 |
| Titel |
Investigating the links between ozone and organic aerosol chemistry in a biomass burning plume from a prescribed fire in California chaparral |
| VerfasserIn |
M. J. Alvarado, C. R. Lonsdale, R. J. Yokelson, S. K. Akagi, H. Coe, J. S. Craven, E. V. Fischer, G. R. McMeeking, J. H. Seinfeld, T. Soni, J. W. Taylor, D. R. Weise, C. E. Wold |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 12 ; Nr. 15, no. 12 (2015-06-17), S.6667-6688 |
| Datensatznummer |
250119833
|
| Publikation (Nr.) |
 copernicus.org/acp-15-6667-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| Within minutes after emission, complex photochemistry in biomass burning
smoke plumes can cause large changes in the concentrations of ozone
(O3) and organic aerosol (OA). Being able to understand and simulate
this rapid chemical evolution under a wide variety of conditions is a
critical part of forecasting the impact of these fires on air quality,
atmospheric composition, and climate. Here we use version 2.1 of the Aerosol
Simulation Program (ASP) to simulate the evolution of O3 and secondary
organic aerosol (SOA) within a young biomass burning smoke plume from the
Williams prescribed fire in chaparral, which was sampled over California in
November 2009. We demonstrate the use of a method for simultaneously
accounting for the impact of the unidentified intermediate volatility,
semi-volatile, and extremely low volatility organic compounds (here
collectively called "SVOCs") on the formation of OA (using the Volatility
Basis Set – VBS) and O3 (using the concept of mechanistic reactivity). We
show that this method can successfully simulate the observations of O3,
OA, NOx, ethylene (C2H4), and OH to within measurement uncertainty using
reasonable assumptions about the average chemistry of the unidentified
SVOCs. These assumptions were (1) a reaction rate constant with OH of
~ 10-11 cm3 s−1; (2) a significant fraction (up to
~ 50 %) of the RO2 + NO reaction resulted in
fragmentation, rather than functionalization, of the parent SVOC; (3)
~ 1.1 molecules of O3 were formed for every molecule of
SVOC that reacted; (4) ~ 60 % of the OH that reacted with
the unidentified non-methane organic compounds (NMOC) was regenerated as HO2; and (5) that
~ 50 % of the NO that reacted with the SVOC peroxy radicals
was lost, presumably to organic nitrate formation. Additional evidence for
the fragmentation pathway is provided by the observed rate of formation of
acetic acid (CH3COOH), which is consistent with our assumed fragmentation rate.
However, the model overestimates peroxyacetyl nitrate (PAN) formation downwind by about 50 %,
suggesting the need for further refinements to the chemistry. This method
could provide a way for classifying different smoke plume observations in
terms of the average chemistry of their SVOCs, and could be used to study
how the chemistry of these compounds (and the O3 and OA they form)
varies between plumes. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|