In situ evaluation of nearshore porewater exchange rates in Flamengo Bay, Brazil

Cable, Jaye, Martin, Jonathan, and Stieglitz, Thomas (2005) In situ evaluation of nearshore porewater exchange rates in Flamengo Bay, Brazil. In: Interactions of Groundwater and Surface Water at the Land-Sea Margin. 191-4. From: 2005 Salt Lake City Annual Meeting , 16-19 October 2005, Salt Lake City, USA.

[img] PDF (Published Version) - Published Version
Restricted to Repository staff only

View at Publisher Website:


As part of a larger IAEA/UNESCO intercomparison study of submarine groundwater discharge measurement techniques in southeastern Brazil, we sampled porewaters from four multilevel piezometers installed along a 45-m long transect normal to shore. In addition, water level recovery rates were estimated using pump tests along a parallel onshore-to-offshore well transect. This coastline is characterized by the Serra do Mar Mountain range, which abuts Flamengo Bay leaving a thin strip of sandy beaches along this rugged Atlantic coast. Tidal ranges measured in the coastal community of Ubatuba adjacent to the bay were about 1 to 1.5 m. The shoreline is steep (~ 0.044) and wave run-up is about 0.3 to 0.6 m above sea level, especially on flood tide. Rn-222 and Cl-, along with conductivity and temperature, were measured at discrete depth intervals from the piezometers down to 1.5 to 2 m below the sediment-water interface to evaluate the contribution of groundwater to the bay. Additionally, a fluorescien dye solution saturated with SF₆ was injected into one discrete depth interval in each piezometer to evaluate the exchange rate between the upper sediments and the surface waters. Using the SF₆, exchange rates were rapid, on the order of 28 to 184 cm/day, in the upper 1 to 2 m of sediments. Rn-222 and Cl- in porewaters support a high turnover rate in these sediments. In this well-mixed sediment-porewater regime, terrestrial groundwater inputs were difficult to quantify. Nonetheless, below about 50 cmbsf, porewater salinities were less than 5 ppt in the nearest piezometers to shore, indicating terrestrial groundwater was discharging to the bay.

Item ID: 27661
Item Type: Conference Item (Non-Refereed Research Paper)
Date Deposited: 05 Jul 2013 05:04
FoR Codes: 04 EARTH SCIENCES > 0402 Geochemistry > 040299 Geochemistry not elsewhere classified @ 40%
04 EARTH SCIENCES > 0405 Oceanography > 040502 Chemical Oceanography @ 40%
04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040603 Hydrogeology @ 20%
SEO Codes: 96 ENVIRONMENT > 9611 Physical and Chemical Conditions of Water > 961102 Physical and Chemical Conditions of Water in Coastal and Estuarine Environments @ 100%
Downloads: Total: 1
More Statistics

Actions (Repository Staff Only)

Item Control Page Item Control Page