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| Titel |
Investigation of the correlation between odd oxygen and secondary organic aerosol in Mexico City and Houston |
| VerfasserIn |
E. C. Wood, M. R. Canagaratna, S. C. Herndon, T. B. Onasch, C. E. Kolb, D. R. Worsnop, J. H. Kroll, W. B. Knighton, R. Seila, M. Zavala, L. T. Molina, P. F. DeCarlo, J. L. Jimenez, A. J. Weinheimer, D. J. Knapp, B. T. Jobson, J. Stutz, W. C. Kuster, E. J. Williams |
| 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. 18 ; Nr. 10, no. 18 (2010-09-27), S.8947-8968 |
| Datensatznummer |
250008789
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| Publikation (Nr.) |
 copernicus.org/acp-10-8947-2010.pdf |
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| Zusammenfassung |
| Many recent models underpredict secondary organic aerosol (SOA) particulate
matter (PM) concentrations in polluted regions, indicating serious
deficiencies in the models' chemical mechanisms and/or missing SOA
precursors. Since tropospheric photochemical ozone production is much better
understood, we investigate the correlation of odd-oxygen ([Ox]≡[O3]+[NO2]) and the oxygenated component of organic aerosol
(OOA), which is interpreted as a surrogate for SOA. OOA and Ox measured
in Mexico City in 2006 and Houston in 2000 were well correlated in air
masses where both species were formed on similar timescales (less than 8 h) and not well correlated when their formation timescales or location
differed greatly. When correlated, the ratio of these two species ranged
from 30 μg m−3/ppm (STP) in Houston during time periods affected
by large petrochemical plant emissions to as high as 160 μg m−3/ppm
in Mexico City, where typical values were near 120 μg m−3/ppm. On
several days in Mexico City, the [OOA]/[Ox] ratio
decreased by a factor of ~2 between 08:00 and 13:00 local time. This
decrease is only partially attributable to evaporation of the least oxidized
and most volatile components of OOA; differences in the diurnal emission
trends and timescales for photochemical processing of SOA precursors
compared to ozone precursors also likely contribute to the observed
decrease. The extent of OOA oxidation increased with photochemical aging.
Calculations of the ratio of the SOA formation rate to the Ox
production rate using ambient VOC measurements and traditional laboratory
SOA yields are lower than the observed [OOA]/[Ox] ratios by factors of
5 to 15, consistent with several other models' underestimates of SOA.
Calculations of this ratio using emission factors for organic compounds from
gasoline and diesel exhaust do not reproduce the observed ratio. Although
not succesful in reproducing the atmospheric observations presented,
modeling P(SOA)/P(Ox) can serve as a useful test of photochemical
models using improved formulation mechanisms for SOA. |
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