The simulated groundwater travel times increase with depth in the aquifer, ranging from about 1.5 to 6.5 years for the shallow wells (screen bottoms 3–4 m below the water table), from about 10 to 25 years for the medium-depth wells (screen bottoms 8–19 m below the water table), and from about 30 to more than 40 years for the deep wells (screen bottoms 24–26 m below the water table).
Apparent groundwater ages based on CFC- and He-dating techniques and model-based travel times could not be statistically differentiated, and all were strongly correlated with depth.
Hany El-Gamal, Infiltration of Lake Water into the Groundwater System Investigated by Tritium/Helium-3 Method: An Example from Wannsee and Lieper Bucht Area, Berlin, Germany, International Journal of Sciences 09(2014):16-25 International Journal of Sciences is Open Access Journal.
Tritium 3he dating of shallow groundwater
Clark, “A 3H/3He Study of Groundwater Flow in a Fractured Bedrock Aquifer,” Ground Water, Vol.
Zimmek, “Performance and Blank Components of a Mass Spectrometric System for Routine Measurement of Helium Isotopes and Tritium by the 3He in Growth Method,” Sitzungsber der Heidelberger Akademie der Wissenschaften, Mathematisch Naturwissenschaftliche Klasse, Jahrgang Springer Verlag.
Confinement of 3He was high because of the rapid vertical flow velocity (of the order of 1 m/yr), resulting in clear delineation of groundwater travel times based on the He and CFC ages indicates that dispersion has had a minimal effect on the tracer-based ages of water in this aquifer.
Differences between the tracer-based apparent ages for seven of the 10 samples were smaller than the error values.
The fully automated, computer-controlled manifold system allows analysis of the full suite of noble gases (3He/4He, He, Ne, Ar, Kr, and Xe concentrations), along with low level tritium for reporting of derived quantities that include tritium/helium-3 groundwater age, noble gas recharge temperature, and dissolved excess air concentration.
This system represents a capability for characterizing groundwater recharge conditions by dissolved gas analysis that is unmatched by any other laboratory.
Water samples for age dating were collected from three sets of nested observation wells (10 wells) with 1.5-m-long screens located near groundwater divides.
Three steady state finite difference groundwater flow models were calibrated by adjusting horizontal and vertical hydraulic conductivities to match measured heads and head differences (range, 0.002–0.23 m) among the nested wells, with a uniform recharge rate of 0.46 m per year and porosities of 0.35 (sand) and 0.45 (silt) that were assumed constant for all model simulations and travel time calculations.
Merzb, “Redox Processes in the Oderbruch Polder Groundwater Flow System in Germany,” Applied Geochemistry, Vol.