Transport and fate of nitrate at the ground-water/surface-water interface
Although numerous studies of hyporheic exchange and denitrification have been conducted in pristine, high-gradient streams, few studies of this type have been conducted in nutrient-rich, low-gradient streams. This is a particularly important subject given the interest in nitrogen (N) inputs to the Gulf of Mexico and other eutrophic aquatic systems. A combination of hydrologic, mineralogical, chemical, dissolved gas, and isotopic data were used to determine the processes controlling transport and fate of NO3 − in streambeds at five sites across the USA. Water samples were collected from streambeds at depths ranging from 0.3 to 3 m at three to five points across the stream and in two to five separate transects. Residence times of water ranging from 0.28 to 34.7 d m−1 in the streambeds of N-rich watersheds played an important role in allowing denitrification to decrease NO3 − concentrations. Where potential electron donors were limited and residence times were short, denitrification was limited. Consequently, in spite of reducing conditions at some sites, NO3 − was transported into the stream. At two of the five study sites, NO3 − in surface water infiltrated the streambeds and concentrations decreased, supporting current models that NO3 − would be retained in N-rich streams. At the other three study sites, hydrogeologic controls limited or prevented infiltration of surface water into the streambed, and ground-water discharge contributed to NO3 − loads. Our results also show that in these low hydrologic-gradient systems, storm and other high-flow events can be important factors for increasing surface-water movement into streambeds.
Citation Information
Publication Year | 2008 |
---|---|
Title | Transport and fate of nitrate at the ground-water/surface-water interface |
DOI | 10.2134/jeq2006.0550 |
Authors | L.J. Puckett, C. Zamora, H. Essaid, J.T. Wilson, H.M. Johnson, M.J. Brayton, J. R. Vogel |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | Journal of Environmental Quality |
Index ID | 70033493 |
Record Source | USGS Publications Warehouse |
USGS Organization | Toxic Substances Hydrology Program |