Faculty Advisor: Dr. Donald Blake, University of California, Irvine

Graduate Mentor: Katherine Paredero, Georgia Institute of Technology

Katherine Paredero, Graduate Mentor

Mikaela Vaughn

Urban Planning Initiative: Investigation of Isoprene Emissions by Tree Species in the LA Basin

Mikaela Vaughn, Virginia Commonwealth University

Elevated ozone concentrations have been a concern in Southern California for decades. The interaction between volatile organic compounds (VOC) and nitrous oxides (𝑁𝑂!) in the presence of sunlight leads to enhanced formation of tropospheric ozone (𝑂”) and secondary organic aerosols (SOA). This can lead to increased health hazards, exposing humans to aerosols that can enter and be absorbed by the lungs, as well as a warming effect caused by ozone’s role as a greenhouse gas in the lower levels of the atmosphere. This study will focus on a VOC that is of particular interest, isoprene, which has an atmospheric lifetime of one hour, making it highly reactive in the presence of the hydroxyl radical (OH) and resulting in rapid ozone formation. Isoprene is a biogenic volatile organic compound (BVOC) emitted by vegetation as a byproduct of photosynthesis. This BVOC has been overlooked but should be investigated further because of its potential to form large sums of ozone. In this study the reactivity of isoprene with OH dominated ozone formation as compared to other VOCs. Ambient isoprene concentrations were measured aboard NASA’s airborne science laboratory (King Air B200) along with whole air sampling canisters. Additionally, isoprene emissions of varying tree species, with one to three samples per type, were compared to propose certain trees to plant in urban areas. Results indicated that Northern Red Oaks and the Palms family emitted the most isoprene out of the nineteen species documented. The species with the lowest observed isoprene emissions was the Palo Verde and the Joshua trees. The difference in isoprene emissions between the Northern Red Oak and Joshua trees is approximately by a factor of 45. These observations show the significance of considering isoprene emissions when selecting tree species to plant in the LA Basin to combat tropospheric ozone formation.

Joshua Lozano

VOC Composition and Ozone Formation Potential Observed Over Long Beach, California

Joshua Lozano, Sonoma State University

Volatile organic compounds (VOCs), when released into the atmosphere, undergo chemical reactions in the presence of sunlight that can generate tropospheric ozone, which can have various health effects. We can gauge this ozone formation by multiplying the observed mixing ratios of VOCs by their respective rate constants (with respect to OH radicals). The OH radical reacts very quickly in the atmosphere and accounts for a large sum of ozone formation from VOCs as a result, giving us an idea of the ozone formation potential (OFP) for each VOC. In this study, we investigate observed mixing ratios of VOCs in order to estimate their contribution to OFP over Long Beach, California. The observed species of VOCs with the highest mixing ratios differs from the observed species with the highest OFP, which highlights that higher mixing ratios of certain VOCs in the atmosphere do not necessarily equate to a higher contribution to ozone formation. This underscores the importance of understanding mixing ratios of VOC species and their reaction rates with OH to gauge impacts on ozone formation. In the summer there were significantly lower VOC concentrations compared to the winter, which was expected because of differences in boundary layer height within the seasons. Additionally, a decrease in average mixing ratios was observed between the summer of 2014 and the summer of 2022. A similar trend was observed in OFP, but by a much smaller factor. This may indicate that even though overall VOC emissions are decreasing in Long Beach, the species that dominate in recent years have a higher OFP. This research provides a more comprehensive view of how VOCs contribute to air quality issues across different seasons and over time, stressing the need for targeted strategies to mitigate ozone pollution based on current and accurate VOC composition and reactivity.

Sean Breslin

Investigating Enhanced Methane and Ethane Emissions over the Long Beach Airport

Sean Breslin, University of Delaware

As climate change continues to worsen, the investigation and tracking of greenhouse gas emissions has become increasingly important. Methane, the second most impactful greenhouse gas, has accounted for over 20% of planetary warming since preindustrial times. Methane emissions primarily originate from biogenic and thermogenic sources, such as dairy farms and natural gas extraction. Ethane, an abundant hydrocarbon emitted from biomass burning and natural gas, contributes to the formation of tropospheric ozone. The data for this project was collected in December 2021 and June 2022 aboard the DC-8 aircraft, where whole air samples were taken during low approaches to find potential sources of methane and ethane emissions. Analysis of these samples using gas chromatography revealed a noticeable increase in methane and ethane concentrations over Long Beach Airport, an area surrounded by numerous plugged oil and gas wells extracting crude oil and natural gas. In this study, we observe that methane and ethane concentrations were lower in the summer and higher in the winter, which can be primarily attributed to seasonal variations in the Atmospheric Boundary Layer height. Our results show that in both summer and winter campaigns, the ratio of these two gases over the airport was approximately 0.03, indicating that for every 100 methane molecules, there are 3 ethane molecules. This work identifies methane and ethane hotspots and provides a critical analysis on potential fugitive emission sources in the Long Beach area. These results emphasize a need to perform in depth analyses on potential point sources of greenhouse gas emissions in the Long Beach area.

