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

Amy K. Hodgson, William T. Morgan, Sebastian O'Shea, Stéphane Bauguitte, James D. Allan, Eoghan Darbyshire, Michael J. Flynn, Dantong Liu, James Lee, Ben Johnson, Jim M. Haywood, Karla M. Longo (+2 others)
2018 Atmospheric Chemistry and Physics  
<p><strong>Abstract.</strong> 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
more » ... 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 (EF<sub>BC</sub> of 0.13<span class="thinspace"></span>±<span class="thinspace"></span>0.04 g kg<sup>−1</sup>) compared to the tropical forest fire (EF<sub>BC</sub> of 0.019<span class="thinspace"></span>±<span class="thinspace"></span>0.006<span class="thinspace"></span>g kg<sup>−1</sup>), and more than 6 times the amount of organic aerosol was emitted from the tropical forest fire per unit of fuel combustion (EF<sub>OM</sub> of 8.00<span class="thinspace"></span>±<span class="thinspace"></span>2.53<span class="thinspace"></span>g kg<sup>−1</sup>, EF<sub>OC</sub> of 5.00<span class="thinspace"></span>±<span class="thinspace"></span>1.58<span class="thinspace"></span>g kg<sup>−1</sup>) compared to the Cerrado fires (EF<sub>OM</sub> of 1.31<span class="thinspace"></span>±<span class="thinspace"></span>0.42<span class="thinspace"></span>g kg<sup>−1</sup>, EF<sub>OC</sub> of 0.82<span class="thinspace"></span>±<span class="thinspace"></span>0.26<span class="thinspace"></span>g kg<sup>−1</sup>). <br><br> 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.</p>
doi:10.5194/acp-18-5619-2018 fatcat:hqabo2ugo5gula3wejyikwaqui