Effect of Altitude Concentration Gradient of Soluble Gaseous Pollutants on Their Scavenging by Falling Rain Droplets

Abstract

This paper analyzes absorption of soluble atmospheric trace gases by falling rain droplets with internal circulation, which is caused by interfacial shear stresses. It is assumed that the concentration of soluble trace gases in the atmosphere varies in a vertical direction. In the analysis the accumulation of the absorbate in the bulk of the falling rain droplet was accounted for. The problem is solved in the approximation of a thin concentration boundary layer in the droplet and in the surrounding air. It was assumed that the bulk of a droplet, beyond the diffusion boundary layer, is completely mixed and that concentration of the absorbate is homogeneous and time dependent in the bulk. By combining the generalized similarity transformation method with Duhamel's theorem, the system of transient conjugate equations of convective diffusion for absorbate transport in liquid and gaseous phases with time-dependent boundary conditions is reduced to a linear-convolution Volterra integral equation of the second kind, which is solved numerically. It is shown that the nonuniform vertical distribution of absorbate in a gaseous phase strongly affects mass transfer during gas absorption by a falling droplet.

Effect of rain scavenging on altitudinal distribution of soluble gaseous pollutants in the atmosphere

“…Georgii and Müller 1974;Georgii 1978). Information the atmosphere affects the rate of gas absorption by rain droplets (see Elperin et al 2009). Note that the existing models of global transport in the atmosphere do not take into account the influence of rains on biogeochemical cycles of different gases.…”

Anomalous Noble Gas Solubility in Liquid Cloud Water: Possible Implications for Noble Gas Temperatures and Cloud Physics

“…This is a very conservative assumption since any stirring or advection within the liquid water will enhance the uptake of noble gases. For example, in Elperin et al (2009), it was assumed that the interior of a droplet has a uniform concentration beneath a thin diffusive boundary layer. Therefore, the model results presented here should be considered the absolute minimum change expected in the C/C ASW value for any noble gas to move from initial ice values toward a value of 1, that is, solubility equilibrium.…”

Wet precipitation scavenging of soluble atmospheric trace gases due to chemical absorption in inhomogeneous atmosphere

“…Physical gas absorption by falling droplets in the inhomogeneous atmosphere was considered, e.g. by Hales (1972) and Elperin et al (2009). Appendix 3: Gas absorption by a falling liquid droplet in the inhomogeneous atmosphere accompanied by the second-order chemical reaction in a liquid phase…”