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University of South Carolina

University of South Carolina. Marine Science. The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina. Arabian Sea. NABE. Coale & Bruland. Bhat et al. Thorium-234. Particle residence times & distribution. “Carbon” Export.

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University of South Carolina

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  1. University of South Carolina Marine Science The History of 234Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina

  2. Arabian Sea NABE Coale & Bruland Bhat et al.

  3. Thorium-234 Particle residence times & distribution “Carbon” Export

  4. First Published 234Th data by the Radiochemistry All-Stars: Bhat, Krishnaswamy, Lal, Rama, Moore 234Th/238U ratios in the Ocean Earth and Planetary Science Letters 5, 483-491 1969

  5. “Please excuse the organization of this letter. In order to speed its posting, I was having the first part typed while counting the spikes and while I was writing the last few paragraphs” Letter from Moore to Swamy, July 31, 1968. “The AGU Meeting was pretty good, but there has been a lot of trouble in Washington the previous weekend and we were confined to the hotel most of the time. Of course nothing was open around the city and all of the army troops gave a grim atmosphere to a beautiful spring.” Letter from Moore to Swamy, May 23, 1968.

  6. “We have added Th-234 spike to millipore filtered seawater and refiltered the water through a 0.45 micron millipore. The retention of Th-234 was less than 5 % of that added on the filter…We also tried to see if live plankton cells pick up Thorium from seawater…initial numbers show the retention (if any) may be very less.” Letter from Swamy to Moore, August 6, 1968. “One of the things we must remember in reference to plankton vs. particle uptake of Th-234 is that there are many types of plankton with a wide spectrum of sizes…” Letter from Moore to Swamy, Sept 6, 1968.

  7. Bhat et al. 1969 Thorium-234 as a tracer of particle dynamics

  8. 234Th (dpm L-1) Suspended Particles (mg kg-1) Kaufman et al. 1981

  9. Sediment Resuspension 234Th Residence Time Santschi et al. 1979 Sediment Resuspension

  10. Aller & Cochran 1976 Bioturbation and accumulation

  11. Particle Coagulation Honeyman et al. 1988

  12. Cochran et al. 1993

  13. Coale & Bruland 1987 Particle Export

  14. Infamous Buesseler (1991) Paper….

  15. North Atlantic Bloom Experiment Particle and “C” Export Buesseler et al. 1992

  16. Thorium-234 approach for estimating particle export 234Th * * * * depth (m) * 238U * At Steady State: (238U - 234Th)  *Z = 234Th Export (dpm m-2 d-1) Measure C/234Th on sinking particles --> Carbon Export

  17. Buesseler 1998

  18. Three Major Issues: C/Th ratios and what’s a sinking particle? Are all “particles” the same? Temporal and spatial effects? All ultimately controlled by sampling restraints….

  19. 3 days (1 sample) MEDFLUX? JGOFS VERTIGO? MEDFLUX? 2 hr (1 sample) 2 hr (24 samples)

  20. Guo et al. 2002 Advances in analytical organic chemistry

  21. Geibert and Usbeck 2004

  22. Buesseler et al. 1995

  23. Advances in sampling and measurement

  24. Waples et al. 2003 Lake Michigan!!!

  25. Where do we go from here???

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