『Abstract
　Large scale redox processes were investigated in a river recharged aquifer in the Oderbruch polder alongside the river Oder in north-eastern Germany. Major hydraulic and hydrochemical processes were identified qualitatively. As a result of intensive drainage activities in the past 250 a, the groundwater level within the polder is situated below the river water level and a levee prevents flooding of the lowland. As a consequence, river water permanently infiltrates into the shallow confined aquifer. A sequence of redox reactions, driven by organic matter degradation, can be observed during infiltration of oxic river water into the groundwater. Up to 3 km from the river, reduction processes from O2 respiration to SO4^2- reduction dominate the groundwater chemistry. While reduction of Fe- and Mn(hydr)oxides is the source of the high amounts of dissolved Fe²⁺ and Mn²⁺, carbonate dissolution/precipitation reactions control the actual groundwater concentration of Mn²⁺. The first order rate constant for SO4^2- reduction was found to be -0.0169 a^-. Fe²⁺ is released into the groundwater at a rate of 0.0033 mmol l^-1 a^-1. The groundwater chemistry is strongly linked to the hydraulic conditions. Near the river, the groundwater is confined and recharged by bank-filtration only. In contrast, in the central polder the groundwater is unconfined and percolation of rainwater through the dried loam is possible because of texture changes such as shrinkage fissures. Geogenic pyrite present within the alluvial loam is oxidised and large amounts of SO4^2- are released into the groundwater.』

1. Introduction
2. The Oderbruch polder
3. Methodology
　3.1. Instrumentation
　3.2. Sampling
　3.3. Water analysis
　3.4. Sediment analysis
　3.5. Pore water extraction
4. Results and discussion
　4.1. Hydrochemistry of the river water
　4.2. Hydrochemistry of the bank-filtrate (zones I-IV)
　　4.2.1. Zone I/O2 and NO3^- reduction
　　4.2.2. Zone II/Mn- and Fe(hydr)oxide reduction
　　4.2.3. Zone III/Mn(II)-removal
　　4.2.4. Zone IV/sulfate reduction
　4.3. Hydrochemistry of the central polder (zone V)
　4.4. Sediment alteration
　4.5. Interdependence of hydraulic and hydrochemical processes
　4.6. Reaction rates
　4.7. Scale of redox zones
5. Summary and conclusions
Acknowledgements
References