Halogenation processes of secondary organic aerosol and implications on halogen release mechanisms 1Atmospheric Chemistry Research Laboratory, University of Bayreuth, Germany
04 Jul 2012
2Institute for Environmental Physics, University of Heidelberg, Germany
3Institute of Materials Chemistry, Vienna University of Technology, Austria
4Research Unit Analytical Biogeochemistry, Helmholtz Zentrum Munich and Chair of Analytical Food Chemistry, TUM, Freising/Weihenstephan, Germany
Received: 01 Dec 2011 – Published in Atmos. Chem. Phys. Discuss.: 27 Jan 2012 Abstract. Reactive halogen species (RHS), such as X·, X2 and HOX
containing X = chlorine and/or bromine, are released by various sources
like photo-activated sea-salt aerosol or from salt pans, and salt lakes.
Despite many studies of RHS reactions, the potential of RHS reacting with
secondary organic aerosol (SOA) and organic aerosol derived from
biomass-burning (BBOA) has been neglected. Such reactions can constitute
sources of gaseous organohalogen compounds or halogenated organic matter in
the tropospheric boundary layer and can influence physicochemical properties
of atmospheric aerosols.
Revised: 06 Jun 2012 – Accepted: 07 Jun 2012 – Published: 04 Jul 2012
Model SOA from α-pinene, catechol, and guaiacol was used to study
heterogeneous interactions with RHS. Particles were exposed to molecular
chlorine and bromine in an aerosol smog-chamber in the presence of UV/VIS
irradiation and to RHS, released from simulated natural halogen sources like
salt pans. Subsequently, the aerosol was characterized in detail using a
variety of physicochemical and spectroscopic methods. Fundamental features
were correlated with heterogeneous halogenation, which results in new
functional groups (FTIR spectroscopy), changes UV/VIS absorption, chemical composition
(ultrahigh resolution mass spectroscopy (ICR-FT/MS)), or aerosol size distribution.
However, the halogen release mechanisms were also found to be affected by
the presence of organic aerosol. Those interaction processes, changing
chemical and physical properties of the aerosol are likely to influence e.g.
the ability of the aerosol to act as cloud condensation nuclei, its
potential to adsorb other gases with low-volatility, or its contribution to
radiative forcing and ultimately the Earth's radiation balance.
Citation: Ofner, J., Balzer, N., Buxmann, J., Grothe, H., Schmitt-Kopplin, Ph., Platt, U., and Zetzsch, C.: Halogenation processes of secondary organic aerosol and implications on halogen release mechanisms, Atmos. Chem. Phys., 12, 5787-5806, doi:10.5194/acp-12-5787-2012, 2012.