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Direct measurements of groundwater seepage into the coastal zone of the NE Gulf of Mexico

Conference · · Geological Society of America, Abstracts with Programs; (United States)
OSTI ID:5949185
; ; ; ;  [1]
  1. Florida State Univ., Tallahassee, FL (United States). Dept. of Oceanography

Direct measurements of submarine groundwater discharge (SGD) in coastal waters of the northeastern Gulf of Mexico are being made to: (1) evaluate the volumetric significance of SGD; and (2) validate two chemical tracers being used to assess this flux. Since [sup 222]Rn and CH[sub 4] are extremely high in groundwater relative to seawater and are largely unreactive in seawater, these tracers should allow areas of SGD to be located. Although the amount of water entering coastal waters via SGD has often been considered negligible, measurements show this input may be very important, perhaps equal to or greater than some of the largest springs in Florida. Three transects were established in the study area with five seepage meters, constructed from a 55-gallon drum, placed 50 meters apart starting approximately 3 meters from the coastline and extending perpendicular offshore. Seawater [sup 222]Rn and CH[sub 4] concentrations near these meters were then compared to the seepage rates. Seepage trends at each transect were consistent over long periods of time and the concentrations of [sup 222]Rn and CH[sub 4] showed similar patterns to these rates. A free flowing spring within the study area was also investigated in order to qualitatively establish the relationship between groundwater and the tracer concentrations. A north-south transect across the spring showed elevated tracer concentrations associated with this groundwater input. This study has shown that: (1) nearshore seepage of groundwater into the ocean is volumetrically important; and (2) a qualitative link exists between rates of groundwater seepage and tracer concentrations.

OSTI ID:
5949185
Report Number(s):
CONF-9304188--
Journal Information:
Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 25:4; ISSN GAAPBC; ISSN 0016-7592
Country of Publication:
United States
Language:
English