Journal Article

PreJuSER-19856

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Volatility of secondary organic aerosol during OH radical induced ageing

Salo, K. ; Hallquist, M. ; Jonsson, A. M. ; Saathoff, H. ; Naumann, K.-H. ; Spindler, C.FZJ* ; Tillmann, R.FZJ* ; Fuchs, H.FZJ* ; Bohn, B.FZJ* ; Rubach, F.FZJ* ; Mentel, T.FZJ* ; Müller, L. ; Reining, M. ; Hoffmann, T. ; Donahue, N. M.

2011
EGU Katlenburg-Lindau

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Please use a persistent id in citations: http://hdl.handle.net/2128/9945  doi:10.5194/acp-11-11055-2011

Abstract: The aim of this study was to investigate oxidation of SOA formed from ozonolysis of alpha-pinene and limonene by hydroxyl radicals. This paper focuses on changes of particle volatility, using a Volatility Tandem DMA (VTDMA) set-up, in order to explain and elucidate the mechanism behind atmospheric ageing of the organic aerosol. The experiments were conducted at the AIDA chamber facility of Karlsruhe Institute of Technology (KIT) in Karlsruhe and at the SAPHIR chamber of Forschungzentrum Julich (FZJ) in Julich. A fresh SOA was produced from ozonolysis of alpha-pinene or limonene and then aged by enhanced OH exposure. As an OH radical source in the AIDA-chamber the ozonolysis of tetramethylethylene (TME) was used while in the SAPHIR-chamber the OH was produced by natural light photochemistry. A general feature is that SOA produced from ozonolysis of alpha-pinene and limonene initially was rather volatile and becomes less volatile with time in the ozonolysis part of the experiment. Inducing OH chemistry or adding a new portion of precursors made the SOA more volatile due to addition of new semi-volatile material to the aged aerosol. The effect of OH chemistry was less pronounced in high concentration and low temperature experiments when lower relative amounts of semi-volatile material were available in the gas phase. Conclusions drawn from the changes in volatility were confirmed by comparison with the measured and modelled chemical composition of the aerosol phase. Three quantified products from the alpha-pinene oxidation; pinonic acid, pinic acid and methylbutanetricarboxylic acid (MBTCA) were used to probe the processes influencing aerosol volatility. A major conclusion from the work is that the OH induced ageing can be attributed to gas phase oxidation of products produced in the primary SOA formation process and that there was no indication on significant bulk or surface reactions. The presented results, thus, strongly emphasise the importance of gas phase oxidation of semi-or intermediate-volatile organic compounds (SVOC and IVOC) for atmospheric aerosol ageing.

Keyword(s): J

Note: We thank the AIDA team at KIT and the SAPHIR team at FZJ for their effective support during the measurement campaigns. Eva Emanuelsson at University of Gothenburg is acknowledged for running the VTDMA in the SAPHIR experiments. The MUCHACHAS campaigns were supported by EUROCHAMP-2 (Integration of European Simulation Chambers for Investigating Atmospheric Processes) a research project within the EC 7th framework programmes. M. H. and K. S. in addition acknowledge support by Formas under contract 214-2006-1204, The Swedish Research Council under contract 80475101 and the Nanoparticles in Interactive Environments platform at the Faculty of Science at the University of Gothenburg.

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Contributing Institute(s):

1. Troposphäre (IEK-8)

Research Program(s):

1. Atmosphäre und Klima (P23)

Appears in the scientific report 2011

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