Sodium has two radioactive cosmogenic isotopes (22Na, half-life
= 2.605 years; 24Na, half-life = ~ 15 hours) that have been
used as tracers in hydrologic studies. Na has received considerable attention
in hydrologic research because it is a mobile element that participates
in precipitation and dissolution reactions in ground water (clay formation,
albitization of plagioclase). Their short half-lives (i.e. high decay rate)
make their measurement relatively easy by common radioanalytical techniques.
Substantial concentrations of 22Na and 24Na have
been measured in precipitation (Roedel, 1970; Perkins et al., 1970). However,
no studies have as yet been published documenting the cosmogenic sodium
systematics in ground or surface waters.
The high degree of mobility combined with the short half-lives suggests
that cosmogenic Na may be useful in characterizing catchment processes
occurring on short time scales, such as soil water movement (macropore
flow versus intergranular flow), storm hydrograph separation (overland
flow versus long-duration throughflow), fracture-facilitated fast-path
infiltration, and chemical mixing in lakes and rivers (Nimz, 1998).
Source of Text: This review was assembled by Eric Caldwell,
primarily from Nimz (1998).
||Nimz, G.J. (1998). "Lithogenic and Cosmogenic Tracers in Catchment
Hydrology." In: C. Kendall and J.J. McDonnell (Eds.), Isotope Tracers
in Catchment Hydrology. Elsevier, Amsterdam, pp. 247-290.
||Perkins, R.W., Thomas, C.Q. and Young, J.A. (1970). "Application
of short-lived cosmogenic radionuclides as tracers of in-cloud scavenging
processes." Jour. of Geophysical Res., 75: 3076.
||Roedel, W., 1970. "Cosmic-ray-produced sodium 24 and other nuclides
in the lower atmosphere." Jour. of Geophysical Res., 75: