17 research outputs found
Emissions of volatile organic compounds (VOCs) from concentrated animal feeding operations (CAFOs): chemical compositions and separation of sources
No full textConcentrated 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
Variability of Ammonia and Methane Emissions from Animal Feeding Operations in Northeastern Colorado
No full textInterannual variability of ammonia concentrations over the United States: sources and implications
No full textInternational audienceThe variability of atmospheric ammonia (NH3), emitted largely from agricultural sources, is an important factor when considering how inorganic fine particulate matter (PM2.5) concentrations and nitrogen cycling are changing over the United States. This study combines new observations of ammonia concentration from the surface, aboard aircraft , and retrieved by satellite to both evaluate the simulation of ammonia in a chemical transport model (GEOS-Chem) and identify which processes control the variability of these concentrations over a 5-year period (2008–2012). We find that the model generally underrepresents the ammonia concentration near large source regions (by 26 % at surface sites) and fails to reproduce the extent of interannual variability observed at the surface during the summer (JJA). Variability in the base simulation surface ammonia concentration is dominated by meteorology (64 %) as compared to reductions in SO2 and NOx emissions imposed by regulation (32 %) over this period. Introduction of year-to-year varying ammonia emissions based on animal population, fertilizer application, and meteorologically driven volatilization does not substantially improve the model comparison with observed ammonia concentrations, and these ammonia emissions changes have little effect on the simulated ammonia concentration variability compared to those caused by the variability of meteorology and acid-precursor emissions. There is also little effect on the PM2.5 concentration due to ammonia emissions variability in the summer when gas-phase changes are favored , but variability in wintertime emissions, as well as in early spring and late fall, will have a larger impact on PM2.5 formation. This work highlights the need for continued improvement in both satellite-based and in situ ammonia measurements to better constrain the magnitude and impacts of spatial and temporal variability in ammonia concentrations
Evaluation of the accuracy of thermal dissociation CRDS and LIF techniques for atmospheric measurement of reactive nitrogen species
No full textAbstract. The sum of all reactive nitrogen species (NOy) includes NOx (NO2 + NO) and all of its oxidized forms, and the accurate detection of NOy is critical to understanding atmospheric nitrogen chemistry. Thermal dissociation (TD) inlets, which convert NOy to NO2 followed by NO2 detection, are frequently used in conjunction with techniques such as laser-induced fluorescence (LIF) and cavity ring-down spectroscopy (CRDS) to measure total NOy when set at > 600 °C or speciated NOy when set at intermediate temperatures. We report the conversion efficiency of known amounts of several representative NOy species to NO2 in our TD-CRDS instrument, under a variety of experimental conditions. We find that the conversion efficiency of HNO3 is highly sensitive to the flow rate and the residence time through the TD inlet as well as the presence of other species that may be present during ambient sampling, such as ozone (O3). Conversion of HNO3 at 400 °C, nominally the set point used to selectively convert organic nitrates, can range from 2 to 6 % and may represent an interference in measurement of organic nitrates under some conditions. The conversion efficiency is strongly dependent on the operating characteristics of individual quartz ovens and should be well calibrated prior to use in field sampling. We demonstrate quantitative conversion of both gas-phase N2O5 and particulate ammonium nitrate in the TD inlet at 650 °C, which is the temperature normally used for conversion of HNO3. N2O5 has two thermal dissociation steps, one at low temperature representing dissociation to NO2 and NO3 and one at high temperature representing dissociation of NO3, which produces exclusively NO2 and not NO. We also find a significant interference from partial conversion (5–10 %) of NH3 to NO at 650 °C in the presence of representative (50 ppbv) levels of O3 in dry zero air. Although this interference appears to be suppressed when sampling ambient air, we nevertheless recommend regular characterization of this interference using standard additions of NH3 to TD instruments that convert reactive nitrogen to NO or NO2.
