Journal cover Journal topic
Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 3.248 IF 3.248
  • IF 5-year value: 3.650 IF 5-year
    3.650
  • CiteScore value: 3.37 CiteScore
    3.37
  • SNIP value: 1.253 SNIP 1.253
  • SJR value: 1.869 SJR 1.869
  • IPP value: 3.29 IPP 3.29
  • h5-index value: 47 h5-index 47
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 60 Scimago H
    index 60
Volume 6, issue 11 | Copyright
Atmos. Meas. Tech., 6, 3115-3130, 2013
https://doi.org/10.5194/amt-6-3115-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 19 Nov 2013

Research article | 19 Nov 2013

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

R. M. Varma3,2,1, S. M. Ball4, T. Brauers5, H.-P. Dorn5, U. Heitmann2, R. L. Jones6, U. Platt7, D. Pöhler7, A. A. Ruth2, A. J. L. Shillings6, J. Thieser7,8, A. Wahner5, and D. S. Venables1 R. M. Varma et al.
  • 1Department of Chemistry and Environmental Research Institute, University College Cork, Cork, Ireland
  • 2Department of Physics and Environmental Research Institute, University College Cork, Cork, Ireland
  • 3Department of Physics, National Institute of Technology Calicut, Kerala, India
  • 4Department of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
  • 5Institute of Energy and Climate Research, IEK-8: Troposphere, Forschungszentrum Jülich, Jülich, Germany
  • 6Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
  • 7Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany
  • 8Max-Planck-Institut für Chemie, Division of Atmospheric Chemistry, Mainz, Germany

Abstract. Broadband 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 sulfate particles, the aerosol extinction coefficients as measured by IBBCEAS were found to be in reasonable agreement with those calculated using the Mie theory. The results of the study demonstrate the potential of broadband cavity spectrometers for determining the optical properties of aerosols.

Publications Copernicus
Download
Citation
Share