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| Titel |
Variability of aerosol optical properties in the Western Mediterranean Basin |
| VerfasserIn |
M. Pandolfi, M. Cusack, A. Alastuey, X. Querol |
| 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. 15 ; Nr. 11, no. 15 (2011-08-10), S.8189-8203 |
| Datensatznummer |
250009998
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| Publikation (Nr.) |
 copernicus.org/acp-11-8189-2011.pdf |
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| Zusammenfassung |
| Aerosol light scattering, absorption and particulate matter (PM)
concentrations were measured at Montseny, a regional background site in the
Western Mediterranean Basin (WMB) which is part of the European Supersite
for Atmospheric Aerosol Research (EUSAAR). Off line analyses of 24 h PM
filters collected with Hi-Vol instruments were performed for the
determination of the main chemical components of PM. Mean scattering and
hemispheric backscattering coefficients (@ 635 nm) were 26.6±23.2 Mm−1
and 4.3±2.7 Mm−1, respectively and the mean aerosol
absorption coefficient (@ 637 nm) was 2.8±2.2 Mm−1. Mean values of
Single Scattering Albedo (SSA) and Ångström exponent (å)
(calculated from 450 nm to 635 nm) at MSY were 0.90±0.05 and 1.3±0.5
respectively. A clear relationship was observed between the
PM1/PM10 and PM2.5/PM10 ratios as a function of the
calculated Ångström exponents. Mass scattering cross sections (MSC)
for fine mass and sulfate at 635 nm were 2.8±0.5 m2 g−1 and
11.8±2.2 m2 g−1, respectively, while the mean aerosol absorption cross
section (MAC) was 10.4±2.0 m2 g−1. The variability in aerosol
optical properties in the WMB were largely explained by the origin and
ageing of air masses over the measurement site. The MAC values appear
dependent of particles aging: similar to the expected absorption
cross-section for fresh emissions under Atlantic Advection episodes and
higher under aerosol pollution episodes. The analysis of the
Ångström exponent as a function of the origin the air masses
revealed that polluted winter anticyclonic conditions and summer
recirculation scenarios typical of the WMB led to an increase of fine
particles in the atmosphere (å = 1.5±0.1) while the aerosol optical
properties under Atlantic Advection episodes and Saharan dust outbreaks were
clearly dominated by coarser particles (å = 1.0±0.4). The sea
breeze played an important role in transporting pollutants from the
developed WMB coastlines towards inland rural areas, changing the optical
properties of aerosols. Aerosol scattering and backscattering coefficients
increased by around 40 % in the afternoon when the sea breeze was fully
developed while the absorption coefficient increased by more than 100 % as
a consequence of the increase in the equivalent black carbon concentration
(EBC) observed at MSY under sea breeze circulation. |
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