Thermodynamic and Physical Controls on Methanogenesis

oils are structured media that have a multitude of pore domains, resulting in varying degrees of advective and diffusive solute and gas transport. A spectrum of biogeochemical processes may therefore function at the aggregate (micron to cm) scale, where the formation of steep chemical gradients is observed. Methane, a potent greenhouse gas, is produced when reducing conditions are prevalent; such conditions are observed within soil and sediment aggregates where microbial consumption of oxygen exceeds the rate of molecular diffusion. Methane may diffuse from the center of soil aggregates to soil macropores, which are conduits to the atmosphere, or be consumed by methanotrophs, which colonize anoxic-oxic boundaries. We are interested in understanding the effects of aggregate geometry on methanogensis and methanotrophy transpiring within soils and sediments, as well as quantifying the linked effects of physical variation and microbial activity responsible for net methane efflux from soils and wetland sediments.