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Nitrate Removal Within Heterogeneous Riparian Aquifers Under Tidal Influence
Author(s) -
Wallace Corey D.,
Sawyer Audrey H.,
Soltanian Mohamad Reza,
Barnes Rebecca T.
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl085699
Subject(s) - hyporheic zone , nitrate , environmental science , groundwater , riparian zone , hydrology (agriculture) , aquifer , silt , sediment , anoxic waters , denitrification , floodplain , estuary , water quality , geology , nitrogen , oceanography , ecology , geomorphology , habitat , chemistry , geotechnical engineering , organic chemistry , biology
Tides in coastal rivers drive river‐groundwater (hyporheic) exchange and provide opportunities for nitrate removal that may improve coastal water quality. Silt and sand layers in coastal floodplain sediments can alter the flow and transformation of nitrate. Our goal was to understand how sediment heterogeneity influences nitrogen dynamics near tidal rivers. Numerical simulations show that oxic, variably saturated sand layers and anoxic, organic‐rich silt layers are sites of nitrification and denitrification, respectively. The exchange of river water and nitrate through heterogeneous sediments increases with sand fraction, as sand lenses become longer and more connected. The amount of nitrate removed from river water also increases but represents a smaller portion of total nitrate exchange through the hyporheic zone, causing removal efficiency to decline. Our results suggest that accurate characterization of aquifer heterogeneity leads to an improved understanding of sites of nutrient transformation within floodplain sediments.