scholarly journals A case study of aerosol depletion in a biomass burning plume over Eastern Canada during the 2011 BORTAS field experiment

2014 ◽  
Vol 14 (3) ◽  
pp. 3395-3426 ◽  
Author(s):  
J. E. Franklin ◽  
J. R. Drummond ◽  
D. Griffin ◽  
J. R. Pierce ◽  
D. L. Waugh ◽  
...  
Keyword(s):  
Long Range ◽  
Biomass Burning ◽  
Forest Fires ◽  
Particulate Material ◽  
Trace Gas ◽  
Eastern Canada ◽  
Air Masses ◽  
Chemical Behaviour ◽  
Physical And Chemical ◽  
The Impact

Abstract. We present measurements of a long range smoke transport event recorded on 20–21 July 2011 over Halifax, Nova Scotia, Canada, during the Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS-B) campaign. Ground-based Fourier transform spectrometers and photometers detected air masses associated with large wildland fires burning in eastern Manitoba and western Ontario. We investigate a plume with high trace gas amounts but low amounts of particles that preceded and overlapped at the Halifax site with a second plume with high trace gas loadings and significant amounts of particulate material. We show that the first plume experienced a meteorological scavenging event but the second plume had not been similarly scavenged. This points to the necessity to account carefully for the plume history when considering long range transport since simultaneous or near-simultaneous times of arrival are not necessarily indicative of either similar trajectories or meteorological history. We investigate the origin of the scavenged plume, and the possibility of an aerosol wet deposition event occurring in the plume ~24 h prior to the measurements over Halifax. The region of lofting and scavenging is only monitored on an intermittent basis by the present observing network, and thus we must consider many different pieces of evidence in an effort to understand the early dynamics of the plume. Through this discussion we also demonstrate the value of having many simultaneous remote-sensing measurements in order to understand the physical and chemical behaviour of biomass burning plumes.

scholarly journals A case study of aerosol scavenging in a biomass burning plume over eastern Canada during the 2011 BORTAS field experiment

2014 ◽  
Vol 14 (16) ◽  
pp. 8449-8460 ◽  
Author(s):  
J. E. Franklin ◽  
J. R. Drummond ◽  
D. Griffin ◽  
J. R. Pierce ◽  
D. L. Waugh ◽  
...  
Keyword(s):  
Long Range ◽  
Biomass Burning ◽  
Forest Fires ◽  
Particulate Material ◽  
Trace Gas ◽  
Eastern Canada ◽  
Air Masses ◽  
Chemical Behaviour ◽  
Physical And Chemical ◽  
The Impact

Abstract. We present measurements of a long-range smoke transport event recorded on 20–21 July 2011 over Halifax, Nova Scotia, Canada, during the Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS-B) campaign. Ground-based Fourier transform spectrometers and photometers detected air masses associated with large wildland fires burning in eastern Manitoba and western Ontario. We investigate a plume with high trace gas amounts but low amounts of particles that preceded and overlapped at the Halifax site with a second plume with high trace gas loadings and significant amounts of particulate material. We show that the first plume experienced a meteorological scavenging event, but the second plume had not been similarly scavenged. This points to the necessity to account carefully for the plume history when considering long-range transport since simultaneous or near-simultaneous times of arrival are not necessarily indicative of either similar trajectories or meteorological history. We investigate the origin of the scavenged plume, and the possibility of an aerosol wet deposition event occurring in the plume ~ 24 h prior to the measurements over Halifax. The region of lofting and scavenging is only monitored on an intermittent basis by the present observing network, and thus we must consider many different pieces of evidence in an effort to understand the early dynamics of the plume. Through this discussion we also demonstrate the value of having many simultaneous remote-sensing measurements in order to understand the physical and chemical behaviour of biomass burning plumes.

scholarly journals Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS) experiment: design, execution and science overview

