Subsurface dissolved N species: Understanding the transport and chemical transformations of subsurface N is crucial to optimizing crop productivity while minimizing ecological impact. We are developing sampling and detection methods to track both gaseous and aqueous N species throughout the nitrogen cycle, with ~hourly time resolution and on mm-to-cm spatial scales. Mapping of dissolved organic matter transformations in the rhizosphere: Microdialysis probes, coupled with a PTR-MS optimized for detection of sugars, amino acids, and organic acids, enable high-resolution spatial and temporal (mm-scale, minutes-scale) tracking of root exudate dynamics. Volatile Organic Compound (VOC) Transport & Transformations in Soil: Subsurface probes are installed at different depths in laboratory soil mesocosms. One probe releases a known VOC mixture while the remaining probes are connected to an Aerodyne Vocus PTR-MS to monitor VOC uptake and transformations at a range of distances from a source under a variety of environmental conditions. Soil Hydrogen: Soil plays an important role in global hydrogen (H2) budget as both a sink and a source. Our soil sampling system (probes + MSS) coupled with a TILDAS measures in situ H2 from roots of designated plants. Observed variations of H2 and CH4 near root nodules of peanut plants reflect fermentation and biological nitrogen fixation processes.
