Heterogeneous reaction of N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;5&amp;lt;/sub&amp;gt; with illite and Arizona test dust particles

M J Tang,J N Crowley,G Schuster

doi:10.5194/acp-14-245-2014

Abstract

Abstract. The heterogeneous reaction of N2O5 with airborne illite and Arizona test dust (ATD) particles was investigated at room temperature and at different relative humidities using an atmospheric pressure aerosol flow tube. N2O5 at concentrations in the range 8 to 24 × 1012 molecule cm−3 was monitored using thermal-dissociation cavity ring-down spectroscopy at 662 nm. At zero relative humidity a large uptake coefficient of N2O5 to illite was obtained, γ(N2O5) = 0.09, which decreased to 0.04 as relative humidity was increased to 67%. In contrast, the uptake coefficient derived for ATD is much lower (~0.006) and displays a weaker (if any) dependence on relative humidity (0–67%). Potential explanations are given for the significant differences between the uptake behaviour for ATD and illite and the results are compared with uptake coefficients for N2O5 on other mineral surfaces.

Highlights

Mineral dust particles, lifted into the atmosphere from arid and semi-arid regions with a global annual flux of ∼ 2000 Tg (Textor et al, 2006), can impact direct radiative forcing by scattering and absorbing solar radiation (Balkanski et al, 2007) and modify indirect radiative forcing by serving as cloud condensation nuclei (Twohy et al, 2009) and ice nuclei (DeMott et al, 2003; Klein et al, 2010)
The heterogeneous reaction of N2O5 with airborne illite and Arizona test dust (ATD) particles was investigated at room temperature and at different relative humidities using an atmospheric pressure aerosol flow tube
This indicates that the gas-particle separation was efficient and there was no additional loss of N2O5 caused by dust particles being progressively deposited onto the inner wall of the sampling tubing during the experiment

Summary

Introduction

Mineral dust particles, lifted into the atmosphere from arid and semi-arid regions with a global annual flux of ∼ 2000 Tg (Textor et al, 2006), can impact direct radiative forcing by scattering and absorbing solar radiation (Balkanski et al, 2007) and modify indirect radiative forcing by serving as cloud condensation nuclei (Twohy et al, 2009) and ice nuclei (DeMott et al, 2003; Klein et al, 2010). The heterogeneous reactions of mineral dust particles during transport can directly and/or indirectly impact the levels of many important trace gases, including NOx, O3, and HOx radicals (Dentener et al, 1996; de Reus et al, 2005; Wang et al, 2012; Zhu et al, 2010). N2O5 thermally decomposes back to NO2 and NO3 radicals, leading to a dynamic equilibrium between NO2, NO3, and N2O5 (Reaction R2) which is usually achieved within a few minutes under most conditions in the lower atmosphere (Crowley et al, 2010b; Osthoff et al, 2007)

Results

Discussion

Conclusion