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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The History of 234Th in Aquatic Ecosystems
Dr. Claudia Benitez-Nelson
University of South Carolina
Coale & Bruland
Bhat et al.
Particle residence times
Bhat, Krishnaswamy, Lal, Rama, Moore
234Th/238U ratios in the Ocean
Earth and Planetary Science Letters 5, 483-491
“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.
“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.
Thorium-234 as a tracer of particle dynamics
Kaufman et al. 1981
Santschi et al. 1979
Honeyman et al. 1988
Particle and “C” Export
Buesseler et al. 1992
At Steady State:
(238U - 234Th) *Z = 234Th Export (dpm m-2 d-1)
Measure C/234Th on sinking particles
--> Carbon Export
C/Th ratios and what’s a sinking particle?
Are all “particles” the same?
Temporal and spatial effects?
All ultimately controlled by sampling restraints….
Advances in analytical organic chemistry