Bedform migration’s impact on streambed oxygen distribution: A novel field experiment

Several studies have investigated the high reactivity of the hyporheic zone (HZ) and the interactions between moving bedforms and biogeochemical processes. However, the impact of bedform migration on the attenuation of trace organic compounds in the streambed has not yet been investigated. The oxygen distribution and dynamics in the HZ play a major role in this regard. So far, there have been no in-situ measurements of two-dimensional oxygen distributions in the HZ. To address this gap, we developed a novel device and tested it for the first time in the Erpe River, Germany. Our setup included a planar optode installed in the streambed to visualize the redox zonation within the HZ. Additionally, we tested five different stream flow velocities (from 10 to 50 cm/s) to investigate typical bedform celerities in lowland streams more thoroughly. By repeatedly sampling the surface and pore water, our aim was to determine how dynamic flow patterns and variable bedform celerities in sandy streams influence water constituents. The field experiment confirmed that changes in flow conditions can non-linearly influence bed movement and oxygen consumption, thereby affecting the fate of trace organic compounds.

Keywords: Biogeochemical processes, bedform celerity, in situ measurements, field experiments, redox zonation, hyporheic zone, oxygen distribution, planar optode.