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Published August 20, 2014 | Published + Supplemental Material
Journal Article Open

Molecular corridors and kinetic regimes in the multiphase chemical evolution of secondary organic aerosol


The dominant component of atmospheric, organic aerosol is that derived from the oxidation of volatile organic compounds (VOCs), so-called secondary organic aerosol (SOA). SOA consists of a multitude of organic compounds, only a small fraction of which has historically been identified. Formation and evolution of SOA is a complex process involving coupled chemical reaction and mass transport in the gas and particle phases. Current SOA models do not embody the full spectrum of reaction and transport processes, nor do they identify the dominant rate-limiting steps in SOA formation. Based on molecular identification of SOA oxidation products, we show here that the chemical evolution of SOA from a variety of VOC precursors adheres to characteristic "molecular corridors" with a tight inverse correlation between volatility and molar mass. The slope of these corridors corresponds to the increase in molar mass required to decrease volatility by one order of magnitude (-dM / dlogC_0). It varies in the range of 10–30 g mol^(−1), depending on the molecular size of the SOA precursor and the O : C ratio of the reaction products. Sequential and parallel reaction pathways of oxidation and dimerization or oligomerization progressing along these corridors pass through characteristic regimes of reaction-, diffusion-, or accommodation-limited multiphase chemical kinetics that can be classified according to reaction location, degree of saturation, and extent of heterogeneity of gas and particle phases. The molecular corridors and kinetic regimes help to constrain and describe the properties of the products, pathways, and rates of SOA evolution, thereby facilitating the further development of aerosol models for air quality and climate.

Additional Information

© 2014 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 21 February 2014 – Published in Atmos. Chem. Phys. Discuss.: 6 March 2014 Revised: 15 July 2014 – Accepted: 16 July 2014 – Published: 20 August 2014. This work was funded by the Max Planck Society and US National Science Foundation grant AGS-1057183. M. Shiraiwa, T. Berkemeier and U. Pöschl thank the European Commission project Pan-European gas-aerosols-climate interaction study (No. 265148, PEGASOS). M. Shiraiwa thanks the Japan Society for the Promotion of Science (JSPS) for Postdoctoral Fellowships for Research Abroad. The service charges for this open access publication have been covered by the Max Planck Society. Edited by: M. C. Facchini

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Published - acp-14-8323-2014.pdf

Supplemental Material - acp-14-8323-2014-supplement.pdf


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August 20, 2023
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