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| Titel |
VOC reactivity in central California: comparing an air quality model to ground-based measurements |
| VerfasserIn |
A. L. Steiner, R. C. Cohen, R. A. Harley, S. Tonse, D. B. Millet, G. W. Schade, A. H. Goldstein |
| 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 ; 8, no. 2 ; Nr. 8, no. 2 (2008-01-29), S.351-368 |
| Datensatznummer |
250005430
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| Publikation (Nr.) |
 copernicus.org/acp-8-351-2008.pdf |
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| Zusammenfassung |
| Volatile organic compound (VOC) reactivity in central California is examined
using a photochemical air quality model (the Community Multiscale Air
Quality model; CMAQ) and ground-based measurements to evaluate the
contribution of VOC to photochemical activity. We classify VOC into four
categories: anthropogenic, biogenic, aldehyde, and other oxygenated VOC.
Anthropogenic and biogenic VOC consist of primary emissions, while aldehydes
and other oxygenated VOC include both primary anthropogenic emissions and
secondary products from primary VOC oxidation. To evaluate the model
treatment of VOC chemistry, we compare calculated and modeled OH and VOC
reactivities using the following metrics: 1) cumulative distribution
functions of NOx concentration and VOC reactivity (ROH,VOC), 2)
the relationship between ROH,VOC and NOx, 3) total OH reactivity
(ROH,total) and speciated contributions, and 4) the relationship
between speciated ROH,VOC and NOx. We find that the model predicts
ROH,total to within 25–40% at three sites representing urban
(Sacramento), suburban (Granite Bay) and rural (Blodgett Forest) chemistry.
However in the urban area of Fresno, the model under predicts NOx and
VOC emissions by a factor of 2–3. At all locations the model is consistent
with observations of the relative contributions of total VOC. In urban
areas, anthropogenic and biogenic ROH,VOC are predicted fairly well
over a range of NOx conditions. In suburban and rural locations,
anthropogenic and other oxygenated ROH,VOC relationships are
reproduced, but calculated biogenic and aldehyde ROH,VOC are often
poorly characterized by measurements, making evaluation of the model with
available data unreliable. In central California, 30–50% of the modeled
urban VOC reactivity is due to aldehydes and other oxygenated species, and
the total oxygenated ROH,VOC is nearly equivalent to anthropogenic VOC
reactivity. In rural vegetated regions, biogenic and aldehyde reactivity
dominates. This indicates that more attention needs to be paid to the
accuracy of models and measurements of both primary emissions of oxygenated
VOC and secondary production of oxygenates, especially formaldehyde and
other aldehydes, and that a more comprehensive set of oxygenated VOC
measurements is required to include all of the important contributions to
atmospheric reactivity. |
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