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

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

The History of 234Th in Aquatic Ecosystems

Dr. Claudia Benitez-NelsonUniversity of South Carolina

Page 2: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Bhat et al.

Coale & Bruland

NABE

Arabian Sea

Page 3: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Thorium-234

Particle residence times & distribution

“Carbon” Export

Page 4: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Bhat, Krishnaswamy, Lal, Rama, Moore234Th/238U ratios in the Ocean

Earth and Planetary Science Letters 5, 483-491

First Published 234Th data by the Radiochemistry All-Stars:

1969

Page 5: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

“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.

Page 6: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

“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.

Page 7: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Bhat et al. 1969

Thorium-234 as a tracer of particle dynamics

Page 8: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Kaufman et al. 1981

234Th (dpm L-1)

Suspended Particles (g kg-1)

Page 9: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Santschi et al. 1979

Sediment Resuspension

234ThResidence

Time

Sediment Resuspension

Page 10: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Aller & Cochran1976

Bioturbation and accumulation

Page 11: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Honeyman et al. 1988

Particle Coagulation

Page 12: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Cochran et al. 1993

Page 13: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Coale & Bruland 1987

Particle Export

Page 14: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Infamous Buesseler (1991) Paper….

Page 15: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

North Atlantic Bloom Experiment

Buesseler et al. 1992

Particle and “C” Export

Page 16: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Thorium-234 approach for estimating particle exportThorium-234 approach for estimating particle export

depthdepth(m)(m)

234Th

238U

At Steady State:(238U - 234Th) *Z = 234Th Export (dpm m-2 d-1)

Measure C/234Th on sinking particles --> Carbon Export

Page 17: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Buesseler 1998

Page 18: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

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….

Page 19: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

JGOFS VERTIGO?

MEDFLUX?

MEDFLUX?

3 days(1 sample)

2 hr(1 sample)

2 hr(24 samples)

Page 20: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Guo et al. 2002

Advances in analytical organic chemistry

Page 21: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Geibert and Usbeck 2004

Page 22: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Buesseler et al. 1995

Page 23: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.
Page 24: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Advances in sampling and measurement

Page 25: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Waples et al. 2003

Lake Michigan!!!

Page 26: The History of 234 Th in Aquatic Ecosystems Dr. Claudia Benitez-Nelson University of South Carolina.

Where do we go from here???


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