Showing papers by "Robert J. Yokelson published in 2017"
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TL;DR: The Global Fire Emissions Database (GFED) as mentioned in this paper has been used to quantify global fire emissions patterns during 1997-2016, with the largest impact on emissions in temperate North America, Central America, Europe, and temperate Asia.
Abstract: . Climate, land use, and other anthropogenic and natural drivers have the potential to influence fire dynamics in many regions. To develop a mechanistic understanding of the changing role of these drivers and their impact on atmospheric composition, long-term fire records are needed that fuse information from different satellite and in situ data streams. Here we describe the fourth version of the Global Fire Emissions Database (GFED) and quantify global fire emissions patterns during 1997–2016. The modeling system, based on the Carnegie–Ames–Stanford Approach (CASA) biogeochemical model, has several modifications from the previous version and uses higher quality input datasets. Significant upgrades include (1) new burned area estimates with contributions from small fires, (2) a revised fuel consumption parameterization optimized using field observations, (3) modifications that improve the representation of fuel consumption in frequently burning landscapes, and (4) fire severity estimates that better represent continental differences in burning processes across boreal regions of North America and Eurasia. The new version has a higher spatial resolution (0.25°) and uses a different set of emission factors that separately resolves trace gas and aerosol emissions from temperate and boreal forest ecosystems. Global mean carbon emissions using the burned area dataset with small fires (GFED4s) were 2.2 × 1015 grams of carbon per year (Pg C yr−1) during 1997–2016, with a maximum in 1997 (3.0 Pg C yr−1) and minimum in 2013 (1.8 Pg C yr−1). These estimates were 11 % higher than our previous estimates (GFED3) during 1997–2011, when the two datasets overlapped. This net increase was the result of a substantial increase in burned area (37 %), mostly due to the inclusion of small fires, and a modest decrease in mean fuel consumption (−19 %) to better match estimates from field studies, primarily in savannas and grasslands. For trace gas and aerosol emissions, differences between GFED4s and GFED3 were often larger due to the use of revised emission factors. If small fire burned area was excluded (GFED4 without the s for small fires), average emissions were 1.5 Pg C yr−1. The addition of small fires had the largest impact on emissions in temperate North America, Central America, Europe, and temperate Asia. This small fire layer carries substantial uncertainties; improving these estimates will require use of new burned area products derived from high-resolution satellite imagery. Our revised dataset provides an internally consistent set of burned area and emissions that may contribute to a better understanding of multi-decadal changes in fire dynamics and their impact on the Earth system. GFED data are available from http://www.globalfiredata.org .
1,135 citations
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TL;DR: In this article, Volatile and intermediate-volatility nonmethane organic gases (NMOGs) released from biomass burning were measured during laboratory-simulated wildfires by proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF).
Abstract: . Volatile and intermediate-volatility non-methane organic gases (NMOGs) released from biomass burning were measured during
laboratory-simulated wildfires by proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF). We identified NMOG
contributors to more than 150 PTR ion masses using gas chromatography (GC) pre-separation with electron ionization,
H3O+ chemical ionization, and NO+ chemical ionization, an extensive literature review, and
time series correlation, providing higher certainty for ion identifications than has been previously available. Our
interpretation of the PTR-ToF mass spectrum accounts for nearly 90 % of NMOG mass detected by PTR-ToF across all fuel
types. The relative contributions of different NMOGs to individual exact ion masses are mostly similar across many fires
and fuel types. The PTR-ToF measurements are compared to corresponding measurements from open-path Fourier transform
infrared spectroscopy (OP-FTIR), broadband cavity-enhanced spectroscopy (ACES), and iodide ion chemical ionization mass
spectrometry ( I− CIMS) where possible. The majority of comparisons have slopes near 1 and values of the linear
correlation coefficient, R2 , of > 0.8, including compounds that are not frequently reported by PTR-MS such as
ammonia, hydrogen cyanide (HCN), nitrous acid (HONO), and propene. The exceptions include methylglyoxal and compounds that
are known to be difficult to measure with one or more of the deployed instruments. The fire-integrated emission ratios to
CO and emission factors of NMOGs from 18 fuel types are provided. Finally, we provide an overview of the chemical
characteristics of detected species. Non-aromatic oxygenated compounds are the most abundant. Furans and aromatics, while
less abundant, comprise a large portion of the OH reactivity. The OH reactivity, its major contributors, and the
volatility distribution of emissions can change considerably over the course of a fire.
204 citations
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University of Colorado Boulder1, Cooperative Institute for Research in Environmental Sciences2, Georgia Institute of Technology3, University of Montana4, University of California, Irvine5, University of Innsbruck6, California State University, San Bernardino7, Langley Research Center8, Los Alamos National Laboratory9, University of Michigan10, California Institute of Technology11, Goddard Space Flight Center12, Brookhaven National Laboratory13, University of Oslo14, National Oceanic and Atmospheric Administration15, Colorado State University16, Pacific Northwest National Laboratory17, University of Maryland, Baltimore County18
TL;DR: In this paper, an extensive set of emission factors (EFs) for over 80 gases and 5 components of submicron particulate matter (PM_1) from three wildfires in the western U.S. were measured from aircraft during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC^4RS) and the Biomass Burning Observation Project (BBOP).
Abstract: Wildfires emit significant amounts of pollutants that degrade air quality. Plumes from three wildfires in the western U.S. were measured from aircraft during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC^4RS) and the Biomass Burning Observation Project (BBOP), both in summer 2013. This study reports an extensive set of emission factors (EFs) for over 80 gases and 5 components of submicron particulate matter (PM_1) from these temperate wildfires. These include rarely, or never before, measured oxygenated volatile organic compounds and multifunctional organic nitrates. The observed EFs are compared with previous measurements of temperate wildfires, boreal forest fires, and temperate prescribed fires. The wildfires emitted high amounts of PM_1 (with organic aerosol (OA) dominating the mass) with an average EF that is more than 2 times the EFs for prescribed fires. The measured EFs were used to estimate the annual wildfire emissions of carbon monoxide, nitrogen oxides, total nonmethane organic compounds, and PM_1 from 11 western U.S. states. The estimated gas emissions are generally comparable with the 2011 National Emissions Inventory (NEI). However, our PM_1 emission estimate (1530 ± 570 Gg yr^(−1)) is over 3 times that of the NEI PM_(2.5) estimate and is also higher than the PM_(2.5) emitted from all other sources in these states in the NEI. This study indicates that the source of OA from biomass burning in the western states is significantly underestimated. In addition, our results indicate that prescribed burning may be an effective method to reduce fine particle emissions.
169 citations
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TL;DR: In this paper, the authors report emission factor (EF, grams of compound emitted per kilogram of fuel burned) measurements in fresh smoke of a diverse subset of critically important trace gases measured using open-path Fourier transform infrared spectroscopy (OP-FTIR).
