Morgan, W., Allan, J., Bower, K., Highwood, E. J., Liu, D., McMeeking, G., Northway, M., Williams, P., Krejci, R. and Coe, H.
Airborne measurements of the spatial distribution of aerosol chemical composition across Europe and evolution of the organic fraction.
Atmospheric Chemistry and Physics, 10.
To link to this article DOI: 10.5194/acp-10-4065-2010
The spatial distribution of aerosol chemical composition and the
evolution of the Organic Aerosol (OA) fraction is investigated based
upon airborne measurements of aerosol chemical composition in the
planetary boundary layer across Europe. Sub-micron aerosol chemical
composition was measured using a compact Time-of-Flight Aerosol Mass
Spectrometer (cToF-AMS). A range of sampling conditions were evaluated,
including relatively clean background conditions, polluted conditions in
North-Western Europe and the near-field to far-field outflow from such
conditions. Ammonium nitrate and OA were found to be the dominant
chemical components of the sub-micron aerosol burden, with mass
fractions ranging from 20--50% each. Ammonium nitrate was found to
dominate in North-Western Europe during episodes of high pollution,
reflecting the enhanced NO_x and ammonia sources in this region. OA was
ubiquitous across Europe and concentrations generally exceeded sulphate
by 30--160%. A factor analysis of the OA burden was performed in order
to probe the evolution across this large range of spatial and temporal
scales. Two separate Oxygenated Organic Aerosol (OOA) components were
identified; one representing an aged-OOA, termed Low Volatility-OOA and
another representing fresher-OOA, termed Semi Volatile-OOA on the basis
of their mass spectral similarity to previous studies. The factors
derived from different flights were not chemically the same but rather
reflect the range of OA composition sampled during a particular flight.
Significant chemical processing of the OA was observed downwind of major
sources in North-Western Europe, with the LV-OOA component becoming
increasingly dominant as the distance from source and photochemical
processing increased. The measurements suggest that the aging of OA can
be viewed as a continuum, with a progression from a less oxidised,
semi-volatile component to a highly oxidised, less-volatile component.
Substantial amounts of pollution were observed far downwind of
continental Europe, with OA and ammonium nitrate being the major
constituents of the sub-micron aerosol burden. Such anthropogenically
perturbed air masses can significantly perturb regional climate far
downwind of major source regions.
|Date Deposited:||09 Jun 2010 10:07|
|Last Modified:||19 Jul 2015 12:25|
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