Wetland soils and hyporheic zones at the base of streams develop redox gradients, producing regions of aerobic and anaerobic microbial activity that make them active sites for biogeochemical processes. Microbial metabolisms driving biogeochemical cycling require trace metal micronutrients as cofactors in key enzymes. Specifically, methane (CH4) production via methanogenesis and nitrous oxide (N2O) reduction during denitrification may be limited by the availability of nickel (Ni) and copper (Cu), respectively. Laboratory studies of pure cultures have established that low availability of trace metal micronutrients may inhibit these biogeochemical processes. However, the factors governing this trace metal limitation in natural aquatic systems are not well understood. This presentation will discuss my research efforts focused on investigating the nitrogen species transformation activity in samples collected from riparian wetlands and streams sediments at background Cu levels and different supplemented Cu loadings. In addition, I will focus on the use of in-situ diffusion-based passive samplers for estimating the bioavailable concentrations of trace metals in surface water and soils and sediments. I will demonstrate the use of passive samplers to illustrate the effect of multiple cycles of fluctuating redox conditions on the bioavailability of trace metal micronutrients in natural aquatic systems. With these specific topics, I aim to improve the scientific understanding of the roles that trace metals play in biogeochemical cycling in natural environments.
Host: Xinning Zhang
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