Absorption of Soluble Gases by Atmospheric Nanoaerosols

TL;DR

This paper models the mass transfer of soluble gases to atmospheric nanoaerosols, highlighting the importance of kinetic effects which significantly influence gas absorption rates.

Contribution

It introduces a flux-matching theory-based integral equation for transient molecular flux and demonstrates the critical role of kinetic effects in nanoaerosol gas absorption.

Findings

Kinetic effects significantly influence gas absorption rates.

Neglecting kinetics overestimates soluble gas flux.

Numerical solutions for SO2, N2O3, Cl2 absorption by nanoaerosols.

Abstract

We investigate mass transfer during absorption of atmospheric trace soluble gases by a single droplet whose size is comparable to the molecular mean free path in air at normal conditions. It is assumed that the trace reactant diffuses to the droplet surface and then reacts with the substances inside the droplet according to the first order rate law. Our analysis applies a flux-matching theory of transport processes in gases and assumes constant thermophysical properties of the gases and liquids. We derive an integral equation of Volterra type for the transient molecular flux density to a liquid droplet and solve it numerically. Numerical calculations are performed for absorption of sulfur dioxide (SO2), dinitrogen trioxide (N2O3) and chlorine (Cl2) by liquid nanoaerosols accompanied by chemical dissociation reaction. It is shown that during gas absorption by nanoaerosols the kinetic effects play significant role, and neglecting kinetic effects leads to significant overestimation of the soluble gas flux into a droplet during all the period of gas absorption.