67 research outputs found
In situ measurements of trace gases, PM, and aerosol optical properties during the 2017 NW US wildfire smoke event
In mid-August through mid-September of 2017 a major wildfire smoke and haze
episode strongly impacted most of the NW US and SW Canada. During this period
our ground-based site in Missoula, Montana, experienced heavy smoke impacts
for âŒâ500 h (up to 471 ”g mâ3 hourly average
PM2.5). We measured wildfire trace gases, PM2.5 (particulate matter
â€2.5 ”m in diameter), and black carbon and submicron aerosol
scattering and absorption at 870 and 401 nm. This may be the most extensive
real-time data for these wildfire smoke properties to date. Our range of
trace gas ratios for ÎNH3âÎCO and ÎC2H4âÎCO confirmed that the smoke from mixed, multiple sources
varied in age from âŒâ2â3 h to âŒâ1â2 days. Our study-average
ÎCH4âÎCO ratio (0.166±0.088) indicated a large
contribution to the regional burden from inefficient smoldering combustion.
Our ÎBCâÎCO ratio (0.0012±0.0005) for our ground
site was moderately lower than observed in aircraft studies (âŒâ0.0015)
to date, also consistent with a relatively larger contribution from
smoldering combustion. Our ÎBCâÎPM2.5 ratio (0.0095±0.0003) was consistent with the overwhelmingly non-BC (black carbon),
mostly organic nature of the smoke observed in airborne studies of wildfire
smoke to date. Smoldering combustion is usually associated with enhanced PM
emissions, but our ÎPM2.5âÎCO ratio (0.126±0.002)
was about half the ÎPM1.0âÎCO measured in fresh
wildfire smoke from aircraft (âŒâ0.266). Assuming PM2.5 is
dominated by PM1, this suggests that aerosol evaporation, at least near
the surface, can often reduce PM loading and its atmospheric/air-quality
impacts on the timescale of several days. Much of the smoke was emitted late
in the day, suggesting that nighttime processing would be important in the
early evolution of smoke. The diurnal trends show brown carbon (BrC),
PM2.5, and CO peaking in the early morning and BC peaking in the early
evening. Over the course of 1 month, the average single scattering albedo for
individual smoke peaks at 870 nm increased from âŒâ0.9 to âŒâ0.96.
Bscat401âBscat870 was used as a proxy for the size and
âphotochemical ageâ of the smoke particles, with this interpretation being
supported by the simultaneously observed ratios of reactive trace gases to
CO. The size and age proxy implied that the Ă
ngström absorption
exponent decreased significantly after about 10 h of daytime smoke aging,
consistent with the only airborne measurement of the BrC lifetime in an
isolated plume. However, our results clearly show that non-BC absorption can
be important in âtypicalâ regional haze and moderately aged smoke, with BrC
ostensibly accounting for about half the absorption at 401 nm on average for
our entire data set.</p
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Airborne measurements of western U.S. wildfire emissions: Comparison with prescribed burning and air quality implications
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 (SEAC4RS) 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 (PM1) 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 PM1 (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 PM1 from 11 western U.S. states. The estimated gas emissions are generally comparable with the 2011 National Emissions Inventory (NEI). However, our PM1 emission estimate (1530 ± 570 Gg yr-1) is over 3 times that of the NEI PM2.5 estimate and is also higher thanthe PM2.5 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
Constraining emissions of volatile organic compounds from western US wildfires with WE-CAN and FIREX-AQ airborne observations
The impact of biomass burning (BB) on the atmospheric burden of volatile organic compounds (VOCs) is highly uncertain. Here we apply the GEOS-Chem
chemical transport model (CTM) to constrain BB emissions in the western USA at âŒâ25âkm resolution. Across three BB emission inventories
widely used in CTMs, the inventoryâinventory comparison suggests that the totals of 14 modeled BB VOC emissions in the western USA agree with each
other within 30â%â40â%. However, emissions for individual VOCs can differ by a factor of 1â5, driven by the regionally averaged emission
ratios (ERs, reflecting both assigned ERs for specific biome and vegetation classifications) across the three inventories. We further evaluate GEOS-Chem
simulations with aircraft observations made during WE-CAN (Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption and Nitrogen) and
FIREX-AQ (Fire Influence on Regional to Global Environments and Air Quality) field campaigns. Despite being driven by different global BB
