Concentrated animal feeding operations (CAFOs) emit a large number of volatile organic compounds (VOCs) to the atmosphere. In this study, we conducted mobile laboratory measurements of VOCs, methane ...(CH4) and ammonia (NH3) downwind of dairy cattle, beef cattle, sheep and chicken CAFO facilities in northeastern Colorado using a hydronium ion time-of-flight chemical-ionization mass spectrometer (H3O+ ToF-CIMS), which can detect numerous VOCs. Regional measurements of CAFO emissions in northeastern Colorado were also performed using the NOAA WP-3D aircraft during the Shale Oil and Natural Gas Nexus (SONGNEX) campaign. Alcohols and carboxylic acids dominate VOC concentrations and the reactivity of the VOCs with hydroxyl (OH) radicals. Sulfur-containing and phenolic species provide the largest contributions to the odor activity values and the nitrate radical (NO3) reactivity of VOC emissions, respectively. VOC compositions determined from mobile laboratory and aircraft measurements generally agree well with each other. The high time-resolution mobile measurements allow for the separation of the sources of VOCs from different parts of the operations occurring within the facilities. We show that the emissions of ethanol are primarily associated with feed storage and handling. Based on mobile laboratory measurements, we apply a multivariate regression analysis using NH3 and ethanol as tracers to determine the relative importance of animal-related emissions (animal exhalation and waste) and feed-related emissions (feed storage and handling) for different VOC species. Feed storage and handling contribute significantly to emissions of alcohols, carbonyls, carboxylic acids and sulfur-containing species. Emissions of phenolic species and nitrogen-containing species are predominantly associated with animals and their waste.
We present measurements of organic aerosol (OA) in urban plumes from Houston and Dallas/Fort Worth as well as in industrial plumes in the Houston area during TexAQS‐2006. Consistent with the ...TexAQS‐2000 study, measurements show greater amount of aerosol mass downwind of the industrial centers compared to urban areas. This is likely due to higher emission and processing of volatile organic compounds (VOCs) from the industrial sources along the Houston ship channel. Comparisons of the current measurements with observations from the northeastern (NE) United States indicate that the observed ratios of the enhancement above background in OA, ΔOA, to the enhancement above background in CO, ΔCO, downwind of urban centers of Houston and Dallas/Fort Worth are within a factor of 2 of the same values in plumes from urban areas in the NE United States. In the ship channel plumes, ΔOA/ΔCO exceeds that in the urban areas by factors ranging from 1.5 to 7. We use a chemical box model to simulate secondary organic aerosol (SOA) formation from anthropogenic and biogenic VOCs in different plumes using recently reported dependencies of SOA yields on VOC/NOx ratios. Modeled SOA to CO enhancement ratios are within a factor of 2 of measurements. The increase in SOA from biogenic VOCs (BVOCs) predicted by the chemical box model as well as by a separate analysis using a Lagrangian particle dispersion model (FLEXPART) is <0.7 μg per standard m3 (sm−3). We find no evidence for a substantial influence of BVOCs on OA formation in our measurements in Houston area.
Nitrogen oxides are important to the regulation of ozone throughout the Earth's atmosphere. Of particular interest for regional air quality is photochemical production and nocturnal destruction of O3 ...in the lower troposphere in high NOx(=NO + NO2) environments. Nocturnal tropospheric odd oxygen (Ox), defined as O3 + NO2 + 2NO3 + 3N2O5, is used to assess the impact of NOx emissions on nocturnal O3 loss. Recent aircraft measurements of the components of Ox and HNO3 yield a detailed accounting of the nocturnal Ox budget in a regionally polluted environment. The analysis demonstrates the role of NO3 and N2O5 reactions in nocturnal O3 destruction and shows that multiple factors, including timing of NOx emissions, hydrocarbon and aerosol loading, seasonality and atmospheric mixing, govern the impact of NOx emissions on regional‐scale air quality.
