7 research outputs found
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
Overview of the Alaskan Layered Pollution and Chemical Analysis (ALPACA) Field Experiment
The Alaskan Layered Pollution And Chemical Analysis (ALPACA) field experiment was a collaborative study designed to improve understanding of pollution sources and chemical processes during winter (cold climate and low-photochemical activity), to investigate indoor pollution, and to study dispersion of pollution as affected by frequent temperature inversions. A number of the research goals were motivated by questions raised by residents of Fairbanks, Alaska, where the study was held. This paper describes the measurement strategies and the conditions encountered during the January and February 2022 field experiment, and reports early examples of how the measurements addressed research goals, particularly those of interest to the residents. Outdoor air measurements showed high concentrations of particulate matter and pollutant gases including volatile organic carbon species. During pollution events, low winds and extremely stable atmospheric conditions trapped pollution below 73 m, an extremely shallow vertical scale. Tethered-balloon-based measurements intercepted plumes aloft, which were associated with power plant point sources through transport modeling. Because cold climate residents spend much of their time indoors, the study included an indoor air quality component, where measurements were made inside and outside a house to study infiltration and indoor sources. In the absence of indoor activities such as cooking and/or heating with a pellet stove, indoor particulate matter concentrations were lower than outdoors; however, cooking and pellet stove burns often caused higher indoor particulate matter concentrations than outdoors. The mass-normalized particulate matter oxidative potential, a health-relevant property measured here by the reactivity with dithiothreiol, of indoor particles varied by source, with cooking particles having less oxidative potential per mass than pellet stove particles
Comprehensive electronic medical record implementation levels not associated with 30-day all-cause readmissions within Medicare beneficiaries with heart failure.
Identification of Trypanosoma brucei AdoMetDC Inhibitors Using a High-Throughput Mass Spectrometry-Based Assay
Human
African trypanosomiasis (HAT) is a fatal infectious disease caused
by the eukaryotic pathogen Trypanosoma brucei (<i>Tb</i>). Available treatments are difficult to administer
and have significant safety issues. <i>S</i>-Adenosylmethionine
decarboxylase (AdoMetDC) is an essential enzyme in the parasite polyamine
biosynthetic pathway. Previous attempts to develop <i>Tb</i>AdoMetDC inhibitors into anti-HAT therapies failed due to poor brain
exposure. Here, we describe a large screening campaign of two small-molecule
libraries (âŒ400,000 compounds) employing a new high-throughput
(âŒ7 s per sample) mass spectrometry-based assay for AdoMetDC
activity. As a result of primary screening, followed by hit confirmation
and validation, we identified 13 new classes of reversible <i>Tb</i>AdoMetDC inhibitors with low-micromolar potency (IC<sub>50</sub>) against both <i>Tb</i>AdoMetDC and <i>T. brucei</i> parasite cells. The majority of these compounds were >10-fold
selective against the human enzyme. Importantly, compounds from four
classes demonstrated high propensity to cross the bloodâbrain
barrier in a cell monolayer assay. Biochemical analysis demonstrated
that compounds from eight classes inhibited intracellular <i>Tb</i>AdoMetDC in the parasite, although evidence for a secondary
off-target component was also present. The discovery of several new <i>Tb</i>AdoMetDC inhibitor chemotypes provides new hits for lead
optimization programs aimed to deliver a novel treatment for HAT
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Overview of the Alaskan Layered Pollution and Chemical Analysis (ALPACA) Field Experiment
The Alaskan Layered Pollution And Chemical Analysis (ALPACA) field experiment was a collaborative study designed to improve understanding of pollution sources and chemical processes during winter (cold climate and low-photochemical activity), to investigate indoor pollution, and to study dispersion of pollution as affected by frequent temperature inversions. A number of the research goals were motivated by questions raised by residents of Fairbanks, Alaska, where the study was held. This paper describes the measurement strategies and the conditions encountered during the January and February 2022 field experiment, and reports early examples of how the measurements addressed research goals, particularly those of interest to the residents. Outdoor air measurements showed high concentrations of particulate matter and pollutant gases including volatile organic carbon species. During pollution events, low winds and extremely stable atmospheric conditions trapped pollution below 73 m, an extremely shallow vertical scale. Tethered-balloon-based measurements intercepted plumes aloft, which were associated with power plant point sources through transport modeling. Because cold climate residents spend much of their time indoors, the study included an indoor air quality component, where measurements were made inside and outside a house to study infiltration and indoor sources. In the absence of indoor activities such as cooking and/or heating with a pellet stove, indoor particulate matter concentrations were lower than outdoors; however, cooking and pellet stove burns often caused higher indoor particulate matter concentrations than outdoors. The mass-normalized particulate matter oxidative potential, a health-relevant property measured here by the reactivity with dithiothreiol, of indoor particles varied by source, with cooking particles having less oxidative potential per mass than pellet stove particles