1. 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.


2. 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 depending upon sample size and application. This approach is becoming a "core" measurement in many biogeochemical studies.


3. 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:

1. Radiochemistry for Plutonium

Many studies of the man-made and natural radionuclides, involve the radiochemical purification of the isotope of interest prior to alpha, beta or gamma counting. One such element is plutonium, which was introduced to the environment primarily from 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 Pu isotopes.


2. 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.