Light extinction by secondary organic aerosol: an intercomparison of three broadband cavity spectrometers

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dc.contributor.authorVarma, Ravi M.
dc.contributor.authorBall, Stephen M.
dc.contributor.authorBrauers, T.
dc.contributor.authorDorn, H. P.
dc.contributor.authorHeitmann, Uwe M.
dc.contributor.authorJones, R. L.
dc.contributor.authorPlatt, U.
dc.contributor.authorPöhler, D.
dc.contributor.authorRuth, Albert A.
dc.contributor.authorShillings, A. J. L.
dc.contributor.authorThieser, J.
dc.contributor.authorWahner, A.
dc.contributor.authorVenables, Dean S.
dc.contributor.funderEnvironmental Protection Agencyen
dc.contributor.funderScience Foundation Irelanden
dc.date.accessioned2013-12-05T17:17:14Z
dc.date.available2013-12-05T17:17:14Z
dc.date.issued2013
dc.date.updated2013-08-15T11:52:34Z
dc.description.abstractBroadband optical cavity spectrometers are maturing as a technology for trace gas detection, but only recently have they been used to retrieve the extinction coefficient of aerosols. Sensitive broadband extinction measurements allow explicit separation of gas and particle phase spectral contributions, as well as continuous spectral measurements of aerosol extinction in favourable cases. In this work, we report an intercomparison study of the aerosol extinction coefficients measured by three such instruments: a broadband cavity ring-down spectrometer (BBCRDS), a cavity-enhanced differential optical absorption spectrometer (CE-DOAS), and an incoherent broadband cavity-enhanced absorption spectrometer (IBBCEAS). Experiments were carried out in the SAPHIR atmospheric simulation chamber as part of the NO3Comp campaign to compare the measurement capabilities of NO3 and N2O5 instrumentation. Aerosol extinction coefficients between 655 and 690 nm are reported for secondary organic aerosols (SOA) formed by the NO3 oxidation of β-pinene under dry and humid conditions. Despite different measurement approaches and spectral analysis procedures, the three instruments retrieved aerosol extinction coefficients that were in close agreement. The refractive index of SOA formed from the β-pinene + NO3 reaction was 1.61, and was not measurably affected by the chamber humidity or by aging of the aerosol over several hours. This refractive index is significantly larger than SOA refractive indices observed in other studies of OH and ozone-initiated terpene oxidations, and may be caused by the large proportion of organic nitrates in the particle phase. In an experiment involving ammonium sulphate particles the aerosol extinction coefficients as measured by IBBCEAS were found to be in reasonable agreement with those calculated using Mie theory. The results of the study demonstrate the potential of broadband cavity spectrometers for determining the optical properties of aerosols.en
dc.description.sponsorshipEnvironmental Protection Agency (2005-ET-MS-28-M3); Science Foundation Ireland (11/RFP/GEO3200, and 06/RFP/CHP055-STTF09); Natural Environment Research Council (NER/T/S/2002/00036); European Commission (FP6 - RII3-CT-2004-505968)en
dc.description.statusNot peer revieweden
dc.description.versionPublished Versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.citationVarma, R. M., Ball, S. M., Brauers, T., Dorn, H.-P., Heitmann, U., Jones, R. L., Platt, U., Pöhler, D., Ruth, A. A., Shillings, A. J. L., Thieser, J., Wahner, A., and Venables, D. S.: Light extinction by Secondary Organic Aerosol: an intercomparison of three broadband cavity spectrometers, Atmos. Meas. Tech. Discuss., 6, 6685-6727, doi:10.5194/amtd-6-6685-2013, 2013.en
dc.identifier.doi10.5194/amtd-6-6685-2013
dc.identifier.endpage6727en
dc.identifier.journaltitleAtmospheric Measurement Techniques Discussionsen
dc.identifier.startpage6685en
dc.identifier.urihttps://hdl.handle.net/10468/1276
dc.identifier.volume6en
dc.language.isoenen
dc.publisherCopernicus Publicationsen
dc.relation.uriwww.atmos-meas-tech-discuss.net/6/6685/2013/
dc.rights© Author(s) 2013. This work is distributed under the Creative Commons Attribution 3.0 License.en
dc.subjectAerosol extinction measurementen
dc.subjectBroadband optical cavity spectrometersen
dc.subjectCEASen
dc.titleLight extinction by secondary organic aerosol: an intercomparison of three broadband cavity spectrometersen
dc.typeArticle (non peer-reviewed)en
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