MODELING DYNAMIC GEOCHEMICAL PROCESSES: HOW WATER TABLE FLUCTUATIONS INFLUENCE REDOX CONDITIONS IN THE PRESENCE OF CONTAMINATION

Understanding groundwater geochemistry is vital when interpreting how their interactions change in a dynamic subsurface environment. Spatial variations, temporal changes, and weather events can greatly influence groundwater geochemistry in a given site and subsequently alter the fate and transport of contaminants. Modeling these changes and establishing diurnal and seasonal trends can be challenging due to the immense data needed to build an adequate, representative model. Here, the software RockWorks is used to interpolate point data to create a continuous, visual model of geochemistry transformations at three different sites with varying nitrate and heavy metal contamination—mild contamination, moderate contamination, and high contamination—across the DOE Oak Ridge Reservation Y-12 Complex in Oak Ridge, Tennessee. In situ measurements of geochemistry (with a specific focus on reduction-oxidation (RedOx) potential) will be correlated to metals and cation/anion analysis from inductively coupled plasma mass spectrometry (ICP-MS) and high pressure ion chromatography (HPIC), respectively. These measurements are made daily (four days a week) over the span of three months to >27 previously established groundwater wells to build both diurnal and seasonal time series of geochemistry. Additionally, fluctuations in geochemistry in the context of extreme weather events versus seasonal fluctuations will be analyzed for RedOx potential due to entrapped oxygen. This work aims to establish predictive models to inform future groundwater and sediment sampling and establish standard protocols for in situ examinations of geochemistry. This deterministic method of groundwater sampling can be implemented into future in situ studies focusing on interactions between hydrogeology, geochemistry, and microbial activity.