Mechanisms Driving Variability in Groundwater-derived Materials Flux to Coastal WatersEPA Grant Number: FP917108
Title: Mechanisms Driving Variability in Groundwater-derived Materials Flux to Coastal Waters
Investigators: Schutte, Charles A
Institution: University of Georgia
EPA Project Officer: Lee, Sonja
Project Period: August 16, 2010 through August 15, 2013
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2010) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Fellowship - Water Quality: Coastal and Estuarine Processes
Nitrogen loading is an important cause of water quality degradation in coastal estuaries and bays, but the amount of nitrogen coming from many sources is not well known. The goal of this project is to better understand the role of groundwater discharge in the nitrogen budget of coastal water bodies and the influence of within-aquifer processes on the nitrogen content of that discharge. The overarching hypothesis for this project is that the response of aquifer microbial nitrogen cycling to tidal forcing acts as an important mechanism driving temporal variability in groundwater-derived nitrogen flux to coastal waters.
Groundwater may act as a critical source of nitrogen to coastal environments where it can lead to decreased water quality through eutrophication and hypoxia. Microorganisms living within coastal aquifers can efficiently alter the amount and type of nitrogen-containing chemicals found in groundwater. This project aims to better understand the role of groundwater in coastal nitrogen budgets by quantifying how microorganisms respond to changes in their environment caused by tides and how this interaction affects rates of nitrogen processing within aquifers.
This project consists of experiments carried out at multiple sites in coastal Georgia during spring and neap tides in order to determine the influence of tidal forcing on aquifer nitrogen cycling. Nitrogen transformation rates will be calculated in situ by adding nitrogen to groundwater within the aquifer and measuring how the concentration of nitrogen changes through time. At the same time, sediment samples will be collected in order to extract microbial mRNA and determine the abundance of active nitrogen cycling genes as a proxy of aquifer microbial activity. Finally, groundwater-derived nitrogen fluxes will be quantified at each time point using radium as a conservative tracer of groundwater movement.
The data generated through this project will allow exploration of the relationship between tidal forcing, aquifer microbial activity, nitrogen transformation rates, and groundwater-derived nitrogen flux. This project will document the role of groundwater as a dynamic and important source of nitrogen to coastal water bodies. It will also generate fundamentally new information about how hydrological (e.g., tides) and biological (e.g., microbial nitrogen cycling) processes alter groundwater composition and drive variability in groundwater-derived nitrogen fluxes to coastal waters, and thus influence coastal water quality.
Potential to Further Environmental/Human Health Protection:
This project will provide a refined understanding of aquifer processes and groundwater flux that will assist policy makers and resource managers in assessing and managing coastal water quality and resources. It will serve to better inform regulations regarding septic tanks and buffer zones and design and implementation of water quality standards such as total maximum daily loads. The mechanistic understanding of a critical pollutant source generated by this research will aid in the creation of such policies by providing a framework for the prediction of the source response to perturbations such as increased coastal development, sea level rise, and climate change.