Transport and fate of nitrate at the ground-water/surface-water interface

Journal of Environmental Quality
By: , and 

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Abstract

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.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Transport and fate of nitrate at the ground-water/surface-water interface
Series title Journal of Environmental Quality
DOI 10.2134/jeq2006.0550
Volume 37
Issue 3
Year Published 2008
Language English
Publisher ACSESS
Contributing office(s) Toxic Substances Hydrology Program
Description 17 p.
First page 1034
Last page 1050