Ubiquitous influence of wildfire emissions and secondary organic aerosol on summertime atmospheric aerosol in the forested Great Lakes region

TitleUbiquitous influence of wildfire emissions and secondary organic aerosol on summertime atmospheric aerosol in the forested Great Lakes region
Publication TypeJournal Article
Year of Publication2018
AuthorsGunsch MJ, May NW, Wen M, Bottenus CLH, Gardner DJ, VanReken TM, Bertman SB, Hopke PK, Ault AP, Pratt KA
JournalAtmospheric Chemistry and Physics
Pagination3701 - 3715
Date PublishedJan-01-2018

Long-range aerosol transport affects locations
hundreds of kilometers from the point of emission, leading
to distant particle sources influencing rural environments
that have few major local sources. Source apportionment was
conducted using real-time aerosol chemistry measurements
made in July 2014 at the forested University of Michigan
Biological Station near Pellston, Michigan, a site representative
of the remote forested Great Lakes region. Size-resolved
chemical composition of individual 0.5–2.0 µm particles was
measured using an aerosol time-of-flight mass spectrometer
(ATOFMS), and non-refractory aerosol mass less than 1 µm
(PM1) was measured with a high-resolution aerosol mass
spectrometer (HR-AMS). The field site was influenced by
air masses transporting Canadian wildfire emissions and urban
pollution from Milwaukee and Chicago. During wildfireinfluenced
periods, 0.5–2.0 µm particles were primarily aged
biomass burning particles (88 % by number). These particles
were heavily coated with secondary organic aerosol
(SOA) formed during transport, with organics (average O/C
ratio of 0.8) contributing 89 % of the PM1 mass. During
urban-influenced periods, organic carbon, elemental carbon–
organic carbon, and aged biomass burning particles were
identified, with inorganic secondary species (ammonium,
sulfate, and nitrate) contributing 41 % of the PM1 mass, indicative
of atmospheric processing. With current models underpredicting
organic carbon in this region and biomass burning
being the largest combustion contributor to SOA by mass,
these results highlight the importance for regional chemical
transport models to accurately predict the impact of longrange
transported particles on air quality in the upper Midwest,
United States, particularly considering increasing intensity
and frequency of Canadian wildfires.

Short TitleAtmos. Chem. Phys.
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