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| Titel |
Black carbon aerosol mixing state, organic aerosols and aerosol optical properties over the United Kingdom |
| VerfasserIn |
G. R. McMeeking, W. T. Morgan, M. Flynn, E. J. Highwood, K. Turnbull, J. Haywood, H. Coe |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 17 ; Nr. 11, no. 17 (2011-09-05), S.9037-9052 |
| Datensatznummer |
250010052
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| Publikation (Nr.) |
 copernicus.org/acp-11-9037-2011.pdf |
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| Zusammenfassung |
| Black carbon (BC) aerosols absorb sunlight thereby leading to a positive
radiative forcing and a warming of climate and can also impact human health
through their impact on the respiratory system. The state of mixing of BC
with other aerosol species, particularly the degree of internal/external
mixing, has been highlighted as a major uncertainty in assessing its
radiative forcing and hence its climate impact, but few in situ observations
of mixing state exist. We present airborne single particle soot photometer
(SP2) measurements of refractory BC (rBC) mass concentrations and mixing
state coupled with aerosol composition and optical properties measured in
urban plumes and regional pollution over the United Kingdom. All data were
obtained using instrumentation flown on the UK's BAe-146-301 large
Atmospheric Research Aircraft (ARA) operated by the Facility for Airborne
Atmospheric Measurements (FAAM). We measured sub-micron aerosol composition
using an aerosol mass spectrometer (AMS) and used positive matrix
factorization to separate hydrocarbon-like (HOA) and oxygenated organic
aerosols (OOA). We found a higher number fraction of thickly coated rBC
particles in air masses with large OOA relative to HOA, higher
ozone-to-nitrogen oxides (NOx) ratios and large concentrations of total
sub-micron aerosol mass relative to rBC mass concentrations. The more ozone-
and OOA-rich air masses were associated with transport from continental
Europe, while plumes from UK cities had higher HOA and NOx and fewer
thickly coated rBC particles. We did not observe any significant change in
the rBC mass absorption efficiency calculated from rBC mass and light
absorption coefficients measured by a particle soot absorption photometer
despite observing significant changes in aerosol composition and rBC mixing
state. The contributions of light scattering and absorption to total
extinction (quantified by the single scattering albedo; SSA) did change for
different air masses, with lower SSA observed in urban plumes compared to
regional aerosol (0.85 versus 0.9–0.95). We attribute these differences to
the presence of relatively rapidly formed secondary aerosol, primarily OOA
and ammonium nitrate, which must be taken into account in radiative forcing
calculations. |
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