Ahlberg, Erik

Brune, W.H

Eriksson, Axel

Frosch, Mia

Pagels, Joakim

Rissler, Jenny

Sjögren, S.

Svenningsson, Birgitta

Swietlicki, Erik

English

Lund University Publications

LUND UNIVERSITYPO Box 117221 00 Lund+46 46-222 00 00Effects of intense ageing on volatility and chemical composition of urban aerosolparticlesFrosch, Mia; Ahlberg, Erik; Eriksson, Axel; Sjögren, S.; Pagels, Joakim; Rissler, Jenny;Swietlicki, Erik; Brune, W.H; Svenningsson, BirgittaPublished in:Proceedings of the Annual Symposium of the Nordic Society for Aerosol Research (NOSA)2012Link to publicationCitation for published version (APA):Frosch, M., Ahlberg, E., Eriksson, A., Sjögren, S., Pagels, J., Rissler, J., Swietlicki, E., Brune, W. H., &Svenningsson, B. (2012). Effects of intense ageing on volatility and chemical composition of urban aerosolparticles. Proceedings of the Annual Symposium of the Nordic Society for Aerosol Research (NOSA).Total number of authors:9General rightsUnless other specific re-use rights are stated the following general rights apply:Copyright and moral rights for the publications made accessible in the public portal are retained by the authorsand/or other copyright owners and it is a condition of accessing publications that users recognise and abide by thelegal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private studyor research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portalRead more about Creative commons licenses: https://creativecommons.org/licenses/Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will removeaccess to the work immediately and investigate your claim.  Effects of intense ageing on volatility and chemical composition of urban aerosol particles  M. Frosch1, E. Ahlberg1, A. Eriksson1, S. Sjögren1, J. Pagels2, J. Rissler2, E. Swietlicki1, W. H. Brune3 and B. Svenningsson1  1 Division of Nuclear Physics, Lund University, Box 118, 22100, Lund, Sweden 2 Division of Ergonomics and Aerosol Technology, Lund University, Box 118, 22100, Lund, Sweden 3 Department of Meteorology, Pennsylvania State University, University Park, PA 16802, USA  Keywords:   Ambient aerosol, oxidative ageing, Potential Aerosol Mass, AMS  Introduction  Aerosol particles form a ubiquitous component of the Earth’s atmosphere, which has profound effect on for example visibility, human health and climate change.  A significant source of organic aerosol (OA) is oxidation of volatile organic compounds (VOC) in the gas phase, leading to formation of less volatile compounds. These can nucleate to form secondary organic aerosol (SOA) particles or condense on existing particles. The lifetimes and fates of atmospheric species depend strongly on physical properties, e.g. phase, and chemical properties. We here characterize particles at street level in central Copenhagen in terms of mass and number, chemical composition and volatility. Particles were in some cases exposed to additional ageing.  Methods  Particles were sampled in central Copenhagen during Jan-Feb 2012 and characterized using a scanning mobility particle sizer (SMPS), an aerosol mass spectrometer (AMS) and a thermodenuder (TD). Effects of ageing were investigated with a potential aerosol mass (PAM) chamber.  PAM is defined as the maximum aerosol mass produced through oxidation of precursor gasses. In the PAM chamber, SOA production occurs in a highly oxidizing environment ensuring rapid reaction of precursor gasses. Thus, all processes instigated by photo-oxidation of gas phase components occur in minutes in PAM as they would over hours or days in the atmosphere (Kang et al., 2007).  In the present study, particles were exposed to high levels of ozone (up to 16 ppm) and OH radical (exposure up to 1-2·1012 molecules·s·cm-3, corresponding to 1-2 weeks of OH exposure under ambient conditions).  Results  Large numbers of fresh particles were generated by nucleation in the PAM chamber, but these were too small to significantly alter the particle mass detected with AMS. However, alterations of the organic fraction were detectable with AMS, possibly a consequence of condensation or heterogeneous reactions. The main change was an increase of O:C 2.01.51.00.50.0Ratio06:002012-02-1812:00 18:00Date and time H/C With PAM Without PAMO/C With PAM Without PAM Figure 1: O:C and H:C ratios sampled with/without PAM chamber.  ratio and decrease in H:C ratio (Figure 1).  Also, volatilities of the OA components were influenced by the reaction in the PAM chamber (see Figure 2): The fractions of m/z 43 and 44 to total OA mass (f43 and f44) were used as markers for hydro-carbon like and oxidized OA, respectively. Absolute values of f43 and f44 of particles exposed to elevated temperatures in the TD varied, depending on whether particles were sampled through the PAM chamber.  0.300.250.200.150.100.050.00Ratio12010080604020Temperature / °CWithout PAM f44 f43With PAM f44 f43 Figure 2: f43 and f44 of particles sampled with/without PAM exposed to different temperatures  We acknowledge support from VR and FORMAS.  Kang, E. Root, M. J., Toohey, D. W. & Brune, W. H. Atmos. Chem. Phys., 7, 5727-5744, 2007. 

Effects of intense ageing on volatility and chemical composition of urban aerosol particles

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Effects of intense ageing on volatility and chemical composition of urban aerosol particles

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