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| Titel |
Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry: results from the CENICA Supersite |
| VerfasserIn |
D. Salcedo, T. B. Onasch, K. Dzepina, M. R. Canagaratna, Q. Zhang, J. A. Huffman, P. F. DeCarlo, J. T. Jayne, P. Mortimer, D. R. Worsnop, C. E. Kolb, K. S. Johnson, B. Zuberi, L. C. Marr, R. Volkamer, L. T. Molina, M. J. Molina, B. Cárdenas, R. M. Bernabé, C. Márquez, J. S. Gaffney, N. A. Marley, A. Laskin, V. Shutthanandan, Y. Xie, W. Brune, R. Lesher, T. Shirley, J. L. Jimenez |
| 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 ; 6, no. 4 ; Nr. 6, no. 4 (2006-03-24), S.925-946 |
| Datensatznummer |
250003622
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| Publikation (Nr.) |
 copernicus.org/acp-6-925-2006.pdf |
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| Zusammenfassung |
| An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at the CENICA
Supersite, during the Mexico City Metropolitan Area field study (MCMA-2003)
from 31 March-4 May 2003 to investigate particle concentrations, sources,
and processes. The AMS provides real time information on mass concentration
and composition of the non-refractory species in particulate matter less
than 1 µm (NR-PM1) with high time and size-resolution. In
order to account for the refractory material in the aerosol, we also present
estimates of Black Carbon (BC) using an aethalometer and an estimate of
the aerosol soil component obtained from Proton-Induced X-ray Emission
Spectrometry (PIXE) analysis of impactor substrates. Comparisons of AMS + BC
+ soil mass concentration with other collocated particle instruments (a
LASAIR Optical Particle Counter, a PM2.5 Tapered Element Oscillating
Microbalance (TEOM), and a PM2.5 DustTrak Aerosol Monitor) show that
the AMS + BC + soil mass concentration is consistent with the total
PM2.5 mass concentration during MCMA-2003 within the combined
uncertainties. In Mexico City, the organic fraction of the estimated
PM2.5 at CENICA represents, on average, 54.6% (standard deviation
σ=10%) of the mass, with the rest consisting of inorganic
compounds (mainly ammonium nitrate and sulfate/ammonium salts), BC, and
soil. Inorganic compounds represent 27.5% of PM2.5 (σ=10%);
BC mass concentration is about 11% (σ=4%);
while soil represents about 6.9% (σ=4%). Size distributions
are presented for the AMS species; they show an accumulation mode that
contains mainly oxygenated organic and secondary inorganic compounds. The
organic size distributions also contain a small organic particle mode that
is likely indicative of fresh traffic emissions; small particle modes exist
for the inorganic species as well. Evidence suggests that the organic and
inorganic species are not always internally mixed, especially in the small
modes. The aerosol seems to be neutralized most of the time; however, there
were some periods when there was not enough ammonium to completely
neutralize the nitrate, chloride and sulfate present. The diurnal cycle and
size distributions of nitrate suggest local photochemical production. On the
other hand, sulfate appears to be produced on a regional scale. There are
indications of new particle formation and growth events when concentrations
of SO2 were high. Although the sources of chloride are not clear, this
species seems to condense as ammonium chloride early in the morning and to
evaporate as the temperature increases and RH decreases. The total and
speciated mass concentrations and diurnal cycles measured during MCMA-2003
are similar to measurements during a previous field campaign at a nearby
location. |
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