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

210 Po, 210 Pb, 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. Outline. Review of 210 Po and 210 Pb behavior 210 Po and POC relationship

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

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  1. 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

  2. Outline • 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

  3. 210Po and 210Pb • 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

  4. Modified from Bacon et al. 1996 210Pb, 210Po and Carbon Cycles ATM Polonium Polonium Polonium Polonium Po Po Po Po Pb Po WHAT HAPPENS IN THE TWILIGHT ZONE?

  5. Sampling Techniques • 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

  6. Spring to Early Summer: Traps POC 210Po Not much loss of POC or 210Po between 200 and 800m

  7. Summer: Traps POC 210Po Evidence of loss of POC and 210Po between 200 and 1940m

  8. Disconnect: POC and Particulate 210Po or Pumps and Bottles? POC - Pumps % Particulate Po - Bottles

  9. From Liu et al. 2005 Bottle and Pump Results at Surface Bottles captured more POC than pumps during spring, not summer Bottles and Pumps captured Identical Chlorophyll a Differences were attributed in part to zooplankton

  10. Po/Pb Ratios in Bottles and Pumps

  11. x 12 x 5 From Stewart et al. 2005 Swimmers Have High Po/Pb

  12. 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

  13. 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

  14. 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

  15. High Activity of 210Po in Bottle Particles

  16. From Stewart et al. submitted DSR Review of Surface Sediment Trap Material Bacterial Degradation Fecal Pellets Fresh Phytoplankton

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