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The uptake of HO2 on meteoric smoke analogues

James, AD, Moon, DR, Feng, W, Lakey, PSJ, Frankland, Victoria, Heard, DE and Plane, JMC (2017) The uptake of HO2 on meteoric smoke analogues Journal of Geophysical Research: Atmospheres, 122 (1). pp. 554-565.

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The kinetics of heterogeneous HO2 uptake onto meteoric smoke particles (MSPs) has been studied in the laboratory using analogues of MSP aerosol entrained into a flow tube. The uptake coefficient, γ, was determined on synthetic amorphous olivine (MgFeSiO4) to be (6.9 ± 1.2) × 10−2 at a relative humidity (RH) of 10%. On forsterite (Mg2SiO4), γ = (4.3 ± 0.4) × 10−3 at RH = 11.6% and (7.3 ± 0.4) × 10−2 at RH = 9.9% on fayalite (Fe2SiO4). These results indicate that Fe plays a more important mechanistic role than Mg in the removal of HO2 from the gas phase. Electronic structure calculations show that Fe atoms exposed at the particle surface provide a catalytic site where HO2 is converted to H2O2 via an Eley-Rideal mechanism, but this does not occur on exposed surface Mg atoms. The impact of this heterogeneous process in the middle atmosphere was then investigated using a whole atmosphere chemistry-climate model which incorporates a microphysical treatment of MSPs. Using a global MSP production rate from meteoric ablation of 44 t/day, heterogeneous uptake (with γ = 0.2) on MSPs significantly alters the HOx budget in the nighttime polar vortex. This impact is highly latitude dependent and thus could not be confirmed using currently available satellite measurements of HO2, which are largely unavailable at latitudes greater than 70°.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Chemistry
Authors :
James, AD
Moon, DR
Feng, W
Lakey, PSJ
Heard, DE
Plane, JMC
Date : 13 January 2017
DOI : 10.1002/2016JD025882
Copyright Disclaimer : ©2016. American Geophysical Union. All Rights Reserved.
Depositing User : Melanie Hughes
Date Deposited : 23 Aug 2017 13:02
Last Modified : 16 Jan 2019 18:55

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