Electrons Move the World: Redox Biogeochemistry for Global Environmental Challenges

Climate change and water pollution are two of the greatest challenges facing humanity today. Efforts to address these challenges depend upon our knowledge of reactions occurring at interface of geochemical phases (such as minerals or organic matter) and microorganisms. Specifically, electron transfer (redox) reactions at the biogeochemical interface play critical roles in carbon emissions and pollutant dynamics in water, air, soil, sediments, and air. My research focuses on elucidating biogeochemical redox processes at the mechanistic level and linking them to large scale phenomena. In this talk, I will give two examples of research projects looking at critical redox processes. In the first example, I focus on systems dominated by iron (Fe) oxides. Iron oxides play major roles in the biogeochemical cycles of nutrients and contaminants, and have been proposed as paleoproxies. Here I discuss the reactivity of iron oxides under reducing conditions, specifically the recrystallization of goethite (a-FeOOH). In the second example, I look at systems dominated by organic matter. I focus on the role of organic matter in the emission of methane (CH₄), a potent greenhouse gas, from northern peatlands. These systems are major carbon sinks (~30% of global soil carbon) while also acting as significant sources of methane (~8% of global methane). By combining laboratory and field work, I investigate how particulate organic matter suppress methane emissions, thereby acting as a major control on carbon dynamics in these carbon-rich ecosystems.