1ETH Zurich, Institute for Atmospheric and Climate Science, Zurich, Switzerland
2Paul Scherrer Institute, Laboratory of Atmospheric Chemistry, 5232 Villigen PSI, Switzerland
3Institute of Aerosol and Sensor Technology, University of Applied Sciences Northwestern Switzerland, Windisch, Switzerland
4Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, 82234 Oberpfaffenhofen, Germany
5Aerodyne Research Inc., Billerica, Massachusetts, USA
6Boston College, Chestnut Hill, Massachusetts, USA
*now at: Aerosol Consulting ML GmbH, Ennetbaden, Switzerland, & Ecotech Pty Ltd., Australia
**now at: Institut für Energie- und Klimaforschung IEK-8: Troposphäre, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
Received: 20 Sep 2013 – Discussion started: 24 Oct 2013
Abstract. We discuss the major mass spectral features of different types of refractory carbonaceous particles, ionized after laser vaporization with an Aerodyne high-resolution soot-particle aerosol mass spectrometer (SP-AMS). The SP-AMS was operated with a switchable 1064 nm laser and a 600 °C thermal vaporizer, yielding respective measurements of the refractory and non-refractory particle components. Six samples were investigated, all of which were composed primarily of refractory material: fuel-rich and fuel-lean propane/air diffusion-flame combustion particles; graphite-spark-generated particles; a commercial fullerene-enriched soot; Regal Black, a commercial carbon black; and nascent aircraft-turbine combustion particles.
Revised: 31 Jan 2014 – Accepted: 05 Feb 2014 – Published: 13 Mar 2014
All samples exhibited a spectrum of carbon-cluster ions Cxn+ in their refractory mass spectrum. Smaller clusters (x < 6) were found to dominate the Cxn+ distribution. For fullerene soot, fuel-rich-flame particles and spark-generated particles, significant Cxn+ clusters at x ≫ 6 were present, with significant contributions from multiply charged ions (n > 1). In all six cases, the ions C1+ and C3+ contributed over 60% to the total C1+ intensity. Furthermore, the ratio of these major ions C1+ / C3+ could be used to predict whether significant Cxn+ signals with x > 5 were present. When such signals were present, C1+ / C3+ was close to 1. When absent, C1+ / C3+ was < 0.8. This ratio may therefore serve as a proxy to distinguish between the two types of spectra in atmospheric SP-AMS measurements.
Significant refractory oxygenated ions such as CO+ and CO2+ were also observed for all samples. We discuss these signals in detail for Regal Black, and describe their formation via decomposition of oxygenated moieties incorporated into the refractory carbon structure. These species may be of importance in atmospheric processes such as water uptake and heterogeneous chemistry.
If atmospherically stable, these oxidized species may be useful for distinguishing between different combustion sources. If unstable, they may provide a means to estimate the atmospheric age of an rBC sample. Future studies should attempt to establish which of these scenarios is more realistic.
Corbin, J. C., Sierau, B., Gysel, M., Laborde, M., Keller, A., Kim, J., Petzold, A., Onasch, T. B., Lohmann, U., and Mensah, A. A.: Mass spectrometry of refractory black carbon particles from six sources: carbon-cluster and oxygenated ions, Atmos. Chem. Phys., 14, 2591-2603, doi:10.5194/acp-14-2591-2014, 2014.