Abstract: Subsurface water drainage networks in agricultural fields, known as "tile drains", represent one of the largest hydrologic engineering endeavors by area in the U.S.A. Extensive installation of these drainage networks greatly alters watershed connectivity and flow paths, lowering the water table and rapidly discharging stormwater. Although the transport of dissolved nutrients such as phosphorus and nitrogen via tile drains is well-studied, the impacts of this widespread engineering on the subsurface carbon cycle and the export of particulate organic carbon (POC) from field soils to river networks are not yet understood. To investigate the role of tiles in POC transport,soil profiles and suspended sediment in tile discharge were sampled across three agriculturally dominated Midwestern watersheds. Samples were analyzed using elemental (C), stable isotope ( 13C), and radiocarbon measurements. Results of high-temporal resolution sampling indicate tile discharge can contain concentrations of POC comparable to that of stream networks, and that there are clear shifts in the sources of exported POC correlated with rain-events. These sources are distinct relative to tile-adjacent soils, suggesting there are rapid transport pathways between shallower soils and tiles and/or a novel C cycling environment within the tiles.

Bio: Katherine DuRussel is a PhD student in the Carbon Biogeochemistry Lab at Northwestern University. Her research focuses on storm-driven biogeochemical dynamics of organic matter in agricultural and riverine systems. Katherine completed her M.S. in Civil and Environmental Engineering at Northwestern University and earned her A.B. in Geosciences and Certificate in Environmental Studies from Princeton University.