CEE Seminar: Forest Fire Alters Dissolved Organic Matter Exports from Forested Watersheds - Impacts on Water Quality & Treatability

McDonnell Douglas Engineering Auditorium (MDEA)
Alex Chow, Ph.D.

Associate Professor
Department of Forestry & Environmental Conservation
Department of Environmental Engineering & Earth Sciences
Clemson University

Abstract: Climate change could lead to more frequent and severe droughts. Hot temperatures and dry conditions increase the likelihood of wildfires. Prescribed fire, which is a fuel reduction technique, is an essential forest management practice to reduce the susceptibility of forests to wildfire. In either wildfire or controlled burn, forest fire rapidly modifies the chemical composition of the detritus layer on forest floors, converting lignin- and polysaccharide-rich and relatively degradable carbon and nitrogen pools to polycyclic aromatic- and charcoal-rich and recalcitrant black carbon and black nitrogen. Dissolved organic matter (DOM) exported from burned watersheds is likely to have different chemical characteristics and treatability compared to DOM exported from unburned watersheds. Notably, forested watersheds are critically important to supply clean drinking water to millions of people in the U.S., and DOM constitutes the main precursor of carcinogenic disinfection byproduct (DBP) such as trihalomethanes (THMs) and haloacetonitriles (HANs) typically formed during water treatment. To investigate the impacts of wildfire and identify management strategies against it, our team has examined several wildland fires in California, Colorado, and North and South Carolinas. These field investigations confirmed the negative impacts of wildfire on water quality and treatability, such as a lower coagulation removal efficiency and an increase of DOM reactivity in forming DBPs. Some of the impacts could even last over a decade. In contrast, managed watersheds with low intensity prescribed burns could have several benefits besides reducing the risk of wildfire, including a lower concentration of DBP precursor in source water and an increase of water export. Our research studies demonstrate prescribed burns could be effective watershed management strategies to reduce the risks of forest fires and to protect source water under the changing climate.

Bio: Alex Chow grew up in Hong Kong and immigrated to the U.S. in 1987. He received his bachelor's degree in chemistry with a minor in chemical engineering from UC Berkeley in 1994. Chow completed his graduate work (master's in 1998 and doctorate in 2000 in hydrologic science) at UC Davis. In 2003, he received an NIH granted post-doctoral career award “Professor of the Future.” He joined Clemson University in December 2008 as an assistant professor and was promoted to associate professor in 2015. Chow's research program is grounded in aquatic chemistry and hydrologic science. He is particularly interested in climate change’s related disasters including wildfire and hurricanes on NOM exports and processes in source waters. Currently he is the associate editor of the Soil Science Society of American Journal and Journal of Environmental Quality. He also was the 2015 outstanding associate editor of the Journal of Environmental Quality. 

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