In various cancer types, the first step towards extended metastatic disease is the presence of lymph node metastases. Imaging methods with sufficient diagnostic accuracy are required to personalize ...treatment. Lymph node metastases can be detected with ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI), but this method needs validation. Here, a workflow is presented, which is designed to compare MRI-visible lymph nodes on a node-to-node basis with histopathology.
In patients with prostate, rectal, periampullary, esophageal, and head-and-neck cancer, in vivo USPIO-enhanced MRI was performed to detect lymph nodes suspicious of harboring metastases. After lymphadenectomy, but before histopathological assessment, a 7 Tesla preclinical ex vivo MRI of the surgical specimen was performed, and in vivo MR images were radiologically matched to ex vivo MR images. Lymph nodes were annotated on the ex vivo MRI for an MR-guided pathological examination of the specimens.
Matching lymph nodes of ex vivo MRI to pathology was feasible in all cancer types. The annotated ex vivo MR images enabled a comparison between USPIO-enhanced in vivo MRI and histopathology, which allowed for analyses on a nodal, or at least on a nodal station, basis.
A workflow was developed to validate in vivo USPIO-enhanced MRI with histopathology. Guiding the pathologist towards lymph nodes in the resection specimens during histopathological work-up allowed for the analysis at a nodal basis, or at least nodal station basis, of in vivo suspicious lymph nodes with corresponding histopathology, providing direct information for validation of in vivo USPIO-enhanced, MRI-detected lymph nodes.
The volatile organic compound (VOC) distribution in the Mexico City Metropolitan Area (MCMA) and its evolution as it is uplifted and transported out of the MCMA basin was studied during the 2006 ...MILAGRO/MIRAGE-Mex field campaign. The results show that in the morning hours in the city center, the VOC distribution is dominated by non-methane hydrocarbons (NMHCs) but with a substantial contribution from oxygenated volatile organic compounds (OVOCs), predominantly from primary emissions. Alkanes account for a large part of the NMHC distribution in terms of mixing ratios. In terms of reactivity, NMHCs also dominate overall, especially in the morning hours. However, in the afternoon, as the boundary layer lifts and air is mixed and aged within the basin, the distribution changes as secondary products are formed. The WRF-Chem (Weather Research and Forecasting with Chemistry) model and MOZART (Model for Ozone and Related chemical Tracers) were able to approximate the observed MCMA daytime patterns and absolute values of the VOC OH reactivity. The MOZART model is also in agreement with observations showing that NMHCs dominate the reactivity distribution except in the afternoon hours. The WRF-Chem and MOZART models showed higher reactivity than the experimental data during the nighttime cycle, perhaps indicating problems with the modeled nighttime boundary layer height. A northeast transport event was studied in which air originating in the MCMA was intercepted aloft with the Department of Energy (DOE) G1 on 18 March and downwind with the National Center for Atmospheric Research (NCAR) C130 one day later on 19 March. A number of identical species measured aboard each aircraft gave insight into the chemical evolution of the plume as it aged and was transported as far as 1000 km downwind; ozone was shown to be photochemically produced in the plume. The WRF-Chem and MOZART models were used to examine the spatial extent and temporal evolution of the plume and to help interpret the observed OH reactivity. The model results generally showed good agreement with experimental results for the total VOC OH reactivity downwind and gave insight into the distributions of VOC chemical classes. A box model with detailed gas phase chemistry (NCAR Master Mechanism), initialized with concentrations observed at one of the ground sites in the MCMA, was used to examine the expected evolution of specific VOCs over a 1–2 day period. The models clearly supported the experimental evidence for NMHC oxidation leading to the formation of OVOCs downwind, which then become the primary fuel for ozone production far away from the MCMA.
