Abstract. Biogeochemical cycling within the hyporheic zone can significantly affect the flux of elements and chemical compounds between groundwater and surface waters. This proposal leverages existing USGS infrastructure and current NSF STC activities to monitor (1) a more extensive array of redox active species and (2) more spatially and temporally dense patterns of nitrogen species using a novel sensor network deployment. Project personnel will analyze hyporheic zone porewater samples for a range of trace elements not being considered by USGS, such as rare earth elements, uranium, and arsenic. A parallel effort will deploy a continuous hyporheic zone sensor network targeting nitrogen redox species. This network will be deployed adjacent to the USGS manual sampling station, and will include commercial nitrate, nitrite and ammonium sensors and developmental nitrate microsensors, and will enhance the spatial resolution and add temporal resolution to the overall investigation.
Intellectual merit. While it is generally understood that groundwater-surface water interactions play an important role in determining sediment and water quality in streams, a quantitative understanding of the chemical flux and biogeochemistry has been lacking for most elements and chemical compounds. The proposed effort will expand the USGS-planned chemical analyses to encompass an array of chemical species which have not been investigated in this environment. The species and trends identified will yield new insight into the biogeochemistry of the hyporheic zone and its capacity to buffer groundwater-surface water interactions. At the same time, the sensor network deployment will reveal spatial and temporal patterns with sufficient resolution to reveal between spatial variability and gradients, and to identify temporal patterns on different timescales (diurnal, seasonal, etc.).
Broader Impact. The results from this investigation will be useful to stakeholders associated with watershed management issues such as setting total maximum daily loads, determining the minimum width of riparian buffer zones necessary to preserve habitat, and others. The successful deployment of the nitrogen species sensor network will contribute to the movement toward an environmental cyberinfrastructure by changing the way in which scientists observe streambeds. The education and training of undergraduate and graduate students at UC Merced will be enriched by this investment in environmental cyberinfrastructure at this site, which is locate about 20 miles from this new UC campus. The mission of UC Merced is to serve the people of the San Joaquin Valley. Merced County census data from 2000 indicate that 45% of the county residents are Latino or Hispanic, less than 11% have college degrees, and more than 21% live below the poverty level.
SGER Justification. The proposed SGER project is possible in the context of on-going (though temporary) USGS efforts. A timely start for the SGER project is critical so that we can coordinate with the planned USGS sampling in March 2004; USGS sampling at this site is planned to take place over a period of only 1-1/2 years.
