Dynamic Changes of the Aerosol Composition and Concentration during Different Burning Phases of Wood Combustion

Abstract

The presented wood combustion emission study employing a logwood stove showed that four burning phases of different aerosol compositions and different amounts of emitted particulate matter (PM) occurred during a combustion batch. As a novel approach, in this study, the burning phases were defined by chemical changes in the aerosol gas phase during combustion, instead of being linked to predefined time periods or the amount of PM emissions. This deeper view into the aerosol chemistry of the different burning phases was possible by employing online mass spectrometry techniques with high time resolution. A special soft ionization technique enabled the selective detection of polyaromatic hydrocarbons (PAHs) in the gas phase, whereas changes in the particle phase were observed by aerosol mass spectrometer (AMS). The use of AMS allowed the description of changes in the particle phase and in the amounts of PM emitted during the burning phases, as well as verification of the observed burning phases. Finally, it was shown that the organic fraction and the amount of particles emitted during the ignition phase were main contributors to the emitted PM. The definition of these four burning phases was supported by a more detailed investigation of the chemistry of the organic matter using a Van Krevelen description (average H/C ratios of 1.32−1.64 and O/C ratios of 0.25−0.44, with individual values up to 1.4) along with our novel approach of employing positive matrix factorization (PMF) as a source apportionment tool for the separation of one emission source into different combustion-dominated processes. In addition, the highly dynamic and complex nature of wood combustion emissions was revealed by these analysis methods. It was shown that different combustion conditions have a strong impact on the amount of emitted PM. For instance, an experiment with an overloaded stove emitted a roughly 4-fold higher mass of PM compared to a stove run under the manufacturer's recommended (normal) combustion conditions. This experiment showed a much higher amount of PAHs, which are very harmful for human health.

Organic Emissions from a Wood Stove and a Pellet Stove Before and After Simulated Atmospheric Aging

“…The major ion was CO C , in contrast to typical atmospheric OM where the CO C and CO C 2 signals are similar (Aiken et al 2008). Overall, this highly oxygenated POM mass spectrum is consistent with previous AMS studies on beech wood combusted in logwood stoves (Weimer et al 2008;Heringa et al 2011;Elsasser et al 2013). Although this study is the first wood-stove study to identify and quantify CO C , two others (Grieshop et al 2009b;Eriksson et al 2014) have reported elevated signals at m/z 28 (most likely CO C or C 2 H C 4 ) and other biomass-burning studies (Ortega et al 2013) have observed similar patterns.…”

“…As discussed in the SI (Section S1.1), negligible amounts of C 2 H C 4 were produced by our sample. It is worth emphasizing that overloaded stoves or poor combustion conditions may create considerably different POM to that observed here, with less oxygenation and significant PAH content (Elsasser et al 2013;Eriksson et al 2014). Figure 5b shows the OOM mass spectrum, which contained less CO C and more CO C 2 than the POM spectrum.…”

Peak-fitting and integration imprecision in the Aerodyne aerosol mass spectrometer: effects of mass accuracy on location-constrained fits

“…Zhang et al, 2007), or during source studies (e.g. Elsasser et al, 2013;Timko et al, 2014;Corbin et al, 2015a).…”

Highly controlled, reproducible measurements of aerosol emissions from combustion of a common African biofuel source

“…Christian et al, 2007;Yokelson et al, 2008). Others, including Schneider et al (2006), Weimer et al (2008) and Elsasser et al (2013) have investigated the chemical composition of BBA emissions in real time during biomass combustion in the laboratory. Attempts to compile all available measurements of emission factors for a number of different species, both gaseous and particulate, have been carried out by Andreae and Merlet (2001) and more recently by Akagi et al (2011).…”

“…Furthermore, the standard approach in many such studies has been to consider only average emission factors from an entire combustion event, which can mask significant changes in emissions that take place throughout combustion. Nonetheless, some recent studies have been carried out, which consider real-time particulate emissions under more controlled conditions, including Alfarra et al (2007) and Elsasser et al (2013).…”