In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 22, No. 15 ( 2022-08-03), p. 9877-9893
Abstract:
Abstract. The size and frequency of wildfires in the western United
States have been increasing, and this trend is projected to continue, with increasing adverse consequences for human health. Gas- and particle-phase
organic compounds are the main components of wildfire emissions. Some of the directly emitted compounds are hazardous air pollutants, while others can
react with oxidants to form secondary air pollutants such as ozone and
secondary organic aerosol (SOA). Further, compounds emitted in the particle
phase can volatize during smoke transport and can then serve as precursors for SOA. The extent of pollutant formation from wildfire emissions is
dependent in part on the speciation of organic compounds. The most detailed
speciation of organic compounds has been achieved in laboratory studies,
though recent field campaigns are leading to an increase in such
measurements in the field. In this study, we identified and quantified
hundreds of gas- and particle-phase organic compounds emitted from
conifer-dominated wildfires in the western US, using two two-dimensional gas
chromatography coupled with time-of-flight mass spectrometry (GC × GC ToF-MS) instruments. Observed emission factors (EFs) and emission ratios
are reported for four wildfires. As has been demonstrated previously,
modified combustion efficiency (MCE) was a good predictor of particle-phase EFs (e.g., R2=0.78 and 0.84 for sugars and terpenoids,
respectively), except for elemental carbon. Higher emissions of
diterpenoids, resin acids, and monoterpenes were observed in the field relative to laboratory studies, likely due to distillation from unburned
heated vegetation, which may be underrepresented in laboratory studies.
These diterpenoids and resin acids accounted for up to 45 % of total
quantified organic aerosol, higher than the contribution from sugar and
sugar derivatives. The low volatility of resin acids makes them ideal
markers for conifer fire smoke. The speciated measurements also show that
evaporation of semi-volatile organic compounds took place in smoke plumes,
which suggests that the evaporated primary organic aerosol can be a precursor of SOAs in wildfire smoke plumes.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-22-9877-2022
DOI:
10.5194/acp-22-9877-2022-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2022
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
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