Rapidly evolving ultrafine and fine mode biomass smoke physical properties: Comparing laboratory and field results

Abstract

Combining field and laboratory results, we present biomass smoke physical properties. We report sub-0.56 μm diameter (D p ) particle sizing (fast mobility particle sizer, FMPS) plus light absorption and scattering at 870 nm (photoacoustic extinctiometer). For D p < 200 nm, the FMPS characterized sizing within ±20% compared to standards. As compared to the traditional scanning mobility particle sizer, the FMPS responded most accurately to single-mode polydispersions with mean D p < 200 nm, which characterized the smoke sampled here. Smoke was measured from laboratory fresh emissions (seconds to hours old), the High Park Fire (hours to < 1 day), and from regional biomass burning (several days). During a High Park Fire episode, light extinction rapidly reached a maximum of σ ep = 569 ± 21 Mm À1 (10 min) with aerosol single scattering albedo peaking at ω = 0.955 ± 0.004. Concurrently, number concentration and size peaked with maximum D p = 126 nm and a unimodal distribution with σ g = 1.5. Long-range transported smoke was substantially diluted (N tot factor of 7 lower) and shifted larger (maximum D p = 143) and wider (σ g = 2.2). We compared ambient data to laboratory burns with representative western U.S. forest fuels (coniferous species Ponderosa pine and Alaska black spruce). Smoldering pine produced an aerosol dominated by larger, more strongly light scattering particles (D p > 100 nm), while flaming combustion produced very high number concentrations of smaller (D p~5 0 nm) absorbing particles. Due to smoldering and particle growth processes, D p approached 100 nm within 3 h after emission. Increased particle cross-sectional area and Mie scattering efficiency shifted the relative importance of light absorption (flaming maximum) and light scattering (smoldering maximum), increasing ω over time. Measurements showed a consistent picture of smoke properties from emission to aging. CARRICO ET AL.RAPIDLY EVOLVING BIOMASS SMOKE 5750

Southwestern U.S. Biomass Burning Smoke Hygroscopicity: The Role of Plant Phenology, Chemical Composition, and Combustion Properties

“…The lower temperature heat gun typically produced a size distribution shifted to larger sizes (geometric number mean diameter of 94 nm versus 30–34 nm for the hotter methods) as shown in Figure . The behavior is consistent with Carrico et al () and others who showed the influence on sizing of combustion characteristics with lower intensity smoldering combustion generally producing larger particles. Notably, this range of size distributions results in a coefficient of variation of 8% in f (RH) holding all else constant.…”

“…Journal of Geophysical Research: Atmospheres Figure 9. The behavior is consistent with Carrico et al (2016) and others who showed the influence on sizing of combustion characteristics with lower intensity smoldering combustion generally producing larger particles. Notably, this range of size distributions results in a coefficient of variation of 8% in f(RH) holding all else constant.…”

Optical Properties of Laboratory and Ambient Biomass Burning Aerosols: Elucidating Black, Brown, and Organic Carbon Components and Mixing Regimes

“…The same trend is shown for number mean diameter. This is in contrast to Gomez et al (2018) and Carrico et al (2016), who show that the number mean diameter for the lower temperature method (heat gun) produced larger sizes when compared to the hotter ignition methods (lighter and resistance heater). This discrepancy can be partially explained by combustion conditions, that is, whether the burn was more flaming, smoldering, or a mixture of these two phases.…”

“…Average mass mean diameter and average number mean diameter from SMPS measurements, average rBC mass concentration from SP2 measurements, and the emission ratio from each fire are presented. Studies such as Einfeld et al (1991), Woods et al (1991), Martins et al (1996), and Reid and Hobbs (1998) agree with Gomez et al (2018) and Carrico et al (2016) that larger particle sizes are present in low-temperature combustion conditions. Likewise, the ignition methods resulted in differing sizes.…”

“…This discrepancy can be partially explained by combustion conditions, that is, whether the burn was more flaming, smoldering, or a mixture of these two phases. Studies such as Einfeld et al (1991), Woods et al (1991), Martins et al (1996), and Reid and Hobbs (1998) agree with Gomez et al (2018) and Carrico et al (2016) that larger particle sizes are present in low-temperature combustion conditions. This is consistent with a smoldering/mixed phase combustion, where a smaller fraction of the fuel is oxidized in the flame, making it available to condense onto the small particles.…”