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

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