Elucidating determinants of aerosol composition through particle-type-based receptor modeling 1Southern Ontario Centre for Atmospheric Aerosol Research, University of Toronto, 200 College St., Toronto, Ontario, Canada
10 Aug 2011
2Air Quality and Research Division, Science and Technology Branch, Environment Canada, 4905 Dufferin St., Toronto, Ontario, Canada
3Department of Chemistry, University of Toronto, St. George St., Toronto, Ontario, Canada
4Cloud Physics and Severe Weather Research Section, Environment Canada, Toronto, Ontario, Canada
*now at: Paul Scherrer Institut, Villigen, Switzerland
Received: 30 Jan 2011 – Published in Atmos. Chem. Phys. Discuss.: 24 Mar 2011 Abstract. An aerosol time-of-flight mass spectrometer (ATOFMS) was deployed at a
semi-rural site in southern Ontario to characterize the size and chemical
composition of individual particles. Particle-type-based receptor modelling
of these data was used to investigate the determinants of aerosol chemical
composition in this region. Individual particles were classified into
particle-types and positive matrix factorization (PMF) was applied to their
temporal trends to separate and cross-apportion particle-types to factors.
The extent of chemical processing for each factor was assessed by evaluating
the internal and external mixing state of the characteristic particle-types.
The nine factors identified helped to elucidate the coupled interactions of
these determinants. Nitrate-laden dust was found to be the dominant type of
locally emitted particles measured by ATOFMS. Several factors associated
with aerosol transported to the site from intermediate local-to-regional
distances were identified: the Organic factor was associated with a
combustion source to the north-west; the ECOC Day factor was characterized
by nearby local-to-regional carbonaceous emissions transported from the
south-west during the daytime; and the Fireworks factor consisted of
pyrotechnic particles from the Detroit region following holiday fireworks
displays. Regional aerosol from farther emissions sources was reflected
through three factors: two Biomass Burning factors and a highly chemically
processed Long Range Transport factor. The Biomass Burning factors were
separated by PMF due to differences in chemical processing which were in
part elucidated by the passage of two thunderstorm gust fronts with
different air mass histories. The remaining two factors, ECOC Night and
Nitrate Background, represented the night-time partitioning of nitrate to
pre-existing particles of different origins. The distinct meteorological
conditions observed during this month-long study in the summer of 2007
provided a unique range of temporal variability, enabling the elucidation of
the determinants of aerosol chemical composition, including source
emissions, chemical processing, and transport, at the Canada-US border.
This paper presents the first study to elucidate the coupled influences of
these determinants on temporal variability in aerosol chemical composition
using single particle-type-based receptor modelling.
Revised: 28 Jun 2011 – Accepted: 21 Jul 2011 – Published: 10 Aug 2011
Citation: McGuire, M. L., Jeong, C.-H., Slowik, J. G., Chang, R. Y.-W., Corbin, J. C., Lu, G., Mihele, C., Rehbein, P. J. G., Sills, D. M. L., Abbatt, J. P. D., Brook, J. R., and Evans, G. J.: Elucidating determinants of aerosol composition through particle-type-based receptor modeling, Atmos. Chem. Phys., 11, 8133-8155, doi:10.5194/acp-11-8133-2011, 2011.