2013 ◽  
Vol 13 (13) ◽  
pp. 6239-6261 ◽  
Author(s):  
P. I. Palmer ◽  
M. Parrington ◽  
J. D. Lee ◽  
A. C. Lewis ◽  
A. R. Rickard ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Forest Fires ◽  
Atmospheric Composition ◽  
Atmospheric Measurements ◽  
Eastern Canada ◽  
Chemical Aging ◽  
Air Masses ◽  
Research Aircraft ◽  
The Uk ◽  
The Impact

Abstract. We describe the design and execution of the BORTAS (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites) experiment, which has the overarching objective of understanding the chemical aging of air masses that contain the emission products from seasonal boreal wildfires and how these air masses subsequently impact downwind atmospheric composition. The central focus of the experiment was a two-week deployment of the UK BAe-146-301 Atmospheric Research Aircraft (ARA) over eastern Canada, based out of Halifax, Nova Scotia. Atmospheric ground-based and sonde measurements over Canada and the Azores associated with the planned July 2010 deployment of the ARA, which was postponed by 12 months due to UK-based flights related to the dispersal of material emitted by the Eyjafjallajökull volcano, went ahead and constituted phase A of the experiment. Phase B of BORTAS in July 2011 involved the same atmospheric measurements, but included the ARA, special satellite observations and a more comprehensive ground-based measurement suite. The high-frequency aircraft data provided a comprehensive chemical snapshot of pyrogenic plumes from wildfires, corresponding to photochemical (and physical) ages ranging from < 1 day to ~

scholarly journals Colorado air quality impacted by long-range-transported aerosol: a set of case studies during the 2015 Pacific Northwest fires

2016 ◽  
Vol 16 (18) ◽  
pp. 12329-12345 ◽  
Author(s):  
Jessie M. Creamean ◽  
Paul J. Neiman ◽  
Timothy Coleman ◽  
Christoph J. Senff ◽  
Guillaume Kirgis ◽  
...  
Keyword(s):  
Air Quality ◽  
Case Studies ◽  
Pacific Northwest ◽  
Long Range ◽  
Biomass Burning ◽  
Forest Fires ◽  
Surface Radiation ◽  
Cloud Formation ◽  
Synoptic Scale ◽  
Transport Pathways

Abstract. Biomass burning plumes containing aerosols from forest fires can be transported long distances, which can ultimately impact climate and air quality in regions far from the source. Interestingly, these fires can inject aerosols other than smoke into the atmosphere, which very few studies have evidenced. Here, we demonstrate a set of case studies of long-range transport of mineral dust aerosols in addition to smoke from numerous fires (including predominantly forest fires and a few grass/shrub fires) in the Pacific Northwest to Colorado, US. These aerosols were detected in Boulder, Colorado, along the Front Range using beta-ray attenuation and energy-dispersive X-ray fluorescence spectroscopy, and corroborated with satellite-borne lidar observations of smoke and dust. Further, we examined the transport pathways of these aerosols using air mass trajectory analysis and regional- and synoptic-scale meteorological dynamics. Three separate events with poor air quality and increased mass concentrations of metals from biomass burning (S and K) and minerals (Al, Si, Ca, Fe, and Ti) occurred due to the introduction of smoke and dust from regional- and synoptic-scale winds. Cleaner time periods with good air quality and lesser concentrations of biomass burning and mineral metals between the haze events were due to the advection of smoke and dust away from the region. Dust and smoke present in biomass burning haze can have diverse impacts on visibility, health, cloud formation, and surface radiation. Thus, it is important to understand how aerosol populations can be influenced by long-range-transported aerosols, particularly those emitted from large source contributors such as wildfires.

scholarly journals Production of peroxy nitrates in boreal biomass burning plumes over Canada during the BORTAS campaign

2016 ◽  
Vol 16 (5) ◽  
pp. 3485-3497 ◽  
Author(s):  
Marcella Busilacchio ◽  
Piero Di Carlo ◽  
Eleonora Aruffo ◽  
Fabio Biancofiore ◽  
Cesare Dari Salisburgo ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Forest Fire ◽  
Biomass Burning ◽  
Forest Fires ◽  
Chemical Mechanism ◽  
Fire Emissions ◽  
Fire Plumes ◽  
Peroxy Nitrates ◽  
In Fire ◽  
The Impact

