Southwestern Atlantic Ocean Margin Workshop Montevideo, Uruguay 16-22 November 2008. Submarine Groundwater Discharge into the ocean off Mangueira Lagoon via 222 Rn and Ra isotopes: Preliminary findings and perspectives . Isaac R. Santos ; William Burnett
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16-22 November 2008
Submarine Groundwater Discharge into the ocean off Mangueira Lagoon via 222Rn and Ra isotopes:
Preliminary findings and perspectives
Isaac R. Santos; William Burnett
Department of Oceanography, Florida State University, Tallahassee, FL, USA
Felipe Niencheski; Karina Attisano; Carlos Andrade; Idel Milani
Department of Chemistry, Fundação Universidade do Rio Grande, Rio Grande, Brazil
- SGD Fe inputs ~10% of atmospheric Fe inputs into the entire South Atlantic (Windom et al., 2006)
- Patos Lagoon and La Plata River are the obvious nutrient sources
Silicate in mM data from Attisano, Niencheski, et al., 2008
222Rn as a SGD tracer
Platform with a continuous Rn monitor system
Push-point piezometer for groundwater sampling
Non-steady state box model
Assume wave action was constant during deployment
222Rn time series
- Some enriched 223Ra and 224Ra samples in the south
- Are the shell deposits a preferential flow path?
Concentrations in dpm/100L
Modeling SGD from radium isotopes
Seawater residence time (t) :
Overall averages: 3.1 cm/day
Area: 220 km long; 10 km wide
Total SGD into the area:
Patos Lagoon Flux:
Is SGD a new source of nutrients (fresh SGD) or purely a recycling mechanism (saline SGD)?
Campos et al., 2007.
- SGD or sub-Antarctic water advection onto the shelf?
1) Radium is the preferred SGD tracer as we cannot model how waves influence radon evasion
2) SGD is potentially a major source of water and nutrients to the Albardão area and the entire SWAOM margin
3) Shell deposits and the La Plata River Paleocanal may represent a preferential flow path for SGD