Abstract: . Western wildfires have a major impact on air quality in the US. In the fall
of 2016, 107 test fires were burned in the large-scale combustion facility at
the US Forest Service Missoula Fire Sciences Laboratory as part of the Fire
Influence on Regional and Global Environments Experiment (FIREX). Canopy,
litter, duff, dead wood, and other fuel components were burned in
combinations that represented realistic fuel complexes for several important
western US coniferous and chaparral ecosystems including ponderosa pine,
Douglas fir, Engelmann spruce, lodgepole pine, subalpine fir, chamise, and
manzanita. In addition, dung, Indonesian peat, and individual coniferous
ecosystem fuel components were burned alone to investigate the effects of
individual components (e.g., “duff”) and fuel chemistry on emissions. The
smoke emissions were characterized by a large suite of state-of-the-art
instruments. In this study we report emission factor (EF, grams of compound
emitted per kilogram of fuel burned) measurements in fresh smoke of a diverse
suite of critically important trace gases measured using open-path Fourier
transform infrared spectroscopy (OP-FTIR). We also report aerosol optical
properties (absorption EF; single-scattering albedo, SSA; and
Angstrom absorption exponent, AAE) as well as black carbon (BC) EF
measured by photoacoustic extinctiometers (PAXs) at 870 and 401 nm. The
average trace gas emissions were similar across the coniferous ecosystems
tested and most of the variability observed in emissions could be attributed
to differences in the consumption of components such as duff and litter,
rather than the dominant tree species. Chaparral fuels produced lower EFs
than mixed coniferous fuels for most trace gases except for NO x and
acetylene. A careful comparison with available field measurements of
wildfires confirms that several methods can be used to extract data
representative of real wildfires from the FIREX laboratory fire data. This is
especially valuable for species rarely or not yet measured in the field. For
instance, the OP-FTIR data alone show that ammonia (1.62 g kg −1) ,
acetic acid (2.41 g kg −1) , nitrous acid (HONO, 0.61 g kg −1) ,
and other trace gases such as glycolaldehyde (0.90 g kg −1) and formic
acid (0.36 g kg −1) are significant emissions that were poorly
characterized or not characterized for US wildfires in previous work. The PAX
measurements show that the ratio of brown carbon (BrC) absorption to BC
absorption is strongly dependent on modified combustion efficiency (MCE) and
that BrC absorption is most dominant for combustion of duff (AAE 7.13) and
rotten wood (AAE 4.60): fuels that are consumed in greater amounts during
wildfires than prescribed fires. Coupling our laboratory data with field data
suggests that fresh wildfire smoke typically has an EF for BC near
0.2 g kg −1 , an SSA of ∼ 0.91, and an AAE of ∼ 3.50, with
the latter implying that about 86 % of the aerosol absorption at 401 nm
is due to BrC.
103 citations
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TL;DR: In this article, fuel-based emission factors (EFs; with units of pollutant mass emitted per kilogram of fuel combusted) were determined for fine particulate matter (PM2.5), organic carbon (OC), elemental carbon (EC), inorganic ions, trace metals, and organic species.
Abstract: . The Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) characterized widespread and under-sampled combustion sources common to South Asia, including brick kilns, garbage burning, diesel and gasoline generators, diesel groundwater pumps, idling motorcycles, traditional and modern cooking stoves and fires, crop residue burning, and heating fire. Fuel-based emission factors (EFs; with units of pollutant mass emitted per kilogram of fuel combusted) were determined for fine particulate matter (PM2.5), organic carbon (OC), elemental carbon (EC), inorganic ions, trace metals, and organic species. For the forced-draft zigzag brick kiln, EFPM2.5 ranged from 12 to 19 g kg−1 with major contributions from OC (7 %), sulfate expected to be in the form of sulfuric acid (31.9 %), and other chemicals not measured (e.g., particle-bound water). For the clamp kiln, EFPM2.5 ranged from 8 to 13 g kg−1, with major contributions from OC (63.2 %), sulfate (23.4 %), and ammonium (16 %). Our brick kiln EFPM2.5 values may exceed those previously reported, partly