Abstract
Atmospheric concentrations of radon were calculated from filtered radon daughter β activity, obtained from 1- and 15-m. elevations at a rural site, and from 1- and 91-m. elevations at a semi-rural site near Washington, D.C. Measurements were obtained from the successive filtration of air over 20-min. periods for durations of several hours, during various meteorological conditions. The extent of secular equilibrium between radon and its daughter products in the atmosphere near the ground (≤ 15 m.) was determined from a calculation of the RaC/RaB atom ratio (ρ) in the air, derived from the measured rate of decay of the filtered β activity. Estimates of an effective residence time (τ) in the atmosphere of the radon conglomerate, based on either a continuous or single emission of radon into the air, are presented. The relationship between ρ and τ for various weather conditions is discussed, as well as possible effects of (a) wind, (b) thermal stability, (c) atmospheric scavenging, and (d) precipitation on measured levels of natural radioactivity. Radon concentrations measured during an “air pollution potential” episode and during fumigation conditions are presented. In general, the response of measured β activity in the air to changes in the turbulent state of the atmosphere near the ground gives evidence of the feasibility of using naturally occurring radon and radon daughter products as tracers for determining atmospheric diffusivity.
