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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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slide1

University of South Carolina

Marine Science

The History of 234Th in Aquatic Ecosystems

Dr. Claudia Benitez-Nelson

University of South Carolina

slide2

Arabian Sea

NABE

Coale & Bruland

Bhat et al.

slide3

Thorium-234

Particle residence times

& distribution

“Carbon” Export

slide4

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

slide5

“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.

slide6

“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.

slide7

Bhat et al. 1969

Thorium-234 as a tracer of particle dynamics

slide8

234Th

(dpm L-1)

Suspended

Particles

(mg kg-1)

Kaufman et al. 1981

slide9

Sediment

Resuspension

234Th

Residence

Time

Santschi et al. 1979

Sediment Resuspension

slide10

Aller & Cochran

1976

Bioturbation and

accumulation

slide11

Particle Coagulation

Honeyman et al. 1988

slide13

Coale & Bruland 1987

Particle Export

slide15

North Atlantic Bloom Experiment

Particle and “C” Export

Buesseler et al. 1992

slide16

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

slide18

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….

slide19

3 days

(1 sample)

MEDFLUX?

JGOFS

VERTIGO?

MEDFLUX?

2 hr

(1 sample)

2 hr

(24 samples)

slide20

Guo et al. 2002

Advances in analytical organic chemistry

slide25

Waples et al. 2003

Lake Michigan!!!