scholarly journals Near-field emission profiling of Rainforest and Cerrado fires in Brazil during SAMBBA 2012

2017 ◽  
Author(s):  
Amy K. Hodgson ◽  
William T. Morgan ◽  
Sebastian O'Shea ◽  
Stéphane Bauguitte ◽  
James D. Allan ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Near Field ◽  
Emission Factors ◽  
Fuel Combustion ◽  
Trace Gas ◽  
Particulate Emissions ◽  
Particulate Emission ◽  
Airborne Measurements ◽  
Modelling Studies ◽  
Fire Conditions

Abstract. We profile trace gas and particulate emissions from near-field airborne measurements of discrete smoke plumes in Brazil during the 2012 biomass burning season. The South American Biomass Burning Analysis (SAMBBA) Project conducted during September and October 2012 sampled across two distinct fire regimes prevalent in the Amazon Basin. Combined measurements from a Compact Time Of Flight Aerosol Mass Spectrometer (C-ToF-AMS) and a Single Particle Soot Photometer (SP2) are reported for the first time in a tropical biomass burning environment. Emissions from a mostly-smouldering rainforest wildfire in Rondonia state and numerous smaller flaming Cerrado fires in Tocantins state are presented. While the Cerrado fires appear to be representative of typical fire conditions in the existing literature, the rainforest wildfire likely represents a more extreme example of biomass burning with a bias towards mostly-smouldering emissions. We determined fire integrated modified combustion efficiencies, emission ratios and emission factors for trace gas and particulate components for these two fire types, alongside aerosol microphysical properties. Seven times more black carbon was emitted from the Cerrado fires per unit of fuel combustion (EFBC of 0.13 ± 0.04 g kg−1) compared to the rainforest fire (EFBC of 0.019 ± 0.006 g kg−1) and more than six times the amount of organic aerosol was emitted from the rainforest fire per unit of fuel combustion (EFOC of 5.00 ± 1.58 g kg−1) compared to the Cerrado fires (EFOC of 0.82 ± 0.26 g kg−1). Particulate phase species emitted from the fires sampled are generally lower than those reported in previous studies and in emission inventories, which is likely a combination of differences in fire combustion efficiency and fuel content, along with different measurement techniques. Previous modelling studies focussed on the biomass burning season in tropical South America have required significant scaling of emissions to reproduce in-situ and satellite aerosol concentrations over the region. Our results do not indicate that emission factors used in inventories are biased low, which could be one potential cause of the reported underestimates in modelling studies. This study supplements and updates trace gas and particulate emission factors for fire type specific biomass burning in Brazil for use in weather and climate models. The study illustrates that initial fire conditions can result in substantial differences in terms of their emitted chemical components, which can potentially perturb the Earth system.

scholarly journals Near-field emission profiling of tropical forest and Cerrado fires in Brazil during SAMBBA 2012

2018 ◽  
Vol 18 (8) ◽  
pp. 5619-5638 ◽  
Author(s):  
Amy K. Hodgson ◽  
William T. Morgan ◽  
Sebastian O'Shea ◽  
Stéphane Bauguitte ◽  
James D. Allan ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Forest Fire ◽  
Biomass Burning ◽  
Near Field ◽  
Emission Factors ◽  
Fuel Combustion ◽  
Trace Gas ◽  
Particulate Emission ◽  
Modelling Studies ◽  
Fire Conditions

