RII Track-4: NSF: Understanding Wildfire Risks to Drinking Water Source Waters: Pyrogenic Changes to Organic Matter and Disinfection By-product Formation

Wildfires are growing in size, severity, and frequency due to drought, forest management, and climate change. Wildfire mobilizes soil organic matter through partial combustion. This partially combusted organic matter is then transported after precipitation events to downstream drinking water treatment plants. Disinfection is a key component of drinking water treatment and inactivates pathogens. However, the chemicals used for disinfection also react with the diverse organic compounds present in all water sources. Some of these reactions result in the production of carcinogenic disinfection by-products, which have regulatory limits in finished drinking water set by the U.S. Environmental Protection Agency. There is currently conflicting evidence of whether partially combusted soil organic matter causes more or fewer disinfection by-products to form than would otherwise, leaving uncertainty about the future security of water supplies in wildfire-prone regions. The overarching goal of this research is to understand how fire severity affects the formation of disinfection by-products at downstream drinking water treatment plants. To achieve this goal, the PI and a graduate student will travel to and conduct experiments at the University of Colorado-Boulder in collaboration with wildfire and organic matter experts currently serving as faculty. This Research Infrastructure Improvement Track-4 EPSCoR Research Fellows (RII Track-4:NSF) project will provide a fellowship to an Assistant Professor and training for a graduate student at the University of Nevada Reno. This work would be conducted in collaboration with researchers at the University of Colorado-Boulder. The PI and one graduate student will 1) learn new organic matter characterization methods from experts in the field and apply them to Caldor Fire samples collected near the PI’s home institution, and 2) apply the learned skills to samples produced under highly controlled laboratory conditions. Success of the two aims will prove or disprove the overall hypothesis, that moderate wildfire severity results in the greatest production of disinfection by-product precursors, which are destroyed at higher temperatures (e.g., above 350°C). The rationale for the proposed research is that disinfection by-products are hazardous to human health, and mitigating exposure (i.e., meeting regulatory standards) is challenging for drinking water utilities without an understanding of how specific fire conditions affect pyrogenic organic matter mobilization and reactivity. The findings will advance the fundamental knowledge of wildfire impacts on organic matter contained in drinking water source catchments, which is somewhat well understood in terms of material transport, but not well understood in terms of potential oxidation chemistry involving disinfectants and transport of small, drinking-water-regulated, pyrogenic molecules. The findings will also inform scientists, regulators, and local utilities of the potential for regulatory exceedances during and after wildfire events. The collaborative research will ultimately improve the research capacity of the home institution and benefit the State of Nevada, which is the driest state in the nation and subject to both water scarcity and wildfire. A graduate student will also benefit through exposure to subject matter experts, improving their technical and communication skills, and providing networking opportunities. One to two undergraduate students will gain experience in sampling remote areas. 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.