Publications
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Recent Publications:
The effects of seasonality and nutrient loading on nutrient uptake in an urban beaver wetland (poster)
Kyra Hoffman and Dr. Deon Knights
2023
Objectives: to understand the role of beaver wetlands in urban settings to nitrate and phosphate removal, and how seasonality and nutrient load affect removal function. Methods include nitrate and phosphate additions monitored with benthic chambers over a six-month period.
Presented at AGU conference in December 2023
The relationship between delta form and nitrate retention revealed by numerical modeling experiments
Deon Knights, Audrey H. Sawyer, Douglass A. Edmonds, Elizabeth A. Olliver, and Rebecca T. Barnes
2021
River deltas display a wide range of morphologic patterns that influence how nutrients interact in channels and wetlands on their way to the coast. To quantify the role of delta morphology on nitrate fate, we simulated reactive nitrate transport over steady base flow conditions for six synthetic, morphologically unique river‐dominated deltas created in Delft3D by varying incoming grain size distributions. We parameterized nitrate removal kinetics using an observed relationship with elevation from Wax Lake Delta (Louisiana, USA). Total nitrate retention across the six synthetic deltas and Wax Lake Delta ranged from 1.3%‐13%, suggesting that these river‐dominated deltas have limited ability to remove nitrate from incoming river water. [...]
Nitrate Removal Across Ecogeomorphic Zones in Wax Lake Delta, Lousiana (USA)
Deon Knights, Audrey H. Sawyer, Rebecca T. Barnes, Anastasia Piliouras, John Schwenk, Douglass A. Edmonds, and Alexander M. Browns
2020
Human activities have increased nitrate export from rivers, degrading coastal water quality. Atdeltaic river mouths, the flow of water through wetlands increases nitrate removal, and the spatialorganization of removal rates influences coastal water quality. To understand the spatial distribution ofnitrate removal in a river‐dominated delta, we deployed 23 benthic chambers across ecogeomorphic zoneswith varying elevation, vegetation, and sediment properties in Wax Lake Delta (Louisiana, USA) in June2018. Regression analyses indicate that normalized difference vegetation index is a useful predictor ofsummertime nitrate removal. [...]
All Publications:
* indicates undergraduate student, ** indicates graduate student
2023:
Hoffman*, Kyra, Knights, Deon (2023). The effects of seasonality and nutrient loading on nutrient uptake in an urban beaver wetland. Poster. In AGU Fall Meeting 2023. AGU.
2021:
Knights, D., Sawyer, A. H., Edmonds, D. A., Olliver, E. A., & Barnes, R. T. (2021). The relationship between delta form and nitrate retention revealed by numerical modeling experiments. Water Resources Research, 57, e2021WR030974.
Lee, E., Byrnes, D. K., Knights, D. H., Guimond, J., Matos, K., Atekwana, E. A., ... & Cisneros, J. (2021, December). Finding Your Place for Change: How and Where to Take an Active Role in DEI Initiatives as Early-Career Researchers and Students. In AGU Fall Meeting 2021. AGU.
Hoitink, T., Keogh, M., Piliouras, A., & Knights, D. H. (2021, December). Rivers and Floodplains, Estuaries and Tidal Flats III Poster. In AGU Fall Meeting 2021. AGU.
2020:
Knights, D., Sawyer, A. H., Barnes, R.T., Piliouras, A., Schwenk, J., Edmonds, D. A., & Brown, A. M. (2020). Nitrate removal across ecogeomorphic zones in Wax Lake Delta, Louisiana (USA). Water Resources Research, 56,e2019WR02686.
Knights, Deon Hanley (2020). The Fate of Nutrients in Two Coastal Freshwater Systems [Dissertation, The Ohio State University]. OhioLINK Electronic Theses and Dissertations Center.
2019:
Alexander M. Brown, Deon Knights, Audrey H. Sawyer, Derek E. Sawyer, Douglas A. Edmonds, and Rebecca T. Barnes (2019). Characterization of Surficial Sediments from a Modern Delta Wetland. 2019 AAPG Eastern Section Meeting: Energy from the Heartland, Columbus, Ohio.
2017:
Knights, D., A. H. Sawyer, R. T. Barnes, C. T. Musial, and S. Bray (2017), Tidal controls on riverbed denitrification along a tidal freshwater zone, Water Resour. Res., 53, 799–816.
Knights, D., Parks, K. C., Sawyer, A. H., David, C. H., Browning, T. N., Danner, K. M., & Wallace, C. D. (2017). Direct groundwater discharge and vulnerability to hidden nutrient loads along the Great Lakes coast of the United States. Journal of Hydrology, 554, 331–341.
Sawyer, A. H., Barnes, R., Wallace, C., Knights, D., Tight, D., Bayer, M. (2017). Dynamic surface water-groundwater exchange and nitrogen transport in the riparian aquifer of a tidal river. American Geophysical Union, Fall Meeting 2017, abstract #B53H-07.
2016 and earlier:
Musial, C. T., Sawyer, A. H., Barnes, R. T., Bray, S., and Knights, D. (2016) Surface water–groundwater exchange dynamics in a tidal freshwater zone. Hydrol. Process., 30: 739–750.
Barnes, R. T., Sawyer, A. H., Wallace, C., Knights, D. (2016). Nitrogen biogeochemistry in the stream and transient storage zones of a freshwater tidal ecosystem, Delaware, U.S.A. American Geophysical Union, Fall Meeting 2016, abstract #B12D-05.
Knights, D. H. (2016). Tidal Controls on Denitrification in Coastal Streambeds [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center.
Sawyer, A. H., D. A. Edmonds, and D. Knights (2015). Surface water-groundwater connectivity in deltaic distributary channel networks. Geophys.Res. Lett., 42, 10,299–10,306.
Sawyer, A. H., Knights, D. H., Barnes, R. T., Wallace, C., Bray, S. N., & Musial, C. (2015). A tale of two interfaces: Dynamic nitrate removal in the hyporheic zone of a tidal fresh river. AGU Fall Meeting Abstracts, 2015, H42B-06.
Sawyer, A., Edmonds, D., & Knights, D. (2015). Numerical investigation of surface water-groundwater interactions in a river-dominated delta. EGU General Assembly Conference Abstracts, 1059.
Knights, D. H., Sawyer, A. H. (2014). A Numerical Study of Tidal Impacts on Denitrification and Redox Zonation in Coastal Sediments. American Geophysical Union, Fall Meeting 2014, abstract id. H31B-0621.
Sawyer, A. H., Barnes, R., Wallace, C., Knights, D., Tight, D., & Bayer, M. (2017). Dynamic surface water-groundwater exchange and nitrogen transport in the riparian aquifer of a tidal river. AGU Fall Meeting Abstracts, 2017, B53H-07.