Browsing by Author "Fischer, Emily V., advisor"
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Item Open Access Daytime evolution of oxidized reactive nitrogen in western U.S. wildfire smoke plumes: in situ and satellite observations(Colorado State University. Libraries, 2020) Juncosa Calahorrano, Julieta Fernanda, author; Fischer, Emily V., advisor; Bond, Tami, committee member; Pierce, Jeffrey R., committee member; Ravishankara, A. R., committee memberThe Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN) deployed the NSF/NCAR C-130 aircraft in summer 2018 across the western U.S. to sample wildfire smoke during its first day of atmospheric evolution. We present a summary of a subset of oxidized nitrogen species (NOy) in plumes sampled in a pseudo-lagrangian fashion. Emissions of nitrogen oxides (NOx = NO + NO2) and nitrous acid (HONO) are rapidly converted to more oxidized forms. Within 4 hours, ∼86% of the measured NOy (∑ NOy) is in the form of peroxy acyl nitrates (PANs) (∼37%), particulate nitrate (pNO3) (∼26%) and gas-phase organic nitrates (∼23%). The average e-folding time and distance for NOx are ∼90 minutes and ∼40 km, respectively. Nearly no enhancements in nitric acid (HNO3) were observed in plumes sampled in a pseudo-lagrangian fashion, implying HNO3-limited ammonium nitrate (NH4NO3) formation, with one notable exception that we highlight as a case study. We also summarize the observed partitioning of ∑ NOy in all the smoke-impacted samples intercepted during WE-CAN. In the smoke-impacted samples intercepted below 3 km above sea level (ASL), HNO3 is the dominant form of ∑ NOy and its relative contribution increases with smoke age. Above 3 km ASL, the contributions of PANs and pNO3 to ∑ NOy increase with altitude. WE-CAN also sampled smoke from multiple fires mixed with anthropogenic emissions over the California Central Valley. We distinguish samples where anthropogenic NOx emissions appear to lead to an increase in NOx abundances by a factor of 4 and contribute to additional PAN formation. We utilize data from the Cross-Track Infrared Sounder (CrIS) on the Suomi National Polar-orbiting Partnership (Suomi-NPP) satellite, which continues the thermal infrared peroxyacetyl nitrate (PAN) satellite record established by the Tropospheric Emission Spectrometer (TES) onboard the Aura satellite. CrIS provides improved spatial resolution, allowing for improved analysis opportunities. Here we present an analysis of CrIS PAN retrievals over the western US during the summer 2018 wildfire season. The analysis period coincides with WE-CAN. CrIS is capable of detecting PAN and CO enhancements from smoke plumes sampled during WE-CAN, especially those that became active before the satellite overpass or burned for several days (e.g., Carr Fire, Mendocino Complex Fire). The analysis show that ∼40 - 70% of PAN over the western U.S. can be attributed to smoke from wildfires. The contribution of smoke from wildfires to free tropospheric PAN generally increases with latitude. We calculate peroxyacetyl nitrate (PAN) excess mixing ratios normalized by CO (NEMRs) in fresh smoke plumes from fires and follow the evolution as these plumes are transported several hours to days downwind. This analysis shows that elevated PAN within smoke plumes can be detected several states downwind from the fire source. The combination of high CrIS spatial resolution and favorable background conditions on 13 September 2018 permits detecting chemical changes within the Pole Creek smoke plume in Utah. In this plume, CrIS PAN NEMRs increase from < 1% to 3.5% within 3 - 4 hours of physical aging. These results are within the range observed in fresh plumes sampled during WE-CAN, where PAN NEMRs increased from 1.5% to 4% within 4 hours of physical aging.Item Open Access Emissions, evolution, and transport of ammonia (NH₃) from large animal feeding operations: a summertime study in northeastern Colorado(Colorado State University. Libraries, 2024) Juncosa Calahorrano, Julieta Fernanda, author; Fischer, Emily V., advisor; Collett, Jeffrey L., Jr., committee member; Pierce, Jeffrey R., committee member; Jathar, Shantanu H., committee memberThe Transport and Transformation of Ammonia (TRANS2Am) airborne field campaign occurred over northeastern Colorado during the summers of 2021 and 2022. TRANS2Am measured ammonia NH3 emissions from cattle feedlots and dairies with the goal of describing the near-field evolution of the NH3 emitted from animal feeding operations. Most of the animal husbandry facilities in Colorado are co-located with oil and gas development within the Denver-Julesburg basin, an important source of methane (CH4) and