Wetland soils display vertical redox gradients that make them active sites for biogeochemical processes that include methanogenesis and denitrification. Recent laboratory studies have highlighted that low bioavailability of trace metals (Cu, Ni, Zn) may inhibit these processes, but the factors controlling this behavior in natural aquatic systems are not well understood. Trace metal bioavailability in aquatic systems, particularly wetlands, is controlled by iron and sulfur redox cycling and organic matter content. In this study, we quantified the uptake behavior of Cu, Ni and Zn on three different wetland soils and explored the causes of variation in uptake.  Soils were collected from sites in Illinois, Tennessee, and South Carolina. New information on metal uptake will help us estimate environmental inputs of trace metal may bring bioavailable concentrations to optimal levels for methanogenesis and denitrification. The adsorption data, normalized to specific surface area, showed that there was significant variability in metal uptake among different metals and between different sites. The variability in uptake was examined with respect to soil organic carbon content, morphology, mineralogy, and sulfur content. X-ray absorption spectroscopy probed the speciation of Cu and Ni taken up by these soils, finding that added metals form species that partially differ than those originally present in the soil. Copper forms CuS, increasing the fraction initially present in each system, but also metallic copper as well as Cu bound to thiol groups on organic matter. Complexation to organic matter and adsorption dominated Ni speciation in the Illinois and South Carolina sites, but an inorganic sulfide species formed when Ni was added to samples from the Tennessee site. These studies highlight that diverse mechanisms are responsible for trace metal uptake at each site.<br/> <br/>

Exploring factors governing metal uptake by wetland soils

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.