Water uptake and chemical composition of fresh aerosols generated in open burning of biomass (original) (raw)
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Atmospheric Chemistry and Physics, 2010
During the 2006 FLAME study (Fire Laboratory at Missoula Experiment), laboratory burns of biomass fuels were performed to investigate the physico-chemical, optical, and hygroscopic properties of fresh biomass smoke. As part of the experiment, two nephelometers simultaneously measured dry and humidified light scattering co-5 efficients (b sp(dry) and b sp(RH) , respectively) in order to explore the role of relative humidity (RH) on the optical properties of biomass smoke aerosols. Results from burns of several biomass fuels showed large variability in the humidification factor (f (RH)=b sp(RH) /b sp(dry) ). Values of f (RH) at RH=85-90% ranged from 1.02 to 2.15 depending on fuel type. We incorporated measured chemical composition and size 10 distribution data to model the smoke hygroscopic growth to investigate the role of inorganic and organic compounds on water uptake for these aerosols. By assuming only inorganic constituents were hygroscopic, we were able to model the water uptake within experimental uncertainty, suggesting that inorganic species were responsible for most of the hygroscopic growth. In addition, humidification factors at 85-90% RH increased 15 for smoke with increasing inorganic salt to carbon ratios. Particle morphology as observed from scanning electron microscopy revealed that samples of hygroscopic particles contained soot chains either internally or externally mixed with inorganic potassium salts, while samples of weak to non-hygroscopic particles were dominated by soot and organic constituents. This study provides further understanding of the compounds re-20 sponsible for water uptake by young biomass smoke, and is important for accurately assessing the role of smoke in climate change studies and visibility regulatory efforts. Spracklen et al., 2007). Quantifying the role of biomass burning aerosols in climate 4227 ACPD 10, 4225-4269, 2010 Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion forcing and visibility degradation requires characterizing their optical, physical, chemical and hygroscopic properties. Many studies have been performed in the ambient atmosphere to measure radiative properties of smoke particles from wild fire and prescribed burning (see the review by Reid et al., 2005a, b). However, interpreting these results is complicated due to the variety of conditions under which the smoke was 5 ACPD 10, 4225-4269, 2010 Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion
Humidification factors from laboratory studies of fresh smoke from biomass fuels
Journal of Geophysical Research, 2006
1] Measurements of smoke aerosol humidification factors were performed in a laboratory for different biomass fuel types and burn conditions. Two nephelometers simultaneously measured dry and humidified light scattering coefficients (b sp(dry) and b sp(RH) , respectively), providing the first observations of the temporal evolution of the humidification factor (f(RH) = b sp(RH) /b sp(dry) ) for fresh (minutes-old) smoke. Hygroscopic characteristics of the smoke aerosols varied with fuel type and fire conditions, with the mean f(RH) ranging from 1.01 to 1.95 for fresh minutes-old smoke for the relative humidity (RH) range of 70-94%. These f(RH) values exhibited temporal variability, with some fuels alternating from hygroscopic to nonhygroscopic within minutes. Humidograms were also obtained, demonstrating that smoke from different fuels begins to take up water at different RH values. Humidification factors for hour-old smoke ranged from 1.10 to 1.51 for RH > 90%. Finally, light-absorbing carbon mass measured with a multiwavelength aethalometer demonstrated different spectral responses as a function of fuel type. These laboratory experiments demonstrate the complexity of smoke hygroscopicity from young fires and are essential for understanding the radiative effects of biomass burning in the ambient atmosphere.
