradient, occurs below 0.5 m at nighttime.