(618d) Novel Field Deployable Sensors to Monitor How Dynamic Hydrology Shapes Nutrient and Element Transformations in a Great Lakes Coastal Estuary: A Two-Year Study

The prediction of redox processes often relies on measured or assumed redox potential (Eh). However, process measurements frequently deviate from predictions based on the traditional thermodynamic “redox tower” paradigm. Poorly measured spatial and temporal soil heterogeneity has been shown to cause apparent departures from thermodynamic exclusion principles at bulk scales, impacting large-scale biogeochemical cycling unresolved in current ecosystem, regional, or global models.

To address this, we developed a 3D printed conductive carbon electrode array for zero resistance ammetry (ZRA) measurements in benthic sediments, enabling real-time detection of biogeochemical processes at various spatial scales. ZRA measures electrical current arising from microbially-induced redox disequilibrium. Prior to field deployment, we characterized the electrodes and conducted laboratory-scale experiments simulating redox conditions using Fe(III) (hydr)oxide-rich soils.

Refining our approach, we deployed a co-located ZRA and Eh multi-sensor system to detect electrochemical signals across and beneath the sediment-water interface at nested scales in the Old Woman Creek wetland. Concurrent data collection included dissolved oxygen dynamics, nutrient concentrations, greenhouse gas fluxes, and soil geochemistry. Future work aims to integrate microsite electrochemical data into ecosystem-scale models for improved representation of soil redox processes in spatially and temporally variable systems. Field data confirms the efficacy of the vertically stacked ZRA electrode in monitoring microbial processes at small scales.