Periodic Table--Uranium
There are three naturally occurring isotopes of uranium: 234U
(< 0.01%), 235U (0.72%), and 238U (99.27%). All
three isotopes are radioactive. 238U (half- life 4.47 x 109
years) decays to 234U (half-life 247,000 years) and then to
206Pb by way of several intermediate daughter products. The
ratio between 238U and 234U is highly variable. A
number of hypotheses have been advanced to explain the disparity, including:
recoil of the daughter isotope during alpha emission (Cherdyntsev et al.,
1961); differential adsorption of isotopes by rocks (Clanet et al., 1976);
and differential absorption of isotopes into solution (Fleischer, 1980).
While this decay series has been used extensively for dating rocks, especially
in conjunction with daughter isotopes in the same decay series, there has
also been some use in hydrology (see, for example, Driscoll et al., 1993;
Kraemer and Genereux, 1998).
235U (half-life 7.04 x 108 years) decays, through
several steps, to form 207Pb. It is relatively uncommon in nature;
the 235U/238U ratio is about 1:139. Consequently,
while it has been used in dating in a manner similar to its sister isotopes
of uranium, it has seen little use in hydrology.
Source of text: This review was assembled by Dan Snyder from
the references below.
| References |
| • |
Bernat, M. and Church, T. M. (1989). "Uranium and thorium decay
series in the modern marine environment." In: P. Fritz and J.-Ch.
Fontes (Eds.), Handbook of Environmental Isotope Geochemistry, Volume
3, Amsterdam, Elsevier Science. pp. 357-384. |
| • |
Cherdyntsev, V. V., Orlov, D. P., Isabaev, E. A., and Ivanov, V. I.
(1961). "Isotopic composition of uranium minerals". Geochemistry,
10, 927-936. |
| • |
Clanet, F., Leclerq, J., Remy, M. L., and Moroni, J. P. (1976). "Mise
en evidence expérimental du role de l'adsorption différentielle
du thorium et de l'uranium sur les roches silicatée dans l'état
d'équilibre entre les activités des radioisotopes 234U
et 238U dans la nature". C. R. Acad. Sci. Paris, Sér.
D, 282, 807-810. |
| • |
Driscoll, C. T., Otton, J. K., and Iverfeldt, Å. (1993). "Trace
metals speciation and cycling." In:B. Moldan and J. Cerný (Eds.),
Biogeochemistry of Small Catchments--A Tool for Environmental Research,
Scientific Committee on Problems of the Environment, Wiley & Sons,
New York. pp. 299-322. |
| • |
Faure, G. (1986). Principles of Isotope Geology, Second Edition.
John Wiley and Sons, New York. 589 pp. |
| • |
Fleischer, R.L. (1980). "Isotopic disequilibrium of uranium: alpha-
recoil damage and preferential solution effects", Science,
215, 667-671. |
| • |
Gebauer, D., and Grünenfelder, M. (1979). "U-Th-Pb dating
of materials", In: Lectures in Isotope Geology (Eds. E. Jäger
and J.C. Hunziker), Springer-Verlag, New York. pp. 105-131. |
| • |
Kraemer, T.F. and Genereux, D.P. (1998). "Applications of Uranium-
and Thorium-Series Radionuclides in Catchment Hydrology Studies."
In: C. Kendall and J.J. McDonnell (Eds.), Isotope
Tracers in Catchment Hydrology, Elsevier, Amsterdam, pp. 679-722. |
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