Characterization of a real-time tracer for isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements - Université Clermont Auvergne Accéder directement au contenu
Article Dans Une Revue Atmospheric Chemistry and Physics Année : 2015

Characterization of a real-time tracer for isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements

Q. Chen
M. Kuwata
  • Fonction : Auteur
Y Liu
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  • PersonId : 4334
  • IdHAL : yi-liu
S. S de Sá
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K. Mckinney
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S T Martin
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M. Hu
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S H Budisulistiorini
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M. Riva
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J. D Surratt
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J. M. St. Clair
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G. Isaacman-van Wertz
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L. D Yee
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A H Goldstein
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S. Carbone
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P. Artaxo
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J. A de Gouw
  • Fonction : Auteur
A. Koss
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A. Wisthaler
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T. Mikoviny
  • Fonction : Auteur
T. Karl
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L. Kaser
  • Fonction : Auteur
W. Jud
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A. Hansel
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K. S Docherty
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M. L Alexander
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N H Robinson
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H. Coe
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J. D Allan
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M. R Canagaratna
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F. Paulot
  • Fonction : Auteur
J. L Jimenez
  • Fonction : Auteur

Résumé

Substantial amounts of secondary organic aerosol (SOA) can be formed from isoprene epoxydiols (IEPOX), which are oxidation products of isoprene mainly under low-NO conditions. Total IEPOX-SOA, which may include SOA formed from other parallel isoprene oxidation pathways, was quantified by applying positive matrix factorization (PMF) to aerosol mass spectrometer (AMS) measurements. The IEPOX-SOA fractions of organic aerosol (OA) in multiple field studies across several continents are summarized here and show consistent patterns with the concentration of gas-phase IEPOX simulated by the GEOS-Chem chemical transport model. During the Southern Oxidant and Aerosol Study (SOAS), 78 % of PMF-resolved IEPOX-SOA is accounted by the measured IEPOX-SOA molecular tracers (2-methyltetrols, C5-Triols, and IEPOX-derived organosul-fate and its dimers), making it the highest level of molecular identification of an ambient SOA component to our knowledge. An enhanced signal at C 5 H 6 O + (m/z 82) is found in PMF-resolved IEPOX-SOA spectra. To investigate the suitability of this ion as a tracer for IEPOX-SOA, we examine f C 5 H 6 O (f C 5 H 6 O = C 5 H 6 O + /OA) across multiple field, chamber, and source data sets. A background of ∼ 1.7 ± 0.1 ‰ (‰ = parts per thousand) is observed in studies strongly influenced by urban, biomass-burning, and other anthropogenic primary organic aerosol (POA). Higher background values of 3.1 ± 0.6 ‰ are found in studies strongly influenced by monoterpene emissions. The average laboratory monoterpene SOA value (5.5 ± 2.0 ‰) is 4 times lower than the average for IEPOX-SOA (22 ± 7 ‰), which leaves some room to separate both contributions to OA. Locations strongly influenced by isoprene emissions under low-NO levels had higher f C 5 H 6 O (∼ 6.5 ± 2.2 ‰ on average) than other sites, consistent with the expected IEPOX-SOA formation in those studies. f C 5 H 6 O in IEPOX-SOA is always elevated (12–40 ‰) but varies substantially between locations , which is shown to reflect large variations in its detailed molecular composition. The low f C 5 H 6 O (< 3 ‰) reported in non-IEPOX-derived isoprene-SOA from chamber studies indicates that this tracer ion is specifically enhanced from IEPOX-SOA, and is not a tracer for all SOA from iso-prene. We introduce a graphical diagnostic to study the presence and aging of IEPOX-SOA as a triangle plot of f CO 2 vs. f C 5 H 6 O. Finally, we develop a simplified method to estimate ambient IEPOX-SOA mass concentrations, which is shown to perform well compared to the full PMF method. The uncertainty of the tracer method is up to a factor of ∼ 2, if the f C 5 H 6 O of the local IEPOX-SOA is not available. When only unit mass-resolution data are available, as with the aerosol chemical speciation monitor (ACSM), all methods may perform less well because of increased interferences from other ions at m/z 82. This study clarifies the strengths and limitations of the different AMS methods for detection of IEPOX-SOA and will enable improved characterization of this OA component.
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Dates et versions

hal-01836107 , version 1 (12-07-2018)

Identifiants

Citer

W. W. Hu, P. Campuzano-Jost, B. B Palm, D A Day, A M Ortega, et al.. Characterization of a real-time tracer for isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements. Atmospheric Chemistry and Physics, 2015, 15 (20), pp.11807-11833. ⟨10.5194/acp-15-11807-2015⟩. ⟨hal-01836107⟩

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