Abstract. The observations collected during the BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS) campaign in summer 2011 over Canada are analysed to study the impact of forest fire emissions on the formation of ozone (O3) and total peroxy nitrates ∑PNs, ∑ROONO2). The suite of measurements on board the BAe-146 aircraft, deployed in this campaign, allows us to calculate the production of O3 and of  ∑PNs, a long-lived NOx reservoir whose concentration is supposed to be impacted by biomass burning emissions. In fire plumes, profiles of carbon monoxide (CO), which is a well-established tracer of pyrogenic emission, show concentration enhancements that are in strong correspondence with a significant increase of concentrations of ∑PNs, whereas minimal increase of the concentrations of O3 and NO2 is observed. The ∑PN and O3 productions have been calculated using the rate constants of the first- and second-order reactions of volatile organic compound (VOC) oxidation. The ∑PN and O3 productions have also been quantified by 0-D model simulation based on the Master Chemical Mechanism. Both methods show that in fire plumes the average production of ∑PNs and O3 are greater than in the background plumes, but the increase of ∑PN production is more pronounced than the O3 production. The average ∑PN production in fire plumes is from 7 to 12 times greater than in the background, whereas the average O3 production in fire plumes is from 2 to 5 times greater than in the background. These results suggest that, at least for boreal forest fires and for the measurements recorded during the BORTAS campaign, fire emissions impact both the oxidized NOy and O3,  but (1 ∑PN production is amplified significantly more than O3 production and (2) in the forest fire plumes the ratio between the O3 production and the ∑PN production is lower than the ratio evaluated in the background air masses, thus confirming that the role played by the ∑PNs produced during biomass burning is significant in the O3 budget. The implication of these observations is that fire emissions in some cases, for example boreal forest fires and in the conditions reported here, may influence more long-lived precursors of O3 than short-lived pollutants, which in turn can be transported and eventually diluted in a wide area.

Trace gases and organic aerosol at a rural site in Vietnam during large scale biomass burning

2021 ◽  
Author(s):  
Simone M. Pieber ◽  
Dac-Loc Nguyen ◽  
Hendryk Czech ◽  
Stephan Henne ◽  
Nicolas Bukowiecki ◽  
...  
Keyword(s):  
Air Quality ◽  
Chemical Composition ◽  
Biomass Burning ◽  
Large Scale ◽  
Trace Gases ◽  
Organic Aerosol ◽  
Trace Gas ◽  
Rural Site ◽  
Air Masses ◽  
Mixing Ratios

