Link to USGS home page

Resources on Isotopes

Periodic Table--Krypton

Krypton-81 is the product of atmospheric reactions with the other naturally occurring isotopes of krypton [78Kr (0.35%), 80Kr (2.25%), 82Kr (11.6%), 83Kr (11.5%), 84Kr (57.0%), 86Kr (17.3%)] and from decay of 238U. It is radioactive with a half-life of 250,000 years. Little use of this isotope has been made due to interference from 85Kr; however, it has been used for age determination in old (50,000-800,000 year) groundwater (Oeschger, 1978; Lehman et al.,1985).

Krypton-85 is an inert radioactive noble gas (half-life = 10.76 years) that is produced by fission of uranium and plutonium. Sources have included nuclear-bomb testing, nuclear reactors, and the release of 85Kr during the reprocessing of fuel rods from nuclear reactors (Sittkus and Stockburger, 1976). Concentrations of 85Kr in the lower atmosphere show considerable spatial variability, primarily reflecting the locations of the major sources (Solomon et al, 1998). A strong gradient also exists between the northern and southern hemispheres where concentrations at the North Pole are approximately 30% higher than the South Pole due to convective mixing (Jacob et al., 1987; Zimmerman et al., 1989).

Although 85Kr has a half-life similar to that of 3H. 85Kr has the advantage of being an environmental tracer with steadily increasing atmospheric input, whereas the 3H atmospheric input is a more complex function of season and latitude and has declined since cessation of atmospheric nuclear-bomb testing in the mid-1960s. Because 85Kr is a noble gas, it is not subject to microbial degradation and other chemical interactions that can alter the concentrations of organic environmental tracers. Krypton-85 enters ground water by equilibration of the infiltration water with air in the unsaturated zone, assumed to have a 85Kr activity similar to that of the atmosphere. If the effects of hydrodynamic dispersion are small, the 85Kr specific activity of groundwater defines the time since the infiltration water was isolated from the atmosphere. The very large amounts of water required for 85Kr analysis (at least 100 L) have prevented much use of this potentially useful tracer.

Source of text: This review was assembled by Dan Snyder from the references below.

Fabryka-Martin, J. T. (1988) Production of Radionuclides in the Earth and their Hydrogeologic Significance, with Emphasis on Chlorine-36 and Iodine-129, University of Arizona, PhD. thesis. 400 pp.
Florkowski, T. and Rózanski, K. (1986). "Radioactive Noble Gases in the Terrestrial Environment." In: P. Fritz and J.-Ch. Fontes (Eds.), Handbook of Environmental Geochemistry, Vol. 2b, Elsevier Science, New York. pp. 481-506.
Jacob, D.J., Prather, M.J., Wofsy, S.C., and McElroy, M.B. (1987). "Atmospheric distribution of 85Kr simulated with a general circulation model." Jour. Geophys. Res., 92: 6614-6626.
Lehman, B.E., Oeschger, H., Loosli., H.H., Hurst, G.S., Allman, S.L., Chen, C.H., Kramer, S.D., Willis, R.D., and Thonnard, N. (1985). "Counting 81Kr atoms for analysis of groundwater". J. Geophy. Res., 90, 11547-11551.
Oeschger, H. (1978). Workshop on Dating Old Ground Water, University of Arizona, March 16-18, Rep., Y/OWI/SUB-78/55412.
Plummer, L.N., Michel, R.L., Thurman, E.M., and Glynn, P.D. (1993) "Environmental tracers for age dating young ground water", In: W.M. Alley (Ed.), Regional Ground-Water Quality, Van Nostrand Reinhold, New York, pp. 255-294.
Solomon, D. K., Cook, P. G., and Sanford, W. E. (1998). "Dissolved gases in subsurface hydrology." In: C. Kendall and J.J. McDonnell (Eds.), Isotope Tracers in Catchment Hydrology. Elsevier, Amsterdam, pp. 291-318.
Sittkus, A., and Stockburger, H. (1976). "Krypton-85 als indikator des kernbrennstoffverbrauchs", in Naturwissenschaften, 63, pp. 266- 72.
Zimmerman, P.H., Feicher, J., Rath, H.K., Crutzer, P.J. and Weiss, W. (1989). "A global three-dimensional source-receptor model investigation using 85Kr." Atmos. Environ., 23: 25-35.
Related Links
Periodic Table
Fundamentals of Stable Isotope Geochemistry
General References
Isotope Publications
Please contact Carol Kendall ( for questions and comments regarding this page.
This page was last changed in January 2004.
To the USGS Home Page
To the Water Resources Information Home Page