A new method to discriminate secondary organic aerosols from different sources using high-resolution aerosol mass spectra 1Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
28 Feb 2012
2European Commission Joint Research Centre Ispra, Institute for Energy and Transport, Sustainable Transport Unit, 21027 Ispra (VA), Italy
*now at: Department of Civil, Architectural and Environmental Engineering, Drexel University, Philadelphia, USA
**now at: Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), UTAPRAD-DIM, Via E. Fermi 45, 00044 Frascati, Italy
***now at: TSI GmbH, Particle Instruments, Neuköllner Str. 4, 52068 Aachen, Germany
****now at: Department of Atmospheric Sciences, University of Washington, Seattle, USA
Received: 12 Oct 2011 – Published in Atmos. Chem. Phys. Discuss.: 27 Oct 2011 Abstract. Organic aerosol (OA) represents a significant and often major fraction of
the non-refractory PM1 (particulate matter with an aerodynamic diameter
da < 1 μm) mass. Secondary organic aerosol (SOA) is an important
contributor to the OA and can be formed from biogenic and anthropogenic
precursors. Here we present results from the characterization of SOA
produced from the emissions of three different anthropogenic sources. SOA
from a log wood burner, a Euro 2 diesel car and a two-stroke Euro 2 scooter
were characterized with an Aerodyne high-resolution time-of-flight aerosol
mass spectrometer (HR-TOF-AMS) and compared to SOA from α-pinene.
Revised: 09 Feb 2012 – Accepted: 16 Feb 2012 – Published: 28 Feb 2012
The emissions were sampled from the chimney/tailpipe by a heated inlet
system and filtered before injection into a smog chamber. The gas phase
emissions were irradiated by xenon arc lamps to initiate photo-chemistry
which led to nucleation and subsequent particle growth by SOA production.
Duplicate experiments were performed for each SOA type, with the averaged
organic mass spectra showing Pearson's r values >0.94 for the
correlations between the four different SOA types after five hours of aging.
High-resolution mass spectra (HR-MS) showed that the dominant peaks in the
MS, m/z 43 and 44, are dominated by the oxygenated ions C2H3O+
and CO2+, respectively, similarly to the relatively fresh
semi-volatile oxygenated OA (SV-OOA) observed in the ambient aerosol. The
atomic O:C ratios were found to be in the range of 0.25–0.55 with no major
increase during the first five hours of aging. On average, the diesel SOA
showed the lowest O:C ratio followed by SOA from wood burning, α-pinene and the scooter emissions. Grouping the fragment ions revealed that
the SOA source with the highest O:C ratio had the largest fraction of small
The HR data of the four sources could be clustered and separated using
principal component analysis (PCA). The model showed a significant
separation of the four SOA types and clustering of the duplicate experiments
on the first two principal components (PCs), which explained 79% of the
total variance. Projection of ambient SV-OOA spectra resolved by positive
matrix factorization (PMF) showed that this approach could be useful to
identify large contributions of the tested SOA sources to SV-OOA. The first
results from this study indicate that the SV-OOA in Barcelona is strongly
influenced by diesel emissions in winter while in summer at SIRTA at the
southwestern edge of Paris SV-OOA is more similar to alpha-pinene SOA.
However, contributions to the ambient SV-OOA from SOA sources that are not
covered by the model can cause major interference and therefore future
expansions of the PCA model with additional SOA sources is recommended.
Citation: Heringa, M. F., DeCarlo, P. F., Chirico, R., Tritscher, T., Clairotte, M., Mohr, C., Crippa, M., Slowik, J. G., Pfaffenberger, L., Dommen, J., Weingartner, E., Prévôt, A. S. H., and Baltensperger, U.: A new method to discriminate secondary organic aerosols from different sources using high-resolution aerosol mass spectra, Atmos. Chem. Phys., 12, 2189-2203, doi:10.5194/acp-12-2189-2012, 2012.