Isotope-hydrogeological case study on the penetration of pollution into the deep tertiary aquifer in the area of Munich, Germany

Abstract In selected subareas of the city of Munich concentrations of 2 H, 3 H, 13 C, 14 C, 18 O and in some cases 3 He and 4 He together with hydrochemical data including concentrations of chlorinated hydrocarbons (CHC) were measured from groundwaters of ∼58 wells tapping the shallow (Quaternary) and the deep (Tertiary) aquifer. The results obtained show that under hydraulic stress young tritium-containing groundwaters in general have penetrated down to depths of as much as ∼60 m. The groundwater model ages decrease from recent values in the Quaternary aquifer to ∼15 kyr at a depth of ∼200 m in the Tertiary aquifer. CHC, Cl − , NO 3 − and SO 4 2− were detected in some places in comparable depths to tritium. The results show clearly that it is necessary to introduce measures for the protection of the deep groundwater against pollution: Consumption should be limited to 7 m 3 yr −1 and the deep groundwater should only be used for purposes which require drinking water quality.