Stormwater runoff is the major contributor to non-point source pollution and can contaminate many aquatic environments. Stormwater Control Measures (SCMs) are structural devices, such as retention ponds and constructed wetlands, used to control stormwater runoff from developed landscapes. One of the main pollutants found in stormwater runoff is nitrogen. Nitrogen is a macronutrient that limits primary productivity. In excess quantities, introduced nitrogen can lead to coastal eutrophication, harmful algal blooms, and coastal hypoxia. Although SCMs tend to be highly effective at removing particulate-associated pollutants, such as phosphorus, they are often much less effective at removing nitrogen. In this research, we aim to provide an estimate of nitrogen removal rates (denitrification) across a series of SCMs along a vegetation gradient. It is hypothesized that SCMs with more vegetation remove greater amounts of nitrogen compared to unvegetated SCMs (e.g., conventional stormwater retention ponds) because organic material provided by vegetation is a substrate for denitrification. We used whole sediment core ¹⁵N-labeled incubations and the isotope pairing method to measure denitrification rates at the center and the edge of several different types of SCMs in Georgetown and Horry Counties, in coastal SC (e.g., conventional unvegetated stormwater ponds, ponds with littoral shelves, constructed wetland). Thus far, we measured higher nitrogen removal rates (up to two orders of magnitude) in the more vegetated SCMs, which supports our main hypothesis. We anticipate results of this research will provide recommendations for improved use of vegetation in SCMs to maximize nitrogen removal and improve the water quality of stormwater runoff associated with coastal development.

Primary Presenter: Darcy Perin, University of South Carolina (dperin@email.sc.edu)

Authors:

Darcy Perin, University of South Carolina   (dperin@email.sc.edu)

Annie Bourbonnais, University of South Carolina  (abourbonnais@seoe.sc.edu)

Erik Smith, University of South Carolina  (erik@baruch.sc.edu)

Claire Matta, University of South Carolina  (camatta@email.sc.edu)