27-2 Control of Water Level and Sediment Saturation on Redox and Hydrogeochemical Parameters in Shallow Alluvial Aquifers along the Rio Grande (New Mexico)

Session: From Data to Decision: Integrating Geophysics, Data Systems, and Modeling for Aquifer Characterization in Data-Sparse Regions (Posters)

Presenting Author:

Authors:

Abstract:

            Characterization of trace element mobility and redox potential in alluvial systems is an ongoing effort in both bio- and hydrogeochemistry. Previous studies have concluded that much of the metabolization of carbon in these shallow and flashy systems occurs at and above the zone of intermittent saturation, but the dynamic nature of alluvial sediments along the Rio Grande make this characterization difficult. Understanding the pathways of element mobilization in this area can have implications for possible contaminant transport, as the Rio Grande and the underlying aquifers supply much of the drinking water to the surrounding population centres. Three sediment cores along the Rio Grande will be cored and analysed through several different techniques. Electron probe microanalysis (EPMA) element maps to characterize mineral phases and element locations, x-ray diffraction (XRD) to identify iron, carbon, and sulphate phases, and a sequential extraction protocol to quantify bulk element composition and redox capacity. Similar extant sites demonstrate highly variable redox conditions during the monsoon season (June – September), and lower variability during the winter months. The aim of this work is to clarify to what degree changes in water level (and rate of change) impact element mobility, concentration, and phase formation in redox-sensitive sediments, and what biotic processes occur in the zone of intermittent saturation to facilitate or encourage these changes.

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