Abstract. We profile trace gas and particulate emissions from near-field airborne measurements of discrete smoke plumes in Brazil during the 2012 biomass burning season. The South American Biomass Burning Analysis (SAMBBA) Project conducted during September and October 2012 sampled across two distinct fire regimes prevalent in the Amazon Basin. Combined measurements from a Compact Time-of-Flight Aerosol Mass Spectrometer (C-ToF-AMS) and a Single Particle Soot Photometer (SP2) are reported for the first time in a tropical biomass burning environment. Emissions from a mostly smouldering tropical forest wildfire in Rondônia state and numerous smaller flaming Cerrado fires in Tocantins state are presented. While the Cerrado fires appear to be representative of typical fire conditions in the existing literature, the tropical forest wildfire likely represents a more extreme example of biomass burning with a bias towards mostly smouldering emissions. We determined fire-integrated modified combustion efficiencies, emission ratios and emission factors for trace gas and particulate components for these two fire types, alongside aerosol microphysical properties. Seven times more black carbon was emitted from the Cerrado fires per unit of fuel combustion (EFBC of 0.13 ± 0.04 g kg−1) compared to the tropical forest fire (EFBC of 0.019 ± 0.006 g kg−1), and more than 6 times the amount of organic aerosol was emitted from the tropical forest fire per unit of fuel combustion (EFOM of 8.00 ± 2.53 g kg−1, EFOC of 5.00 ± 1.58 g kg−1) compared to the Cerrado fires (EFOM of 1.31 ± 0.42 g kg−1, EFOC of 0.82 ± 0.26 g kg−1). Particulate-phase species emitted from the fires sampled are generally lower than those reported in previous studies and in emission inventories, which is likely a combination of differences in fire combustion efficiency and fuel mixture, along with different measurement techniques. Previous modelling studies focussed on the biomass burning season in tropical South America have required significant scaling up of emissions to reproduce in situ and satellite aerosol concentrations over the region. Our results do not indicate that emission factors used in inventories are biased low, which could be one potential cause of the reported underestimates in modelling studies. This study supplements and updates trace gas and particulate emission factors for fire-type-specific biomass burning in Brazil for use in weather and climate models. The study illustrates that initial fire conditions can result in substantial differences in terms of their emitted chemical components, which can potentially perturb the Earth system.

Airborne measurements of trace gas emissions from African biomass burning during the MOYA Campaign

2020 ◽  
Author(s):  
Patrick Barker ◽  
Grant Allen ◽  
Thomas Bannan ◽  
Joseph Pitt ◽  
Stephane Bauguitte ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Carbon Emissions ◽  
Linear Trend ◽  
Emission Factors ◽  
Climate Feedback ◽  
Trace Gas ◽  
Atmospheric Measurements ◽  
African Region ◽  
Airborne Measurements

<p>Biomass burning (BB) is known to contribute significantly to the global budgets of atmospheric trace gases and aerosols.  Approximately 1.6–4.1 Pg of CO<sub>2</sub>, 11–53 Tg CH<sub>4</sub> and 0.1–0.3 Tg of N<sub>2</sub>O is emitted to the atmosphere per year as a result of biomass burning on a global scale (Crutzen and Andreae, 2016). The contribution of BB to global GHG budgets is likely to increase over time due to climate feedback of warming and more widespread drought conditions increasing the likelihood and spread of wildfire events (Liu et al., 2014).</p><p>It is estimated that Africa accounts for approximately 52% of all BB carbon emissions, with the Northern Sub-Saharan African region alone accounting for 20-25% of global BB carbon emissions (van der Werf et al. 2010; Ichoku et al. 2016). Many of these fires are anthropogenic in origin, and occur for reasons such as clearing land for agricultural use, management of natural savannah vegetation, or as pest control (Andreae, 1991).  Despite the African contribution to global BB emissions, there are limited in situ studies of African wildfire emissions.</p><p>In situ measurements of CH<sub>4</sub>, CO<sub>2</sub> and N<sub>2</sub>O and CO in biomass burning plumes were carried out in Senegal in February 2017 and in Uganda in January 2019 during the Methane Observations and Yearly Assessments (MOYA) project. These observations were carried out using the Facility for Airborne Atmospheric Measurements BAe-146 Atmospheric Research Aircraft (ARA), which is fitted with a range of specialist instrumentation for in situ trace gas sampling. Emission factors for these species were calculated for both near-field and far-field biomass burning plumes. A notable difference in the linear trend between methane emission factors and completeness-of-combustion was identified between Senegalese and Ugandan fires.</p>

scholarly journals Emissions of trace gases from Australian temperate forest fires: emission factors and dependence on modified combustion efficiency

2018 ◽  
Vol 18 (5) ◽  
pp. 3717-3735 ◽  
Author(s):  
Elise-Andrée Guérette ◽  
Clare Paton-Walsh ◽  
Maximilien Desservettaz ◽  
Thomas E. L. Smith ◽  
Liubov Volkova ◽  
...  
Keyword(s):  
Forest Fires ◽  
Temperate Forest ◽  
Combustion Efficiency ◽  
Emission Factors ◽  
Trace Gas ◽  
Ion Flow ◽  
Airborne Measurements ◽  
Trace Gas Emissions ◽  
Open Path ◽  
Modified Combustion Efficiency