because we sampled emissions at ambient temperature after emission from the stack or kiln allowing some particle-phase OC and sulfate to form from gaseous precursors. The combustion of mixed household garbage under dry conditions had an EFPM2.5 of 7.4 ± 1.2 g kg−1, whereas damp conditions generated the highest EFPM2.5 of all combustion sources in this study, reaching up to 125 ± 23 g kg−1. Garbage burning emissions contained triphenylbenzene and relatively high concentrations of heavy metals (Cu, Pb, Sb), making these useful markers of this source. A variety of cooking stoves and fires fueled with dung, hardwood, twigs, and/or other biofuels were studied. The use of dung for cooking and heating produced higher EFPM2.5 than other biofuel sources and consistently emitted more PM2.5 and OC than burning hardwood and/or twigs; this trend was consistent across traditional mud stoves, chimney stoves, and three-stone cooking fires. The comparisons of different cooking stoves and cooking fires revealed the highest PM emissions from three-stone cooking fires (7.6–73 g kg−1), followed by traditional mud stoves (5.3–19.7 g kg−1), mud stoves with a chimney for exhaust (3.0–6.8 g kg−1), rocket stoves (1.5–7.2 g kg−1), induced-draft stoves (1.2–5.7 g kg−1), and the bhuse chulo stove (3.2 g kg−1), while biogas had no detectable PM emissions. Idling motorcycle emissions were evaluated before and after routine servicing at a local shop, which decreased EFPM2.5 from 8.8 ± 1.3 to 0.71 ± 0.45 g kg−1 when averaged across five motorcycles. Organic species analysis indicated that this reduction in PM2.5 was largely due to a decrease in emission of motor oil, probably from the crankcase. The EF and chemical emissions profiles developed in this study may be used for source apportionment and to update regional emission inventories.
93 citations
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TL;DR: In this article, fine particulate matter (PM2.5) was collected in situ from peat smoke during the 2015 El Nino peat fire episode in Central Kalimantan, Indonesia.
Abstract: . Fine particulate matter (PM2.5) was collected in situ from peat smoke during the 2015 El Nino peat fire episode in Central Kalimantan, Indonesia. Twenty-one PM samples were collected from 18 peat fire plumes that were primarily smoldering with modified combustion efficiency (MCE) values of 0.725–0.833. PM emissions were determined and chemically characterized for elemental carbon (EC), organic carbon (OC), water-soluble OC, water-soluble ions, metals, and organic species. Fuel-based PM2.5 mass emission factors (EFs) ranged from 6.0 to 29.6 g kg−1 with an average of 17.3 ± 6.0 g kg−1. EC was detected only in 15 plumes and comprised ∼ 1 % of PM mass. Together, OC (72 %), EC (1 %), water-soluble ions (1 %), and metal oxides (0.1 %) comprised 74 ± 11 % of gravimetrically measured PM mass. Assuming that the remaining mass is due to elements that form organic matter (OM; i.e., elements O, H, N) an OM-to-OC conversion factor of 1.26 was estimated by linear regression. Overall, chemical speciation revealed the following characteristics of peat-burning emissions: high OC mass fractions (72 %), primarily water-insoluble OC (84 ± 11 %C), low EC mass fractions (1 %), vanillic to syringic acid ratios of 1.9, and relatively high n-alkane contributions to OC (6.2 %C) with a carbon preference index of 1.2–1.6. Comparison to laboratory studies of peat combustion revealed similarities in the relative composition of PM but greater differences in the absolute EF values. The EFs developed herein, combined with estimates of the mass of peat burned, are used to estimate that 3.2–11 Tg of PM2.5 was emitted to atmosphere during the 2015 El Nino peatland fire event in Indonesia. Combined with gas-phase measurements of CO2, CO, CH4, and volatile organic carbon from Stockwell et al. (2016), it is determined that OC and EC accounted for 2.1 and 0.04 % of total carbon emissions, respectively. These in situ EFs can be used to improve the accuracy of the representation of Indonesian peat burning in emission inventories and receptor-based models.
73 citations
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TL;DR: In this paper, a dual-smog-chamber method was used to compare the secondary organic aerosol (SOA) formation from the same biomass burning emissions under two different atmospheric conditions.
