Photochemistry of wildfire-generated polycyclic aromatic compounds in surface waters

The National Science Foundation Division of Chemistry awarded Utah State University $425,000 on January 1, 2027, under the Mathematical and Physical Sciences program (CFDA 47.049) to investigate the photochemistry of polycyclic aromatic hydrocarbons and carboxylated polycyclic aromatic hydrocarbons in surface waters impacted by wildfires.

Professor Kyle Moor and his students will use laser spectroscopy—including singlet oxygen phosphorescence and transient absorption—to measure the photosensitizing abilities and photolysis kinetics of these wildfire-generated aromatic compounds in aqueous environments. The research will determine singlet oxygen formation quantum yields and triplet excited state properties including triplet lifetimes and intersystem crossing quantum yields. The team will also characterize the photosensitization abilities of pyrogenic dissolved organic matter created from realistic wildfire chars. The work aims to advance understanding of how wildfires impact drinking water supplies and to inform efficient water treatment strategies in downstream rural and urban communities, with potential to limit disinfection byproduct formation and protect human health. Undergraduate and graduate students will receive interdisciplinary training in wildfire science.

Performance will take place in Logan, Utah from January 1, 2027, through December 31, 2029. This is a Project Grant assistance type.

Abstract

Professor kyle moor at utah state university is investigating the photophysics and photochemistry of polycyclic aromatic hydrocarbons (pahs) and carboxylated pahs (carboxyl-pahs) in aqueous environments to connect photochemical processes post-wildfire with the fate and transport of wildfire combustion products in surface waters. Wildfires release many low molecular weight aromatic compounds into surface waters. These compounds, especially pahs and carboxy-pahs, are photochemically active and their reactivity has potential to majorly influence post-wildfire surface water quality. Professor moor and his students will use state-of-the-art laser spectroscopy, including singlet oxygen phosphorescence and transient absorption, to explore the photosensitizing abilities and photolysis kinetics of pahs and carboxyl-pahs in water. They will also determine the photosensitization abilities of pyrogenic dissolved organic matter (pydom) created from realistic wildfire chars. Their studies will advance understanding of the impacts of wildfires on drinking water supplies and could help inform efficient water treatment in downstream rural and urban communities to limit disinfection byproducts formation and protect human health. Undergraduate and graduate students will receive interdisciplinary training in wildfire science to create a future-ready workforce that is equipped to address the challenges of wildfires. The overall objective of this project is to determine the potential of pahs and carboxyl-pahs to impact aquatic photochemistry in wildfire-impacted surface waters. A major focus is determining the photosensitizing abilities of pahs and carboxyl-pahs in aqueous environments using laser spectroscopy. This will be accomplished by measuring: 1) singlet oxygen formation quantum yields; and 2) triplet excited state properties, including triplet lifetimes and intersystem crossing quantum yields. The photolysis kinetics and pathways of carboxyl-pahs in water will additionally be explored, yielding insight into how long they persist in surface waters post-wildfire. Results will be connected to the more chemically complex pools of real wildfire-generated materials by studying the photosensitizing abilities of pydom generated under realistic combustion conditions. A series of grass and wood chars created in open air burn tables will be used to generate pydom to explore the impacts of burn material and severity on pydom photosensitizing abilities. The role of low molecular weight sensitizers in pydom will be further elucidated. Results impact many scientific areas beyond wildfire-impacted surface waters, including photosensitization processes by ubiquitous combustion-derived pahs and in atmospheric particles (e.g., biomass burning aerosols). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the foundation's intellectual merit and broader impacts review criteria.- subawards are not planned for this award.