Abstract. We characterised trace gas emissions from Australian temperate forest fires through a mixture of open-path Fourier transform infrared (OP-FTIR) measurements and selective ion flow tube mass spectrometry (SIFT-MS) and White cell FTIR analysis of grab samples. We report emission factors for a total of 25 trace gas species measured in smoke from nine prescribed fires. We find significant dependence on modified combustion efficiency (MCE) for some species, although regional differences indicate that the use of MCE as a proxy may be limited. We also find that the fire-integrated MCE values derived from our in situ on-the-ground open-path measurements are not significantly different from those reported for airborne measurements of smoke from fires in the same ecosystem. We then compare our average emission factors to those measured for temperate forest fires elsewhere (North America) and for fires in another dominant Australian ecosystem (savanna) and find significant differences in both cases. Indeed, we find that although the emission factors of some species agree within 20 %, including those of hydrogen cyanide, ethene, methanol, formaldehyde and 1,3-butadiene, others, such as acetic acid, ethanol, monoterpenes, ammonia, acetonitrile and pyrrole, differ by a factor of 2 or more. This indicates that the use of ecosystem-specific emission factors is warranted for applications involving emissions from Australian forest fires.

scholarly journals Emissions of trace gases from Australian temperate forest fires: emission factors and dependence on modified combustion efficiency

2017 ◽  
Author(s):  
Elise-Andrée Guérette ◽  
Clare Paton-Walsh ◽  
Maximilien Desservettaz ◽  
Thomas E. L. Smith ◽  
Liubov Volkova ◽  
...  
Keyword(s):  
Forest Fires ◽  
Temperate Forest ◽  
Combustion Efficiency ◽  
Emission Factors ◽  
Trace Gas ◽  
Airborne Measurements ◽  
Trace Gas Emissions ◽  
Open Path ◽  
Modified Combustion Efficiency

Abstract. We characterised trace gas emissions from Australian temperate forest fires through a mixture of in situ open-path FTIR measurements spectroscopy and selective ion flow tube mass spectrometry (SIFT-MS) and White cell FTIR spectroscopy of grab samples. We report emission factors for a total of 25 trace gas species measured in smoke from nine prescribed fires. We find significant dependence on modified combustion efficiency (MCE) for some species, although regional differences indicate that the use of MCE as a proxy may be limited. We also find that the fire-integrated MCE values derived from our in situ on-the-ground open-path measurements are not significantly different from those reported for airborne measurements of smoke from fires in the same ecosystem. We then compare our average emission factors to those measured for fires in North American temperate ecosystems and for fires in Australian savanna and find that, although emission factors of some species agree within 20 %, others differ by a factor of 2 or more. This indicates that the use of ecosystem-specific emission factors is warranted for applications involving emissions from Australian forest fires.

scholarly journals Coupling field and laboratory measurements to estimate the emission factors of identified and unidentified trace gases for prescribed fires

2013 ◽  
Vol 13 (1) ◽  
pp. 89-116 ◽  
Author(s):  
R. J. Yokelson ◽  
I. R. Burling ◽  
J. B. Gilman ◽  
C. Warneke ◽  
C. E. Stockwell ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Proton Transfer ◽  
Gas Phase ◽  
Biomass Burning ◽  
Organic Soil ◽  
Emission Factors ◽  
Trace Gas ◽  
Prescribed Fires ◽  
Unidentified Species ◽  
Semiarid Shrubland

