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

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

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

4. Bhat, Krishnaswamy, Lal, Rama, Moore 234 Th/ 238 U ratios in the Ocean Earth and Planetary Science Letters 5, 483-491 First Published 234 Th data by the Radiochemistry All-Stars: 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 Mooreto 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. Kaufman et al. 1981 234 Th (dpm L -1 ) Suspended Particles (  g kg -1 )

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

10. Aller & Cochran 1976 Bioturbation and accumulation

11. Honeyman et al. 1988 Particle Coagulation

12. Cochran et al. 1993

13. Coale & Bruland 1987 Particle Export

14. Infamous Buesseler (1991) Paper….

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

16. Thorium-234 approach for estimating particle export depth(m) 234 Th 238 U       At Steady State: ( 238 U - 234 Th) *Z = 234 Th Export (dpm m -2 d -1 ) Measure C/ 234 Th 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. JGOFSVERTIGO? MEDFLUX? 3 days (1 sample) 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

24. Advances in sampling and measurement

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

26. Where do we go from here???