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Transport and Fate of Nitrate at the Ground‐Water/Surface‐Water Interface
Author(s) -
Puckett Larry J.,
Zamora Celia,
Essaid Hedeff,
Wilson John T.,
Johnson Henry M.,
Brayton Michael J.,
Vogel Jason R.
Publication year - 2008
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2006.0550
Subject(s) - environmental science , surface water , hydrology (agriculture) , denitrification , streams , nitrate , subsurface flow , eutrophication , groundwater , infiltration (hvac) , wetland , transect , nutrient , environmental chemistry , nitrogen , ecology , chemistry , environmental engineering , geology , oceanography , computer network , physics , geotechnical engineering , organic chemistry , computer science , biology , thermodynamics
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 NO 3 − 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 NO 3 − concentrations. Where potential electron donors were limited and residence times were short, denitrification was limited. Consequently, in spite of reducing conditions at some sites, NO 3 − was transported into the stream. At two of the five study sites, NO 3 − in surface water infiltrated the streambeds and concentrations decreased, supporting current models that NO 3 − 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 NO 3 − 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.