Abstract. An extensive program of experiments focused on biomass burning emissions began with a laboratory phase in which vegetative fuels commonly consumed in prescribed fires were collected in the southeastern and southwestern US and burned in a series of 71 fires at the US Forest Service Fire Sciences Laboratory in Missoula, Montana. The particulate matter (PM2.5) emissions were measured by gravimetric filter sampling with subsequent analysis for elemental carbon (EC), organic carbon (OC), and 38 elements. The trace gas emissions were measured by an open-path Fourier transform infrared (OP-FTIR) spectrometer, proton-transfer-reaction mass spectrometry (PTR-MS), proton-transfer ion-trap mass spectrometry (PIT-MS), negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS), and gas chromatography with MS detection (GC-MS). 204 trace gas species (mostly non-methane organic compounds (NMOC)) were identified and quantified with the above instruments. Many of the 182 species quantified by the GC-MS have rarely, if ever, been measured in smoke before. An additional 153 significant peaks in the unit mass resolution mass spectra were quantified, but either could not be identified or most of the signal at that molecular mass was unaccounted for by identifiable species. In a second, "field" phase of this program, airborne and ground-based measurements were made of the emissions from prescribed fires that were mostly located in the same land management units where the fuels for the lab fires were collected. A broad variety, but smaller number of species (21 trace gas species and PM2.5) was measured on 14 fires in chaparral and oak savanna in the southwestern US, as well as pine forest understory in the southeastern US and Sierra Nevada mountains of California. The field measurements of emission factors (EF) are useful both for modeling and to examine the representativeness of our lab fire EF. The lab EF/field EF ratio for the pine understory fuels was not statistically different from one, on average. However, our lab EF for "smoldering compounds" emitted from the semiarid shrubland fuels should likely be increased by a factor of ~2.7 to better represent field fires. Based on the lab/field comparison, we present emission factors for 357 pyrogenic species (including unidentified species) for 4 broad fuel types: pine understory, semiarid shrublands, coniferous canopy, and organic soil. To our knowledge this is the most comprehensive measurement of biomass burning emissions to date and it should enable improved representation of smoke composition in atmospheric models. The results support a recent estimate of global NMOC emissions from biomass burning that is much higher than widely used estimates and they provide important insights into the nature of smoke. 31–72% of the mass of gas-phase NMOC species was attributed to species that we could not identify. These unidentified species are not represented in most models, but some provision should be made for the fact that they will react in the atmosphere. In addition, the total mass of gas-phase NMOC divided by the mass of co-emitted PM2.5 averaged about three (range ~2.0–8.7). About 35–64% of the NMOC were likely semivolatile or of intermediate volatility. Thus, the gas-phase NMOC represent a large reservoir of potential precursors for secondary formation of ozone and organic aerosol. For the single lab fire in organic soil about 28% of the emitted carbon was present as gas-phase NMOC and ~72% of the mass of these NMOC was unidentified, highlighting the need to learn more about the emissions from smoldering organic soils. The mass ratio of total NMOC to "NOx as NO" ranged from 11 to 267, indicating that NOx-limited O3 production would be common in evolving biomass burning plumes. The fuel consumption per unit area was 7.0 ± 2.3 Mg ha−1 and 7.7 ± 3.7 Mg ha−1 for pine-understory and semiarid shrubland prescribed fires, respectively.

scholarly journals Airborne observations of trace gases over boreal Canada during BORTAS: campaign climatology, air mass analysis and enhancement ratios

2013 ◽  
Vol 13 (24) ◽  
pp. 12451-12467 ◽  
Author(s):  
S. J. O'Shea ◽  
G. Allen ◽  
M. W. Gallagher ◽  
S. J.-B. Bauguitte ◽  
S. M. Illingworth ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Biomass Burning ◽  
Dry Matter ◽  
Emission Factors ◽  
Far Field ◽  
Air Mass ◽  
Air Masses ◽  
Airborne Measurements ◽  
Northwestern Ontario ◽  
The Impact

Abstract. In situ airborne measurements were made over eastern Canada in summer 2011 as part of the BORTAS experiment (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites). In this paper we present observations of greenhouse gases (CO2 and CH4) and other biomass burning tracers (CO, HCN and CH3CN), both climatologically and through case studies, as recorded on board the FAAM BAe-146 research aircraft. Vertical profiles of CO2 were generally characterised by depleted boundary layer concentrations relative to the free troposphere, consistent with terrestrial biospheric uptake. In contrast, CH4 concentrations were found to rise with decreasing altitude due to strong local and regional surface sources. BORTAS observations were found to be broadly comparable with both previous measurements in the region during the regional burning season and with reanalysed composition fields from the EU Monitoring Atmospheric Composition and Change (MACC) project. We use coincident tracer–tracer correlations and a Lagrangian trajectory model to characterise and differentiate air mass history of intercepted plumes. In particular, CO, HCN and CH3CN were used to identify air masses that have been recently influenced by biomass burning. Examining individual cases we were able to quantify emissions from biomass burning. Using both near-field (< 1 day) and far-field (> 1 day) sampling, boreal forest fire plumes were identified throughout the troposphere. Fresh plumes from fires in northwestern Ontario yield emission factors for CH4 and CO2 of 8.5 ± 0.9 g (kg dry matter)−1 and 1512 ± 185 g (kg dry matter)−1, respectively. We have also investigated the efficacy of calculating emission factors from far-field sampling, in which there might be expected to be limited mixing with background and other characteristic air masses, and we provide guidance on best practice and limitations in such analysis. We have found that for measurements within plumes that originated from fires in northwestern Ontario 2–4 days upwind, emission factors can be calculated that range between 1618 ± 216 and 1702 ± 173 g (kg dry matter)−1 for CO2 and 1.8 ± 0.2 and 6.1 ± 1 g (kg dry matter)−1 for CH4.