Katherine Skeen

Investigating Elevated Levels of Toluene during Winter in the Imperial Valley

Katherine Skeen, University of North Carolina at Charlotte

The Imperial County in Southern California experiences pollutants that do not meet the National Ambient Air Quality Standards, and as a result, residents are suffering from adverse health effects. Volatile organic compounds (VOCs) are compounds with a high vapor pressure at room temperature. They are readily emitted into the atmosphere and form ground level ozone. Toluene is a VOC and exposure poses significant health risks, including neurological and respiratory effects. This study aims to use airborne data to investigate areas with high toluene concentrations and investigate potential source. Flights over the Imperial Valley were conducted in the B200 King Air. Whole air canisters were used to collect ambient air samples from outside the plane. These Whole Air Canisters were put through the UCI Rowland Blake Lab’s gas chromatograph mass spectrometer, which identifies different gasses and quantifies their concentrations. Elevated values of toluene were found in the winter as compared to the summer in the Imperial Valley, with the town of Brawley having the most elevated amounts in the air. Excel and QGIS were utilized to analyze data trends. Additionally, a backward trajectory calculated using the NOAA HYSPLIT model revealed the general air flow on days exhibiting high toluene concentrations. Here we suggest Long Beach may be a source of enhanced toluene levels in Brawley. Both areas exhibited enhanced levels of toluene with slightly lower concentrations observed in Brawley. We additionally observed other VOCs commonly emitted in urban areas, and saw a similar decrease in gasses from Long Beach to Brawley. This trend may indicate transport of toluene from Long Beach to Brawley. Further research could be done to investigate the potential for other regions that may contribute to high toluene concentrations in Brawley. My study contributes valuable insights to the poor air quality in the Imperial Valley, providing a foundation for future studies on how residents are specifically being affected.

Ella Erskine

Characterizing Volatile Organic Compound (VOC) Emissions from Surface Expressions of the Salton Sea Geothermal System (SSGS)

Ella Erskine, Tufts University

At the southeastern end of the Salton Sea, surface expressions of an active geothermal system are emitting an assemblage of potentially toxic and tropospheric ozone-forming gasses. Gas measurements were taken from ~1 to 8 ft tall mud cones, called gryphons, in the Davis-Schrimpf seep field (~50,000 ft2). The gaseous compounds emitted from the gryphons were collected using whole air sampling canisters. The canisters were then sent to the Rowland-Blake laboratory for analysis using gas chromatography techniques. Samples from June of 2022, 2023, and 2024 were utilized for a time-series analysis of VOC distribution. Originally, an emission makeup similar to petroleum was expected, as it has previously been found in some of the seeps. It is thought that hydrothermal fluid can rapidly mature organic matter into hydrothermal petroleum, so it is logical that the emission makeup could be similar. However, unexpectedly high levels of the VOC benzene were recorded, unlike concentrations generally observed in crude oil emissions. This may indicate a difference between the two sources in regard to their formation process or parent material composition. A possible cause of the elevated benzene could be its relatively high aqueous solubility compared to other hydrocarbons, which could allow it to be more readily incorporated into the hydrothermal fluid. Since the gryphons attract almost daily visitors, it is important to quantify their human health effects. Benzene harms the bone marrow, which can result in anemia. It is also a carcinogen. Additionally, benzene can react with the OH radical to form ozone, an additional health hazard. Future studies should revisit the Davis-Schrimpf field to continue the time series analysis and collect samples of the water seeps. Additionally, drone and ground studies should be conducted in the geothermal power plant adjacent to the gryphons to determine if benzene is being emitted from drilling activities.

Amelia Brown

Airborne and Ground-Based Analysis of Los Angeles County Landfill Gas Emissions

Amelia Brown, Hamilton College

California has the highest number of landfills of any individual US state. These landfills are concentrated in densely populated areas of California, especially within the Los Angeles metropolitan area. Landfills produce three main byproducts: heat, leachate, and landfill gas (LFG). LFG is primarily composed of methane (CH₄) and carbon dioxide (CO₂), with small concentrations of volatile organic compounds (VOCs) and other trace gases. The CH4 and CO2 components of LFG are well documented, but the VOCs and trace gases in LFG remain underexplored. This study investigates the emission of trace gases from four landfills in Los Angeles County, with a particular focus on substances known to have high Ozone Depletion Potentials (ODPs) and Global Warming Potentials (GWPs). The four landfills sampled were Chiquita Canyon Landfill, Lopez Canyon Landfill, Sunshine Canyon Landfill, and Toyon Canyon Landfill. Airborne samples were taken above the four landfills and ground samples were taken at Lopez Canyon as this was the only site accessible by our research team. The substances of interest were chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), and halons. Airborne CH4 and CO2 measurements over the four landfills were obtained using the Picarro instrument onboard NASA’s B-200 aircraft. Ground samples were collected using whole air sampling canisters and were analyzed to determine the concentrations of these gases. The analytical approach for the ground samples combined Gas Chromatography-Mass Spectrometry (GCMS) with Flame Ionization Detection (FID) and Mass Selective Detection (MSD), providing a comprehensive profile of the emitted compounds. Findings reveal elevated levels of substances with high ODP and GWP, which were banned under the Montreal Protocol of 1987 and its subsequent amendments due to their contributions to stratospheric ozone depletion and climate change. These results underscore the importance of monitoring and mitigating landfill gas emissions, particularly for those containing potent greenhouse gases and ozone-depleting substances.

Click here watch the Atmospheric Aerosols Group presentations.

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