Water Residence Times and Circulation of the Savannah River Using Short-lived Radium Isotopes

Document Type

Presentation

Presentation Date

Fall 2014

Abstract or Description

Dredging the Savannah Harbor will address the present insufficiencies of marine transportation through the Savannah River. Dredging will likely impact water circulation and residence times in the harbor. The primary goal of our research is to monitor groundwater discharge, groundwater-river water mixing, and water residence times prior to dredging. This will allow us to identify any hydrological changes, such as aquifer breeches that occur as a result of dredging. Short-lived radium isotopes (224Ra, t1/2 = 3.6 d and 223Ra, t1/2 = 11 d) are ideally suited for this research because they decay at rates comparable to these groundwater-river water interaction processes. We conducted our study along a transect of the Savannah River starting at the mouth and ending upstream, near the city of Savannah. We collected surface and bottom water during two cruises (February 2014 and April 2014) onboard the Research Vessel Savannah. Our samples were collected from nine different locations (18 samples from each cruise). The locations were determined by designated salinity intervals from 32 to < 3 practical salinity units. Sample sizes ranged from 19 to 40 liters of water. Radium isotopes were pre-concentrated on fibers that were counted using a Radium Delayed Coincidence Counter (RaDeCC). We found that 224Ra excess was higher than 223Ra during both cruises. Furthermore, both short-lived radium isotopes were higher in April than in February. Results of this study will be compared to a duplicate study of the Savannah Harbor once the dredging is complete.

Sponsorship/Conference/Institution

Southeastern Estuarine Research Society Fall Meeting (SEERS)

Location

Carolina Beach, NC

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