Biomass burning smoke aerosol properties measured during Fire Laboratory at Missoula Experiments (FLAME)

Abstract

[1] During the Fire Laboratory at Missoula Experiments (FLAME), we studied the physical, chemical, and optical properties of biomass burning smoke from the laboratory combustion of various wildland fuels. A good understanding of these properties is important in determining the radiative effects of biomass burning aerosols, with impacts on both local and regional visibility and global climate. We measured aerosol size distributions with two instruments: a differential mobility particle sizer (DMPS) and an optical particle counter (OPC). Volume size distributions from different burns varied from monomodal to multimodal, with geometric mean diameters ranging from 0.20-0.57 mm and geometric standard deviations ranging from 1.68-2.97. By reconciling the differences between the two sizing instruments, we estimated aerosol effective refractive indices with values ranging from 1.41 to 1.61. We reconstructed aerosol chemical composition for each burn using data from filters collected and analyzed with the Interagency Monitoring of Protected Visual Environments (IMPROVE) samplers and protocols. Aerosols were generally comprised of carbon with organic species accounting for the largest mass fraction in most cases. We used composition data to calculate aerosol density, which ranged from 1.22-1.92 g cm −3 , and real and imaginary refractive indices, which had ranges of 1.55-1.80 and 0.01-0.50 respectively. Aerosol physical, chemical, and optical characterizations were combined to calculate dry mass scattering (MSE) and absorption (MAE) efficiencies at 532 nm. These parameters had values between 1.6-5.7 m 2 g −1 and 0.04-0.94 m 2 g −1 .

Light absorption of brown carbon aerosol in the PRD region of China

“…Therefore, the larger AAE BC obtained at the rural site could be a result of the smaller BC diameters of biomass burning in PRD. It should be noted that previous studies showed that AAE of ambient aerosol can also be influenced by a couple of other factors, such as size distribution, mixing state, and fractal dimension of BC particles (Levin et al, 2010;Gyawali et al, 2009;Scarnato et al, 2013;Bond and Bergstrom, 2006), but it is quite complicated and almost impossible to consider the influence of all these factors simultaneously. Scarnato et al (2013) also pointed out that it is very difficult to clarify the relationship between AAE and aerosol morphology and mixing state due to quite complicated mechanisms in real cases.…”

Aerosol loading in the Southeastern United States: reconciling surface and satellite observations

“…Therefore, a seasonal shift towards larger particles in summertime could account for some of the model-measurement discrepancy. However, measurements of the geometric mean diameters for ambient SOAdominated aerosol and fresh smoke are similar (Levin et al, 2009(Levin et al, , 2010. Additionally, the fraction of total AOD accounted for by organics in the model is on average less than 15 % in the summertime, and substantial seasonal changes in the size of inorganic aerosol are less likely (e.g., Stanier et al, 2004;Zhang et al, 2008), so it is unlikely that shifts in the fine aerosol size distribution are a dominant source of model error.…”

Three-dimensional factorization of size-resolved organic aerosol mass spectra from Mexico City

“…BBOA has a slightly smaller mode at ∼300 nm. Although BBOA is generated as primary aerosol from a combustion process, BBOA has a smaller fraction of ultrafine (d va < 100 nm) particles than OOA (McMeeking et al, 2005;Levin et al, 2010). In contrast, the size distribution of HOA is quite broad, with the largest fraction of ultrafine particles of any of these factors.…”