Compilation and evaluation of gas phase diffusion coefficients of reactive trace gases in the atmosphere: volume 1. Inorganic compounds

Abstract

Abstract. Diffusion of gas molecules to the surface is the first step for all gas-surface reactions. Gas phase diffusion can influence and sometimes even limit the overall rates of these reactions; however, there is no database of the gas phase diffusion coefficients of atmospheric reactive trace gases. Here we compile and evaluate, for the first time, the diffusivities (pressure-independent diffusion coefficients) of atmospheric inorganic reactive trace gases reported in the literature. The measured diffusivities are then compared with estimated values using a semi-empirical method developed by Fuller et al. (1966). The diffusivities estimated using Fuller's method are typically found to be in good agreement with the measured values within ±30 %, and therefore Fuller's method can be used to estimate the diffusivities of trace gases for which experimental data are not available. The two experimental methods used in the atmospheric chemistry community to measure the gas phase diffusion coefficients are also discussed. A different version of this compilation/evaluation, which will be updated when new data become available, is uploaded online (https://sites.google.com/ site/mingjintang/home/diffusion).

Modelling the physical multiphase interactions of HNO<sub>3</sub> between snow and air on the Antarctic Plateau (Dome C) and coast (Halley)

“…b Sander (1999), with an effective molecular diffusivity, D s = D a /τ g , where the tortuosity τ g = 2, and molecular diffusivity in free air at 296 K, D a (296 K) = 87 Torr cm 2 s −1 (Tang et al, 2014). c Waddington et al (1996), with a snow layer thickness, z = 4 mm.…”

Heterogeneous reaction of ClONO<sub>2</sub> with TiO<sub>2</sub> and SiO<sub>2</sub> aerosol particles: implications for stratospheric particle injection for climate engineering

“…Under our experimental conditions, the entrance length needed to develop the laminar flow is ∼ 12 cm. The mixing length is calculated to be ∼ 14 cm, using a diffusion coefficient of 0.12 cm 2 s −1 for ClONO 2 in N 2 at 296 K (Tang et al, 2014b). Only the middle part of the flow tube (30-80 cm) was used to measure the uptake kinetics.…”

Features in air ions measured by an air ion spectrometer (AIS) at Dome C

“…In most applications, α is assumed to be unity while Kn can be connected to D via the mean free path of vapour molecules (λ v ) using the mean free-path theory (Mason and McDaniel, 1988;Pirjola et al, 1998). The diffusion coefficient of vapour molecules is determined using the Fuller's model (Poling et al, 2004;Tang et al, 2014), which describes a binary gas system of species A diffusing in B:…”