inventories or applying various injection height assumptions, the modelâobservation comparison suggests that GEOS-Chem simulations underpredict
observed vertical profiles by a factor of 3â7. The model shows small to no bias for most species in low-/no-smoke conditions. We thus attribute the
negative model biases mostly to underestimated BBÂ emissions in these inventories. Tripling BBÂ emissions in the model reproduces observed vertical
profiles for primary compounds, i.e., CO, propane, benzene, and toluene. However, it shows no to less significant improvements for oxygenated
VOCs, particularly for formaldehyde, formic acid, acetic acid, and lumped â„âC3 aldehydes, suggesting the model is missing secondary
sources of these compounds in BB-impacted environments. The underestimation of primary BBÂ emissions in inventories is likely attributable to
underpredicted amounts of effective dry matter burned, rather than errors in fire detection, injection height, or ERs, as constrained by aircraft
and ground measurements. We cannot rule out potential sub-grid uncertainties (i.e., not being able to fully resolve fire plumes) in the nested
GEOS-Chem which could explain the negative model bias partially, though back-of-the-envelope calculation and evaluation using longer-term ground
measurements help support the argument of the dry matter burned underestimation. The total ERs of the 14Â BB VOCs implemented in GEOS-Chem only
account for half of the total 161 measured VOCs (âŒâ75 versus 150âppbâppmâ1). This reveals a significant amount of missing reactive
organic carbon in widely used BBÂ emission inventories. Considering both uncertainties in effective dry matter burned (Ăâ3) and unmodeled
VOCs (Ăâ2), we infer that BB contributed to 10â% in 2019 and 45â% in 2018 (240 and 2040âGgâC) of the total VOC primary
emission flux in the western USA during these two fire seasons, compared to only 1â%â10â% in the standard GEOS-Chem.</p
Constraining emissions of volatile organic compounds from western US wildfires with WE-CAN and FIREX-AQ airborne observations
The impact of biomass burning (BB) on the atmospheric burden of volatile organic compounds (VOCs) is highly uncertain. Here we apply the GEOS-Chem chemical transport model (CTM) to constrain BB emissions in the western US at ~25 km resolution. Across three BB emission inventories widely used in CTMs, the total of 14 modeled BB VOC emissions in the western US agree with each other within 30–40 %. However, emissions for individual VOC differ by up to a factor of 5 (i.e., lumped ≥ C4 alkanes), driven by the regionally averaged emission ratios (ERs) among inventories. We further evaluate GEOS-Chem simulations with aircraft observations made during WE-CAN (Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen) and FIREX-AQ (Fire Influence on Regional to Global Environments and Air Quality) field campaigns. Despite being driven by different global BB inventories or applying various injection height assumptions, GEOS-Chem simulations underpredict observed vertical profiles by a factor of 3–7. The model shows small-to-no bias for most species in low/no smoke conditions. We thus attribute the negative model biases mostly to underestimated BB emissions in these inventories. Tripling BB emissions in the model reproduces observed vertical profiles for primary compounds, i.e., CO, propane, benzene, and toluene. However, it shows no-to-less significant improvements for oxygenated VOCs, particularly formaldehyde, formic acid, acetic acid, and lumped ≥ C3 aldehydes, suggesting the model is missing secondary sources of these compounds in BB-impacted environments. The underestimation of primary BB emissions in inventories is likely attributable to underpredicted amounts of effective dry matter burned, rather than errors in fire detection, injection height, or ERs. We cannot rule out potential sub-grid uncertainties (i.e., not being able to fully resolve fire plumes) in the nested GEOS-Chem which could explain the model negative bias partially, though the back-of-the-envelope calculation and evaluation using longer-term ground measurements help increase the argument of the dry matter burned underestimation. The ERs of the 14 BB VOCs implemented in GEOS-Chem account for about half of the total 161 measured VOCs (~75 versus 150 ppb ppm-1). This reveals a significant amount of missing reactive organic carbon in widely-used BB emission inventories. Considering both uncertainties in effective dry matter burned and unmodeled VOCs, we infer that BB contributed up to 10 % in 2019 and 45 % in 2018 (240 and 2040 GgC) of the total VOC primary emission flux in the western US during these two fire seasons, compared to only 1–10 % in the standard GEOS-Chem.</p
