A model analysis of the tidal engine that drives nitrogen cycling in coastal riparian aquifers
|Authors:||Corey D. Wallace Audrey H. Sawyer Rebecca T. Barnes Mohamad Reza Soltanian Rachel S. Gabor Michael J. Wilkins Myles T. Moore|
|Resource type:||Composite Resource|
|Storage:||The size of this resource is 44.5 KB|
|Created:||Mar 26, 2019 at 2:46 p.m.|
|Last updated:|| May 24, 2019 at 4:23 p.m.
|Citation:||See how to cite this resource|
In coastal rivers, tides facilitate surface water-groundwater exchange and strongly coupled nitrification-denitrification near the fluctuating water table. We used numerical fluid flow and reactive transport models to explore longitudinal variations in reactive nitrogen transport along a tidal freshwater zone (White Clay Creek, Delaware, USA). Nitrate removal capacity initially increases with downstream distance as tidal range increases but then declines as sediment grain size and permeability decrease, limiting the supply of nitrate to the riparian aquifer. Over the entire model reach, nitrification provides roughly the same amount of nitrate as the combined contributions from surface and groundwater. More than half (~66%) of nitrate removed via denitrification is produced in-situ, while the vast majority of remaining nitrate removed comes from groundwater sources. In contrast, average nitrate removal from surface water due to tidal pumping amounts to only 1.77 kg of nitrate along the reach each day, or ~1% of the average daily in-channel riverine nitrate load. As a result, tidal bank storage zones may not be major sinks for nitrate in coastal rivers, but can act as effective sinks for groundwater nitrate. By extension, tidal bank storage zones provide a critical ecosystem service, reducing contributions of groundwater nitrate, often derived from septic tanks and fertilizers, to coastal rivers.
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This resource was created using funding from the following sources:
|Agency Name||Award Title||Award Number|
|National Science Foundation||EAR||1752995|
|National Science Foundation||EAR||1446724|
|Geologic Society of America|
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