Issue 12, 2015

Nanoscale interfacial gradients formed by the reactive uptake of OH radicals onto viscous aerosol surfaces

Abstract

A key but poorly understood chemical process is how gas phase uptake is governed by the relative mobility of molecules at an interface of an atmospheric aerosol. Citric acid (CA), a model system for oxygenated organic aerosol, is used to examine how changes in viscosity, due to changing water content, govern the reactive uptake of gas phase hydroxyl radicals (OH). By comparing the reaction kinetics measured when probing the outer aerosol surface layers with measurements of the bulk particle composition, the effective OH reaction probability is observed to be a complex and non-linear function of the relative humidity (RH). At RH < 50%, the reactive decay of CA is controlled by the viscosity of the particle, where the depletion of CA and the formation of reaction products occurs over a narrow region near the aerosol interface, on the order of 8 nm at 20% RH. At RH = 50% the reaction zone increases to the particle dimensions (i.e. ∼50 nm) and at RH > 50%, the aerosol becomes aqueous and well-mixed on the timescale of the heterogeneous reaction. These results imply that in the atmosphere, the formation and dissipation of interfacial chemical gradients could be significant in viscous and semisolid aerosol and play important roles altering gas-particle partitioning and aging mechanisms (i.e. bulk vs. interface).

Graphical abstract: Nanoscale interfacial gradients formed by the reactive uptake of OH radicals onto viscous aerosol surfaces

Supplementary files

Article information

Article type
Edge Article
Submitted
26 Jun 2015
Accepted
05 Sep 2015
First published
08 Sep 2015
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2015,6, 7020-7027

Author version available

Nanoscale interfacial gradients formed by the reactive uptake of OH radicals onto viscous aerosol surfaces

J. F. Davies and K. R. Wilson, Chem. Sci., 2015, 6, 7020 DOI: 10.1039/C5SC02326B

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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