Trace Metal Dynamics and Limitations on Biogeochemical Cycling in Wetland Soils and Hyporheic Zones

(3) identify how fluctuating redox conditions affect trace metal availability in wetland soils and hyporheic zone sediments. We hypothesize that solid-phase speciation is the primary control on metal availability and that biogeochemical processes utilizing a pathway containing single, metal-requiring enzyme are most susceptible to metal limitations. This project will integrate field and laboratory studies of trace metal availability and biogeochemical processes occurring in wetland soils and hyporheic zone sediments. Primary field studies will investigate (1) a riparian wetland, Tims Branch and Steed Pond, at the Savannah River National Laboratory, South Carolina, in collaboration with the Argonne National Laboratory Scientific Focus Area (SFA) team and (2) the hyporheic zone of the East Fork Poplar Creek field site in Tennessee in collaboration with the Oak Ridge National Laboratory SFA team. Additional studies will investigate marsh wetlands at the Argonne National Laboratory site in Illinois as well as a site in Missouri near Washington University. Our field investigations will assess the spatial and temporal variations in metal availability in wetland soils and hyporheic zone sediments. Our complementary laboratory studies will investigate how biogeochemical processes in soils and sediments from our field sites respond to increased metal availability as well as how fluctuating redox conditions affect such availability. These studies will utilize DOE-supported synchrotron lightsources as well as unique instrumentation at EMSL. The proposed research will document the role of metals in controlling the biogeochemistry or carbon, nitrogen, and mercury in subsurface aquatic systems. This work may reveal novel ways in which human modification of natural hydrologic conditions and releases of metals to the environment associated with energy production alter biogeochemical processes by perturbing trace metal availability.