Riparian areas are considered to be biogeochemical "hotspots", where biogeochemical reactions and atmospheric emissions are heightened. New monitoring and modeling strategies are needed to develop a process-based understanding of the fluxes and transformations that take place across the terrestrial-aquatic interface. This research centers on applying new technology with micrometeorological methods to bridge the sub-disciplines of land-atmosphere interaction and watershed hydrology. The results will help constrain the rate and timing of biogeochemical processes in riparian hotspots and better define the role of hydrological factors in controlling these fluxes. In particular, this project will focus on cases of nitrogen and mercury cycling in watersheds.
In agricultural areas where nitrogen-based fertilizers are applied, significant emissions of nitrous oxide (N2O) can occur. N2O is a potent greenhouse gas that has been implicated in the breakdown of atmospheric ozone. Riparian areas are hypothesized to be hotspots of N2O emissions due to the mixing of high levels of nitrate and dissolved organic carbon. A tunable diode laser trace gas analyzer will measure N2O fluxes in a coastal riparian marsh, where stream discharge and groundwater chemistry will also be monitored. A watershed hydrological model will be integrated with a process-based model of N2O production to interpret and scale up the observations.
Mercury concentrations in surface water have been found to be high in even remote locations due to effects of atmospheric deposition. This research will test the theory that riparian areas control stream water mercury concentrations through interacting timescales associated with hydrological transport and chemical transformations. Mercury emissions will be measured, at both point and landscape scales, in an upland riparian wetland in conjunction with aqueous mercury concentrations and stream discharge. The effect of interacting timescales on stream water mercury concentrations will evaluate the impact of transient discharge on mercury fluxes.
This research will link with the Schoolyard LTER program at the Virginia Coastal Reserve LTER site, where students from nearby Northampton County High School will take part on summer research projects. A watershed module for the Environmental Science II class will be developed to interface with the students' ongoing water quality monitoring program. University of Virginia undergraduates will take part in this research, through both independent study and distinguished major theses, and through participation in a Field Methods and Data Analysis class. This research involves the training of Ph.D. students, who will have active mentoring roles while carrying out field work and modeling activities. This work will engage a range of students in multi-disciplinary research and in the application of emerging technology.
