Heterogeneous Aging Mechanisms of Combustion and Biomass Burning Emissions

Grants and Contracts Details


Natural and anthropogenic emissions of gaseous aromatic hydrocarbons (e.g., benzene, toluene, and anisole) from biomass burning, agro-industrial settings, and fossil fuel combustion contribute precursors to secondary aerosol formation (SOA). These aromatic hydrocarbons can react quickly with atmospheric hydroxyl radicals (HO) forming phenols (e.g., phenol, cresol, and methoxyphenol) and polyphenols (e.g., catechol, pyrogallol, 3-methylcatechol, 4-methylcatechol, and 3-methoxycatechol) of lower vapor pressure, which can condense on the surface of particles and are found of humic-like substances (HULIS). The further oxidative processing of these polyphenols can continue at atmospheric interfaces by new mechanisms caused by the action of ozone (O3), nitrate radical (NO3), and HO. However, explaining how these mechanisms operate at air/water and air/solid (under variable relative humidity) interfaces is a major challenge. Tackling such an effort will not only explain the fate of these pollutants but also generate new chemical understanding of processes operative in the troposphere that influence SOA formation affecting climate, visibility and air quality. The proposed project will investigate important heterogeneous oxidation pathways of polyphenols and will contribute new mechanisms for HULIS formation. Specifically, the work will study how catechol, pyrogallol, 3-methylcatechol, 4-methylcatechol, and 3-methoxycatechol (all proxies for oxygenated aromatics derived from benzene, toluene, and anisole) are oxidized by O3, HO and NO3 at the air/water interface and at the air/solid interface under variable relative humidity. The work will contrast processes that dominate daytime and nighttime chemistry using a variety of advanced instrumentation to also monitor the effect of important electrolytes (e.g., Na+, NH4+, SO42-) and naturally occurring surfactants. New fundamental understanding of heterogeneous reaction mechanisms will be revealed during this project. Solutions containing the proxy polyphenol will be aerosolized forming microdroplets that will be exposed during a contact time of 1 ìs to each O3(g), NO3, and HO to simulate their processing at the air/water interface. Similarly, the same oxidations will be study in the time scale of minutes to hours on solid thin films of the polyphenol under variable relative humidity (RH = 0-90%). The project will utilize an interdisciplinary approach and tools to investigate structure–activity relationships, study chemical reaction mechanisms, and correlate chemical structure with optical properties of extracted films under relevant tropospheric conditions. The broader impacts of this project include advancing the scientific community’s understanding of the mechanisms of SOA formation with implications to air quality, climate, and health. The results of this project will contribute to institutional objectives of the University of Kentucky by integrating collaborative efforts between the Environmental Chemistry Group of the Department of Chemistry and the Power Generation and Utility Fuels. As a faculty member at the most research active and diverse institution of the state of Kentucky, Guzman will act as a role model and mentor to students from a broad range of backgrounds. The project will allow the PI to continue developing the first atmospheric chemistry research and education program in the state to supervise from graduate to K-12 underrepresented students. The PI will continue his current research-mentoring relationships with the local Lafayette High School Pre-Engineering Program. The outreach activities are specifically oriented to training underrepresented students pursuing careers in science.
Effective start/end date8/15/197/31/23


  • National Science Foundation: $460,914.00


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