Southwestern Atlantic Ocean Margin Workshop
Download
1 / 16

Submarine Groundwater Discharge into the ocean off Mangueira Lagoon via 222 Rn and Ra isotopes: Preliminary findings a - PowerPoint PPT Presentation


  • 545 Views
  • Uploaded on

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

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Submarine Groundwater Discharge into the ocean off Mangueira Lagoon via 222 Rn and Ra isotopes: Preliminary findings a' - LionelDale


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Slide1 l.jpg

Southwestern Atlantic Ocean Margin Workshop

Montevideo, Uruguay

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


Slide2 l.jpg

  • Outline

  • Area background

  • Tracing SGD via 222Rn and radium isotopes

  • Is the La Plata River Paleocanal a preferential SGD pathway?


Slide3 l.jpg

Brazil

- SGD Fe inputs ~10% of atmospheric Fe inputs into the entire South Atlantic (Windom et al., 2006)

Patos

Mirim

  • Higher SGD than North of Patos Lagoon?

  • Mangueira Lagoon level is higher than

  • Patos Lagoon level

  • Lagoon closer to the ocean

  • Sediments more permeable (shell deposits)

Mangueira




Slide6 l.jpg

Alongshore distribution of silicate (10 m depth)

- Patos Lagoon and La Plata River are the obvious nutrient sources

  • No N-S trends suggest an additional source –

  • Widespread, diffuse SGD?

Silicate in mM data from Attisano, Niencheski, et al., 2008


Slide7 l.jpg

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


Slide8 l.jpg

222Rn time series

Concheiros Hermenegildo

  • Background 226Ra: ~70 dpm/m3

  • Excess radon in spite of breaking waves

  • Modeled SGD rates 2.22.4 cm/day



Slide10 l.jpg

- Some enriched 223Ra and 224Ra samples in the south

- Are the shell deposits a preferential flow path?

Radium

along-shore transect

  • Fresher seawater in the winter

  • No seasonal radium changes

Concentrations in dpm/100L


Slide11 l.jpg

Radium in beach groundwater

C*gw

Modeling SGD from radium isotopes

Seawater residence time (t) :

Advection rates:


Slide12 l.jpg

Estimated SGD inputs (cm/day)

Overall averages: 3.1 cm/day

Area: 220 km long; 10 km wide

Total SGD into the area:

~800 m3/s

Patos Lagoon Flux:

~2400 m3/s

Is SGD a new source of nutrients (fresh SGD) or purely a recycling mechanism (saline SGD)?


Slide13 l.jpg

Offshore radium transect

  • Onshore radium source, likely SGD

  • Mixing coefficients >3000 m2/s (too high!).

  • Violates assumption of no inputs offshore?

  • Peak at ~100 km indicates an additional source or advection of nearshore waters


Slide14 l.jpg

La Plata paleocanal

  • 70 km long

  • 20 km wide

  • - 30 m deep

Campos et al., 2007.


Slide15 l.jpg

Silicate in bottom waters

- SGD or sub-Antarctic water advection onto the shelf?

mM

Paleocanal

slope


Slide16 l.jpg

Summary

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