Articles | Volume 8, issue 8
Atmos. Meas. Tech., 8, 3337–3353, 2015
Atmos. Meas. Tech., 8, 3337–3353, 2015

Research article 18 Aug 2015

Research article | 18 Aug 2015

Hyphenation of a EC / OC thermal–optical carbon analyzer to photo-ionization time-of-flight mass spectrometry: an off-line aerosol mass spectrometric approach for characterization of primary and secondary particulate matter

J. Diab1, T. Streibel1,2, F. Cavalli3, S. C. Lee5, H. Saathoff6, A. Mamakos4, J. C. Chow7, L.-W. A. Chen9, J. G. Watson7, O. Sippula1,8, and R. Zimmermann1,2 J. Diab et al.
  • 1Joint Mass Spectrometry Centre/Chair of Analytical Chemistry, University of Rostock, 18051 Rostock, Germany
  • 2Joint Mass Spectrometry Centre/Institute of Ecological Chemistry, Helmholtz Centre Munich, Research Centre for Environmental Health (GmbH), 85764 Munich, Germany
  • 3JRC European Commission – Joint Research Centre, Institute for Environment and Sustainability – Air & Climate Unit, 21027 Ispra, Italy
  • 4JRC European Commission – Joint Research Centre, Institute for Energy – Sustainable Transport Unit, 21027 Ispra, Italy
  • 5The Hong Kong Polytechnic University, Department of Civil & Structural Engineering, Hung Hom, Kowloon, Hong Kong, China
  • 6Karlsruhe Institute of Technology (KIT), Institute for Meteorology and Climate Research, Atmospheric Aerosol Research Division, 76344 Eggenstein-Leopoldshafen, Germany
  • 7DRI-Desert Research Institute, Division of Atmospheric sciences, Reno, NV 89512, USA
  • 8Department of Environmental Science, University of Eastern Finland, P.O. Box 1627, 70211, Kuopio, Finland
  • 9Department of Environmental and Occupational Health, University of Nevada, Las Vegas, NV 89154, USA

Abstract. Source apportionment and characterization of primary and secondary aerosols remains a challenging research field. In particular, the organic composition of primary particles and the formation mechanism of secondary organic aerosols (SOAs) warrant further investigations. Progress in this field is strongly connected to the development of novel analytical techniques. In this study an off-line aerosol mass spectrometric technique based on filter samples, a hyphenated thermal–optical analyzer photo-ionization time-of-flight mass spectrometer (PI-TOFMS) system, was developed. The approach extends the capability of the widely used particulate matter (PM) carbon analysis (for elemental / organic carbon, EC / OC) by enabling the investigation of evolved gaseous species with soft and selective (resonance enhanced multi-photon ionization, REMPI) and non-selective photo-ionization (single-photon ionization, SPI) techniques. SPI was tuned to be medium soft to achieve comparability with results obtained by the electron ionization aerosol mass spectrometer (AMS). Different PM samples including wood combustion emission samples, smog chamber samples from the reaction of ozone with different SOA precursors, and ambient samples taken at Ispra, Italy, in winter as well as in summer were tested. The EC / OC–PI-TOFMS technique increases the understanding of the processes during thermal–optical analysis and identifies marker substances for the source apportionment. Composition of oligomeric or polymeric species present in PM can be investigated by the analysis of the thermal breakdown products. In the case of wood combustion, in addition to the well-known markers at m/z ratios of 60 and 73, two new characteristic masses (m/z 70 and 98) have been revealed as potentially linked to biomass burning. All four masses were also the dominant signals in an ambient sample taken in winter time in Ispra, Italy, confirming the finding that wood burning for residential heating is a major source of PM in winter at this location. The summer sample from the same location showed no influence of wood burning, but seems to be dominated by SOAs, which was confirmed from the comparison with chamber experiment samples. The experiments conducted with terpenes as precursors showed characteristic masses at m/z 58 and 82, which were not observable in any other emission samples and could serve as a marker for SOA from terpenes.

Short summary
This paper depicts several fields of application of a new analytical method, which expands the well-established EC/OC method, which enables one to measure the carbon content (organic and elemental) of particulate aerosols. It was coupled to photo-ionization mass spectrometry to get structural information of the evolving carbonaceous species. Application fields such as smoke chamber-, ambient - and wood combustion particles were addressed, covering exemplary primary and secondary aerosol sources.