ethane (C2H6) in the region. Leveraging TRANS2Am observations, this dissertation presents estimates of NH3 emissions ratios with respect to CH4 (NH3 EmR), with and without correction of CH4 from oil and gas, for 29 feedlots and dairies in the region. The data show larger emissions ratios than previously reported in the literature with a large range of values (i.e., 0.1 - 2.6 ppbv ppbv-1). Facilities housing cattle and dairy had a mean (std) of 1.20 (0.63) and 0.29 (0.08) ppbv ppbv-1, respectively. NH3 emissions have a strong dependency with time of day, with peak emissions around noon and lower emissions earlier in the morning and during the evening. Only 15% of the total ammonia (NHx) is in the particle phase (i.e., NH4+) near major sources during the warm summer months. Finally, estimates of NH3 emission rates from 4 optimally sampled facilities range from 4 - 29 g NH3 · h-1 · hd-1. This work also investigates the nearfield evolution of NH3 in five plumes from large animal husbandry facilities observed during TRANS2Am using a mass balance approach with CH4 as a conservative tracer in the timescales of plume transport. Since the plumes in TRANS2Am were not sampled in a pseudo-lagrangian manner, an empirical model is needed to correct for variations in summertime NH3 emissions as a function of local time (LT) (CF = 1.87ln(LT) - 3.95). Results from the mass balance approach show that the average summertime NH3 decay time below 80% and 60% against deposition in plumes from large animal feeding operations is ~1 and ~2 hours, respectively. Additionally, we present estimates of deposition/emission fluxes every 5 km downwind of the plume. We found that deposition almost always happens in the first 10 km from the emission source. Beyond that, the complex environmental exchange of NH3 between the atmosphere and the surface suggests that fresh NH3 emissions from small nearby sources, water bodies, and crops/soil could contribute to sufficient NH3 to switch the direction of the flux (to emission). Large uncertainties still remain in emission and deposition fluxes, shining light on the need for more measurements in the region. To our knowledge, this is the first study presenting NH3 evolution in the atmosphere using a conservative tracer and airborne measurements. The second goal of TRANS2Am was to investigate easterly wind conditions capable of moving agricultural emissions of ammonia (NH3) through urban areas and into the Rocky Mountains. TRANS2Am captured 6 of these events, unveiling important commonalities. 1) NH3 enhancements are present over the mountains on summer afternoons when easterly winds are present in the foothills region. 2) The abundance of summertime gas-phase NH3 is 1 and 2 orders of magnitude higher than particle-phase NH4+ over the mountains and major agricultural sources, respectively. 3) During thermally driven circulation periods, emissions from animal husbandry sources closer to the mountains likely contribute more to the NH3 observed over the mountains than sources located further east. 4) Transport of summertime plumes from major animal husbandry sources in northeastern Colorado westward across the foothills requires ~5 hours. 5) Winds drive variability in the transport of NH3 into nearby mountain ecosystems, producing both direct plume transport and recirculation. A similar campaign in other seasons, including spring and autumn, when synoptic scale events can produce sustained upslope transport, would place these results in context.Item Open Access Estimating spatiotemporal trends in wildfire smoke concentrations in the western United States(Colorado State University. Libraries, 2018) O'Dell, Katelyn, author; Pierce, Jeffrey R., advisor; Fischer, Emily V., advisor; Ford, Bonne, committee member; Magzamen, Sheryl, committee memberThe United States (US) has seen significant improvements in seasonal air quality over the past several decades. However, particulate air quality in summer over the majority of the western US has seen little improvement in recent decades. Particulate matter with diameters < 2.5 microns (PM2.5) is a large component of ambient air quality that is associated with negative health effects and visibility degradation. Wildfires are a major summer source of PM2.5 in the western US. While anthropogenic-related sources of PM2.5 have decreased across the US, wildfires have increased in both frequency and burn area since the 1980s. It is currently uncertain how this increase in wildfires has impacted seasonal air quality trends and how the health effects of wildfire-emitted PM2.5 may differ from anthropogenic-sourced PM2.5. We do not directly address the latter uncertainty, but