Browsing by Author "Collett, Jeffrey L., Jr., advisor"
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Item Open Access Air quality impacts from unconventional oil and gas development(Colorado State University. Libraries, 2024) Ku, I-Ting, author; Collett, Jeffrey L., Jr., advisor; Fischer, Emily V., committee member; Carlson, Kenneth H., committee member; Kreidenweis, Sonia, committee memberUnconventional oil and natural gas development (UOGD) has expanded rapidly across the United States raising concerns about associated air quality impacts. While significant effort has been made to quantify and limit methane emissions, relatively few observations have been made of emitted Volatile Organic Compounds (VOCs). Extensive air monitoring during development of several large, multi-well pads in Broomfield, Colorado, in the Denver-Julesburg Basin, provides a novel opportunity to examine changes in local concentrations of air toxics and other VOCs during drilling and completions of new wells. With simultaneous measurements of methane and 50 VOCs from October 2018 to December 2022 at as many as 19 sites near well pads, in adjacent neighborhoods, and at a more distant reference location, we identify impacts from each phase of well development and production. In Part 1, we report how emissions from Broomfield pre-production and production operations influence air toxics and other VOC concentrations at nearby locations. Use of weekly, time-integrated canisters, a Proton Transfer Reaction Mass Spectrometer (PTR-MS), continuous photoionization detectors (PID) to trigger canister collection upon detection of VOC-rich plumes, and an instrumented vehicle, provided a powerful suite of measurements to characterize both transient plumes and longer-term changes in air quality. Prior to the start of well development, VOC gradients were small across Broomfield. Once drilling commenced, concentrations of oil and gas (O&G) related VOCs, including alkanes and aromatics, increased around active well pads. Concentration increases were clearly apparent during certain operations, including drilling, coil tubing/millout operations, and production tubing installation. Emissions of C8-C10 n-alkanes during drilling operations highlighted the importance of VOC emissions from a synthetic drilling mud chosen to reduce odor impacts. More than 90 transient plumes were sampled and connected with specific UOGD operations. The chemical signatures of these plumes differed by operation type. Concentrations of individual, O&G-related VOCs in these plumes were often several orders of magnitude higher than in background air, with maximum ethane and benzene concentrations of 79,600 and 819 ppbv, respectively. Study measurements highlight future emission mitigation opportunities during UOGD operations, including better control of emissions from shakers that separate drill cuttings from drilling mud, production separator maintenance operations, and periodic emptying of sand cans during flowback operations. In Part 2 OH reactivities (OHR) were calculated to examine the potential of emitted VOCs to contribute to regional ozone formation. NO2 was the largest contributor to OHR during winter when OHR values peaked, while VOCs dominated OH sinks during summer. Oxygenated VOCs and C3-C7 n-alkanes, closely associated with O&G activities, were primary contributors to OHR levels during the summer ozone season. In Part 3 we leverage observations from Broomfield and other Colorado O&G air quality studies to examine relationships between O&G emissions of methane and VOCs. A key goal is to determine whether more commonly measured methane emissions can serve as a surrogate to estimate emissions of less frequently measured compounds such as benzene, a key air toxic. While strong correlations are observed between benzene and methane emissions in some situations, considerable variability is observed in this relationship across locations and operations suggesting caution in assuming that reductions in methane emissions will yield proportionate reductions in releases of air toxics.Item Open Access Spatial patterns and particle size distributions of atmospheric amines in northern Colorado(Colorado State University. Libraries, 2020) Bangs, Evelyn J., author; Collett, Jeffrey L., Jr., advisor; Kreidenweis, Sonia, committee member; Carter, Ellison, committee member; Benedict, Katherine B., committee memberEmissions of reactive nitrogen along the Front Range in Northern Colorado have implications for sensitive and protected environments such as those in Rocky Mountain National Park (RMNP). Nitrogen-containing pollutants exert a variety of adverse effects on the environment, including visibility impairment and excessive