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| Titel |
Physical and chemical properties of the regional mixed layer of Mexico's Megapolis |
| VerfasserIn |
D. Baumgardner, M. Grutter, J. Allan, C. Ochoa, B. Rappenglueck, L. M. Russell, P. Arnott |
| 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 ; 9, no. 15 ; Nr. 9, no. 15 (2009-08-11), S.5711-5727 |
| Datensatznummer |
250007566
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| Publikation (Nr.) |
 copernicus.org/acp-9-5711-2009.pdf |
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| Zusammenfassung |
The concentration of gases and aerosol particles have been measured at the
mountain site of Altzomoni, 4010 m in altitude, located 60 km southeast of
Mexico City, 50 km east of Puebla and 70 km northeast of Cuernavaca. The
objective of this study was to evaluate the properties of gases and
particles in the Regional Mixed Layer (RML) of Mexico's Megapolis. Altzomoni
is generally above the RML from late evening until late morning at which
time the arrival of the RML is marked by increasing concentrations of CO and
aerosol particles that reach their maxima in mid-afternoon. The average
diurnal cycles for fourteen days in March, 2006 were evaluated during which
time the synoptic scale circulation had three principal patterns: from the
east (E), southwest (SW) and west northwest (WNW). The original hypothesis
was that air arriving from the direction of Mexico City would have much
higher concentrations of anthropogenic gases and particles than air from
Puebla or Cuernavaca, due to the relatively large differences in
populations. In fact, not only were the average, maximum concentrations of
CO and O3 (0.3 and 0.1 ppmv) approximately the same for air originating
from the WNW and E, but the average maximum concentrations of Peroxyacyl
nitrates (PAN,PPN) and particle organic matter (POM) in air from the E
exceeded those in air from the WNW.
Comparisons of measurements from the mountain site with those made by
aircraft during the same period, using the same type of aerosol mass
spectrometer, show that the total masses of POM, NO3−,
SO42− and NH4+ were approximately the same from aircraft
measurements made over Mexico City and when winds were from the east at the
mountain site. In contrast 75% of the total aerosol mass at the mountain
site was POM whereas over Mexico City the fraction of POM was less than
60%.
The measurements suggest the occasional influence of emissions from the
nearby volcano, Popocatepetl, as well as possible incursions of biomass
combustion; however, the large concentrations of O3, PAN and POM
suggest that secondary processes are the major source for these gases and
particles. The similar concentrations in gases and particles when air is
coming from the E and NWN raises the possibility of recirculation of air
from Mexico City and the importance of this mechanism for impacting the
regional air quality. |
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