Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 15, 11807-11833, 2015
http://www.atmos-chem-phys.net/15/11807/2015/
doi:10.5194/acp-15-11807-2015
© Author(s) 2015. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
23 Oct 2015
Characterization of a real-time tracer for isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements
W. W. Hu1,2, P. Campuzano-Jost1,2, B. B. Palm1,2, D. A. Day1,2, A. M. Ortega1,3, P. L. Hayes1,2,a, J. E. Krechmer1,2, Q. Chen4,5, M. Kuwata4,6, Y. J. Liu4, S. S. de Sá4, K. McKinney4, S. T. Martin4, M. Hu5, S. H. Budisulistiorini7, M. Riva7, J. D. Surratt7, J. M. St. Clair8,b,c, G. Isaacman-Van Wertz9, L. D. Yee9, A. H. Goldstein9,10, S. Carbone11, J. Brito11, P. Artaxo11, J. A. de Gouw1,2,12, A. Koss2,12, A. Wisthaler13,14, T. Mikoviny13, T. Karl15, L. Kaser14,16, W. Jud14, A. Hansel14, K. S. Docherty17, M. L. Alexander18, N. H. Robinson19,d, H. Coe19, J. D. Allan19,20, M. R. Canagaratna21, F. Paulot22,23, and J. L. Jimenez1,2 1Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
2Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA
3Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, CO, USA
4School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
5State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China
6Earth Observatory of Singapore, Nanyang Technological University, Singapore
7Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
8Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
9Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, USA
10Department of Civil and Environmental Engineering, University of California, Berkeley, CA, USA
11Department of Applied Physics, University of Sao Paulo, Sao Paulo, Brazil
12NOAA Earth System Research Laboratory, Boulder, CO, USA
13Department of Chemistry, University of Oslo, Oslo, Norway
14Institute for Ion Physics and Applied Physics, University of Innsbruck, Innsbruck, Austria
15Institute of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innsbruck, Austria
16Atmospheric Chemistry Division (ACD), National Center for Atmospheric Research, Boulder, CO, USA
17Alion Science and Technology, Research Triangle Park, NC, USA
18Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA
19School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester, UK
20National Centre for Atmospheric Science, University of Manchester, Oxford Road, Manchester, UK
21Aerodyne Research, Inc., Billerica, MA, USA
22NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ, USA
23Program in Atmospheric and Oceanic Sciences, Princeton University, Princeton, NJ, USA
anow at: Department of Chemistry, Université de Montréal, Montréal, QC, Canada
bnow at: Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
cnow at: Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, MD, USA
dnow at: Met Office, Exeter, UK
Abstract. 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 organosulfate and its dimers), making it the highest level of molecular identification of an ambient SOA component to our knowledge. An enhanced signal at C5H6O+ (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 fC5H6O (fC5H6O= C5H6O+/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 fC5H6O (~ 6.5 ± 2.2 ‰ on average) than other sites, consistent with the expected IEPOX-SOA formation in those studies. fC5H6O 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 fC5H6O (< 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 isoprene. We introduce a graphical diagnostic to study the presence and aging of IEPOX-SOA as a triangle plot of fCO2 vs. fC5H6O. 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 fC5H6O 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.

Citation: Hu, W. W., Campuzano-Jost, P., Palm, B. B., Day, D. A., Ortega, A. M., Hayes, P. L., Krechmer, J. E., Chen, Q., Kuwata, M., Liu, Y. J., de Sá, S. S., McKinney, K., Martin, S. T., Hu, M., Budisulistiorini, S. H., Riva, M., Surratt, J. D., St. Clair, J. M., Isaacman-Van Wertz, G., Yee, L. D., Goldstein, A. H., Carbone, S., Brito, J., Artaxo, P., de Gouw, J. A., Koss, A., Wisthaler, A., Mikoviny, T., Karl, T., Kaser, L., Jud, W., Hansel, A., Docherty, K. S., Alexander, M. L., Robinson, N. H., Coe, H., Allan, J. D., Canagaratna, M. R., Paulot, F., and Jimenez, J. L.: Characterization of a real-time tracer for isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements, Atmos. Chem. Phys., 15, 11807-11833, doi:10.5194/acp-15-11807-2015, 2015.
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This work summarized all the studies reporting isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) measured globally by aerosol mass spectrometer and compare them with modeled gas-phase IEPOX, with results suggestive of the importance of IEPOX-SOA for regional and global OA budgets. A real-time tracer of IEPOX-SOA is thoroughly evaluated for the first time by combing multiple field and chamber studies. A quick and easy empirical method on IEPOX-SOA estimation is also presented.
This work summarized all the studies reporting isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA)...
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