Periodic Table--Sodium

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).