rather focus on improving smoke-exposure estimates, which are a critical, yet challenging, component to understanding the health effects of wildfire-emitted PM2.5. In this thesis, we use a combination of satellite estimates, surface observations, and chemical transport models to distinguish wildfire smoke PM2.5 from non-wildfire-smoke PM2.5 during the summer in the US. We update the record of seasonal trends in PM2.5 observed at surface monitors and provide the first estimates of trends in wildfire smoke-specific PM2.5. We find continued decreases in total-PM2.5 in most seasons and regions of the US. In the summer in heavily fire-impacted regions of the western US, we find non-decreasing total-PM2.5 while wildfire smoke-specific PM2.5 has increased and non-wildfire-smoke PM2.5 has decreased. We test the application of blended smoke exposure models, which use multiple data sources as input variables (e.g. satellite-derived aerosol optical depth, chemical transport models, etc.), across the full western US. We incorporate a novel dataset into the model, Facebook posts, which have been shown to correlate well with surface PM2.5 concentrations during the western US wildfire season. We find the blended smoke exposure model performs well across the western US (R2 = 0.66). However, the Facebook dataset is well correlated with interpolated surface monitors (another input variable) and thus does not significantly improve blended smoke-exposure estimates in the western US.Item Open Access Health-relevant pollutants in US landscape fire smoke: abundance, health impacts, and influence on indoor and outdoor air quality(Colorado State University. Libraries, 2021) O'Dell, Katelyn, author; Pierce, Jeffrey R., advisor; Fischer, Emily V., advisor; Collett, Jeffrey L., Jr., committee member; Ford, Bonne, committee member; Magzamen, Sheryl, committee memberLandscape (wild, prescribed, and agricultural) fires have a significant impact on air quality in the United States (US). As anthropogenic emissions decline and emissions from landscape fires increase across the coming century, the relative importance of landscape fire smoke on US air quality and health will increase. Landscape fire smoke is a complex mixture of multiple gas- and particle-phase pollutants, which are harmful to human health. The health impacts of landscape fire smoke may differ from urban pollution as the seasonal and spatial distribution, particle size distribution and composition, and relative abundance of gas-phase species in landscape fire smoke are different from urban pollution sources. Epidemiology studies of smoke events, which often rely on particulate matter (PM) concentrations as a smoke exposure tracer, show smoke negatively impacts respiratory health. The contribution of gas-phase hazardous air pollutants (HAPs) to the health impacts of smoke has yet to be directly quantified. In addition, the implications of episodic landscape fire emissions on the sub-national temporal and spatial distribution of health events are not well characterized. Finally, a majority of the work on the health and air quality impacts of landscape fire smoke has focused on outdoor air. Recent works have shown that landscape fire smoke can impact indoor air quality, but there is large heterogeneity in both smoke events and the indoor environments impacted by smoke events. To date, no study of US wildfire smoke influence on indoor air quality has analyzed indoor fine particulate matter (PM2.5) concentrations across multiple western US cities during multiple extreme smoke events. In the first chapter of this dissertation, we combine aircraft-based in-situ smoke plume observations with interpolated regulatory surface monitor observations to quantify the health risk of HAPs in US smoke. Using observations from the Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN), a 2018 aircraft-based field campaign that measured HAPs and PM in western US wildfire smoke plumes, we identify the relationships be- tween HAPs and associated health risks, PM, and smoke age. We find the ratios between acute, chronic noncancer, and chronic cancer HAPs health risk and PM in smoke decrease as a function of smoke age by up to 72% from fresh (<1 day of aging) to old (>3 days of aging) smoke. We show that acrolein, formaldehyde, benzene, and hydrogen cyanide are the dominant contributors to gas-phase HAPs risk in smoke plumes. We use ratios of HAPs to PM along with annual average smoke-specific PM to estimate current and potential future smoke HAPs risks. Next, we use a health impact assessment with observation-based smoke PM2.5 to determine the sub-national distribution of mortality