A radiocarbon method and multi-tracer approach to quantifying groundwater discharge to coastal waters

Groundwater discharge into estuaries and the coastal ocean is an important mechanism for the transport of dissolved chemical species to coastal waters. Because many dissolved species are present in groundwater in concentrations that are orders of magnitude higher than typical river concentrations, groundwater-borne nutrients and pollutants can have a substantial impact on the chemistry and biology of estuaries and the coastal ocean. However, direct fluxes of groundwater into the coastal ocean (submarine groundwater discharge, or SGD) can be difficult to quantify. Geochemical tracers of groundwater discharge can reflect the cumulative SGD flux from numerous small, widely dispersed, and perhaps ephemeral sources such as springs, seeps, and diffuse discharge. The natural radiocarbon content (A14C) of dissolved inorganic carbon (DIC) was developed as a tracer of fresh, terrestrially driven fluxes from confined aquifers. This A14C method was tested during five sampling periods from November 1999 to April 2002 in two small estuaries in southeastern North Carolina. In coastal North Carolina, fresh water artesian discharge is characterized by a low A14C signature acquired from the carbonate aquifer rock. Mixing models were used to evaluate the inputs from potential sources of DIC-A'4C to each estuary, including seawater, springs, fresh water stream inputs, and salt marsh respiration DIC additions. These calculations showed that artesian discharge dominated the total fresh water input to these estuaries during nearly all sampling periods.

Department dc:contributor.department

Joint Program in Marine Geology and Geophysics

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Gramling, Carolyn M

Advisor dc:contributor.advisor

• Daniel C. McCorkle.

• Joint Program in Marine Geology and Geophysics.
• Earth, Atmospheric, and Planetary Sciences.
• Woods Hole Oceanographic Institution.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/69769

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/69769