Water Resources Research Act Program

Details for Project ID 2012OH259B

Green-House-Gas budget of constructed wetlands: Understanding the sources to maximize benefits

Institute: Ohio
Year Established: 2012 Start Date: 2012-04-01 End Date: 2014-02-28
Total Federal Funds: $51,354 Total Non-Federal Funds: $102,906

Principal Investigators: Gil Bohrer

Abstract: Fixed nitrogen (N) is required for the growth for all biological organisms, and agriculture is dependent upon nitrogen for fertilizer. Ohio exports significant levels of nitrogen in its surface waters to Lake Erie and the Mississippi Basin due to its geology and agricultural land management techniques. Constructed wetlands can be used for nitrogen removal through the biologically-mediated process of denitrification, where nitrite is reduced to nitrogen gas and released to the atmosphere. Unfortunately, denitrification in wetlands comes with the tradeoff of increased Green House Gas (GHG) production. Wetlands sequester large amounts of carbon (C) from the atmosphere, removing the most common GHG CO2 but produce another and more potent GHG methane (CH4). In order to allow development of wetlands as a solution for N removal without concerns of GHG emissions, it is critical to understand how methane production in the wetland responds to different environmental conditions such as water and soil temperature, water chemistry. GHG emission rates and water and meteorological conditions can be measured simultaneously over wetlands using eddy-flux sensors that measure the combined emissions from a broad flux footprint area, and chamber measurements at specific points and provide spatially anecdotal and temporally sparse information. Highly variable rates of methane production and carbon sequestration at different sub-ecosystems within the wetland at a very small scale (meters) prohibits the generalization of measured environmental relationships from either eddy-flux or chamber measurements. The proposed work will use a combination of meteorological, water, and GHG flux and chamber measurements in a constructed wetland at the Olentagy River Wetland Research Center (ORWRP) over 2 years to parameterize a novel high-resolution flux footprint model. The model will be used to determine the atmospheric exchange rates of methane sources and carbon sinks at different sub-ecosystem components of the wetland. This will allow determining the strength of different environmental variables that control methane production, and will facilitate the parameterization of an empirical model to predict whole-wetland GHG budgets at ORWRP, and ultimately GHG budgets in other constructed and urban wetland ecosystems.