Hyporheic exchange in recirculating flumes under heterogeneous bacterial and morphological conditions

Abstract Hyporheic exchange (HE) contributes to the biogeochemical turnover of macro- and micro-pollutants in rivers. However, spatiotemporal complexity variability HE hinder understanding its role overall functioning riverine ecosystems. The present study focuses on investigating bacterial diversity sediment morphology using a multi-flume experiment. A fully coupled surface–subsurface numerical model was used highlight complex patterns between surface water underlying flow field sediments. Under experimental conditions, induced by bedforms has prominent effect both local trajectories residence time distributions hyporheic paths, whereas mean retention times are mainly modulated average flowrates. In case bedform morphologies, successfully reproduces estimated means salt dilution tests. 2D representation system falls short predicting absence bedforms, highlighting intrinsic circulation real scenarios. Finally, results show that higher diversities stream sediments can significantly reduce fluxes. This work provides framework interpret micropollutants light physical transport processes zone. emphasizes importance better tradeoff physically driven dynamics zone quantify fate pollutants streams