1. Tracers for long residence times He, (Rn), 40Ar

2. Noble gases in groundwater
solubility equilibrium => He, Ne, Ar, Kr, Xe
excess air => He, Ne, Ar, Kr, Xe
3H => 3He, T1/2=12.43y
U, Th (a) decay series => 4He
6Li(n,a)3H => 3He
Mantel sources => 3He, 4He
40K => 40Ar
U fission => 136Xe, 134Xe, 132Xe, 86Kr
226Ra => 222Rn

3. Release mechanisms, 4He, 222Rn (etc)
222Rn halflife: 3.8 days
use of Rn as measure of U, Th concentrations
depends very much on grain size
useful tracer for discharge of groundwater into
surface waters
Torgersen, 1980

4. Non-atmospheric noble gases in groundwater
Isotope ~1% increase in liquid phase
222Rn <day
4He y
40Ar 5·106y
86Kr 6 ·1010y
131Xe 2 ·1010y
132Xe 3 ·109y
134Xe 9 ·108y
136Xe 7 ·108y *
(assume in situ production, only local accumulation, complete release)

5. He in groundwater 4He Concentration 3He/4He (ccSTP/g)
Solubility equilibrium: ~4.6• •10-6
Excess air: 0….5 • •10-6
Crustal He: up to ….10-7
U, Th => a => 4He
6Li(n,a)3H => 3He
Mantel He: up to •10-5
primordial He: •10-4
Tritium: 

6. Mantle He
R/Ra: He isotope ratio
relative to the atmosphere

7. He balance
He excess:

8. Separation of the components

9. Crustal (‘radiogenic’) in situ production
A: 4He accumulation rate in water
CU, CTh: concentrations in solid phase in mg/g
N, neff: porosity, effective (flushed) porosity
L: release factor
Typical rate: 5*10-12 ccSTPg-1

10. Great Artesian Basin
Torgersen & Clarke, 1985 Torgersen & Ivey, 1985

11. Model:

12. He excess, Namibia He excess (ccSTP/g) C age (years) 0 10 2 10 4 10
2 10 -5
4 10
6 10
8 10
1 10 -4
1.2 10
1.4 10
10000
20000
30000
40000
He excess (ccSTP/g) 14
C age (years)
He excess, Namibia

13. Great Hungarian Plain
Stute et al., 1992

15. Great Hungarian Plain

16. 4He accumulation model
U, Th => a => 4He

17. Great Hungarian Plain

18. Great Hungarian Plain

19. Great Hungarian Plain

20. Great Hungarian Plain
Peclet number:

21. Sturgeon Falls, Ontario
Solomon et al., 1996

22. Solomon et al., 1996

23. Presence of crustal Helium! Release rate 300x in situ production
Source is non equilibrium diffusion out of sediments
Solomon et al., 1996

24. The paradox of gw age
Bethge and Johnson, 2002