Typical measurements and services offered
- Sediments by gamma spectrometry
We anticipate the largest use of the facility to be for the
analyses of gamma emitting
radionuclides in marine sediments. Dried and ground sediment
samples are placed in
calibrated counting jars on the gamma counter for 12-48 hours.
From measurement of
isotopes such as 210Pb, 226Ra, 234Th, 137Cs and 7Be, one can
often calculate the rates of
mixing (bioturbation and physical mixing) and sedimentation
in coastal and deep ocean
sediments, on time scales of days to 100 years.
- Water, particles, sediment traps for 234Th
Thorium-234 is a particle-reactive naturally occurring decay
product of uranium-238.
Measurement of the difference in 234Th and 238U activities
in seawater provides an in-situ
tracer of particle export and cycling in the upper ocean on
time scales of days-weeks.
Detection of 234Th can be accomplished via beta or gamma methods
sample size and application. This approach is becoming a "core"
measurement in many
- Groundwater and coastal waters for radium isotopes
The radium isotopes 226Ra (t1/2 1620 years), 228Ra (t1/2
5.75 years), 224Ra (t1/2 3.66
days), and 223Ra (t1/2 11.4 days), are naturally produced
in sediments and are highly
soluble and enriched in groundwater and coastal surface waters.
As such, measurement
of the flux of Ra out of sediments can be used to quantify
groundwater discharge, and
measurement of surface water Ra gradients can be used to quantify
flow and horizontal
mixing processes in the coastal ocean. Recently pioneered
methods by Dr. W. Moore
(U. So. Carolina) now allow for the rapid detection of 223Ra
and 224Ra using a
customized delayed coincidence counter. 226Ra and 228Ra are
efficiently detected using a gamma "well" detector.
In addition to the above mentioned radiation detection services,
we anticipate some use
of the Café Thorium facility for more complicated radiochemical
purification and sampling
activities. Other scientists have expressed interest in our
including, on a cost-per-sample basis, the following two services:
- Radiochemistry for Plutonium
Many studies of the man-made and natural radionuclides, involve
purification of the isotope of interest prior to alpha, beta
or gamma counting. One such
element is plutonium, which was introduced to the environment
atmospheric nuclear weapons testing in the 1960's. This tracer
is often used in marine
sciences to constrain sedimentation and mixing rates in sediments
(in addition to 210Pb
measured via gamma counting).The Café Thorium facility
would offers sample costs for
- Sampling preparation & consultation- water 234Th
We have provided 234Th "sampling kits" for scientists
interested in using this tracer in their
own biogeochemical study, which enable the researcher to collect
234Th samples (using
pre-packaged filtration and Thorium specific adsorbers) that
are mailed back to WHOI
for immediate analyses. Such arrangements would be made on
an individual request basis.