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

The impact of climatic and vegetation conditions over the past 15 Ka on the chemical composition and C-14 dating of ground water 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 C-14 Of dissolved inorganic carbon (DIC) and aqueous fulvic acid as well as O-18. C-14 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 how-distance. On the other hand,C-14 dating via DIC requires correction of the C-14 value due to perturbation by different geochemical processes. Up to a groundwater how distance of approximately 17 km and an age of about 10 Ka, the C-14 dating by DIC shows considerable dependence on the C-14-correction model applied. Beyond this groundwater age,C-14-DIC dating results in an overestimation by two to three C-14 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. (C) 2000 Elsevier Science Ltd. All rights reserved.