210Po, 210Pb, and poc in the mesopelagic: multi-technique water column sampling in medflux



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210Po, 210Pb, and POC in the mesopelagic: multi-technique water column sampling in MEDFLUX

  • G. Stewart

  • P. Masque, J.K. Cochran, J.C. Miquel, B. Gasser, D. Hirschberg, A. Rodriguez y Baena, and S. Fowler


Review of 210Po and 210Pb behavior

  • Review of 210Po and 210Pb behavior

  • 210Po and POC relationship

  • What happens in the Mesopelagic?

    • Sediment traps indicate loss of 210Po and POC
    • Water column POC decreases (Pumps)
    • No evidence of water column 210Po decrease
    • Pumps vs. Bottles
  • Possible explanations and conclusions



Ubiquitous Trace Natural Radionuclides

  • Ubiquitous Trace Natural Radionuclides

  • Both Highly Particle-Reactive

  • 210Po Specific Affinity for Organic Matter, Protein

  • Correlated with Biological Activity

    • Predictable uptake by planktonic particles
    • Elevated concentrations in higher trophic levels
    • Highest dose of radiation to organisms
  • 210Pb Effective Surface Area Tracer

  • Relationship between 210Po and 210Pb May Provide Additional Information Beyond 234Th



210Pb, 210Po and Carbon Cycles



210Po, 210Pb profiles in both pumps and bottles

  • 210Po, 210Pb profiles in both pumps and bottles

  • Water column profiles of POC only from pumps

  • Sediment traps at 2 depths during 2 periods (Spring: 200m, 800m and Summer: 200m, 1940m)

    • POC
    • 210Po
    • 210Pb






Disconnect: POC and Particulate 210Po or Pumps and Bottles?







Swimmers Have High Po/Pb



Bottles vs. Pumps

  • Bottles capture high 210Po swimmers at depth

  • March through May Po/Pb differs

  • June profiles are similar

  • Neither pump nor bottle Po/Pb reflects evidence of POC remineralization

  • Decoupling of water column measurements and sediment trap collection



Mesopelagic Story

  • No evidence of Polonium remineralization: WHY?

    • Long radioactive half-life?
    • Sorption with depth?
    • Mediterranean water bodies?
    • Rapid sinking?
  • Need to investigate further Po/Pb as POC tracer below the euphotic zone



Acknowledgements

  • Funding for research from NSF to MEDFLUX, AAUW to GMS

  • Funding for this conference from CUNY OEODP, Queens College DMNS

  • Captain and Crew of R.V.Tethys (Monaco) and R. V. Seward Johnson (Harbor Branch)

  • All the participants in MEDFLUX





Review of Surface Sediment Trap Material





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