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Beryllium

Beryllium has one stable isotope and one cosmogenic isotope. 10Be is a radioactive isotope that is produced in the atmosphere and at the surface of the earth. It is most commonly used for dating geomorphic features and determining erosion rates.

 


Cost of Analysis (return to top)

Accelerated Mass Spectrometry (AMS): $175 to $500, varying by level of precision required and type of sample.

(See, for example, the Purdue Rare Isotope Measurement Laboratory (PRIME Lab)



Origin
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9Be, 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 low.

Cosmogenic production in the upper atmosphere
10Be (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 marine sediments.

Cosmogenic production at the earth's surface
10Be 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; 26Al 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 and 26Al abundance.


Measurement Techniques (return to top)

Sample preparation
Care must be taken in the laboratory to distinguish 10Be produced in the upper atmosphere from that produced in situ through interaction with rocks and soils.
(See 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).

Decay-counting
Although in principle, the radioactive decay of 10Be can be measured, the specific activity is so low that this method is not applicable.

AMS

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.
(See the AMS page for more information)



Hydrological Applications (return to top)

Because atmospheric Be flushed by precipitation is rapidly incorporated into sediments, this species of 10Be 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, 36Cl, and 26Al) to determine the time of first exposure or to determine erosion rates of continuously exposed materials. Saturation of quartz with 10Be and 26Al requires ~10 million years. Rock that has been shielded by overlying material shows deficiencies in 10Be and 26Al at a rate that may be compared to expected concentrations in order to determine the average erosion rate. Similarly, exposed rock saturated with 10Be and 26Al 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; 10Be and 26Al abundances can be used to date the event.

Since 7Be 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., 1991).

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.


References and further reading (return to top)

  • 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, 1981.

  • 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, 1998.

  • 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, 1996.

  • Nishiizumi, K., C.P. Kohl, J.R. Arnold, J. Klein, D. Fink, and R. Middleton, Cosmic ray produced 10Be and 26Al in Antarctic rocks: exposure and erosion history, Earth and Planet. Sci. Let., 104, 440-454, 1991.

  • 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.

Internet Resources (return to top)

Australian National University, Research School of Physical Sciences and Engineering, Nuclear Physics, Accelerated Mass Spectrometry, Exposure Dating and Erosion Studies

Dartmouth University, Dept. of Earth Sciences, Environmental Earth Science Projects

Lawrence Berkeley National Laboratory, The Berkeley Laboratory Isotopes Project, Exploring the Table of Isotopes.

Mook, W.G., and J.J. de Vries, Environmental Isotopes in the Hydrological Cycle: Principles and Applications, vol. 1, Centre for Isotope Research, Groningen, Netherlands.

USGS Periodic Table - Beryllium

von 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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