Development of climatic and vegetation conditions and the geochemical and isotopic composition in the Franconian Albvorland aquifer system

Abstract The impact of climatic and vegetation conditions over the past 15 Ka on the chemical composition and 14 C dating of groundwater from the Franconian Albvorland aquifer system is discussed. Seven groundwaters over a flow distance of 25.5 km are investigated. Groundwater dating is made by 14 C of dissolved inorganic carbon (DIC) and aqueous fulvic acid as well as 18 O. 14 C dating via fulvic acid gives groundwater ages consistent with climatic and vegetation records and variations in the groundwater composition. No correction for geochemical processes is required, since under these geochemical conditions fulvic acid remains stable over this time period and flow-distance. On the other hand, 14 C dating via DIC requires correction of the 14 C value due to perturbation by different geochemical processes. Up to a groundwater flow distance of approximately 17 km and an age of about 10 Ka, the 14 C dating by DIC shows considerable dependence on the 14 C-correction model applied. Beyond this groundwater age, 14 C-DIC dating results in an overestimation by two to three 14 C half-lives ( T 1/2 =5730 a). This deviation may result from different groundwater recharge conditions at the end of the past glaciation and geochemical processes acting on DIC that cannot be adequately characterized. The present study has implications for humic substance mediated transport of pollutants in natural aquatic systems over long time periods.