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| Titel |
Inter-community variability in total particle number concentrations in the eastern Los Angeles air basin |
| VerfasserIn |
N. Hudda, K. Cheung, K. F. Moore, C. Sioutas |
| 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 ; 10, no. 23 ; Nr. 10, no. 23 (2010-12-01), S.11385-11399 |
| Datensatznummer |
250008928
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| Publikation (Nr.) |
 copernicus.org/acp-10-11385-2010.pdf |
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| Zusammenfassung |
| Ultrafine Particles (UFP) can display sharp gradients in their number
concentrations in urban environment due to their transient nature and rapid
atmospheric processing. The ability of using air pollution data generated at
a central monitoring station to assess exposure relies on our understanding
of the spatial variability of a specific pollutant associated with a region.
High spatial variation in the concentrations of air pollutants has been
reported at scales of 10s of km for areas affected by primary emissions.
Spatial variability in particle number concentrations (PNC) and size
distributions needs to be investigated, as the representativeness of a
monitoring station in a region is premised on the assumption of homogeneity
in both of these metrics. This study was conducted at six sites, one in
downtown Los Angeles and five located about 40–115 km downwind in the
receptor areas of Los Angeles air basin. PNC and size distribution were
measured using Condensation Particle Counters (CPC) and Scanning Mobility
Particle Sizer (SMPS). The seasonal and diurnal variations of PNC implied
that PNC might vary significantly with meteorological conditions, even
though the general patterns at the sites may remain generally similar across
the year due to consistency of sources around them. Regionally transported
particulate matter (PM) from upwind urban areas of Los Angeles lowered
spatial variation by acting as a "homogenizing" factor during favorable
meteorological conditions. Spatial variability also increased during hours
of the day during which the effects of local sources predominate. The
spatial variability associated with PNC (quantified using Coefficients of
Divergence, CODs), averaged about 0.3, which was generally lower than that
based on specific size ranges. Results showed an inverse relationship of COD
with particles size, with fairly uniform values in the particle range which
is associated with regional transport. Our results suggest that spatial
variability, even in the receptor regions of Los Angeles Basin, should be
assessed for both PNC and size distributions, and should be interpreted in
context of seasonal and diurnal influences, and suitably factored if values
for exposure are ascertained using a central monitoring station. |
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