Journal of Geophysical Research, 2008
1] In this laboratory closure study, we compare sub-and supersaturated water uptake properties for aerosol particles possessing a range of hygroscopicity. Measurements for water sub-saturated conditions used a hygroscopic tandem differential mobility analyzer (HTDMA). Simultaneously, measurements of particle critical supersaturation were conducted on the same sample stream with a continuous flow cloud condensation nuclei (CCN) counter. For these experiments, we used filter-collected samples of biomass smoke generated in the combustion of two common wildland fire fuels, western sagebrush and Alaskan duff core. Extractions of separate sections of the filter were performed using two solvents, ultrapure water and methanol. The extracts were subsequently atomized, producing aerosols having a range of hygroscopic responses. HTDMA and CCN measurements were fit to a single-parameter model of water uptake, in which the fit parameter is denoted k, the hygroscopicity parameter. Here, for the four extracts we observed mean values of the hygroscopicity parameter of 0.06 < k < 0.30, similar to the range found previously for numerous pure organic compounds. Particles generated from the aqueous extracts of the filters had consistently larger k than methanol extracts, while western sagebrush extract aerosols k exceeded those from Alaskan duff core. HTDMAand CCN-derived values of k for each experiment agreed within approximately 20%. Applicability of the k-parameterization to other multicomponent aerosols relevant to the atmosphere remains to be tested. Citation: Carrico, C. M., M. D. Petters, S. M. Kreidenweis, J. L. Collett Jr., G. Engling, and W. C. Malm (2008), Aerosol hygroscopicity and cloud droplet activation of extracts of filters from biomass burning experiments,
Journal of Atmospheric Chemistry, 2006
We used both a conventional transmission electron microscope and an environmental transmission electron microscope (ETEM) to determine morphology, composition, and water uptake of 80 individual aerosol particles collected from the young smoke of flaming and smoldering fires during SAFARI-2000, a comprehensive air quality campaign in southern Africa. Six representative carbonaceous particle types are described, including soot, tar balls, and heterogeneously internally mixed particles containing C with S-, K-, Mg-or Narich inorganic phases. The hygroscopic behavior of these particles over the range 0-100% relative humidity (RH) was studied in detail. Soot and tar balls did not take up water, whereas the mixed organic-inorganic particles took up water between 55 and 100% RH, the exact value depending on the composition of their water-soluble phases. The inorganic phase appeared to determine the hygroscopic properties of all mixed organic-inorganic particles. Thus, incorporation of inorganic plant material or reactions with inorganic atmospheric components can dramatically alter the hygroscopic properties of carbonaceous particles in smoke plumes. The fraction of these mixed organic-inorganic particles plausibly increases with time, which will modulate the effects of smoke on radiative budgets.
Environmental Science & Technology, 2008
Biomass fuel combustion for residential energy significantly influences both emissions and the atmospheric burden of aerosols in world regions, i.e., east and south Asia. This study reports measurements of climate-relevant properties of particles emitted from biomass fuels widely used for cooking in south Asia, in laboratory experiments simulating actual cooking in the region. Fuel burn rates of 1-2 kg h(-1) for wood species, and 1.5-2 kg h(-1) for crop residues and dried cattle dung, influenced PM2.5 emission factors which were 1.7-2 g kg(-1) at low burn rates but 5-9 gkg(-1) at higher burn rates. Total carbon accounted for 45-55% and ions and trace elements for 2-12% of PM2.5 mass. The elemental carbon (EC) content was variable and highest (22-35%) in particles emitted from low burn rate combustion (wood and jute stalks) but significantly lower (2-4%) from high burn rate combustion (dried cattle dung and rice straw). The mass absorption cross-section (MAC, m2 g(-1)) correlated with EC content for strongly absorbing particles. Weakly absorbing particles, from straw and dung combustion, showed absorption that could not be explained by EC content alone. On average, the MAC of biofuel emission particles was significantly higher than reported measurements from forest fires but somewhat lower than those from diesel engines, indicating potential to significantly influence atmospheric absorption. Both for a given fuel and across different fuels, increased burn rates result in higher emission rates of PM2.5, larger organic carbon (OC) content, larger average particle sizes, and lower MAC. Larger mean particle size (0.42-1.31 microm MMAD) and organic carbon content, than in emissions from combustion sources like diesels, have potential implications for hygroscopic growth and cloud nucleation behavior of these aerosols. These measurements can be used to refine regional emission inventories and derive optical parametrizations, for climate modeling, representative of regions dominated by primary particles from biomass fuel combustion.
Journal of Geophysical Research, 2010
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 .
