Assessment of groundwater discharges into West Neck Bay, New York, via natural tracers
Burnett, William C.
Chanton, Jeffrey P.
Moore, Willard S.
Bokuniewicz, H. J.
Charette, Matthew A.
Sholkovitz, Edward R.
MetadataShow full item record
A field experiment to compare methods of assessing submarine groundwater discharge (SGD) was held on Shelter Island, NY, in May 2002. We evaluated the use of radon, radium isotopes, and methane to assess SGD rates and dynamics from a glacial aquifer in the coastal zone. Fluxes of radon across the sediment-water interface were calculated from changes in measured surface water inventories following evaluation and correction for tidal effects, atmospheric evasion, and mixing with offshore waters. These fluxes were then converted to SGD rates using the measured radon concentration in the groundwater. We used the short-lived radium isotopes to calculate a horizontal mixing coefficient to assess radon loss by mixing between nearshore and offshore waters. We also made an independent calculation of SGD using the Ra-derived mixing coefficient and the long-lived 226Ra concentration gradient in the bay. Seepage rates were calculated to range between 0 and 34 cm.day-1 using the radon measurements and 15 cm.day-1 as indicated by the radium isotopes. The radiotracer results were consistent and comparable to SGD rates measured directly with vented benthic chambers (seepage meters) deployed during this experiment. These meters indicated rates between 2 and 200 cm.day-1 depending on their location. Both the calculated radon fluxes and rates measured directly by the automated seepage meters revealed a clear reproducible pattern of higher fluxes during low tides. Considering that the two techniques are completely independent, the agreement in the SGD dynamics is significant. Methane concentration in groundwater was very low (~30 nM) and not suitable as SGD tracer at this study site.
Author Posting. © Elsevier B.V., 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Continental Shelf Research 29 (2006): 1971-1983, doi:10.1016/j.csr.2006.07.011.
Showing items related by title, author, creator and subject.
Geochemical and physical sources of radon variation in a subterranean estuary — implications for groundwater radon activities in submarine groundwater discharge studies Dulaiova, Henrieta; Gonneea, Meagan E.; Henderson, Paul B.; Charette, Matthew A. (2007-12-13)Submarine groundwater discharge (SGD), in form of springs and diffuse seepage, has long been recognized as a source of chemical constituents to the coastal ocean. Because groundwater is two to four orders of magnitude ...
DeFoor, Whitney; Person, Mark; Larsen, Hans Christian; Lizarralde, Daniel; Cohen, Denis; Dugan, Brandon (American Geophysical Union, 2011-07-28)Isotopically light (−1‰ to −8‰ δ18O) and fresh pore fluids (300–520 mM Cl−) were found in continental shelf sediments up to 100 km offshore of southeastern (SE) Greenland, suggesting infiltration and mixing of ice sheet ...
How significant is submarine groundwater discharge and its associated dissolved inorganic carbon in a river-dominated shelf system? Liu, Q.; Dai, Minhan; Chen, W.; Huh, C.-A.; Wang, Guihua; Li, Q.; Charette, Matthew A. (Copernicus Publications on behalf of the European Geosciences Union, 2012-05-22)In order to assess the role of submarine groundwater discharge (SGD) and its impact on the carbonate system on the northern South China Sea (NSCS) shelf, we measured seawater concentrations of four radium isotopes ...