Possible evidence for ¹⁴C isotope exchange between groundwater and carbonate rocks in the eastern Donau Ried, Bavaria, Germany.

Abstract

Isotope hydrological investigations of groundwaters yielded very low 14C contents, together with normal δ13C values for dissolved inorganic carbon (DIC) and correspondingly high 14CDIC model ages. However, the 2H, 18O and 4He contents suggested a Holocene age for most of the groundwaters. New data from 14C measurements on dissolved organic carbon (DOC) and 39Ar indicate significantly lower groundwater ages (<7500 years). Furthermore, the isotopic composition (34S and 18O) of the aqueous sulphates accounts for its meteoric origin. Such values also characterize recent karst groundwaters on the Swabian-Franconian Alb. The discrepancies between the different isotopic ages are possibly explained by carbon isotope exchange with terrestrial carbonates found in this area. -Author