We analyze an expanded data set of oxygenated volatile organic compounds (OVOCs) in air measured by several instruments at a surface site in Pasadena near Los Angeles during the National Oceanic and ...Atmospheric Administration California Nexus study in 2010. The contributions of emissions, chemical formation, and removal are quantified for each OVOC using CO as a tracer of emissions and the OH exposure of the sampled air masses calculated from hydrocarbon ratios. The method for separating emissions from chemical formation is evaluated using output for Pasadena from the Weather Research and Forecasting‐Chemistry model. The model is analyzed by the same method as the measurement data, and the emission ratios versus CO calculated from the model output agree for ketones with the inventory used in the model but overestimate aldehydes by ~70%. In contrast with the measurements, nighttime formation of OVOCs is significant in the model and is attributed to overestimated precursor emissions and overestimated rate coefficients for the reactions of the precursors with ozone and NO3. Most measured aldehydes correlated strongly with CO at night, suggesting a contribution from motor vehicle emissions. However, the emission ratios of most aldehydes versus CO are higher than those reported in motor vehicle emissions and the aldehyde sources remain unclear. Formation of several OVOCs is investigated in terms of the removal of specific precursors. Direct emissions of alcohols and aldehydes contribute significantly to OH reactivity throughout the day, and these emissions should be accurately represented in models describing ozone formation.
Plain Language Summary
We report new measurements of volatile organic compounds (VOCs) in ambient air in the Los Angeles basin. Chemical reactions between VOCs and nitrogen oxides form ozone and fine particles, two important pollutants in Los Angeles smog. It is therefore important to understand VOC emission sources. In this work, we derive the composition of VOC emissions using ambient measurements at Pasadena in 2010. The study is complicated due to rapid chemical reactions that can form and remove VOCs in between the time of emission and measurement. After correcting for this chemistry, it is shown that emissions of many oxygen‐containing VOCs are important for the formation of ozone.
Key Points
An extensive and expanded data set of oxygenated VOCs in ambient air in the Los Angeles basin is analyzed
The composition of directly emitted oxygenated VOCs is determined after accounting for the effects of their chemical formation and removal
Aldehydes are important for urban photochemistry, but their sources remain poorly understood
Isoprene is the dominant nonmethane organic compound emitted to the atmosphere, where it drives ozone and aerosol production, modulates atmospheric oxidation, and interacts with the global nitrogen ...cycle. Isoprene emissions are highly variable and uncertain, as is the nonlinear chemistry coupling isoprene and its primary sink, the hydroxyl radical. Space‐based isoprene measurements can help close the gap on these uncertainties, and when combined with concurrent formaldehyde data provide a new constraint on atmospheric oxidation regimes. Here, we present a next‐generation machine‐learning isoprene retrieval for the Cross‐track Infrared Sounder (CrIS) that provides improved sensitivity, lower noise, and thus higher space‐time resolution than earlier approaches. The Retrieval of Organics from CrIS Radiances (ROCR) isoprene measurements compare well with previous space‐based retrievals as well as with the first‐ever ground‐based isoprene column measurements, with 20%–50% discrepancies that reflect differing sources of systematic uncertainty. An ensemble of sensitivity tests points to the spectral background and isoprene profile specification as the most relevant uncertainty sources in the ROCR framework. We apply the ROCR isoprene algorithm to the full CrIS record from 2012 to 2020, showing that it can resolve fine‐scale spatial gradients at daily resolution over the world's isoprene hotspots. Results over North America and Amazonia highlight emergent connections between isoprene abundance and daily‐to‐interannual variations in temperature and nitrogen oxides.
Plain Language Summary
Isoprene is a naturally occurring trace gas emitted primarily from the leaves of woody plants. Isoprene has important impacts on both air quality and climate; however, these impacts are difficult to assess and predict given large uncertainties in its sources and atmospheric chemistry. Space‐based measurements can help to address these uncertainties. Here, we present new satellite measurements of isoprene from the Cross‐track Infrared Sounder (CrIS), using a computationally efficient machine‐learning framework (Retrieval of Organics from CrIS Radiances; ROCR). ROCR measurements provide improved sensitivity and richer spatiotemporal information on atmospheric isoprene than was previously available. Results compare well to previous satellite‐based approaches and to new ground‐based observations. We apply the ROCR framework to measure daily, global isoprene distributions from 2012 to 2020. Results over North America and Amazonia highlight the processes controlling isoprene abundances and their variability over time.
