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Published September 11, 2008 | Supplemental Material
Journal Article Open

Organosulfate Formation in Biogenic Secondary Organic Aerosol


Organosulfates of isoprene, α-pinene, and β-pinene have recently been identified in both laboratory-generated and ambient secondary organic aerosol (SOA). In this study, the mechanism and ubiquity of organosulfate formation in biogenic SOA is investigated by a comprehensive series of laboratory photooxidation (i.e., OH-initiated oxidation) and nighttime oxidation (i.e., NO₃-initiated oxidation under dark conditions) experiments using nine monoterpenes (α-pinene, β-pinene, d-limonene, l-limonene, α-terpinene, γ-terpinene, terpinolene, Δ³-carene, and β-phellandrene) and three monoterpenes (α-pinene, d-limonene, and l-limonene), respectively. Organosulfates were characterized using liquid chromatographic techniques coupled to electrospray ionization combined with both linear ion trap and high-resolution time-of-flight mass spectrometry. Organosulfates are formed only when monoterpenes are oxidized in the presence of acidified sulfate seed aerosol, a result consistent with prior work. Archived laboratory-generated isoprene SOA and ambient filter samples collected from the southeastern U.S. were reexamined for organosulfates. By comparing the tandem mass spectrometric and accurate mass measurements collected for both the laboratory-generated and ambient aerosol, previously uncharacterized ambient organic aerosol components are found to be organosulfates of isoprene, α-pinene, β-pinene, and limonene-like monoterpenes (e.g., myrcene), demonstrating the ubiquity of organosulfate formation in ambient SOA. Several of the organosulfates of isoprene and of the monoterpenes characterized in this study are ambient tracer compounds for the occurrence of biogenic SOA formation under acidic conditions. Furthermore, the nighttime oxidation experiments conducted under highly acidic conditions reveal a viable mechanism for the formation of previously identified nitrooxy organosulfates found in ambient nighttime aerosol samples. We estimate that the organosulfate contribution to the total organic mass fraction of ambient aerosol collected from K-puszta, Hungary, a field site with a similar organosulfate composition as that found in the present study for the southeastern U.S., can be as high as 30%.

Additional Information

© 2008 American Chemical Society. Received: March 17, 2008; Revised Manuscript Received: May 16, 2008. Web Release Date: August 19, 2008. Research at Caltech was funded by the U.S. Department of Energy Biological and Environmental Research Program (Grant DE-FG02-05ER63983) and U.S. Environmental Protection Agency Science to Achieve Results (STAR) Grant RD-83374901. Research at the University of Antwerp and Ghent University was supported by the Belgian Federal Science Policy Office (Contract SD/AT/02A), the Research Foundation−Flanders (FWO), and the Special Research Funds of both universities. The Waters UPLC-LCT Premier XT time-of-flight mass spectrometer was purchased in 2006 with a grant from the National Science Foundation, Chemistry Research Instrumentation and Facilities Program (CHE-0541745). The Electric Power Research Institute provided support for the SEARCH network field samples. This article has been jointly developed and published by the EPA and the California Institute of Technology. It was produced under Cooperative Agreement CR-83194001 and is subject to 40 CFR 30.36. The article has been reviewed by EPA personnel under EPA scientific and technical peer review procedures and approved for joint publication based on its scientific merit, technical accuracy, or contribution to advancing public understanding of environmental protection. However, the Agency's decision to publish the article jointly with Caltech is intended to further the public purpose supported by Cooperative Agreement No. CR-83194001 and not to establish an official EPA rule, regulation, guidance, or policy through the publication of this article. The U.S. Environmental Protection Agency through its Office of Research and Development also funded research described here under Contract EP-D-05-065 to Alion Science and Technology. Jason D. Surratt was supported, in part, by the U.S. Environmental Protection Agency (EPA) under the STAR Graduate Fellowship Program. We would like to thank Professor Roger Atkinson of the University of California, Riverside for providing the standard needed for the β-phellandrene/d-limonene photooxidation experiment. Supporting Information Available: Tables containing the detailed accurate mass measurements for all experiments conducted in Table 2, MS2 data for the three m/z 294 nitrooxy organosulfates formed in the α-pinene/H2O2/NO/highly acidic seed experiment, MS2/MS3 data for the m/z 294 nitrooxy organosulfates formed in the β-pinene/H2O2/NO/highly acidic seed experiment, UPLC/(−)ESI-TOFMS EICs of m/z 296 for three selected limonene experiments and one SEARCH field site, MS2/MS3 data for the three m/z 296 nitrooxy organosulfates formed in the limonaketone/H2O2/NO/highly acidic seed experiment, MS2/MS3 data for the three m/z 296 nitrooxy organosulfates found in the BHM field site, MS2/MS3 data for the m/z 310 nitrooxy organosulfates from an α-pinene/H2O2/NO/highly acidic seed experiment and a β-pinene/H2O2/NO/highly acidic seed experiment, UPLC/(−)ESI-TOFMS EICs of m/z 373 for two selected limonene experiments and one SEARCH field site, and MS2/MS3 data for the three last-eluting m/z 305 compounds from an isoprene/NOx/SO2 EPA photooxidation experiment. This material is available free of charge via the Internet at http://pubs.acs.org.

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