6 research outputs found
Chemical Fingerprinting of Biomass Burning Organic Aerosols from Sugar Cane Combustion: Complementary Findings from Field and Laboratory Studies
Agricultural fires are a major source of biomass-burning
organic
aerosols (BBOAs) with impacts on health, the environment, and climate.
In this study, globally relevant BBOA emissions from the combustion
of sugar cane in both field and laboratory experiments were analyzed
using comprehensive two-dimensional gas chromatography time-of-flight
mass spectrometry. The derived chemical fingerprints of fresh emissions
were evaluated using targeted and nontargeted evaluation approaches.
The open-field sugar cane burning experiments revealed the high chemical
complexity of combustion emissions, including compounds derived from
the pyrolysis of (hemi)cellulose, lignin, and further biomass, such
as pyridine and oxime derivatives, methoxyphenols, and methoxybenzenes,
as well as triterpenoids. In comparison, laboratory experiments could
only partially model the complexity of real combustion events. Our
results showed high variability between the conducted field and laboratory
experiments, which we, among others, discuss in terms of differences
in combustion conditions, fuel composition, and atmospheric processing.
We conclude that both field and laboratory studies have their merits
and should be applied complementarily. While field studies under real-world
conditions are essential to assess the general impact on air quality,
climate, and environment, laboratory studies are better suited to
investigate specific emissions of different biomass types under controlled
conditions
Volatile Organic Compounds from Logwood Combustion: Emissions and Transformation under Dark and Photochemical Aging Conditions in a Smog Chamber
Residential wood combustion (RWC)
emits high amounts of volatile
organic compounds (VOCs) into ambient air, leading to formation of
secondary organic aerosol (SOA), and various health and climate effects.
In this study, the emission factors of VOCs from a logwood-fired modern
masonry heater were measured using a Proton-Transfer-Reactor Time-of-Flight
Mass Spectrometer. Next, the VOCs were aged in a 29 m<sup>3</sup> Teflon
chamber equipped with UV black lights, where dark and photochemical
atmospheric conditions were simulated. The main constituents of the
VOC emissions were carbonyls and aromatic compounds, which accounted
for 50%–52% and 30%–46% of the detected VOC emission,
respectively. Emissions were highly susceptible to different combustion
conditions, which caused a 2.4-fold variation in emission factors.
The overall VOC concentrations declined considerably during both dark
and photochemical aging, with simultaneous increase in particulate
organic aerosol mass. Especially furanoic and phenolic compounds decreased,
and they are suggested to be the major precursors of RWC-originated
SOA in all aging conditions. On the other hand, dark aging produced
relatively high amounts of nitrogen-containing organic compounds in
both gas and particulate phase, while photochemical aging increased
especially the concentrations of certain gaseous carbonyls, particularly
acid anhydrides
Effective Density and Morphology of Particles Emitted from Small-Scale Combustion of Various Wood Fuels
The effective density
of fine particles emitted from small-scale
wood combustion of various fuels were determined with a system consisting
of an aerosol particle mass analyzer and a scanning mobility particle
sizer (APM-SMPS). A novel sampling chamber was combined to the system
to enable measurements of highly fluctuating combustion processes.
In addition, mass-mobility exponents (relates mass and mobility size)
were determined from the density data to describe the shape of the
particles. Particle size, type of fuel, combustion phase, and combustion
conditions were found to have an effect on the effective density and
the particle shape. For example, steady combustion phase produced
agglomerates with effective density of roughly 1 g cm<sup>–3</sup> for small particles, decreasing to 0.25 g cm<sup>–3</sup> for 400 nm particles. The effective density was higher for particles
emitted from glowing embers phase (ca. 1–2 g cm<sup>–3</sup>), and a clear size dependency was not observed as the particles
were nearly spherical in shape. This study shows that a single value
cannot be used for the effective density of particles emitted from
wood combustion
Photochemical Aging Induces Changes in the Effective Densities, Morphologies, and Optical Properties of Combustion Aerosol Particles
Effective density (ρeff) is an important
property
describing particle transportation in the atmosphere and in the human
respiratory tract. In this study, the particle size dependency of
ρeff was determined for fresh and photochemically
aged particles from residential combustion of wood logs and brown
coal, as well as from an aerosol standard (CAST) burner. ρeff increased considerably due to photochemical aging, especially
for soot agglomerates larger than 100 nm in mobility diameter. The
increase depends on the presence of condensable vapors and agglomerate
size and can be explained by collapsing of chain-like agglomerates
and filling of their voids and formation of secondary coating. The
measured and modeled particle optical properties suggest that while
light absorption, scattering, and the single-scattering albedo of
soot particle increase during photochemical processing, their radiative
forcing remains positive until the amount of nonabsorbing coating
exceeds approximately 90% of the particle mass
Photochemical Aging Induces Changes in the Effective Densities, Morphologies, and Optical Properties of Combustion Aerosol Particles
Effective density (ρeff) is an important
property
describing particle transportation in the atmosphere and in the human
respiratory tract. In this study, the particle size dependency of
ρeff was determined for fresh and photochemically
aged particles from residential combustion of wood logs and brown
coal, as well as from an aerosol standard (CAST) burner. ρeff increased considerably due to photochemical aging, especially
for soot agglomerates larger than 100 nm in mobility diameter. The
increase depends on the presence of condensable vapors and agglomerate
size and can be explained by collapsing of chain-like agglomerates
and filling of their voids and formation of secondary coating. The
measured and modeled particle optical properties suggest that while
light absorption, scattering, and the single-scattering albedo of
soot particle increase during photochemical processing, their radiative
forcing remains positive until the amount of nonabsorbing coating
exceeds approximately 90% of the particle mass
Real-Time Chemical Composition Analysis of Particulate Emissions from Woodchip Combustion
Residential wood combustion is one
of the major sources of fine
particles. The chemical composition of the particles plays a key role
in both adverse health and environmental effects. It is important
to understand how chemical composition of particulate emissions varies
during different combustion processes and conditions. In this work,
combustion of wood chips was studied in a moving step-grate burner
in different combustion conditions (efficient, intermediate, and smoldering)
in the laboratory. The particulate emissions were measured with an
Aerodyne high-resolution time-of-flight aerosol mass spectrometer
(HR-TOF-AMS). It was found that two phases were occurring frequently
in the intermediate and smoldering combustion. Phase 1 took place
when gaseous carbon monoxide (CO) was rapidly increasing after the
new fuel addition. Phase 2 was a stable, burn-out period with low
CO emissions until the new fuel addition and automatic removal of
fuel leftovers from the grate. The analysis on the organic aerosol
by positive matrix factorization (PMF) extracted out five factors:
hydrocarbon-like organic aerosol (HOA), low-volatile-oxidized organic
aerosol (LV-OOA), biomass burning organic aerosol (BBOA), and two
additional factors of “polycyclic aromatic hydrocarbon (PAH)
factor” and “aromatic factor”. PAH and LV-OOA
were found to be forming mainly during phase 1. HOA showed similar
behavior as a PAH factor and LV-OOA in a time series. BBOA was consistent
with levoglucosan formation during the combustion and became higher
during phase 2. The aromatic factor was mainly composed of fragment
ions of <i>n</i>-butyl benzenesulfonamide compound, which
was observed in both phases. To our knowledge, this is the first work
to report the particulate organics of combustion aerosols and PAH
distinguished by PMF. The results prove that the particulate organic
emissions can be reduced efficiently when keeping combustion efficiency
high. This may help in targeting the efforts on emission reduction
better in the future