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| Titel |
Emissions of carbon species, organic polar compounds, potassium, and mercury from prescribed burning activities |
| VerfasserIn |
Y. Zhang, D. Obrist, B. Zielinska, A. Gerler |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250069547
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| Zusammenfassung |
| Biomass burning is an important emission source of pollutants to the atmosphere, but few
studies have focused on the chemical composition of emissions from prescribed burning
activities. Here we present results from a sampling campaign to quantify particulate-phase
emissions from various types of prescribed fires including carbon species (Elemental Carbon:
EC; Organic Carbon: OC; and Total Carbon: TC); polar organic compounds (12 different
compounds and four functional classes); water-soluble potassium (K+); and mercury (Hg).
We measured emissions from the following types of prescribed biomass burning in the Lake
Tahoe basin located on the California/Nevada border: (i) log piles stacked and dried in the
field; (ii) log piles along with green understory vegetation; and (iii) understory green
vegetation and surface litter; further emissions were collected from burns conducted in a
wood stove: (iv) dried wooden logs; (v) green foliage of understory vegetation collected from
the field; and (vi) surface organic litter collected from the field; finally, samples were also
taken from (vii) ambient air in residential areas during peak domestic wood combustion
season.
Results show that OC/EC ratios of prescribed burns in the field ranged from 4
to 10, but lower values (around 1) were observed in controlled stove fires. These
results are consistent with an excess of OC emissions over EC found in wildfires.
OC/EC ratios, however, showed clear separations between controlled wood stove
combustion (higher EC) and prescribed burns in the field (lower EC). We attribute
this difference to a higher combustion temperatures and dominance of flaming
combustion in wood stove fires. OC positively and linearly correlated to the sum of polar
organic compounds across all burn types (r2 of 0.82). The most prevalent group of
polar compounds emitted during prescribed fires was resin acids (dehydroabietic,
pimaric, and abietic acids), followed by levoglucosan plus mannositol. Negligible
contributions were observed for inositols, arabitols, and lignin derivates. Although
some of these polar compound classes are linked to specific woody or green tissues,
we found no significant differences of emission ratios between different types of
fires. Water-soluble K+, a common tracer for biomass combustion, showed a clear
separation between understory burns (low K+) and wooden pile burns (10 to 20 times
higher), suggesting that K+ can potentially be used for differentiating between
green versus dry, wooden biomass combustion. Finally, Hg emissions were very low
across all fire emissions collected, but were enhanced in urban air sampling which
might allow for differentiating sources from biomass combustion from other urban
sources. |
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