Open AccessFormation of secondary organic aerosol from irradiated α ‐pinene/toluene/NO x mixtures and the effect of isoprene and sulfur dioxide
Author(s) -
Jaoui Mohammed,
Edney Edward O.,
Kleindienst Tadeusz E.,
Lewandowski Michael,
Offenberg John H.,
Surratt Jason D.,
Seinfeld John H.
Publication year - 2008
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 - 10.1029/2007jd009426
Subject(s) - isoprene , toluene , chemistry , mass spectrometry , aerosol , gas chromatography , chemical ionization , sulfuric acid , sulfur , hydrocarbon , sulfur dioxide , chemical composition , pinene , environmental chemistry , chromatography , organic chemistry , ionization , ion , copolymer , polymer
Secondary organic aerosol (SOA) was generated by irradiating a series of α ‐pinene/toluene/NO x mixtures in the absence and presence of isoprene or sulfur dioxide. The purpose of the experiment was to evaluate the extent to which chemical perturbations to this base‐case ( α ‐pinene/toluene) mixture led to changes in the gas‐phase chemistry which strongly influences mass and composition of SOA and secondary organic carbon (SOC) formed. The chemical composition was examined by gas chromatography‐mass spectrometry (GC‐MS) and laser desorption ionization‐mass spectrometry (LDI‐MS). The results showed that the addition of isoprene to the base‐case mixture significantly lowered the amount of toluene reacted, and thereby lowered the amount SOC produced. Simultaneous measurement of the organic NO y showed that reactions of isoprene effectively sequester NO 2 by producing gas‐phase organic nitrates. The addition of SO 2 to the base‐case mixture, while having little effect on the gas‐phase chemistry, formed sulfuric acid which led to a modest enhancement of the SOC through acid‐catalyzed or sulfur‐incorporating reactions of α ‐pinene. The contribution of each hydrocarbon to the composition of the SOA was estimated using an organic tracer method. SOC from the tracer technique tended to underpredict the measured SOC, although the underprediction was especially pronounced with SO 2 present. A comparison of the chromatographic results from samples of the irradiation of the α ‐pinene/toluene/isoprene/NO x /SO 2 mixture and ambient PM 2.5 showed the presence of two unique peaks that were associated with reactions of isoprene and SO 2 .