Application of the chlorine-36 method for the delineation of groundwater infiltration of large river systems: example of the Danube River in western Hungary (Szigetkoz area)

摘要

The gravel aquifer within the Szigetkoz Plain in northern Hungary is mainly fed by the infiltration of the Danube River. This infiltration process can be identified using the tritium/helium method to a distance of about 30 km away from the infiltration area of the Danube. In this study, chlorine-36 analyses are used as additional method. This natural radioisotope was also produced by nuclear bomb tests in the atmosphere. It is an ideal, stable constituent for this particular study due to its very long half-life (300,000 years), and consequently acts as an independent check of the established model of aquifer recharge. The chlorine-36 data of the analysed selected groundwater samples of this area clearly show the effect of the atmospheric nuclear bomb tests, with enhanced Cl-36/Cl ratios of up to a factor 10 higher than the unaffected groundwater of the pre-bomb period within the study area. Finally, the observed Cl-36 values were introduced into a transport model with dispersion/advection-type flow of groundwater to deduce the transport parameters.