Thorium-234 Activity in Particulate and Dissolved Components Measured during the JGOFS Equatorial Pacific Process Study (EQPAC)

The Equatorial Pacific Process Study (EQPAC) was conducted along 140 deg W
longitude during 1992.

Four cruises took place: February 3 - March 9, March 19 - April 15,
August 5 - September 18, and September 24 - October 21. A fifth benthic
cruise and sediment trap legs were added. During the first cruise
(TT007), 15 stations were occupied along 140 deg W longitude from
12 deg N latitude to 12 deg S latitude. During the second cruise
(TT008), data were collected at 8 stations along 140 deg W longitude
from 9 deg S latitude to 9 deg N latitude. During the third cruise
(TT011), data were collected at 15 stations along 140 deg W from 12 deg N
latitude to 12 deg S latitude. During the fourth cruise (TT012), data were
collected at 5 stations along 140 deg W longitude from 17 deg S
latitude to the equator.

Thorium-234 can be used as a tracer to estimate particle and
carbon fluxes and cycling rates. Water samples were collected by in
situ pump at various depths at the stations. Dissolved thorium-234
was measured by non-destructive gamma spectrometry. Particulate
thorium-234 was measured in three different size classes: 0.7-1
micrometer, 1-53 micrometer, and >53 micrometer by low-level beta
counting. The thorium-234 data were only collected during the second
(TT008) and fourth (TT012) cruises.

The data is public domain and can be retrieved on-line at
"http://usjgofs.whoi.edu/jg/dir/jgofs/"

[The information in this summary was taken from the JGOFS
World Wide Web pages.]