&lt;p&gt;Open biomass burning (BB) is a globally widespread phenomenon. The fires release pollutants, which are harmful for human and ecosystem health and alter the Earth's radiative balance. Yet, the impact of various types of BB on the global radiative forcing remains poorly constrained concerning greenhouse gas emissions, BB organic aerosol (OA) chemical composition and related light absorbing properties. Fire emissions composition is influenced by multiple factors (e.g., fuel and thereby vegetation-type, fuel moisture, fire temperature, available oxygen). Due to regional variations in these parameters, studies in different world regions are needed. Here we investigate the influence of seasonally recurring BB on trace gas concentration and air quality at the regional Global Atmosphere Watch (GAW) station Pha Din (PDI) in rural Northwestern Vietnam. PDI is located in a sparsely populated area on the top of a hill (1466 m a.s.l.) and is well suited to study the large-scale fires on the Indochinese Peninsula, whose pollution plumes are frequently transported towards the site [1]. We present continuous trace gas observations of CO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt;, CO, and O&lt;sub&gt;3&lt;/sub&gt; conducted at PDI since 2014 and interpret the data with atmospheric transport simulations. Annually recurrent large scale BB leads to hourly time-scale peaks CO mixing ratios at PDI of 1000 to 1500 ppb around every April since the start of data collection in 2014. We complement this analysis with carbonaceous PM&lt;sub&gt;2.5 &lt;/sub&gt;chemical composition analyzed during an intensive campaign in March-April 2015. This includes measurements of elemental and organic carbon (EC/OC) and more than 50 organic markers, such as sugars, PAHs, fatty acids and nitro-aromatics [2]. For the intensive campaign, we linked CO, CO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt; and O&lt;sub&gt;3&lt;/sub&gt; mixing ratios to a statistical classification of BB events, which is based on OA composition. We found increased CO and O&lt;sub&gt;3&lt;/sub&gt; levels during medium and high BB influence during the intensive campaign. A backward trajectory analysis confirmed different source regions for the identified periods based on the OA cluster. Typically, cleaner air masses arrived from northeast, i.e., mainland China and Yellow sea during the intensive campaign. The more polluted periods were characterized by trajectories from southwest, with more continental recirculation of the medium cluster, and more westerly advection for the high cluster. These findings highlight that BB activities in Northern Southeast Asia significantly enhances the regional OA loading, chemical PM&lt;sub&gt;2.5 &lt;/sub&gt;composition and the trace gases in northwestern Vietnam. The presented analysis adds valuable data on air quality in a region of scarce data availability.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;REFERENCES&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;[1] Bukowiecki, N. et al. Effect of Large-scale Biomass Burning on Aerosol Optical Properties at the GAW Regional Station Pha Din, Vietnam. AAQR. 19, 1172&amp;#8211;1187 (2019).&lt;/p&gt;&lt;p&gt;[2] Nguyen, D. L, et al. Carbonaceous aerosol composition in air masses influenced by large-scale biomass burning: a case-study in Northwestern Vietnam. ACPD., https://doi.org/10.5194/acp-2020-1027, in review, 2020.&lt;/p&gt;

scholarly journals Identifying the sources driving observed PM<sub>2.5</sub> variability over Halifax, Nova Scotia, during BORTAS-B

2013 ◽  
Vol 13 (2) ◽  
pp. 4491-4533 ◽  
Author(s):  
M. D. Gibson ◽  
J. R. Pierce ◽  
D. Waugh ◽  
J. S. Kuchta ◽  
L. Chisholm ◽  
...  
Keyword(s):  
Nova Scotia ◽  
Atmospheric Chemistry ◽  
Forest Fires ◽  
Back Trajectory ◽  
Valuable Insight ◽  
Eastern Canada ◽  
Average Mass ◽  
Fire Emissions ◽  
Pmf Model ◽  
The Impact

Abstract. The source attribution of observed variability of total PM2.5 concentrations over Halifax, Nova Scotia was investigated between 11 July–26 August 2011 using measurements of PM2.5 mass and PM2.5 chemical composition (black carbon, organic matter, anions, cations and 33 elements). This was part of the BORTAS-B (quantifying the impact of BOReal forest fires on Tropospheric oxidants using aircraft and satellites) experiment, which investigated the atmospheric chemistry and transport of seasonal boreal wild fire emissions over eastern Canada in 2011. The US EPA Positive Matrix Factorization (PMF) receptor model was used to determine the average mass (percentage) source contribution over the 45 days, which was estimated to be: Long-Range Transport (LRT) Pollution 1.75 μg m−3 (47%), LRT Pollution Marine Mixture 1.0 μg m−3 (27.9%), Vehicles 0.49 μg m−3 (13.2%), Fugitive Dust 0.23 μg m−3 (6.3%), Ship Emissions 0.13 μg m−3 (3.4%) and Refinery 0.081 μg m−3 (2.2%). The PMF model describes 87% of the observed variability in total PM2.5 mass (bias = 0.17 and RSME = 1.5 μg m−3). The factor identifications are based on chemical markers, and they are supported by air mass back trajectory analysis and local wind direction. Biomass burning plumes, found by other surface and aircraft measurements, were not significant enough to be identified in this analysis. This paper presents the results of the PMF receptor modelling, providing valuable insight into the local and upwind sources impacting surface PM2.5 in Halifax during the BORTAS-B mission.

