Investigation of groundwater residence times during bank filtration in Berlin: a multi‐tracer approach |
| |
| Authors: | Gudrun Massmann Jürgen Sültenfuß Uwe Dünnbier Andrea Knappe Thomas Taute Asaf Pekdeger |
| |
| Institution: | 1. Freie Universit?t Berlin, Institute of Geological Sciences, Hydrogeology Group, Malteserstr. 74‐100, 12249 Berlin, Germany;2. Universit?t Bremen, Institute for Environmental Physics, Otto Hahn Allee, 28359 Bremen, Germany;3. Berliner Wasserbetriebe, Laboratory, Germany, PO Box 310180, 10631 Berlin, Germany;4. Alfred Wegener Institut Potsdam, Potsdam Research Unit, Telegrafenberg A 43, D‐14473 Potsdam, Germany |
| |
| Abstract: | Berlin relies on induced bank filtration from a broad‐scale, lake‐type surface water system. Because the surface water contains treated sewage, wastewater residues are present in surface water and groundwater. Multiple environmental tracers, including tritium and helium isotopes (3H, 3He, 4He), stable isotopes (δ18O and δ2H) and a number of persistent sewage indicators, such as chloride, boron and a selection of pharmaceutical residues (phenazone‐type analgesics and their metabolites, carbamazepine and anthropogenic gadolinium, Gdexcess), were used to estimate travel times from the surface water to individual production and observation wells at two sites. The study revealed a strong vertical age stratification throughout the upper aquifer, with travel times varying from a few months to several decades in greater depth. Whereas the shallow bank filtrate is characterized by the reflection of the time‐variant tracer input concentrations and young 3H/3He ages, the deeper, older bank filtrate displays no tracer seasonality, 3H/3He ages of a few years to decades and strongly deviating concentrations of several pharmaceutical residues, reflecting concentrations of the source surface water over time. The phenazone‐type pharmaceuticals persist in the aquatic environments for decades. Bank filtration in Berlin is only possible at the sandy lakeshores. In greater water depth, impermeable lacustrine sapropels inhibit infiltration. The young bank filtrate originates from the nearest shore, whereas the older bank filtrate infiltrates at more distant shores. This paper illustrates the importance of using multiple tracer methods, capable of resolving a broad range of residence times, to gain a comprehensive understanding of time‐scales and infiltration characteristics in a bank filtration system. Copyright © 2007 John Wiley & Sons, Ltd. |
| |
| Keywords: | bank filtration sewage indicators age dating stable isotopes pharmaceutical residues helium isotopes Tritium |
|
|