and the sub-national and sub-annual distribution of morbidity attributable to US smoke PM2.5 from 2006-2018. We estimate disability-adjusted life years (DALYs) for PM2.5 and 18 gas-phase HAPs in smoke using the HAPs to PM ratios developed in Chapter 2. Although the majority of large landscape fires occur in the western US, we find the majority of mortality (74%) and morbidity (on average 75% across 2006-2018) attributable to smoke PM2.5 occurs outside the West due to a higher population density in the East. Across the US, smoke-attributable morbidity predominantly occurs in spring and summer. The number of DALYs associated with smoke PM2.5 are approximately three orders of magnitude higher than DALYs associated with gas-phase smoke HAPs. These results indicate that awareness and mitigation of landscape fire smoke exposure is important across the US, not just in regions in proximity to large wildfires. Finally, we use a large low-cost sensor network of indoor and outdoor PM2.5 monitors to characterize the relationship between indoor and outdoor air quality during smoke events. We identify smoke-impacted regions of the western US with a high density of co-located (distance < 1000 m) indoor and outdoor PurpleAir monitors. In these regions, we calculate indoor PM2.5/outdoor PM2.5 ratios on smoke-impacted and smoke-free days and find this ratio is < 1 (indoor PM2.5 less than outdoor PM2.5) at 98% of the monitor pairs for smoke-impacted days, compared to 54% on smoke- free days. On smoke-impacted days, indoor PM2.5 concentrations increase as outdoor PM2.5 Air Quality Index (AQI) increases by 25% per AQI bin, on average. However, the ratio of indoor PM2.5 to outdoor PM2.5 decreases by 28% per AQI bin. These results show that landscape fire smoke influences indoor air quality across many indoor environments in multiple cities, and this impact increases with smoke event intensity. In addition, this work highlights the utility of low-cost monitoring in quantifying indoor air quality during smoke events. However, we show that the present distribution of these indoor monitors suggests a bias towards census tracts of lower social vulnerability.Item Open Access Investigating contributions to elevated surface ozone in the Colorado Front Range during summer 2015(Colorado State University. Libraries, 2018) Lindaas, Jakob, author; Fischer, Emily V., advisor; Farmer, Delphine K., committee member; Ravishankara, A. R., committee memberTropospheric ozone (O3) is a significant pollutant in the Colorado Front Range. The northern Front Range metropolitan area (NFRMA) has exceeded the U.S. EPA national ambient air quality standard for O3 since 2008. While many regions in the country have experienced downward trends in ground-level O3, the NFRMA O3 mixing ratios have remained stagnant despite efforts to reduce precursor emissions. Rapid population growth and a boom in oil and natural gas development over the past 15 years have changed the quantity and spatial distributions of many important O3 precursors. O3 precursors may also be transported into the NFRMA, such as during wildfire smoke events. Here I use in situ measurements of O3, a suite of volatile organic compounds (VOCs), and reactive oxidized nitrogen species collected during summer 2015 at the Boulder Atmospheric Observatory (BAO) in Erie, CO, to investigate the contribution of different VOC sources to elevated surface O3 in the NFRMA. The first analysis combines observations of acyl peroxy nitrates (APN) and a previously described positive matrix factorization of the VOCs to investigate the contribution of different VOC sources to high O3 abundances at BAO. Based on the ratio of PPN to PAN, I find that anthropogenic VOC precursors dominate APN production when O3 is most elevated. Propane and higher alkanes, primarily from oil and natural gas emissions in the Colorado Front Range, drive elevated PPN to PAN ratios during high O3 events. The percentage of OH reactivity associated with oil and gas emissions is also positively correlated with O3 and PPN/PAN. Lastly, idealized box model simulations are used to probe the chemical mechanisms for these observations. I find that VOC precursor mixtures dominated by oil and gas emissions create abundant and more efficient peroxy radical intermediates compared to mixtures dominated by traffic or biogenic emissions. This work may help guide efforts to control O3 precursors in the NFRMA. The second analysis examines the impact of wildfire smoke on O3 abundances via a case study. Aged wildfire smoke impacted BAO during two distinct time periods during summer 2015: 6 – 10 July and 16 – 30 August. The smoke was transported from the