Scavenging of radioactive gases due to adsorption by atmospheric nanoaerosols

We analyze an influence of radioactive decay and kinetic effects on the rate of trace gas scavenging due to adsorption by an ensemble of solid porous nanoparticles. The size of nanoparticles is comparable to the mean free path in the air at normal conditions. We employ a transient model of adsorption of radioactive gases by an ensemble of porous particles. Our analysis applies a flux-matching theory of transport processes in gases and assumes constant thermophysical properties of the gases and particles. It is demonstrated that evolution of concentration of adsorbed gas inside particles is determined by an ordinary differential equation of the first order. Calculated temporal dependences of adsorbed amount of radioactive gas by particles are compared with experimental results of Noguchi et al. (Jpn J Health Phys 25:209–219, 1990) for gaseous Iodine-131 adsorption by carbon-based atmospheric nanoaerosols. We also showed that when an approximation of uniform distribution of concentration of adsorbed gas inside particles is not valid, temporal evolution of concentration of an active trace gas in a gaseous phase is governed by an integro-differential equation.