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| Titel |
Compound specific 13C- and 18O-isotope analysis of organic aerosols |
| VerfasserIn |
Jan Blees, Matthias Saurer, Rolf T. W. Siegwolf, Josef Dommen, Urs Baltensperger |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250098899
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| Publikation (Nr.) |
 EGU/EGU2014-14620.pdf |
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| Zusammenfassung |
| The wide ranging environmental and health effects of aerosols are increasingly coming to
light. Various studies have further highlighted the complex nature of organic aerosols,
particularly oxidised organics with multiple functional groups. Source apportionment studies
on aerosols are crucial to successful implementation of mitigation strategies, but this is
complicated by their complex nature. Ideally, individual components of aerosols can be
tracked from their source to their atmospheric sink. However, chemical alteration and the
formation of secondary aerosols in the atmosphere often preclude this direct tracking on a
compound specific basis. Compound specific isotope analysis could overcome these
problems, as certain processes and sources impose characteristic isotope ratios on
products, which may be retained even after chemical alteration in the atmosphere.
Progress has been made over the past decades in the separation and identification of
individual compounds that contribute to aerosol formation. Compound separation by gas
chromatography (GC), coupled to mass spectrometry (MS), has enabled identification of
organic compounds of various sources. On the other hand, only few studies have
addressed the isotopic composition of these compounds. For successful isotopic
analysis of specific compounds, using GC coupled to isotope ratio MS (GC-irMS),
several challenges must be faced that go beyond the requirements for GC-MS-based
compound identification. Sample extraction and handling techniques must avoid isotope
fractionation. This is especially important in the light of sample extraction by e.g. thermal
desorption, which may impose a temperature-induced fractionation on complex
organics. Furthermore, derivatisation techniques, necessary for adequate GC compound
separation, must not lead to exchange reactions of the element of interest, which
would alter the measured isotope ratio. So far most studies have dealt with carbon,
and other elements have been neglected. Elements other than carbon may provide
valuable additional information. Here we report on the development of methods for the
analysis of stable carbon and oxygen isotope ratios of organic compounds in aerosols,
through GC-combustion-irMS and GC-pyrolysis-irMS. We apply these analyses to
environmental aerosol samples and samples of smog-chamber experiments, with the aim of
identifying isotopic signatures of sources and pathways. We will pay special attention to
derivatisation techniques – notably alternatives to the often-used trimethylsilyl
derivatives in GC-pyrolysis-irMS for δ18O analysis – and to compound separation and
identification. We present initial data of combined δ13C and δ18O studies on (secondary)
organic aerosol samples, and their added value for source apportionment studies. |
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