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| Titel |
Aerosol and precipitation chemistry in the southwestern United States: spatiotemporal trends and interrelationships |
| VerfasserIn |
A. Sorooshian, T. Shingler, A. Harpold, C. W. Feagles, T. Meixner, P. D. Brooks |
| 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 ; 13, no. 15 ; Nr. 13, no. 15 (2013-08-01), S.7361-7379 |
| Datensatznummer |
250018797
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| Publikation (Nr.) |
 copernicus.org/acp-13-7361-2013.pdf |
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| Zusammenfassung |
| This study characterizes the spatial and temporal patterns of aerosol and
precipitation composition at six sites across the United States Southwest
between 1995 and 2010. Precipitation accumulation occurs mostly during the
wintertime (December–February) and during the monsoon season (July–September). Rain and snow pH levels are usually between 5–6, with
crustal-derived species playing a major role in acid neutralization. These
species (Ca2+, Mg2+, K+, Na+) exhibit their highest
concentrations between March and June in both PM2.5 and precipitation
due mostly to dust. Crustal-derived species concentrations in precipitation
exhibit positive relationships with SO42−, NO3−, and
Cl−, suggesting that acidic gases likely react with and partition to
either crustal particles or hydrometeors enriched with crustal constituents.
Concentrations of particulate SO42− show a statistically
significant correlation with rain SO42− unlike snow
SO42−, which may be related to some combination of the vertical
distribution of SO42− (and precursors) and the varying degree to
which SO42−-enriched particles act as cloud condensation nuclei
versus ice nuclei in the region. The coarse : fine aerosol mass ratio was
correlated with crustal species concentrations in snow unlike rain,
suggestive of a preferential role of coarse particles (mainly dust) as ice
nuclei in the region. Precipitation NO3− : SO42− ratios
exhibit the following features with potential explanations discussed: (i)
they are higher in precipitation as compared to PM2.5; (ii) they
exhibit the opposite annual cycle compared to particulate
NO3− : SO42− ratios; and (iii) they are higher in snow
relative to rain during the wintertime. Long-term trend analysis for the
monsoon season shows that the NO3− : SO42− ratio in rain
increased at the majority of sites due mostly to air pollution regulations
of SO42− precursors. |
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