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| Titel |
Measurements of reactive trace gases and variable O3 formation rates in some South Carolina biomass burning plumes |
| VerfasserIn |
S. K. Akagi, R. J. Yokelson, I. R. Burling, S. Meinardi, I. Simpson, D. R. Blake, G. R. McMeeking, A. Sullivan, T. Lee, S. Kreidenweis, S. Urbanski, J. Reardon, D. W. T. Griffith, T. J. Johnson, D. R. Weise |
| 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 ; 13, no. 3 ; Nr. 13, no. 3 (2013-02-01), S.1141-1165 |
| Datensatznummer |
250017621
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| Publikation (Nr.) |
 copernicus.org/acp-13-1141-2013.pdf |
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| Zusammenfassung |
| In October–November 2011 we measured trace gas emission
factors from seven prescribed fires in South Carolina (SC), US, using two
Fourier transform infrared spectrometer (FTIR) systems and whole air
sampling (WAS) into canisters followed by gas-chromatographic analysis. A
total of 97 trace gas species were quantified from both airborne and
ground-based sampling platforms, making this one of the most detailed field
studies of fire emissions to date. The measurements include the first
emission factors for a suite of monoterpenes produced by heating vegetative
fuels during field fires. The first quantitative FTIR observations of
limonene in smoke are reported along with an expanded suite of monoterpenes
measured by WAS including α-pinene, β-pinene, limonene,
camphene, 4-carene, and myrcene. The known chemistry of the monoterpenes and
their measured abundance of 0.4–27.9% of non-methane organic compounds
(NMOCs) and ~ 21% of organic aerosol (mass basis) suggests
that they impacted secondary formation of ozone (O3), aerosols, and
small organic trace gases such as methanol and formaldehyde in the sampled
plumes in the first few hours after emission. The variability in the initial
terpene emissions in the SC fire plumes was high and, in general, the
speciation of the initially emitted gas-phase NMOCs was 13–195% different
from that observed in a similar study in nominally similar pine forests in
North Carolina ~ 20 months earlier. It is likely that
differences in stand structure and environmental conditions contributed to
the high variability observed within and between these studies. Similar
factors may explain much of the variability in initial emissions in the
literature. The ΔHCN/ΔCO emission ratio, however, was found
to be fairly consistent with previous airborne fire measurements in other
coniferous-dominated ecosystems, with the mean for these studies being 0.90 ± 0.06%, further confirming the value of HCN as a biomass burning
tracer. The SC results also support an earlier finding that C3-C4
alkynes may be of use as biomass burning indicators on the time-scale of
hours to a day. It was possible to measure the downwind chemical evolution
of the plume on four of the fires and significant O3 formation (ΔO3/ΔCO from 10–90%) occurred in all of these plumes within
two hours. The slowest O3 production was observed on a cloudy day with
low co-emission of NOx. The fastest O3 production was observed on
a sunny day when the downwind plume almost certainly incorporated
significant additional NOx by passing over the Columbia, SC
metropolitan area. Due to rapid plume dilution, it was only possible to
acquire high-quality downwind data for two other trace gas species
(formaldehyde and methanol) during two of the fires. In all four of these
cases, significant increases in formaldehyde and methanol were observed in
<2 h. This is likely the first direct observation of post-emission
methanol production in biomass burning plumes. Post-emission production of
methanol does not always happen in young biomass burning plumes, and its
occurrence in this study could have involved terpene precursors to a
significant extent. |
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