Atmos. Chem. Phys. Discuss., 12, 5519-5550, 2012
www.atmos-chem-phys-discuss.net/12/5519/2012/
doi:10.5194/acpd-12-5519-2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Modes in the size distributions and neutralization extent of fog-processed ammonium salt aerosols observed at Canadian rural locations
X. H. Yao1 and L. Zhang2
1Key Lab of Marine Environmental Science and Ecology, Ministry of Education, Ocean University of China, Qingdao 266100, China
2Air Quality Research Division, Science and Technology Branch, Environment Canada, 4905 Dufferin Street, Toronto, Ontario, M3H 5T4, Canada

Abstract. Among the 192 samples of size-segregated water-soluble inorganic ions collected using a Micro-Orifice Uniform Deposit Impactor (MOUDI) at eight rural locations in Canada, ten samples were identified to have gone through fog processing. The supermicron particle modes of ammonium salt aerosols were found to be the fingerprint of fog processed aerosols. However, the patterns and the sizes of the supermicron modes varied with ambient temperature (T) and particle acidity and also differed between inland and coastal locations. Under T > 0 °C condition, fog-processed ammonium salt aerosols were completely neutralized and had a dominant mode at 1–2 μm and a minor mode at 5–10 μm if particles were in neutral condition, and ammonium sulfate was incompletely neutralized and only had a 1–2 μm mode if particles were in acidic conditions. Under T < 0 °C at the coastal site, fog-processed aerosols exhibited a bi-modal size distribution with a dominant mode of incompletely-neutralized ammonium sulfate at about 3 μm and a minor mode of completely-neutralized ammonium sulfate at 8–9 μm. Under T < 0 °C condition at the inland sites, fog-processed ammonium salt aerosols were sometimes completely neutralized and sometimes incompletely neutralized, and the size of the supermicron mode was in the range from 1 to 5 μm. Overall, fog-processed ammonium salt aerosols under T < 0 °C condition were generally distributed at larger size (e.g., 2–5 μm) than those under T > 0 °C condition (e.g., 1–2 μm).

Citation: Yao, X. H. and Zhang, L.: Modes in the size distributions and neutralization extent of fog-processed ammonium salt aerosols observed at Canadian rural locations, Atmos. Chem. Phys. Discuss., 12, 5519-5550, doi:10.5194/acpd-12-5519-2012, 2012.
 
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