Assessing the Impact of Residential Development and Recreational Land Use on Shallow Groundwater Quality in Coastal Environments
Samantha Joye (Dept of
Marine Sciences, Univ of Georgia, Athens, GA, USA)
Sea Grant College Program (R/WQ-19)
Project Overview. The
objectives of this project were to:
1) compare and contrast ground water and surface water nutrient and organic matter concentrations;
2) determine rates of dissolved inorganic nitrogen (DIN) processing within the aquifer using push-pull experiments;
3) determine rates of groundwater DIN, dissolved organic matter (DOM), dissolved inorganic phosphorus (DIP) processing within marsh and creek bank sediments using flow through bioreactor experiments;
A microbial community's processing of organic matter is solely a function of the available electron acceptor. Plug-flow studies showed that when sulfate was the electron acceptor, acetate accumulated while when nitrate was the electron acceptor, no dissolved organic intermediates accumulated.
The impact of periodic versus extensive drought differed from conditions when the marsh sediments were continually inundated with water. Cycling of sulfate, nitrate and metals were strongly regulated by the hydrological regime.
Consistent fluctuations in nitrogen speciation from spring to neap tide throughout the study period suggest a tidal influence on nitrogen transformation processes taking place within the aquifer. The rates of these processes were determined using slurry experiments in March 2009. The measured rates indicate that nitrification and denitrification may be coupled within this system. This coupling could be the result of temporal segregation of the two processes as the redox state of the aquifer fluctuates with the stage of the spring/neap tidal cycle.
We have worked closely with Dr. C. Meile linking our biogeochemical data with his modeling effort. A joint manuscript on this work at Moses Hammock was published (see below).
Porubsky, W. P., S.B. Joye, W. S. Moore, K. Tuncay, and C.D. Meile (2010). Field measurements and modeling of groundwater flow and biogeochemistry at Moses Hammock, a backbarrier island on the Georgia coast. Biogeochemistry (Online First, DOI: 10.1007/s10533-010-9484-8)
Porubsky, W. P., W. S. Moore, N. B. Weston, C. Ruppel, and S. B. Joye (submitted) Groundwater as a potential source of nutrients and dissolved organic matter to the Okatee
estuary, South Carolina. Submitted to Limnology & Oceanography, in review.
Dissolved Inorganic Nitrogen and Nitrous Oxide Concentrations in the Groundwater
of Two Selected Sites in Coastal Georgia and South Carolina