Open AccessRelating cloud condensation nuclei activity and oxidation level of α ‐pinene secondary organic aerosols
Author(s) -
Frosch M.,
Bilde M.,
DeCarlo P. F.,
Jurányi Z.,
Tritscher T.,
Dommen J.,
Donahue N. M.,
Gysel M.,
Weingartner E.,
Baltensperger U.
Publication year - 2011
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011jd016401
Subject(s) - cloud condensation nuclei , ozonolysis , aerosol , chemistry , sulfate , pinene , kinetics , ozone , mass spectrometry , condensation , photodissociation , analytical chemistry (journal) , photochemistry , environmental chemistry , chromatography , organic chemistry , meteorology , physics , quantum mechanics
During a series of smog chamber experiments, the effects of chemical and photochemical aging on the ability of organic aerosols generated from ozonolysis of α ‐pinene to act as cloud condensation nuclei (CCN) were investigated. In particular, the study focused on the relation between oxygenation and the CCN‐derived single hygroscopicity parameter κ for different experimental conditions: varying precursor concentrations (10–40 ppb), different OH sources (photolysis of HONO either with or without the addition of NO or ozonolysis of tetramethylethylene), and exposure to light. Oxygenation was described by the contribution of the aerosol mass spectrometer (AMS) mass fragment m / z 44 to the total organic signal ( f 44 ) and the oxygen to carbon molar ratio (O/C), likewise determined with AMS. CCN activity, described by the hygroscopicity parameter κ, was determined with a CCN counter. It was found that f 44 increases with decreasing precursor concentration and with chemical aging, whereas neither of these affects CCN activity. Overall, κ is largely independent of O/C in the range 0.3 < O/C < 0.6 (0.07 < f 44 < 0.12), although an empirical unweighted least squares fit was determined: κ = (0.071 ± 0.02) · (O/C) + (0.0785 ± 0.009) for particles with diameter in the range 59–200 nm. Growth kinetics of activating secondary organic aerosols were found to be comparable to those of ammonium sulfate and were not influenced by chemical aging.