scholarly journals Measurement report: Long-range transport patterns into the tropical northwest Pacific during the CAMP<sup>2</sup>Ex aircraft campaign: chemical composition, size distributions, and the impact of convection

2021 ◽  
Vol 21 (5) ◽  
pp. 3777-3802
Author(s):  
Miguel Ricardo A. Hilario ◽  
Ewan Crosbie ◽  
Michael Shook ◽  
Jeffrey S. Reid ◽  
Maria Obiminda L. Cambaliza ◽  
...  
Keyword(s):  
Long Range ◽  
Southwest Monsoon ◽  
Long Range Transport ◽  
Northwest Pacific ◽  
Back Trajectories ◽  
Air Masses ◽  
China Sea ◽  
Range Transport ◽  
Transport Patterns ◽  
The Impact

Abstract. The tropical Northwest Pacific (TNWP) is a receptor for pollution sources throughout Asia and is highly susceptible to climate change, making it imperative to understand long-range transport in this complex aerosol-meteorological environment. Measurements from the NASA Cloud, Aerosol, and Monsoon Processes Philippines Experiment (CAMP2Ex; 24 August to 5 October 2019) and back trajectories from the National Oceanic and Atmospheric Administration Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) were used to examine transport into the TNWP from the Maritime Continent (MC), peninsular Southeast Asia (PSEA), East Asia (EA), and the West Pacific (WP). A mid-campaign monsoon shift on 20 September 2019 led to distinct transport patterns between the southwest monsoon (SWM; before 20 September) and monsoon transition (MT; after 20 September). During the SWM, long-range transport was a function of southwesterly winds and cyclones over the South China Sea. Low- (high-) altitude air generally came from MC (PSEA), implying distinct aerosol processing related to convection and perhaps wind shear. The MT saw transport from EA and WP, driven by Pacific northeasterly winds, continental anticyclones, and cyclones over the East China Sea. Composition of transported air differed by emission source and accumulated precipitation along trajectories (APT). MC air was characterized by biomass burning tracers while major components of EA air pointed to Asian outflow and secondary formation. Convective scavenging of PSEA air was evidenced by considerable vertical differences between aerosol species but not trace gases, as well as notably higher APT and smaller particles than other regions. Finally, we observed a possible wet scavenging mechanism acting on MC air aloft that was not strictly linked to precipitation. These results are important for understanding the transport and processing of air masses with further implications for modeling aerosol lifecycles and guiding international policymaking to public health and climate, particularly during the SWM and MT.

scholarly journals Reactive nitrogen, ozone and ozone production in the Arctic troposphere and the impact of stratosphere-troposphere exchange

2011 ◽  
Vol 11 (24) ◽  
pp. 13181-13199 ◽  
Author(s):  
Q. Liang ◽  
J. M. Rodriguez ◽  
A. R. Douglass ◽  
J. H. Crawford ◽  
J. R. Olson ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Stratospheric Ozone ◽  
Arctic Region ◽  
Ozone Production ◽  
The Arctic ◽  
Subsequent Formation ◽  
Air Masses ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
The Impact