Speciated and total emission factors of particulate organics from burning western US wildland fuels and their dependence on combustion efficiency
Western US wildlands experience frequent and large-scale wildfires which are
predicted to increase in the future. As a result, wildfire smoke emissions
are expected to play an increasing role in atmospheric chemistry while
negatively impacting regional air quality and human health. Understanding the
impacts of smoke on the environment is informed by identifying and
quantifying the chemical compounds that are emitted during wildfires and by
providing empirical relationships that describe how the amount and
composition of the emissions change based upon different fire conditions and
fuels. This study examined particulate organic compounds emitted from burning
common western US wildland fuels at the US Forest Service Fire Science
Laboratory. Thousands of intermediate and semi-volatile organic compounds
(I/SVOCs) were separated and quantified into fire-integrated emission factors
(EFs) using a thermal desorption, two-dimensional gas chromatograph with
online derivatization coupled to an electron ionization/vacuum ultraviolet
high-resolution time-of-flight mass spectrometer
(TD-GC Ă GC-EI/VUV-HRToFMS). Mass spectra, EFs as a function of
modified combustion efficiency (MCE), fuel source, and other defining
characteristics for the separated compounds are provided in the accompanying
mass spectral library. Results show that EFs for total organic carbon (OC),
chemical families of I/SVOCs, and most individual I/SVOCs span 2â5 orders of
magnitude, with higher EFs at smoldering conditions (low MCE) than flaming.
Logarithmic fits applied to the observations showed that log (EFs) for
particulate organic compounds were inversely proportional to MCE. These
measurements and relationships provide useful estimates of EFs for OC,
elemental carbon (EC), organic chemical families, and individual I/SVOCs as a
function of fire conditions.</p
Thymosin ÎČ10 Expression Driven by the Human TERT Promoter Induces Ovarian Cancer-Specific Apoptosis through ROS Production
Thymosin ÎČ10 (TÎČ10) regulates actin dynamics as a cytoplasm G-actin sequestering protein. Previously, we have shown that TÎČ10 diminishes tumor growth, angiogenesis, and proliferation by disrupting actin and by inhibiting Ras. However, little is known about its mechanism of action and biological function. In the present study, we establish a new gene therapy model using a genetically modified adenovirus, referred to as Ad.TERT.TÎČ10, that can overexpress the TÎČ10 gene in cancer cells. This was accomplished by replacing the native TÎČ10 gene promoter with the human TERT promoter in Ad.TERT.TÎČ10. We investigated the cancer suppression activity of TÎČ10 and found that Ad.TERT.TÎČ10 strikingly induced cancer-specific expression of TÎČ10 as well as apoptosis in a co-culture model of human primary ovarian cancer cells and normal fibroblasts. Additionally, Ad.TERT.TÎČ10 decreased mitochondrial membrane potential and increased reactive oxygen species (ROS) production. These effects were amplified by co-treatment with anticancer drugs, such as paclitaxel and cisplatin. These findings indicate that the rise in ROS production due to actin disruption by TÎČ10 overexpression increases apoptosis of human ovarian cancer cells. Indeed, the cancer-specific overexpression of TÎČ10 by Ad.TERT.TÎČ10 could be a valuable anti-cancer therapeutic for the treatment of ovarian cancer without toxicity to normal cells
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Investigating biomass burning aerosol morphology using a laser imaging nephelometer
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
Primary emissions of glyoxal and methylglyoxal from laboratory measurements of open biomass burning
We report the emissions of glyoxal and methylglyoxal from the open burning of
biomass during the NOAA-led 2016 FIREX intensive at the Fire Sciences
Laboratory in Missoula, MT. Both compounds were measured using cavity-enhanced spectroscopy, which is both more sensitive and more selective than
methods previously used to determine emissions of these two compounds. A
total of 75 burns were conducted, using 33 different fuels in 8 different
categories, providing a far more comprehensive dataset for emissions than was
previously available. Measurements of methylglyoxal using our instrument
suffer from spectral interferences from several other species, and the values
reported here are likely underestimates, possibly by as much as 70 %.
