Dynamic hyporheic zone: Impact of non-steady stream flow and moving streambeds on the fate of trace organic contaminants

The occurrence of trace organic compounds (TrOCs) such as pharmaceuticals and personal care products in aquatic ecosystems has been a growing concern in urban environments in recent decades. Incomplete removal of organic compounds in conventional wastewater treatment along with increasing use of chemicals, especially due to urbanization, increase the contamination of rivers and groundwaters with high loads of TrOCs. Different strategies to combat this type of environmental pollution have been researched, leading to a better understanding of the occurrence and fate of these contaminants. For instance, the natural attenuation of TrOCs by processes occurring in the hyporheic zone has been recognized as an efficient alternative for contaminant removal. However, little is known about the effects of stream flow velocity and bedform celerity on TrOCs removal, although bedform migration is a common process in many natural and urban streams. Our research project evaluates the influence of bedform migration on the fate of sixteen organic contaminants and their transformation products due to dynamic hyporheic zone exchange. Both controlled flume experiments and field measurements in a side channel of the River Erpe in Germany contribute to understanding the effects of dynamic flow conditions on the biotransformation of TrOCs. The knowledge obtained may be applied to enhance water management remediation programs, considering water bodies' ecological and chemical status.

Keywords: TrOCs, hyporheic zone, bedform migration, flume experiments, attenuation, biotransformation.