Pacific Northwest and Canada across much of the continental U.S. Carbon monoxide and particulate matter increased during the smoke-impacted periods, along with acyl peroxy nitrates and several VOCs that have atmospheric lifetimes longer than the transport timescale of the smoke. During the August smoke-impacted period, nitrogen dioxide was also elevated during the morning and evening compared to the smoke-free periods. There were nine empirically defined high O3 days during our study period at BAO, and two of these days were smoke-impacted. I examined the relationship between O3 and temperature at BAO and found that for a given temperature, O3 mixing ratios were greater (~10 ppbv) during the smoke-impacted periods. Enhancements in O3 during the August smoke-impacted period were also observed at two long-term monitoring sites in Colorado: Rocky Mountain National Park and the Arapahoe National Wildlife Refuge near Walden, CO. Given that the relative importance of wildfire smoke for air quality over the western U.S. is expected to increase as the climate warms and anthropogenic emissions decline, this case study offers important insights into how aged wildfire smoke can influence atmospheric composition at an urban site.Item Open Access Observations of acyl peroxy nitrates during the Front Range air pollution and photochemistry éxperiment (FRAPPÉ)(Colorado State University. Libraries, 2016) Zaragoza, Jake, author; Fischer, Emily V., advisor; Collett, Jeffrey L., committee member; Farmer, Delphine, committee memberThe Colorado Front Range is an ozone (O3) nonattainment region. The photochemistry of the region is influenced by emissions from the urban and oil and gas sectors, the complex terrain, and the meteorology. The Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) was a field intensive carried out in the Colorado Front Range during summer 2014 to characterize the regional chemical environment. Acyl peroxy nitrates (PANs) play important roles in atmospheric chemistry, acting as either sinks or sources for nitrogen oxides (NOx) depending on conditions. PANs and other trace gas species were measured at the Boulder Atmospheric Observatory (BAO) during FRAPPÉ. Situated at the southwestern edge of the Denver-Julesburg Basin and 35 km north of Denver, BAO has been the site of multiple field studies aiming to characterize the influence of emissions from the oil and gas sector. Here we focus on an analysis of the PANs measurements from BAO during FRAPPÉ. In particular, we focus on peroxyacetic nitric anhydride (PAN, CH3C(O)O2NO2), peroxymethacrylic nitric anhydride (MPAN, CH2C(CH3)C(O)O2NO2) and peroxypropionic nitric anhydride (PPN, CH3CH2C(O)O2NO2). Mean and maximum PAN mixing ratios (5-minute point) were 275 and 1519 pptv respectively. There were four days during FRAPPÉ where the observed PAN abundance exceeded 1 ppbv. These days were examined using FLEXible PARTicle dispersion model (FLEXPART) back trajectories in order to determine air mass origin. The high PAN days occurred when air masses were recirculating in the region, often under Denver Cyclones. However, a visual inspection of FLEXPART trajectories throughout FRAPPÉ showed that recirculation events in the region occurred on days with high (>1 ppbv), moderate (500 pptv − 1 ppbv), and low (<500 pptv) afternoon PAN mixing ratios. The PPN/PAN ratio observed at the BAO tower during the summer of 2014 was 21%, which suggests anthropogenically enhanced photochemical activity. The ratio was very consistent (R2 = 92%) and not dependent on wind direction, potentially reflecting a lack of variability in regional non-methane volatile organic compound (NMVOC) chemistry. The MPAN/PAN ratio was <5%, indicating that isoprene oxidation had very little influence on photochemistry compared to many other regions in the U.S. The relative abundances of PPN and MPAN were used to estimate the contribution of isoprene oxidation to local O3 production. It was found that the contribution to local O3 from isoprene oxidation was consistently less than 20%. The findings of this study suggest that anthropogenic emissions are the key drivers of PANs and O3 formation in the region.Item Open Access Spatiotemporal variability of peroxy acyl nitrates (PANs) over megacities from satellite observations(Colorado State University. Libraries, 2023) Shogrin, Madison J., author; Fischer, Emily V., advisor; Payne, Vivienne H., committee member; Pierce, Jeffrey, committee member; Miller, Steven, committee member; Magzamen, Sheryl, committee memberPeroxy acyl nitrates (PANs) are photochemical pollutants with implications for health and atmospheric oxidation capacity. PANs are formed via