Bridging the Scale: Connecting the Colloid Scale to Hydrodynamic Characteristics.

The stature of wetlands as important systems in current and future global challenges has increased with continued understanding of these complex systems. However, progress is needed in understanding environmental role and function of wetlands. Colloids are an attractive option as it is a scale at which constant change is undergoing within wetlands. Colloids have traditionally been studied in the fate and transport of pollutants within aquifer systems. Within wetlands colloids consist of many organic and inorganic shapes, sizes, and forms unlike their more uniform inorganic aquifer counterparts. Hydro-physio wetland characteristics impact both seasonal and spatial biogeochemical responses at the colloid scale. Three wetlands with contrasting vertical and lateral hydrodynamics were selected to identify drivers and show patterns and relationships between components. Specifically, iron and dissolved organic carbon (DOC) are strong influences within soils and their concentrations and properties change drastically with season and according to wetland hydro-physio characteristics. In addition to ferrous iron (Fe II) and DOC, measurements of nitrogen (N), phosphorus (P), Eh, pH, EC and colloids were taken. Results have shown the most flux within systems with active hydroperiod and the least flux within systems of lateral preferential flow. Spatial variation from inlet to outlet within each system, due to differences in lateral flow, illustrates residence time or general ratios of transported vs. independently mobilized colloids throughout each wetland. Differences in shallow and deep wells can be seen due to hydroperiod and soil profile. It is hypothesized that evaporation is a key driver in the static system, preferential lateral flow within headwater wetland, and hydroperiod and high DOC within the perched system. Specific mechanisms such as facilitated colloid mobilization through reductive iron dissolution have been published by collaborators. Overall the study has shown that explainable variation is possible through the colloid scale warranting further replication. Better understanding of wetland hydro-physio impact on function can result in efficient planning and policy of wetland issues.