nitrogen input to sensitive alpine ecosystems. Northern Colorado has many urban, agricultural, and oil and natural gas production activities that emit various forms of reactive nitrogen to the atmosphere. Model simulations and past measurements demonstrate that these emissions are capable of being transported long distances in gaseous and particulate forms. RMNP is particularly exposed to increased concentrations of reactive nitrogen pollutants during periods of easterly, upslope flow when emissions along the Front Range and sources from even farther away (e.g. the Western United States coast) are transported into the mountains. A detailed understanding of the composition of transported reactive nitrogen pollution is needed to predict environmental impacts within RMNP. While emissions of ammonia and nitrogen oxides have received significant attention in previous studies, relatively little is known about organic nitrogen pollution, despite its ability to contribute to excess N deposition and to formation of particulate matter (PM). Amines are organic analogs of ammonia, where one or more hydrogen atoms are replaced by organic functional groups. The animal agriculture industry is known to be a major source of some amines, while the beer and wine industry, sugar beet industry, leather manufacturing, and chemical manufacturing are also potentially important sources. Many of these industries are located along Colorado's Front Range, providing a good opportunity to study amine atmospheric chemistry. While the chemical lifetime of many gas phase amines is relatively short (hours), they are strong bases that can compete with ammonia to form longer-lived particles that are transported over substantial distances. The work carried out in this study focused on assessing a spatial gradient of particulate amines between RMNP, Fort Collins, and Greeley. Greater concentrations of many amines were typically observed near source emissions in Greeley and/or Fort Collins, but significant concentrations of amines such as dimethylamine, were also observed in the more remote environment at RMNP. To better understand amines, their chemistry and their contribution to PM, size distributions of 16 different amines were analyzed from measurements with a Micro-Orifice Uniform Deposit Impactor (MOUDI). Of 16 analyzed amines, nine were found above the detection limits in summertime Fort Collins and five during the winter. Several organic acids and inorganic acid anions particle size distributions were also assessed to understand contributions from potential anion species involved in salt formation with amine cations. Organic acid particle size distributions, particularly oxalate, overlap with fine particle mode size distributions of both ammonia and amine cations. The size distribution measurements also reveal important reactions between gaseous nitric acid and coarse soil particles to generate coarse mode nitrate particles. Continued measurements of amines and other species size distributions and spatial gradients at more locations would help improve understanding of amine PM chemistry. This understanding would allow necessary changes to be made to better protect the health of living beings and the sensitive ecosystems like those found in Rocky Mountain National Park.Item Open Access Summertime ozone production at Carlsbad Caverns National Park, New Mexico: influence of oil and natural gas development(Colorado State University. Libraries, 2023) Marsavin, Andrey, author; Collett, Jeffrey L., Jr., advisor; Fischer, Emily V., committee member; Willis, Megan D., committee memberSoutheastern New Mexico's Carlsbad Caverns National Park (CAVE) has increasingly experienced summertime ground-level ozone (O3) levels surpassing the US Environmental Protection Agency's National Ambient Air Quality Standard (NAAQS) of 70 parts per billion by volume (ppbv). The park is located in the western part of the Permian oil and natural gas (O&G) basin, where production rates have more than tripled in the last decade. We investigate O3–precursor relationships by constraining a zero-dimensional (0-D) model to an hourly nitrogen oxides (NOx = NO + NO2) and speciated volatile organic compound (VOC) data set collected at CAVE during the summer of 2019. O&G-related VOCs dominated the calculated VOC reactivity with hydroxyl radicals (OH) on days when O3 concentrations were primarily controlled by local photochemistry. Radical budget analysis showed that NOx levels were high enough to impose VOC sensitivity on O3 formation in the morning hours, while subsequent NOx loss through photochemical consumption led to NOx-sensitive conditions in the afternoon. Daily maximum O3 was sensitive to both NOx and O&G-related