19 July 2023
10:00 –11:00 AM (CST)
Understanding rapid solute transport in the subsurface of agricultural systems is crucial for quantifying nutrient loading into surrounding surface waters. In this study, time-lapse three-dimensional electrical resistivity imaging (ERI) was employed to capture solute transport dynamics in a flat, agricultural field. A saline tracer was injected directly into the saturated zone and the following day a 20-year storm event was simulated using a sprinkler system. A fanned array of 96 electrodes was used to acquire twelve 3D ERI data sets over the entire experiment. Spectral induced polarization (SIP) was run on soil cores in the lab and paired with time domain induced polarization (TDIP) to get estimates of electrolytic conductivity from the ERI data sets. These electrical geophysical methods revealed the presence of a preferential flow path, activated by the simulated storm event, as well as an impermeable soil layer that redirected the solute around it. A hydrological model was calibrated using the electrical geophysical data sets as proxies for changes in solute concentration. This study provides unique insights into the role of preferential flow pathways in a flat agricultural field delivering nutrient rich groundwater to drainage ditches.
Joshua Thompson is a PhD student at Rutgers University in Newark, New Jersey under the guidance of Lee Slater. His research has focused on using geophysical techniques to better understand solute transport in two different settings. The first portion is focused on rehabilitated coastal marsh systems. In this setting, he is investigating how salts brought in from the tides get trapped in regions with fine grain sediments, creating a less mobile domain. The other half of Joshua’s research is focused on nutrient transport in agricultural fields.