the oxidation of non-methane volatile organic compounds (NMVOCs) in the presence of nitrogen oxide radicals (NOx = NO + NO2). PANs serve as reservoir species and sources for NOx in outflow regions of megacities, facilitating O3 production downwind. While urban environments are large sources of PANs, in-situ observations in urban areas are generally limited. Here we use satellite measurements of PANs from the Tropospheric Emission Spectrometer (TES) and the S-NPP Cross-Track Infrared Sounder (CrIS) to evaluate the spatiotemporal variability of PANs over and surrounding 9 megacities: Mexico City, Beijing, Los Angeles, Tokyo, São Paulo, Delhi, Mumbai, Lagos, and Karachi. We use monthly mean values of PANs to determine the seasonal cycle within the urban center of megacities. We find pronounced seasonal cycles of PANs in megacities and seasonal maxima in PANs correspond to seasonal peaks in local photochemical activity. Local fire activity can explain some of the observed interannual variability in PANs over and around megacities. We use S-NPP CrIS data to probe the spatial outflow pattern of PANs produced within urban Mexico City during the month with the largest mixing ratios of PANs (April). Peak outflow in April occurs to the northeast of the city and over the mountains south of the city. Outflow to the northwest appears infrequent. CrIS is used to further explore changes in PANs associated with substantial declines in megacity NOx in response to the COVID-19 pandemic. We only identify two cities over which PANs changed significantly in response to NOx perturbations: Beijing and Los Angeles. This work demonstrates that the space-based observations provided by CrIS and TES can increase understanding of the spatiotemporal variability and sensitivity to precursor emissions of PANs over and around global megacities.Item Embargo The abundance and sources of ice nucleating particles (INPs) within Alaskan ice fog(Colorado State University. Libraries, 2024) Lill, Emily, author; Fischer, Emily V., advisor; Creamean, Jessie, advisor; Kreidenweis, Sonia, committee member; Wall, Diana, committee memberFairbanks, Alaska often experiences low visibility due to air pollution. Low wind speeds and strong temperature inversions paired with local emissions from burning of wood, oil, gasoline, and coal lead to wintertime pollution events where concentrations of fine particulate matter (PM2.5) often reach 50 μg m-3, exceeding the Environmental Protection Agency (EPA) 24-hour National Ambient Air Quality Standard (NAAQS) of 35 μg m-3. When temperatures fall below -15°C and sufficient moisture is present, these pollution events can facilitate the formation of ice fog, further worsening air quality and visibility issues for aviation and transportation. The formation of ice crystals from supercooled droplets is aided by a small, but critical, number of aerosol particles that potentially act as ice nucleating particles (INPs). However, studies evaluating the quantities and sources of INPs during ice fog are limited. The Alaskan Layered Pollution and Chemical Analysis (ALPACA) field campaign included the deployment of a suite of atmospheric measurements in January - February 2022 with the goal of better understanding atmospheric processes and pollution under cold and dark conditions. We report on measurements of particle composition, particle size, INP composition, and INP size during an ice fog period (29 January - 3 February). There was a 153% increase in coarse particulate matter (PM10) during the ice fog period, associated with a decrease in air temperature. Results also show a 58% decrease in INPs active at -15°C during the ice fog period, indicating that particles were scavenged by ice fog ice crystals, likely via nucleation. Peroxide and heat treatments were performed on INPs in order to determine the fraction of INPs that were biological, organic, or inorganic. One hypothesis consistent with the results of the peroxide treatments is that more efficient INPs derived from biological materials or organics that typically activate at warmer freezing temperatures may have been depleted during the ice fog event. The reduction in heat-labile INPs during the ice fog event was unexpected for Fairbanks in the winter due to the very low temperatures and limited biological aerosol sources. Aerosol compositional measurements corroborate the presence of INPs from biomass burning and road dust.Item Open Access The influence of prescribed burning on springtime PM2.5 concentrations in eastern Kansas(Colorado State University. Libraries, 2023) Sablan, Olivia, author; Fischer, Emily V., advisor; Pierce, Jeffrey R., advisor; Magzamen, Sheryl, committee