Airborne measurements of trace gas and aerosol particle emissions from biomass burning in Amazonia

Abstract

Abstract. As part of the LBA-SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia -Smoke, Aerosols, Clouds, Rainfall, and Climate) 2002 campaign, we studied the emission of carbon monoxide (CO), carbon dioxide (CO 2 ), and aerosol particles from Amazonian deforestation fires using an instrumented aircraft. Emission ratios for aerosol number (CN) relative to CO (ER CN/CO ) fell in the range 14-32 cm −3 ppb −1 in most of the investigated smoke plumes. Particle number emission ratios have to our knowledge not been previously measured in tropical deforestation fires, but our results are in agreement with values usually found from tropical savanna fires. The number of particles emitted per amount biomass burned was found to be dependent on the fire conditions (combustion efficiency). Variability in ER CN/CO between fires was similar to the variability caused by variations in combustion behavior within each individual fire. This was confirmed by observations of CO-to-CO 2 emission ratios (ER CO/CO 2 ), which stretched across the same wide range of values for individual fires as for all the fires observed during the sampling campaign, reflecting the fact that flaming and smoldering phases are present simultaneously in deforestation fires. Emission factors (EF) for CO and aerosol particles were computed and a correction was applied for the residual smoldering combustion (RSC) fraction of emissions that are not sampled by the aircraft, which increased the EF by a factor of 1.5-2.1. Vertical transport of smoke from the boundary layer (BL) to the cloud detrainment layer (CDL) and the free troposphere (FT) was found Correspondence to: M. O. Andreae (andreae@mpch-mainz.mpg.de) to be a very common phenomenon. We observed a 20% loss in particle number as a result of this vertical transport and subsequent cloud processing, attributable to in-cloud coagulation. This small loss fraction suggests that this mode of transport is very efficient in terms of particle numbers and occurs mostly via non-precipitating clouds. The detrained aerosol particles released in the CDL and FT were larger than in the unprocessed smoke, mostly due to coagulation and secondary growth, and therefore more efficient at scattering radiation and nucleating cloud droplets. This process may have significant atmospheric implications on a regional and larger scale.

A permanent Raman lidar station in the Amazon: description, characterization, and first results

“…Latter, the LBA -Smoke, Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC) campaign found aerosol scattering increasing with altitude by a factor of 2 to 10, which Chand et al (2006) attributed to the aging of biomass burning particles. From the same experiment, Guyon et al (2005) showed that as aerosols are transported above the mixing layer the particle number concentration was reduced by only 20 % while the particle size increased. The authors concluded that the transport by non-precipitating shallow clouds was the most important.…”

Black and brown carbon over central Amazonia: Long-term aerosol measurements at the ATTO site

“…An important part of forest fires occurs in the form of smoldering combustion due to higher fuel moisture (Guyon et al, 2005 other hand, flaming fires, which produce abundant BC aerosol particles, tend to exhibit lower ω 0 and higher ER BC (Akagi et al, 2011). The smoke that arrives at the ATTO site during the dry season is a mixture of smoldering and flaming emissions with varying relative fractions.…”

“…4a, show a decreasing dominance of ESE winds from August to November, whereas from October to November there is an increasing influence of ENE winds, indicating the south-to-north air mass trajectory shift that occurs during the transition from the dry to the wet season. It is important to note that southerly and easterly winds are most likely to bring BB aerosol to the ATTO site during the dry season, given that very active open fire areas during this period are located in the southern Amazon and the Cerrado region (Andreae et al, 2012;Guyon et al, 2005) and, more remotely, in southern Africa (Andreae et al, 1994;Barbosa et al, 1999;Das et al, 2017). Aerosol optical depth at 550 nm is used in this study as a parameter to study the seasonal pattern of BB emission transport from both areas.…”

“…The ratio between aerosol mass or number concentrations and CO has been used to trace air masses origin and age (Guyon et al, 2005;Janhäll et al, 2010). Enhancement ratios (ER BC ) for open biomass burning measured for boreal forest smoldering fires have an average ER BC of 1.7 ng m -3 ppb -1 (Kondo et al, 2011).…”

Evaluation of the carbon content of aerosols from the burning of biomass in the Brazilian Amazon using thermal, optical and thermal-optical analysis methods

“…Also, the addition of secondary organic aerosol could have led to lower EC a /TC ratios and masked the nature of the fires responsible for the EC a emissions. However, aircraft and groundbased measurements of CO-to-CO 2 emission ratios during SMOCC-2002 and other campaigns have shown that smoldering combustion, which releases aerosols with low EC a /TC ratios, makes a large contribution to the emissions from deforestation fires, especially when sampled at ground level (Guyon et al, 2005;Yokelson et al, 2008).…”