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| Titel |
The dispersion characteristics of air pollution from the world's megacities |
| VerfasserIn |
M. Cassiani, A. Stohl, S. Eckhardt |
| 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. 19 ; Nr. 13, no. 19 (2013-10-10), S.9975-9996 |
| Datensatznummer |
250085742
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| Publikation (Nr.) |
 copernicus.org/acp-13-9975-2013.pdf |
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| Zusammenfassung |
| Megacities are extreme examples of the continuously growing urbanization of
the human population that pose (new) challenges to the environment and human
health at a local scale. However, because of their size megacities also have
larger-scale effects, and more research is needed to quantify their regional-
and global-scale impacts. We performed a study of the characteristics of
pollution plumes dispersing from a group of 36 of the world's megacities
using the Lagrangian particle model FLEXPART and focusing on black carbon
(BC) emissions during the years 2003–2005. BC was selected since it is
representative of combustion-related emissions and has a significant role
as a short-lived climate forcer. Based on the BC emissions two artificial
tracers were modeled: a purely passive tracer and one subject to wet and dry
deposition more closely resembling the behavior of a true aerosol. These
tracers allowed us to investigate the role of deposition processes in
determining the impact of megacities' pollutant plumes. The particles
composing the plumes have been sampled in space and time. The time sampling
allowed us to investigate the evolution of the plume from its release up to
48 days after emission and to generalize our results for any substance
decaying with a timescale sufficiently shorter than the time window of 48
days. The physical characteristics of the time-averaged plume have been
investigated, and this showed that, although local conditions are important,
overall a city's latitude is the main factor influencing both the local and
the regional-to-global dispersion of its pollution. We also repeated the
calculations of some of the regional-pollution-potential metrics previously
proposed by Lawrence et al. (2007), thus extending their results to a depositing scalar and
retaining the evolution in time for all the plumes. Our results agreed well
with their previous results despite being obtained using a totally different
modeling framework. For the environmental impact on a global scale we
focused on the export of mass from the megacities to the sensitive polar
regions. We found that the sole city of Saint Petersburg contributes more to
the lower-troposphere pollution and deposition in the Arctic than the whole
ensemble of Asian megacities. In general this study showed that the
pollution of urban origin in the lower troposphere of the Arctic is mainly
generated by northern European sources. We also found that the deposition of
the modeled artificial BC aerosol in the Antarctic due to megacities is
comparable to the emissions of BC generated by local shipping activities.
Finally multiplying population and ground level concentration maps, we found
that the exposure of human population to megacity pollution occurs mainly
inside the city boundaries, and this is especially true if deposition is
accounted for. However, some exceptions exist (Beijing, Tianjin, Karachi)
where the impact on population outside the city boundary is larger than that
inside the city boundary. |
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