Fig. 1. The continuous water flow system (A–H) with a gas and water tight lid (I–O). Components: reservoir (A), sampling outlet for reservoir water (B), peristaltic pump (C), sediment core (D), bottom cap (E), outflow to drain (F), water sampling with a syringe (G), water sampling with a flask (H), inflow (I), gas trap (J), outflow (K), magnetic stirrer (L), rotating magnet (M), port for electrodes (N), removable clamp (O).