Date of Award

1-1-2015

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

First Advisor

Richard F. Viso

Second Advisor

Richard N. Peterson

Third Advisor

Jenna C. Hill

Additional Advisors

Christof Meile

Abstract

Groundwater discharge in the coastal environment is known to be a complex process. The driving mechanisms of groundwater discharge vary on spatial and temporal scales that can significantly impact coastal water chemistry and play a role in ecological zonation. Evolving combinations of observational and modeling approaches provide a basis to quantify groundwater discharge in a spatial and temporal sense. Here we employ a combination of geochemical (naturally occurring radon isotope) and geophysical (electrical resistivity) techniques to measure groundwater-surface water interactions along a back-barrier tidal creek. In addition to field measurements, a unique non-steady state radon mass balance equation was developed to better constrain groundwater estimates. The radon mass balance shows spatial and temporal variance in groundwater composition along the tidal creek. Our estimates suggest that groundwater discharge is grater in the Upper Duplin compared to the Lower Duplin section. Spring tide conditions yielded greater groundwater discharge at all sites, but the Lower Duplin section had significantly greater discharge when compared to neap tide discharge. Electrical resistivity serves as a qualitative assessment to support the radon mass balance findings of marsh zone water circulation on both daily and spring/neap cycles. Our observations proved baseline groundwater contributions to the Duplin River system. This can be used to constrain aquifer characteristic used in numerical simulations of chemical and nutrient transport the systems.

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