Key Points
We present a next‐generation spaced‐based isoprene retrieval with higher sensitivity and resolution than previous approaches
Global, daily isoprene distributions are derived from 2012 to 2020 that compare well with the first ground‐based isoprene column observations
High‐resolution results over isoprene hotspots highlight processes controlling isoprene abundance and its daily‐to‐interannual variability
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 2–3 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)−1, while emission
factors averaged 0.66±0.50 g methylglyoxal (kg fuel burned)−1. 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)−1, while
emission factors averaged 0.20±0.12 g glyoxal (kg fuel burned)−1, 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.
Petroleum and dairy operations are prominent sources of gas-phase organic compounds in California's San Joaquin Valley. It is essential to understand the emissions and air quality impacts of these ...relatively understudied sources, especially for oil/gas operations in light of increasing US production. Ground site measurements in Bakersfield and regional aircraft measurements of reactive gas-phase organic compounds and methane were part of the CalNex (California Research at the Nexus of Air Quality and Climate Change) project to determine the sources contributing to regional gas-phase organic carbon emissions. Using a combination of near-source and downwind data, we assess the composition and magnitude of emissions, and provide average source profiles. To examine the spatial distribution of emissions in the San Joaquin Valley, we developed a statistical modeling method using ground-based data and the FLEXPART-WRF transport and meteorological model. We present evidence for large sources of paraffinic hydrocarbons from petroleum operations and oxygenated compounds from dairy (and other cattle) operations. In addition to the small straight-chain alkanes typically associated with petroleum operations, we observed a wide range of branched and cyclic alkanes, most of which have limited previous in situ measurements or characterization in petroleum operation emissions. Observed dairy emissions were dominated by ethanol, methanol, acetic acid, and methane. Dairy operations were responsible for the vast majority of methane emissions in the San Joaquin Valley; observations of methane were well correlated with non-vehicular ethanol, and multiple assessments of the spatial distribution of emissions in the San Joaquin Valley highlight the dominance of dairy operations for methane emissions. The petroleum operations source profile was developed using the composition of non-methane hydrocarbons in unrefined natural gas associated with crude oil. The observed source profile is consistent with fugitive emissions of condensate during storage or processing of associated gas following extraction and methane separation. Aircraft observations of concentration hotspots near oil wells and dairies are consistent with the statistical source footprint determined via our FLEXPART-WRF-based modeling method and ground-based data. We quantitatively compared our observations at Bakersfield to the California Air Resources Board emission inventory and find consistency for relative emission rates of reactive organic gases between the aforementioned sources and motor vehicles in the region. We estimate that petroleum and dairy operations each comprised 22% of anthropogenic non-methane organic carbon at Bakersfield and were each responsible for 8-13% of potential precursors to ozone. Yet, their direct impacts as potential secondary organic aerosol (SOA) precursors were estimated to be minor for the source profiles observed in the San Joaquin Valley.
Recent studies suggest overestimates in current U.S. emission inventories of nitrogen oxides (NO x = NO + NO2). Here, we expand a previously developed fuel-based inventory of motor-vehicle emissions ...(FIVE) to the continental U.S. for the year 2013, and evaluate our estimates of mobile source emissions with the U.S. Environmental Protection Agency’s National Emissions Inventory (NEI) interpolated to 2013. We find that mobile source emissions of NO x and carbon monoxide (CO) in the NEI are higher than FIVE by 28% and 90%, respectively. Using a chemical transport model, we model mobile source emissions from FIVE, and find consistent levels of urban NO x and CO as measured during the Southeast Nexus (SENEX) Study in 2013. Lastly, we assess the sensitivity of ozone (O3) over the Eastern U.S. to uncertainties in mobile source NO x emissions and biogenic volatile organic compound (VOC) emissions. The ground-level O3 is sensitive to reductions in mobile source NO x emissions, most notably in the Southeastern U.S. and during O3 exceedance events, under the revised standard proposed in 2015 (>70 ppb, 8 h maximum). This suggests that decreasing mobile source NO x emissions could help in meeting more stringent O3 standards in the future.
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