Each hydrological system shows specific geochemical features, hydrochemical compositions, and isotopic
signatures of the aqueous species, which strongly depend on the individual geological conditions. The elements
strontium, calcium and iron are of lithogenic origin, and the distributions of the related isotopes vary as a result of
changes in the mineralogical compositions within catchment areas and aquifers. In addition, kinetic or biologically
induced processes in soils and in the water column cause fractionation of calcium and iron isotopes. The resulting
pattern reveals important information on solute transport and sources of aqueous species, dissolution-precipitation
kinetics along flow paths, and redox processes.
In the present study the isotopic compositions of strontium, calcium, and iron will be investigated in different
hydrogeological settings of karstic and unconsolidated sedimentary catchment areas. Comparison of isotopic
signatures and fractionation pattern in the various environments provides an insight to inorganic and biologically
induced hydrochemical processes and their effects on the water composition. In conjunction with conventional
chemical and isotope parameters hydrological and mass balance models will be developed for the investigated sites.