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Accelerated Mass Spectrometry
(AMS): $175 to $500, varying by level of precision
required and type of sample.
for example, the Purdue
Rare Isotope Measurement Laboratory (PRIME
the only stable isotope of beryllium, occurs naturally
on earth. However, for a light isotope the abundance
of beryllium in the solar system is anomalously
in the upper atmosphere
(half-life of 1.6 million years) and 7Be
(half-life of 53 days) are continuously produced
in the atmosphere by the high-energy proton component
in cosmic radiation, causing spallation of atmospheric
oxygen and nitrogen atoms. Beryllium is rapidly
washed from the atmosphere by precipitation, and
is subsequently incorporated in continental and
at the earth's surface
is also produced at the surface of the earth by
direct cosmic ray irradiation of target atoms
in geologic materials. In quartz, 10Be
is produced by spallation from the interaction
of cosmic rays with oxygen and silicon and by
negative mu-meson capture of 28Si;
is similarly produced in quartz by cosmic ray
spallation of 26Si
and mu-meson capture. The rate of this production
is dependent on cosmic-ray flux, which increases
with latitude and elevation. Because quartz does
not absorb radionuclides from precipitation, the
"exposure age," or the length of time
present at the surface of the earth may be effectively
determined by 10Be
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Care must be taken in the laboratory to distinguish
produced in the upper atmosphere from that produced
in situ through interaction with rocks and soils.
Paul Bierson's guidelines for the Cosmogenic
Nuclide Extraction Lab at the University of Vermont
for a detailed description of sample preparation
techniques for 10Be).
Although in principle, the radioactive decay of
can be measured, the specific activity is so low
that this method is not applicable.
Routine analysis of 10Be
has become possible by the introduction of ultra-sensitive
mass spectrometers. The AMS process measures the
ratio of 10Be/9Be,
and calculates the age of the sample by comparing
this ratio to the modern value of 2.68*10-11.
the AMS page for
Because atmospheric Be flushed by precipitation
is rapidly incorporated into sediments, this species
is most often used to determine erosion and sedimentation
rates, and may also be used for dating glacial
ice. However, 10Be
produced in situ also is increasingly being shown
to also be useful for dating sediments in studies
that examine basin-scale rates of denudation (Bierman
et al., 1998).
Landform-evolution studies look at the build-up
of long-lived radioisotopes produced on the surface
of the earth (i.e., 10Be,
to determine the time of first exposure or to
determine erosion rates of continuously exposed
materials. Saturation of quartz with 10Be
requires ~10 million years. Rock that has been
shielded by overlying material shows deficiencies
at a rate that may be compared to expected concentrations
in order to determine the average erosion rate.
Similarly, exposed rock saturated with 10Be
may have been uncovered during a sudden geologic
event such as a rockslide, the recession of a
glacier, or the cooling of a volcanic eruption;
abundances can be used to date the event.
decays by electron capture to 7Li
with a half-life of 53 days, it can be used effectively
to study rapidly changing processes, such as atmospheric
processes, surface ocean waters, etc. (Aaboe et
al 1981). The atmospheric flux of 7Be
has also been measured to determine erosion rates
and fluvial transport mechanisms (Dominik et al.,
1987) and to determine direct contribution of
rainfall to terrestrial waters (Cooper et al.,
Solar surface magnetic activity and the strength
of solar geomagnetic dipoles affect the galactic
cosmic ray influx that produces atmospheric 10Be.
By analyzing changes in the production rate of
this species of 10Be
and geomagnetic field intensity for the last 200,000
years, researchers are calculating variations
in solar activity during that time period.
- Aaboe, E., E.P. Dion, and K.K. Turekian, 7Be
in Sargasso Sea and Long Island Sound waters,
J. Geophys. Res., 86(C4), 3255-3257,
- Bierman, P.R., et al, Erosion, weathering,
and sedimentation, in Isotope Tracers in
Catchment Hydrology, ed. by C. Kendall and
J.J. McDonnell, 647-678, Elsevier, Amsterdam,
- Cooper, L. W., C.R. Olsen, D.K. Solomon, I.L.
Larsen, R.B. Cook, and J.M. Grebmeier, J. M.
Stable isotopes of oxygen and natural fallout
radionuclides used for tracing runoff during
snowmelt in an Arctic watershed, Water Resour.
Res., 27( 9), 2171- 2179, 1991.
- Domink, J., D. Burrus, and J.-P. Vernet, Transport
of environmental radionuclides in an alpine
watershed, Earth Planet. Sci. Lett.,
84, 165, 1987.
- Faure, G., Principles of Isotope Geology,
2nd ed., John Wiley and Sons, 1986.
- Granger, D.E., J.W. Kirchner, and R. Finkel,
Spatially averaged long-term erosion rates measured
from in situ-produced cosmogenic nuclides in
alluvial sediment, J. Geology 104, 249-257,
- Nishiizumi, K., C.P. Kohl, J.R. Arnold, J.
Klein, D. Fink, and R. Middleton, Cosmic ray
in Antarctic rocks: exposure and erosion history,
Earth and Planet. Sci. Let., 104, 440-454,
- Schaller, M., F. von Blanckenburg, N. Hovius,
and P.W. Kubik, Large scale erosion rates from
in-situ produced cosmogenic nuclides in European
river sediments, Earth and Planet. Sci Let.,
188, 441-458, 2001.
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Australian National University, Research School
of Physical Sciences and Engineering, Nuclear
Physics, Accelerated Mass Spectrometry, Exposure
Dating and Erosion Studies
University, Dept. of Earth Sciences, Environmental
Earth Science Projects
Berkeley National Laboratory, The
Berkeley Laboratory Isotopes Project, Exploring
the Table of Isotopes.
W.G., and J.J. de Vries, Environmental
Isotopes in the Hydrological Cycle: Principles
and Applications, vol. 1, Centre for Isotope Research,
Periodic Table - Beryllium
Blanckenburg, F., M. Schaller, T. Hewawasam, P.
Kubik, and N. Hovius, Quantification
of Continental Erosion Processes. http://www.earthsci.unibe.ch/isotope/erosion.htm
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