DETERMINING VADOSE ZONE GEOCHEMICAL AND GROUNDWATER PROCESSES WITHIN A SOIL-WEATHERED ARGILLITE MANTLED HILLSLOPE
To quantify the extent of weathering and the associated mineralogical changes with depth in the Rivendell system , mass transfer coefficients, τ, (using Ti as the immobile element) will be determined through elemental concentration measurements of digested weathered bedrock samples collected from depths of 4.6- 24.4m. Concentration determination for a suite of elements will be accomplished through the use of an ICP-MS for weathered bedrock samples and cations as well as Ion Chromatography for anions. Preliminary anion and cation analysis of groundwater samples generated from the VMS (Vadose Monitoring System) depict relatively high sulfate and cation concentrations at the ppm level for some elements (i.e. Mg, Al, Fe, Mn, and Sr). Yet, these concentrations may be influenced by other factors outside of the system such as the recent VMS wells installation. With time and additional data sets, cation and anion concentrations should better reflect the actual composition of the groundwater. By analyzing temporal variability of solutes in unsaturated and saturated water within the hillslope as well as the elemental composition of soil and weathered rock, we can identify the controls on the development of the weathering zone, groundwater chemistry evolution, and the transport of nutrients to vegetative and aquatic ecosystems.