Nitrate Removal in Urban Wetlands: Examining the Roles of Vegetation, Soils, and Hydrology in the Creation of ‘Hot Spots’ and ‘Hot Moments’ of Denitrification

EPA Grant Number: F6F11264
Title: Nitrate Removal in Urban Wetlands: Examining the Roles of Vegetation, Soils, and Hydrology in the Creation of ‘Hot Spots’ and ‘Hot Moments’ of Denitrification
Investigators: Palta, Monica M.
Institution: Rutgers, The State University of New Jersey
EPA Project Officer: Hahn, Intaek
Project Period: September 1, 2006 through September 1, 2009
Project Amount: $111,172
RFA: STAR Graduate Fellowships (2006) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Terrestrial Systems Ecology


In recent decades, interest has increased worldwide in restoring ecological functions to urbanized watersheds. However, managers often lack quantitative, predictive models relating riparian processes to specific combinations of biological communities, flooding patterns, and soils. Little research has addressed how urbanization may be affecting N retention of stream ecosystems. I propose to undertake empirical research that can be utilized by managers in the design of restoration plans targeting wetland processes, specifically nitrogen (N) removal from surface water inputs. My research examines (1) how specific combinations of vegetation type, hydrologic conditions, and soil properties interact to mediate nitrogen (N) cycling in wetland soils, and (2) how specific anthropogenic alterations may be affecting these interactions.


A recently developed paradigm has been adopted by restoration projects that aim for higher N removal across wetland landscapes; this paradigm involves “hot spots” and “hot moments” of nitrate (NO3-) removal within wetlands. Periods or areas of high NO3- removal occur when and where episodic hydrological flowpaths reactivate and/or mobilize accumulated reactants. My study examines how combinations of particular hydrologic conditions (well-drained vs. poorly drained), plant community types (woody vs. herbaceous), and soil characteristics (texture, bulk density, % organic matter) influence the spatial and temporal distributions of NO3- removal “hot spots” and “hot moments” in urban wetland soils. Patches of wetland that differ in soils, hydrology, and/or plant characteristics will be located in field sites undergoing restoration and mimicked using mesocosms. Information gathered from field and lab studies will be used to identify which characteristics are the most important in facilitating NO3- removal. Empirical models will be constructed and used to predict changes in N cycling following restoration.

Expected Results:

The combination of high NO3-, high labile C, high temperature, and low oxygen results in the highest levels of denitrification, a measure of NO3- removal. It is expected that soils with the highest C content, the highest root biomass at the deepest depths, and the optimal drainage (i.e. intermediate between poorly and very well-drained) will sustain the highest levels of denitrification. This research will allow for quantitative predictions at the patch scale of what characteristics in vegetation, hydrology, and soils are necessary to facilitate the highest NO3- removal. My study will therefore serve to inform the restoration design of urban watersheds.

Supplemental Keywords:

RFA, Scientific Discipline, Water, Water & Watershed, Environmental Monitoring, Ecology and Ecosystems, Watersheds, dentrification, nitrogen loading, alternative urbanization scenarios, conservation, hydrology, wetland restoration, ecology assessment models, watershed assessment, restoration planning

Progress and Final Reports:

  • 2007
  • 2008
  • Final