Methylglyoxal emissions were 2â3 times higher than glyoxal emissions on a
molar basis, in contrast to previous studies that report methylglyoxal
emissions lower than glyoxal emissions. Methylglyoxal emission ratios for all
fuels averaged 3.6±2.4 ppbv methylglyoxal (ppmv CO)â1, while emission
factors averaged 0.66±0.50 g methylglyoxal (kg fuel burned)â1. Primary
emissions of glyoxal from biomass burning were much lower than previous
laboratory measurements but consistent with recent measurements from
aircraft. Glyoxal emission ratios for all fuels averaged 1.4±0.7 ppbv glyoxal (ppmv CO)â1, while
emission factors averaged 0.20±0.12 g glyoxal (kg fuel burned)â1, values that are at least a factor of 4 lower than
assumed in previous estimates of the global glyoxal budget. While there was
significant variability in the glyoxal emission ratios and factors between
the different fuel groups, glyoxal and formaldehyde were highly correlated
during the course of any given fire, and the ratio of glyoxal to
formaldehyde, RGF, was consistent across many different fuel
types, with an average value of 0.068±0.018. While RGF values
for fresh emissions were consistent across many fuel types, further work is
required to determine how this value changes as the emissions age.</p
High- and low-temperature pyrolysis profiles describe volatile organic compound emissions from western US wildfire fuels
Biomass burning is a large source of volatile organic compounds
(VOCs) and many other trace species to the atmosphere, which can act as
precursors to secondary pollutants such as ozone and fine particles.
Measurements performed with a proton-transfer-reaction time-of-flight mass
spectrometer during the FIREX 2016 laboratory intensive were analyzed with
positive matrix factorization (PMF), in order to understand the
instantaneous variability in VOC emissions from biomass burning, and to
simplify the description of these types of emissions. Despite the complexity
and variability of emissions, we found that a solution including just two
emission profiles, which are mass spectral representations of the relative
abundances of emitted VOCs, explained on average 85âŻ% of the VOC emissions
across various fuels representative of the western US (including various
coniferous and chaparral fuels). In addition, the profiles were remarkably
similar across almost all of the fuel types tested. For example, the
correlation coefficient r2 of each profile between ponderosa pine
(coniferous tree) and manzanita (chaparral) is higher than 0.84. The
compositional differences between the two VOC profiles appear to be related
to differences in pyrolysis processes of fuel biopolymers at high and low
temperatures. These pyrolysis processes are thought to be the main source of
VOC emissions. High-temperature and low-temperature pyrolysis
processes do not correspond exactly to the commonly used flaming and
smoldering categories as described by modified combustion efficiency
(MCE). The average atmospheric properties (e.g., OH reactivity, volatility,
etc) of the high- and low-temperature profiles are significantly different.
We also found that the two VOC profiles can describe previously reported VOC
data for laboratory and field burns.</p
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