Atmospheric Chemistry and Physics, 2005
The last decade has seen tremendous advances in atmospheric aerosol particle research that is often performed in the context of climate and global change science. Biomass burning, one of the largest sources of accumulation mode particles globally, has been closely studied for its radiative, geochemical, and dynamic impacts. These 5 studies have taken many forms including laboratory burns, in situ experiments, remote sensing, and modeling. While the differing perspectives of these studies have ultimately improved our qualitative understanding of biomass burning issues, the varied nature of the work make inter-comparisons and resolutions of some specific issues difficult. In short, the literature base has become a milieu of small pieces of the 10 20 we present simplified models for particle size and emission factors. We close this review paper with a discussion of the community experimental data, point to lapses in the data set, and prioritize future research topics. Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Print Version Interactive Discussion © EGU 2004 last decade, biomass-burning studies have spawned hundreds of manuscripts on the physical, chemical, and thermodynamic properties of biomass-burning particles. Qualitatively, smoke particle properties are well understood. For example, approximately 80-90% of their volume is in the accumulation mode (d p <1 µm). Smoke particles are composed of ∼60% organic carbon and ∼5-10% black carbon. Biomass smoke par-5 ticles effectively scatter and absorb solar radiation. Given sufficient updraft velocity, smoke particles are good cloud condensation nuclei. But despite this qualitative understanding, the determination of key parameters for estimating atmospheric effects of biomass burning is not straightforward. Smoke properties vary between fires depending on fuel type and moisture, combustion phase, wind conditions, and several other 10
Atmospheric Chemistry and Physics, 2009
Smoke particle emissions from the combustion of biomass fuels typical for the western and southeastern United States were studied and compared under high humidity and ambient conditions in the laboratory. The fuels used were Montana ponderosa pine (Pinus ponderosa), southern California chamise (Adenostoma fasciculatum), and Florida saw palmetto (Serenoa repens). Information on the nonrefractory chemical composition of biomass burning aerosol from each fuel was obtained with an aerosol mass spectrometer and through estimation of the black carbon concentration from light absorption measurements at 870 nm. Changes in the optical and physical particle properties under high humidity conditions were observed for hygroscopic smoke particles containing substantial inorganic mass fractions that were emitted from combustion of chamise and palmetto fuels. Light scattering cross sections increased under high humidity for these particles, consistent with the hygroscopic growth measured for 100 nm particles in HTDMA measurements.
Atmospheric Environment, 2012
Biomass burning smoke and associated aerosol particles from wildfires near Moscow, Russia during summer 2010 had a significant impact on air quality both in the close vicinity of the burning area and to a lesser extent in other parts of Eastern Europe. Smoke was also observed in Eastern Finland, about 1000 km northwest of the fire area, in city of Kuopio, at Puijo tower atmospheric measurement station and at the city of Kuopio air quality monitoring sites. The origin of air masses was confirmed by remote sensing observations and trajectory analyses. Despite the distance between Kuopio and the fire area and a travel time of 1e2 days, exceptional physical and optical properties of aerosol particles were evident. During smoke events, aerosol particles twice as large (geometric mean diameter 158 nm) as in background conditions (geometric mean diameter 76.3 nm) were observed and they contained recordbreaking amounts of black carbon, up to 1.23 mg m À3 , which exceeds typical values by a factor of 12. Thus, absorption coefficient was significantly different when compared to background summer conditions (8.12 Mm À1 vs. 0.651 Mm À1). Also scattering coefficients experienced a remarkable increase, on average from 12.0 Mm À1 , 7.2 Mm À1 and 4.2 Mm À1 to 245 Mm À1 , 169 Mm À1 and 111 Mm À1 for blue, green and red light, respectively. The amount of particulate mass also experienced a multifold increase. Depending on the measurement site, PM 2.5 grew from 3 to 6 mg m À3 to 34e48 mg m À3 and PM 10 from 4 to 17 mg m À3 to 40e76 mg m À3. Trace gas concentrations were also affected by the smoke presence, especially carbon monoxide, which is commonly used as a tracer for biomass burning smoke. The concentration of nitric oxide, nitrogen dioxide, ozone and sulfur dioxide was affected only moderately and partly masked by the emissions from local pollutant sources.
Atmospheric Chemistry and Physics, 2010
Aerosol emissions from vegetation fires have a large impact on air quality and climate. In this study, we use published experimental data and different fitting procedures to derive dynamic particle number and mass emission factors (EF PN , EF PM ) related to the fuel type, burning conditions and the mass of dry fuel burned, as well as characteristic 5 CO-referenced emission ratios (PN/CO, PM/CO). Moreover, we explore and characterize the variability of the particle size distribution of fresh smoke, which is typically dominated by a lognormal accumulation mode with count median diameter around 120 nm (depending on age, fuel and combustion efficiency), and its effect on the relationship between particle number and mass emission factors. 10 on a rather limited amount of experimental data which should be complemented by further measurements. Nevertheless, the presented parameterizations appear sufficiently robust for exploring the influence of vegetation fires on aerosol particle number 17184 ACPD 9Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion and mass concentrations in regional and global model studies. 20