Abstract: Biomass burning (BB) is a major source of atmospheric pollutants. Field and laboratory studies indicate that secondary organic aerosol (SOA) formation from BB emissions is highly variable. We investigated sources of this variability using a novel dual-smog-chamber method that directly compares the SOA formation from the same BB emissions under two different atmospheric conditions. During each experiment, we filled two identical Teflon smog chambers simultaneously with BB emissions from the same fire. We then perturbed the smoke with UV-lights, UV-lights plus HONO, or dark ozone in one or both chambers. These perturbations caused SOA formation in nearly every experiment with an average organic aerosol (OA) mass enhancement ratio of 1.78 ± 0.91 (mean ± 1σ). However, the effects of the perturbations were highly variable ranging with OA mass enhancement ratios ranging from 0.7 (30% loss of OA mass) to 4.4 across the set of perturbation experiments. There was no apparent relationship between OA enhancement and perturbation type, fuel type, and modified combustion efficiency. To better isolate the effects of different perturbations, we report dual-chamber enhancements (DUCE), which quantity the effects of a perturbation relative to a reference condition. DUCE values were also highly variable, even for the same perturbation and fuel type. Gas measurements indicate substantial burn-to-burn variability in the magnitude and composition of SOA precursor emissions, even in repeated burns of the same fuel under nominally identical conditions. Therefore, the effects of different atmospheric perturbations on SOA formation from BB emissions appear to be less important than burn-to-burn variability.
42 citations
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TL;DR: In a previous work as discussed by the authors, we have discussed the relationship between atmospheric composition and climate, and NASA's upper atmosphere research program (UAP45G, NNX14AP75G), which is a part of the NASA Earth Science Division.
Abstract: NOAA Atmospheric Composition and Climate Program; NASA Radiation Sciences Program; NASA Upper Atmosphere Research Program; NASA [NNX12AC10G, NNX14AP75G, NNX14AK79H, NNX12AC03G, NNX15AT96G]; NASA Earth Science Division [NNX12AC20G, NNX14AP45G]
24 citations
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TL;DR: In this paper, a laser imaging nephelometer was deployed at the Missoula Fire-Sciences Laboratory to sample biomass burning aerosol from controlled fires during the FIREX intensive laboratory study.
Abstract: . Particle morphology is an important parameter affecting aerosol
optical properties that are relevant to climate and air quality, yet it is
poorly constrained due to sparse in situ measurements. Biomass burning is a
large source of aerosol that generates particles with different morphologies.
Quantifying the optical contributions of non-spherical aerosol populations is
critical for accurate radiative transfer models, and for correctly
interpreting remote sensing data. We deployed a laser imaging nephelometer at
the Missoula Fire Sciences Laboratory to sample biomass burning aerosol from
controlled fires during the FIREX intensive laboratory study. The laser
imaging nephelometer measures the unpolarized scattering phase function of an
aerosol ensemble using diode lasers at 375 and 405 nm. Scattered light from
the bulk aerosol in the instrument is imaged onto a charge-coupled device
(CCD) using a wide-angle
field-of-view lens, which allows for measurements at 4–175 ∘
scattering angle with ∼ 0.5 ∘ angular resolution. Along with a
suite of other instruments, the laser imaging nephelometer sampled fresh
smoke emissions both directly and after removal of volatile components with a
thermodenuder at 250 ∘ C. The total integrated aerosol scattering
signal agreed with both a cavity ring-down photoacoustic spectrometer system
and a traditional integrating nephelometer within instrumental uncertainties.
We compare the measured scattering phase functions at 405 nm to theoretical
models for spherical (Mie) and fractal (Rayleigh–Debye–Gans) particle
morphologies based on the size distribution reported by an optical particle
counter. Results from representative fires demonstrate that particle
morphology can vary dramatically for different fuel types. In some cases, the
measured phase function cannot be described using Mie theory. This study
demonstrates the capabilities of the laser imaging nephelometer instrument to
provide realtime, in situ information about dominant particle morphology,
which is vital for understanding remote sensing data and accurately
describing the aerosol population in radiative transfer calculations.
19 citations
01 Dec 2017
2 citations