Accelerator Mass Spectrometry (AMS):
$200 for batch processing plus $175 to $350 for
analysis (depending on precision required).
for example, the Purdue
Rare Isotope Measurement Laboratory (PRIME Lab)
for more information)
our AMS page for
more information about the technique)
The natural sources of 129I
are cosmic spallation of xenon and fission of uranium
found in the subsurface. The fission of uranium
generates a release of 129I
into the groundwater and into the atmosphere from
volcanic emissions. The residence time for 129I
in the atmosphere is 2 weeks, whereas in the oceans
it is 40,000 years. Therefore, oceanic stable iodine
buffers the 129I
/I ratio to an average constant value of 1.1 x 10-12.
Young groundwaters, marine sediments, and current
precipitation have a 129I/I
ratio on the order of 10-12.
Anthropogenic sources are responsible for the
majority of 129I
in the atmosphere, particularly the chemical reprocessing
of irradiated fuel from nuclear power reactors.
is mainly a fission product of 235U
The isotopic ratio increased in some parts of
the world in the 1960's due to above ground nuclear
testing. The 129I/I
ratio in the atmosphere increased to ~10-7,
and has been as high as 10-4.
Release of 129I
also has occurred by accident. In April 1986,
Chernobyl Reactor 4 in the Ukraine experienced
a series of explosions that destroyed the reactor
core. Radioactive xenon, iodine, cesium, krypton,
and tellurium were released into the environment
for nine days.
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ratios were measured by ß-
decay counting, neutron activation to 130I,
and negative-ion mass spectrometry (Delmore 1982).
Now they are typically measured with accelerated
mass spectrometry, which provides higher precision
with a smaller sample size. Nevertheless, because
of the normally low concentration of 129I,
5 to 10 liters of water, and 300 to 500 grams
of ice are normally required for this analysis.
page for more information)
is used for estimating groundwater residence times,
tracing brine migration, identification of hydrocarbon
source rocks, and as a tracer of radioactive contaminant
plumes. Its long half-life extends the opportunity
to date groundwater to 80 million years, but some
limitations must be considered:
1. The estimate of the initial atmospheric
ratio is uncertain due to shifts in production
rates over time. A possible solution that has
been suggested is to measure the ratio in marine
sediments, coral, peat and organic soils.
2. Sources of 129I
and stable iodine are different. The transformation
and equilibration rates from these sources to
waters need to be estimated.
3. Old groundwater in contact with uranium-bearing
minerals may result in 129I
from spontaneous fission of 238U.
The rate of release is dependent on the contact
area and porosity.
4. The release of stable iodine from sediments
or fluid inclusions must be estimated.
5. The amount of 129I
released by volcanic emissions is not known
and cannot be separated from the overall atmospheric
production of 129I.
is a potentially useful tracer of groundwater
contamination from nuclear facilities. However,
studies indicate that it may bind with organic
compounds, limiting its use. For more information
see I. Clark's "Partitioning
in the Environment"
- Clark, I., and P. Fritz, Environmental
Isotopes in Hydrogeology, Lewis Publishers,
Boca Raton, 1997.
- Delmore, J.E., Isotopic analysis of iodine
using negative surface ionization, Int. J.
Mass Spectrometry and Ion Phys. 43: 273-281,
- Fabryka-Martin, J., Iodine-129 as a groundwater
tracer, in Radioactive tracers in Hydrogeology,
edited by P.G. Cook and A.L. Herczeg, 504-510,
Kluwer Academic Publishers, Boston, 2000.
- Fontes, J.C., and J.N. Andrews, Accelerator
mass spectrometry in hydrology, Nucl. Instrum.
Phys. Res. B92, 367-375, 1994.
- Kocher, D.C., A dynamic model of the global
iodine cycle and estimation of dose to the world
population from releases of iodine-129 to the
environment, Environ. Int. 5, 15-31,
- Martin, J.K., S.N. Fabryka, and D. Davis,
Applications of 129I
in hydrology, Nucl. Instrum. Meth. Phys.
Res. B29, 361-371, 1987.
- Paul, M., D. Fink, G. Hollos, A. Kaufman,
W. Kutschera, and M. Magaritz, Measurement of
in the environment after the Chernobyl reactor
accident, Nucl. Instrum. Meth. Phys. Res.
B29, 341-345, 1987.
Periodic Table - Iodine
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