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Tidal Controls on Denitrification in Coastal Streambeds

Knights, Deon Hanley
http://rave.ohiolink.edu/etdc/view?acc_num=osu1461146542

Abstract Details

2016, Master of Science, Ohio State University, Earth Sciences.
In coastal rivers, tidal pumping enhances the exchange of oxygen-rich river water across sediment-water interfaces, controlling nitrogen cycling in suboxic riverbed sediments. I developed a one-dimensional, coupled fluid flow and solute transport model that quantifies the influence of tidal pumping on redox zonation and nitrate removal in the hyporheic zones of coastal rivers, and applied it to the tidal freshwater zone (TFZ) of White Clay Creek (Delaware, USA). At high tide when oxygen-rich river water infiltrates into the bed, denitrification rates decrease by ~20% relative to low tide when nitrate-rich anoxic groundwater discharges to the channel. Tidal pumping deepens the aerobic zone by a factor of 6, decreasing denitrification rates by 10%. Therefore, along TFZs nitrate removal rates decrease as tidal amplitude increases due to enhanced oxygen exchange across the sediment-water interface. Sensitivity analyses suggest that denitrification hot spots in TFZs will occur in less permeable, organic-rich sediment under lower tidal ranges and higher rates of ambient groundwater discharge. Tidal pumping is not efficient at removing surface water nitrate but removes up to 81% of groundwater nitrate that would discharge to White Clay Creek. Given the high population densities of coastal watersheds and thus the tendency towards high nitrate inputs from groundwater to rivers, the hyporheic zones of TFZs play a critical role in mitigating new nitrogen loads to coasts.
Audrey Sawyer, PhD (Advisor)
William Lyons, PhD (Committee Member)
Joachim Moortgat, PhD (Committee Member)
48 p.
Earth; Environmental Geology; Geology; Hydrology
tidal freshwater zone; coastal rivers; water quality; hyporheic exchange; tidal pumping

Recommended Citations

Citations

  • Knights, D. H. (2016). Tidal Controls on Denitrification in Coastal Streambeds [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461146542

    APA Style (7th edition)

  • Knights, Deon. Tidal Controls on Denitrification in Coastal Streambeds. 2016. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1461146542.

    MLA Style (8th edition)

  • Knights, Deon. "Tidal Controls on Denitrification in Coastal Streambeds." Master's thesis, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461146542

    Chicago Manual of Style (17th edition)

osu1461146542
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© 2016, some rights reserved.Creative Commons License Tidal Controls on Denitrification in Coastal Streambeds by Deon Hanley Knights is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by The Ohio State University and OhioLINK.