Abstract. We use aircraft observations obtained during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission to examine the distributions and source attributions of O3 and NOy in the Arctic and sub-Arctic region. Using a number of marker tracers, we distinguish various air masses from the background troposphere and examine their contributions to NOx, O3, and O3 production in the Arctic troposphere. The background Arctic troposphere has a mean O3 of ~60 ppbv and NOx of ~25 pptv throughout spring and summer with CO decreasing from ~145 ppbv in spring to ~100 ppbv in summer. These observed mixing ratios are not notably different from the values measured during the 1988 ABLE-3A and the 2002 TOPSE field campaigns despite the significant changes in emissions and stratospheric ozone layer in the past two decades that influence Arctic tropospheric composition. Air masses associated with stratosphere-troposphere exchange are present throughout the mid and upper troposphere during spring and summer. These air masses, with mean O3 concentrations of 140–160 ppbv, are significant direct sources of O3 in the Arctic troposphere. In addition, air of stratospheric origin displays net O3 formation in the Arctic due to its sustainable, high NOx (75 pptv in spring and 110 pptv in summer) and NOy (~800 pptv in spring and ~1100 pptv in summer). The air masses influenced by the stratosphere sampled during ARCTAS-B also show conversion of HNO3 to PAN. This active production of PAN is the result of increased degradation of ethane in the stratosphere-troposphere mixed air mass to form CH3CHO, followed by subsequent formation of PAN under high NOx conditions. These findings imply that an adequate representation of stratospheric NOy input, in addition to stratospheric O3 influx, is essential to accurately simulate tropospheric Arctic O3, NOx and PAN in chemistry transport models. Plumes influenced by recent anthropogenic and biomass burning emissions observed during ARCTAS show highly elevated levels of hydrocarbons and NOy (mostly in the form of NOx and PAN), but do not contain O3 higher than that in the Arctic tropospheric background except some aged biomass burning plumes sampled during spring. Convection and/or lightning influences are negligible sources of O3 in the Arctic troposphere but can have significant impacts in the upper troposphere in the continental sub-Arctic during summer.

scholarly journals Evaluating the influences of biomass burning during 2006 BASE-ASIA: a regional chemical transport modeling

2012 ◽  
Vol 12 (9) ◽  
pp. 3837-3855 ◽  
Author(s):  
J. S. Fu ◽  
N. C. Hsu ◽  
Y. Gao ◽  
K. Huang ◽  
C. Li ◽  
...  
Keyword(s):  
Southeast Asia ◽  
East Asia ◽  
Long Range ◽  
Biomass Burning ◽  
Cross Sections ◽  
Southern China ◽  
Source Region ◽  
Long Range Transport ◽  
Range Transport ◽  
The Impact

Abstract. To evaluate the impact of biomass burning from Southeast Asia to East Asia, this study conducted numerical simulations during NASA's 2006 Biomass-burning Aerosols in South-East Asia: Smoke Impact Assessment (BASE-ASIA). Two typical episode periods (27–28 March and 13–14 April) were examined. Two emission inventories, FLAMBE and GFED, were used in the simulations. The influences during two episodes in the source region (Southeast Asia) contributed to the surface CO, O3 and PM2.5 concentrations as high as 400 ppbv, 20 ppbv and 80 μg m−3, respectively. The perturbations with and without biomass burning of the above three species during the intense episodes were in the range of 10 to 60%, 10 to 20% and 30 to 70%, respectively. The impact due to long-range transport could spread over the southeastern parts of East Asia and could reach about 160 to 360 ppbv, 8 to 18 ppbv and 8 to 64 μg m−3 on CO, O3 and PM2.5, respectively; the percentage impact could reach 20 to 50% on CO, 10 to 30% on O3, and as high as 70% on PM2.5. In March, the impact of biomass burning mainly concentrated in Southeast Asia and southern China, while in April the impact becomes slightly broader and even could go up to the Yangtze River Delta region. Two cross-sections at 15° N and 20° N were used to compare the vertical flux of biomass burning. In the source region (Southeast Asia), CO, O3 and PM2.5 concentrations had a strong upward transport from surface to high altitudes. The eastward transport becomes strong from 2 to 8 km in the free troposphere. The subsidence process during the long-range transport contributed 60 to 70%, 20 to 50%, and 80% on CO, O3 and PM2.5, respectively to surface in the downwind area. The study reveals the significant impact of Southeastern Asia biomass burning on the air quality in both local and downwind areas, particularly during biomass burning episodes. This modeling study might provide constraints of lower limit. An additional study is underway for an active biomass burning year to obtain an upper limit and climate effects.

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.

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