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Mitigation of Shallow Groundwater Nitrate in a Poorly Drained Riparian Area and Adjacent Cropland
Author(s) -
Davis Jennifer H.,
Griffith Stephen M.,
Horwath William R.,
Steiner Jeffrey J.,
Myrold David D.
Publication year - 2007
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/jeq2006.0186
Subject(s) - riparian zone , nitrate , groundwater , environmental science , hydrology (agriculture) , riparian buffer , dissolved organic carbon , groundwater recharge , environmental chemistry , chemistry , ecology , geology , aquifer , geotechnical engineering , organic chemistry , habitat , biology
Riparian ecosystems, through their unique position in the agricultural landscape and ability to influence nutrient cycles, can potentially reduce NO 3 loading to surface and ground waters. The purpose of this study was to determine the fate of NO 3 in shallow groundwater moving along a lateral flowpath from a grass seed cropping system through an undisturbed mixed‐species herbaceous riparian area. Soil A (30–45 cm) and C horizon (135–150 cm) NO 3 , dissolved oxygen, and nitrous oxide concentrations were significantly higher in the cropping system than the adjacent riparian area. Nitrate concentrations in both horizons of the riparian soil were consistently at or below 0.05 mg N L −1 while cropping system concentrations ranged from 1 to 12 mg N L −1 Chloride data suggested that NO 3 dilution occurred from recharge by precipitation. However, a sharp decrease in NO 3 /Cl ratios as water moved into the riparian area indicated that additional dilution of NO 3 concentrations was unlikely. Riparian area A horizon soil water had higher dissolved organic carbon than the cropping system and when the riparian soil became saturated, available electron acceptors (O 2 , NO 3 ) were rapidly reduced. Dissolved inorganic carbon was significantly higher in the riparian area than the cropping system for both horizons indicating high biological activity. Carbon limitation in the cropping system may have led to microbial respiration using primarily O 2 and to a lesser degree NO 3 Within 6 m of the riparian/cropping system transition, NO 3 was virtually undetectable.