VOC emission reductions, with NOx reductions generally being more effective. The model could not reproduce a 5-day high O3 episode when constrained to observed NOx and primary VOCs, likely due to influence from O3 produced during air mass transport from regional O&G basins as indicated by back-trajectory analysis, low i/n-pentane ratios consistent with O&G emissions, increased concentrations of secondary VOCs, and extensive oxidation of emitted NOx. Constraining the model with observed total oxidized reactive nitrogen (NOy), which approximates NOx at the time of emission, greatly improves model-observation agreement during this episode, reaffirming NOx-sensitive conditions in photochemically aged air masses.Item Open Access Using modelling tools to advance the understanding of ammonia dry-deposition and bidirectional flux processes next to large animal feeding operations(Colorado State University. Libraries, 2020) Lassman, William, author; Pierce, Jeffrey R., advisor; Collett, Jeffrey L., Jr., advisor; Fischer, Emily V., committee member; Ham, Jay M., committee memberAmmonia in the atmosphere is a trace gas that can play a big role in the Earth's climate, as well as human and ecological health. Due to its stickiness and solubility, ammonia can enter the biosphere via wet and dry deposition, where excess ammonia input often results in soil acidification, disruption of natural ecological equilibria, and loss of biodiversity. Additionally, ammonia is the most abundant alkaline species in the atmosphere and can react with atmospheric acids to form aerosols, which can affect the earth's radiative balance as well as human health. Ammonia emissions tend to be associated with agricultural sources, such as fertilized fields or animal waste at concentrated Animal Feeding Operations (CAFOs). Consequently, ammonia emissions tend to be dynamic and highly heterogeneous, and ammonia surface-fluxes are difficult to measure. However, in regions with many large CAFOs, ammonia can be an important regional pollutant, especially if there are sensitive ecosystems or other regional sources of atmospheric acids present. In this dissertation, I study ammonia dry-deposition fluxes immediately downwind of CAFOs using a variety of modelling tools. First, I discuss original research where I use a coupled a K-epsilon model with a Lagrangian-Stochastic ammonia bidirectional exchange surface model to simulate the dispersion and deposition of ammonia downwind of an idealized CAFO. Based on these simulations, the amount of ammonia that undergoes dry deposition depends greatly on the land surface downwind of the CAFO; replacing bare soil or unmanaged grassland with leafier surfaces such as cropland or forests can increase the fraction of total ammonia emissions that deposits from 2 - 10% to 30 - 50%, though this is sensitive to the ammonia emission potential in the model plant canopy. Next, I describe a separate study where I use a 3-D Large-Eddy Simulation model to simulate the dispersion of ammonia and methane from a CAFO with a time-resolved modelling tool. I use this modelling system to produce synthetic observations, which are used to develop an inversion approach to quantify the ammonia dry deposition near a CAFO with colocated mobile measurements of ammonia and methane. While I demonstrate that such an inversion technique is feasible with surface-based measurements, considerable value is added, in terms of minimizing method bias and increasing method precision, by mounting measurements on a small Unmanned Aerial System (sUAS). Finally, I present measurements of PM2.5 concentration and composition that were made in Palapye, Botswana. Botswana is a developing country with a hot and arid climate. Beef and livestock production are important economic activities in Botswana; however, the agricultural practices differ considerably from the CAFOs discussed in the rest of the dissertation. Furthermore, these livestock activities occur against a backdrop of emissions and air pollutants that differ considerably from the United States and Europe. The measurements show that PM2.5 concentrations were on average 9 μg m-3 during the 5-week measurement period. While below levels that are typically considered hazardous, there was considerable variability in the measured concentrations, and the measurement period is too short to conclusively determine that air pollution is not a public health concern in this region. The aerosol composition is dominated by carbonaceous species, probably from biomass burning, though inorganic sulfate also is abundant in the aerosol phase. As Botswana continues to undergo economic development, the types of emissions and pollution present will continue to change.