Isotope tracing of submarine groundwater discharge offshore Ubatuba, Brazil : results of the IAEA–UNESCO SGD project

View/ Open
Date
2008-06-12Author
Povinec, Pavel P.
Concept link
Bokuniewicz, Henry J.
Concept link
Burnett, William C.
Concept link
Cable, J.
Concept link
Charette, Matthew A.
Concept link
Comanducci, J.-F.
Concept link
Konta, E. A.
Concept link
Moore, Willard S.
Concept link
Oberdorfer, J. A.
Concept link
de Oliveira, J.
Concept link
Peterson, R.
Concept link
Stieglitz, T.
Concept link
Taniguchi, M.
Concept link
Metadata
Show full item recordCitable URI
https://hdl.handle.net/1912/2593As published
https://doi.org/10.1016/j.jenvrad.2008.06.010Keyword
Submarine groundwater discharge; Groundwater; Seawater; Stable isotopes; δD; δ18O; Tritium; Radium isotopes; Radon; Coastal zone; Ubatuba; BrazilAbstract
Results of groundwater and seawater analyses for radioactive (3H, 222Rn, 223Ra, 224Ra, 226Ra, 228Ra) and stable (2H, 18O)
isotopes are presented together with in situ spatial mapping and time-series 222Rn measurements in seawater, direct seepage
measurements using manual and automated seepage meters, pore water investigations using different tracers and piezometric
techniques, and geoelectric surveys probing the coast. This study represents first time that such a new complex arsenal of radioactive
and non-radioactive tracer techniques and geophysical methods have been used for simultaneous submarine groundwater discharge
(SGD) investigations. Large fluctuations of SGD fluxes were observed at sites situated only a few meters apart (from 0 cm d-1 to 360
cm d-1; the unit represents cm3/cm2/day), as well as during a few hours (from 0 cm d-1 to 110 cm d-1), strongly depending on the tidal
fluctuations. The average SGD flux estimated from continuous 222Rn measurements is 17±10 cm d-1. Integrated coastal SGD flux
estimated for the Ubatuba coast using radium isotopes is about 7x103 m3 d-1 per km of the coast. The isotopic composition (δ2H and
δ18O) of submarine waters was characterised by significant variability and heavy isotope enrichment, indicating that the contribution
of groundwater in submarine waters varied from a small percentage to 20%. However, this contribution with increasing offshore
distance became negligible. Automated seepage meters and time-series measurements of 222Rn activity concentration showed a
negative correlation between the SGD rates and tidal stage. This is likely caused by sea level changes as tidal effects induce variations of hydraulic gradients. The geoelectric probing and piezometric measurements contributed to better understanding of the spatial distribution of different water masses present along the coast. The radium isotope data showed scattered distributions with offshore distance, which imply that seawater in a complex coast with many small bays and islands was influenced by local currents and
groundwater/seawater mixing. This has also been confirmed by a relatively short residence time of 1-2 weeks for water within 25 km
offshore, as obtained by short-lived radium isotopes. The irregular distribution of SGD seen at Ubatuba is a characteristic of fractured
rock aquifers, fed by coastal groundwater and recirculated seawater with small admixtures of groundwater, which is of potential
environmental concern and has implications on the management of freshwater resources in the region.
Description
Author Posting. © Elsevier B.V., 2008. 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 Journal of Environmental Radioactivity 99 (2008): 1596-1610, doi:10.1016/j.jenvrad.2008.06.010.
Collections
Suggested Citation
Preprint: Povinec, Pavel P., Bokuniewicz, Henry J., Burnett, William C., Cable, J., Charette, Matthew A., Comanducci, J.-F., Konta, E. A., Moore, Willard S., Oberdorfer, J. A., de Oliveira, J., Peterson, R., Stieglitz, T., Taniguchi, M., "Isotope tracing of submarine groundwater discharge offshore Ubatuba, Brazil : results of the IAEA–UNESCO SGD project", 2008-06-12, https://doi.org/10.1016/j.jenvrad.2008.06.010, https://hdl.handle.net/1912/2593Related items
Showing items related by title, author, creator and subject.
-
Nonhomogeneous seawater Sr isotopic composition in the coastal oceans : a novel tool for tracing water masses and submarine groundwater discharge
Huang, Kuo-Fang; You, Chen-Feng; Chung, Chuan-Hsiung; Lin, In-Tian (American Geophysical Union, 2011-05-07)Here we present high-precision (2σ = ±3 ppm) 87Sr/86Sr measurements in coastal waters, together with salinity, to evaluate water mass mixing and the influence of submarine groundwater discharge (SGD) in coastal waters and ... -
Isotopic, geophysical and biogeochemical investigation of submarine groundwater discharge : IAEA-UNESCO intercomparison exercise at Mauritius Island
Povinec, Pavel P.; Burnett, William C.; Beck, A.; Bokuniewicz, Henry J.; Charette, Matthew A.; Gonneea, Meagan E.; Groening, M.; Ishitobi, T.; Kontar, E.; Kwong, L. Liong Wee; Marie, D. E. P.; Moore, Willard S.; Oberdorfer, J. A.; Peterson, R.; Ramessur, R.; Rapaglia, J.; Stieglitz, T.; Top, Zafer (2011-09)Submarine groundwater discharge (SGD) into a shallow lagoon on the west coast of Mauritius Island (Flic-en-Flac) was investigated using radioactive (3H, 222Rn, 223Ra, 224Ra, 226Ra, 228Ra) and stable (2H, 18O) isotopes and ... -
Investigating boron isotopes for identifying nitrogen sources supplied by submarine groundwater discharge to coastal waters
Tamborski, Joseph; Brown, Caitlin; Bokuniewicz, Henry J.; Cochran, J. Kirk; Rasbury, E. Troy (Frontiers Media, 2020-08-11)Stable isotopes of oxygen, nitrogen, and boron were used to identify the sources of nitrate (NO3–) in submarine groundwater discharge (SGD) into a large tidal estuary (Long Island Sound, NY, United States). Potential ...