scholarly journals Measurements of reactive trace gases and variable O<sub>3</sub> formation rates in some South Carolina biomass burning plumes

2013 ◽  
Vol 13 (3) ◽  
pp. 1141-1165 ◽  
Author(s):  
S. K. Akagi ◽  
R. J. Yokelson ◽  
I. R. Burling ◽  
S. Meinardi ◽  
I. Simpson ◽  
...  
Keyword(s):  
South Carolina ◽  
Biomass Burning ◽  
Stand Structure ◽  
Trace Gases ◽  
Field Studies ◽  
Emission Factors ◽  
Trace Gas ◽  
Methanol Production ◽  
Fire Emissions ◽  
Reactive Trace Gases

Abstract. 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.

scholarly journals Properties and evolution of biomass burning organic aerosol from Canadian boreal forest fires

2014 ◽  
Vol 14 (18) ◽  
pp. 25095-25138 ◽  
Author(s):  
M. D. Jolleys ◽  
H. Coe ◽  
G. McFiggans ◽  
J. W. Taylor ◽  
S. J. O'Shea ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Biomass Burning ◽  
Forest Fires ◽  
Spatial Scales ◽  
Near Field ◽  
Organic Aerosol ◽  
Charge Ratio ◽  
Far Field ◽  
Airborne Measurements ◽  
The Impact

Abstract. Airborne measurements of biomass burning organic aerosol (BBOA) from boreal forest fires reveal highly contrasting properties for plumes of different ages. These measurements, performed using an Aerodyne Research Inc. compact time-of-flight aerosol mass spectrometer (C-ToF-AMS) during the BORTAS (quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites) experiment in the summer of 2011, have been used to derive normalised excess organic aerosol (OA) mass concentrations (ΔOA/ΔCO), with higher average ratios observed closer to source (0.190 ± 0.010) than in the far-field (0.097 ± 0.002). The difference in ΔOA/ΔCO between fresh and aged plumes is influenced by a change in dominant combustion conditions throughout the campaign. Measurements at source sampled largely smouldering fires, while plumes encountered in the far-field originated from fires occurring earlier in the campaign when fire activity had been more intense. Changing combustion conditions also affect the vertical distribution of biomass burning emissions, as aged plumes from more flaming-dominated fires are injected to higher altitudes of up to 6000 m. Proportional contributions of the mass-to-charge ratio (m/z) 60 and 44 peaks in the AMS mass spectra to the total OA mass (denoted f60 and f44) are used as tracers for primary and oxidized BBOA, respectively. Given the shorter aging times associated with near-field plumes, f44 is lower on average than in more aged, transported plumes. However, high levels of ΔO3/ΔCO and -log(NOx/NOy) close to source indicate that emissions can be subject to very rapid oxidation over short timescales. Conversely, the lofting of plumes into the upper troposphere can lead to the retention of source profiles after transportation over extensive temporal and spatial scales, with f60 also higher on average in aged plumes. Evolution of OA composition with aging is comparable to observations of BB tracers in previous studies, revealing a consistent progression from f60 to f44. The elevated levels of oxygenation in aged plumes, and their association with lower average ΔOA/ΔCO, highlight the influence of OA losses during aging, although there remain considerable uncertainties regarding the role of combustion processes on BBOA production and composition.

scholarly journals Measurements of reactive trace gases and variable O<sub>3</sub> formation rates in some South Carolina biomass burning plumes

2012 ◽  
Vol 12 (9) ◽  
pp. 25255-25328 ◽  
Author(s):  
S. K. Akagi ◽  
R. J. Yokelson ◽  
I. R. Burling ◽  
S. Meinardi ◽  
I. Simpson ◽  
...  
Keyword(s):  
South Carolina ◽  
Biomass Burning ◽  
Stand Structure ◽  
Trace Gases ◽  
Field Studies ◽  
Emission Factors ◽  
Trace Gas ◽  
Methanol Production ◽  
Fire Emissions ◽  
Reactive Trace Gases

Abstract. 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 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.

Sign in / Sign up

Export Citation Format

Share Document