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Observations of VOC Emissions and Photochemical Products Over US Oil- and Gas-Producing Regions Using High-Resolution H3O+ CIMS (PTR-ToF-MS)
No full textAbstract. VOCs related to oil and gas extraction operations in the United States were measured by H3O+ chemical ionization time-of-flight mass spectrometry (H3O+ ToF-CIMS/PTR-ToF-MS) from aircraft during the Shale Oil and Natural Gas Nexus (SONGNEX) campaign in March–April 2015. This work presents an overview of major VOC species measured in nine oil- and gas-producing regions, and a more detailed analysis of H3O+ ToF-CIMS measurements in the Permian Basin within Texas and New Mexico. Mass spectra are dominated by small photochemically produced oxygenates and compounds typically found in crude oil: aromatics, cyclic alkanes, and alkanes. Mixing ratios of aromatics were frequently as high as those measured downwind of large urban areas. In the Permian, the H3O+ ToF-CIMS measured a number of underexplored or previously unreported species, including aromatic and cycloalkane oxidation products, nitrogen heterocycles including pyrrole (C4H5N) and pyrroline (C4H7N), H2S, and a diamondoid (adamantane) or unusual monoterpene. We additionally assess the specificity of a number of ion masses resulting from H3O+ ion chemistry previously reported in the literature, including several new or alternate interpretations.Version of Recor
Observations of VOC Emissions and Photochemical Products over US Oil- and Gas-Producing Regions Using High-Resolution H3O+ CIMS (PTR-ToF-MS)
No full textVOCs (Volatile Organic Compounds) related to oil and gas extraction operations in the United States were measured by H3O (sup plus) chemical ionization time-of-flight mass spectrometry (H3O (sup plus) ToFCIMS/PTR-ToF-MS (Time of Flight Chemical Ionization Mass Spectrometry/Proton Transfer Reaction-Time of Flight-Mass Spectroscopy) from aircraft during the Shale Oil and Natural Gas Nexus (SONGNEX) campaign in March-April 2015. This work presents an overview of major VOC species measured in nine oil- and gas-producing regions, and a more detailed analysis of H3O (sup plus) ToF-CIMS measurements in the Permian Basin within Texas and New Mexico. Mass spectra are dominated by small photochemically produced oxygenates and compounds typically found in crude oil: aromatics, cyclic alkanes, and alkanes. Mixing ratios of aromatics were frequently as high as those measured downwind of large urban areas. In the Permian, the H3O (sup plus) ToF-CIMS measured a number of underexplored or previously unreported species, including aromatic and cycloalkane oxidation products, nitrogen heterocycles including pyrrole (C4H5N) and pyrroline (C4H7N), H2S, and a diamondoid (adamantane) or unusual monoterpene. We additionally assess the specificity of a number of ion masses resulting from H3O (sup plus) ion chemistry previously reported in the literature, including several new or alternate interpretations
Observations of VOC emissions and photo chemical products over US oil- and gas-producing regions using high-resolution H&lt;sub&gt;3&lt;/sub&gt;O&lt;sup&gt;+&lt;/sup&gt; CIMS (PTR-ToF-MS)
No full textAbstract. VOCs related to oil and gas extraction operations in the United States were measured by H3O+ chemical ionization time-of-flight mass spectrometry (H3O+ ToF-CIMS / PTR-ToF-MS) from aircraft during the SONGNEX campaign in March–April 2015. This work presents an overview of major VOC species measured in nine oil and gas producing regions, and a more detailed analysis of H3O+ ToF-CIMS measurements in the Permian Basin within Texas and New Mexico. Mass spectra are dominated by small photochemically produced oxygenates, and compounds typically found in crude oil: aromatics, cyclic alkanes, and alkanes. Mixing ratios of aromatics were frequently as high as those measured downwind of large urban areas. In the Permian, the H3O+ ToF-CIMS measured a number of underexplored or previously unreported species, including aromatic and cycloalkane oxidation products, nitrogen heterocycles including pyrrole (C4H5N) and pyrroline (C4H7N), H2S, and a diamondoid (adamantane) or unusual monoterpene. We additionally assess the specificity of a number of ion masses resulting from H3O+ ion chemistry previously reported in the literature, including several new or alternate interpretations.
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Observations of VOC emissions and photochemical products over US oil- and gas-producing regions using high-resolution H₃O⁺ CIMS (PTR-ToF-MS)
No full textVOCs related to oil and gas extraction operations in the United States were measured by H₃O⁺ chemical ionization time-of-flight mass spectrometry (H₃O⁺ ToF-CIMS/PTR-ToF-MS) from aircraft during the Shale Oil and Natural Gas Nexus (SONGNEX) campaign in March–April 2015. This work presents an overview of major VOC species measured in nine oil- and gas-producing regions, and a more detailed analysis of H₃O⁺ ToF-CIMS measurements in the Permian Basin within Texas and New Mexico. Mass spectra are dominated by small photochemically produced oxygenates and compounds typically found in crude oil: aromatics, cyclic alkanes, and alkanes. Mixing ratios of aromatics were frequently as high as those measured downwind of large urban areas. In the Permian, the H₃O⁺ ToF-CIMS measured a number of underexplored or previously unreported species, including aromatic and cycloalkane oxidation products, nitrogen heterocycles including pyrrole (C₄H₅N) and pyrroline (C₄H₇N), H₂S, and a diamondoid (adamantane) or unusual monoterpene. We additionally assess the specificity of a number of ion masses resulting from H₃O⁺ ion chemistry previously reported in the literature, including several new or alternate interpretations.Abigail Koss acknowledges funding from the National Science Foundation (NSF) Graduate Fellowship Program. We thank the NOAA Aircraft Operations Center for their support with instrument installation on the NOAA WP-3D, research flights, and meteorological and aircraft data. We thank Ralf Staebler (Environment and Climate Change Canada) for the use of the Picarro H2S instrument. We thank Andy Neuman for his scientific advice and thoughtful comments on the manuscript. Thomas Hanisco, Glenn M. Wolfe, Jason M. St. Clair, Mitchell Thayer, and Frank N. Keutsch acknowledge NASA GEOstationary Coastal and Air Pollution Events (GEO-CAPE) award number NNX15AH83G for funding.https://amt.copernicus.org/articles/10/2941/2017