member; Ford, Bonne, committee memberAnnual springtime (March - May) prescribed burning is practiced in the Flint Hills of eastern Kansas to mitigate wildfire risk, improve nutritional value of vegetation for cattle grazing, limit woody encroachment, and maintain the health of the tall grass prairie ecosystem. Smoke from these prescribed fires produces fine particulate matter (PM2.5), degrading air quality. Smoke from prescribed fires is understudied due to their short duration and a lack of monitoring in the rural regions where prescribed burning occurs. To quantify the contribution of springtime prescribed burning to PM2.5 concentrations in the Flint Hills and downwind regions, we deployed 38 PurpleAir PM2.5 sensors for the 2022 burning season. We used observations from this ground-based network alongside a suite of satellite products to determine the PM2.5 attributable to smoke. In 2022, the Flint Hills were also impacted by dust and transported smoke from high winds, drought, and wildfires in New Mexico. We separated the local and transported smoke effects for our exposure estimates. Across the low-cost sensor network, 24-hour median PM2.5 increased by 5.2 µg m-3 on days impacted by smoke from fires in the eastern Kansas region versus smoke-free days. We compared our findings to two existing PM2.5 estimates derived from satellites and ground-based measurements. Satellite-based products show a similar daily smoke-driven median increase in PM2.5 concentration and a consistent increase in seasonal average PM2.5 concentrations in the Flint Hills region as our estimates based on in situ monitors.Item Open Access Using operational HMS smoke observations to gain insights on North American smoke transport and implications for air quality(Colorado State University. Libraries, 2016) Brey, Steven J., author; Fischer, Emily V., advisor; Barnes, Elizabeth, committee member; Pierce, Jeffrey, committee member; Rocca, Monique, committee memberWildfires represent a major challenge for air quality managers, as they are large sources of particulate matter (PM) and ozone (O3) precursors, and they are highly dynamic and transient events. Smoke can be transported thousands of kilometers to deteriorate air quality over large regions. Under a warming climate, fire severity and frequency are likely to in- crease, exacerbating an existing problem. Using the National Environmental Satellite, Data and Information Service (NESDIS) Hazard Mapping System (HMS) smoke data for the U.S. and Canada for the period 2007 to 2014, I examine a subset of fires that are confirmed to have produced sufficient smoke to warrant the initiation of a National Weather Service smoke forecast. The locations of these fires combined with Hybrid Single Particle Lagragian Integrated Trajectory Model (HYSPLIT) forward trajectories, satellite detected smoke plume data, and detailed land-cover data are used to develop a climatology of the land- cover, location, and seasonality of the smoke that impacts the atmospheric column above 10 U.S. regions. I examine the relative contribution of local versus long-range transport to the presence of smoke in different regions as well as the prevalence of smoke generated by agricultural burning versus wildfires. This work also investigates the influence of smoke on O3 abundances over the contiguous U.S. Using co-located observations of particulate matter and the NESDIS HMS smoke data, I identify summertime days between 2005 and 2014 that Environmental Protection Agency Air Quality System O3 monitors are influenced by smoke. I compare O3 mixing ratio distributions for smoke-free and smoke-impacted days for each monitor, while accounting for temperature. This analysis shows that (i) the mean O3 abundance measured on smoke-impacted days is higher than on smoke-free days at 20% of monitoring locations, and (ii) the magnitude of the difference between smoke-impacted and smoke-free mixing ratios varies by location and is sensitive to the minimum temperature allowed for smoke-free days. For each site, I present the percentage of days when the 8-hr average O3 mixing ratio (MDA8) exceeds 75 ppbv and smoke is present. When our most lenient temperature criteria are applied to smoke-free days, smoke-impacted O3 mixing ratios are most elevated in locations with the highest emissions of nitrogen oxides. The Northeast corridor, Dallas, Houston, Atlanta, Birmingham, and Kansas City stand out as having smoke present 10-20% of the days when 8-hr MDA8 O3 mixing ratios exceed 75 ppbv. Most U.S. cities maintain a similar proportion of smoke-impacted exceedance days when they are held against the new MDA8 limit of 70 ppbv.