Transport of Phosphorus in the Hyporheic Zone

Abstract

AbstractPhosphorus is not only an essential nutrient for organisms but also a major contributor to the eutrophication of fluvial ecosystems. Previous studies have focused on the flux of phosphorus at the water‐sediment interface, and very little is known about the transport and distribution of phosphorus in bedforms. In this study, a series of flume experiments and numerical simulations were conducted to investigate phosphorus dynamics in the hyporheic zone. The results show that the phosphorus concentration in the overlying water decreases faster than that of conservative solutes because of sediment adsorption. It is also found that the hyporheic exchange flux of phosphorus is more sensitive to the maximum adsorption capacity than to the equilibrium isotherm distribution coefficient, and the penetration depth is inhibited at higher maximum adsorption capacity. The mass proportion of phosphorus is decreased by 19.5% in the pore water but increased by 95.9% in the sediment with the increase of the maximum adsorption capacity from 0.5 to 1. These findings provide a better understanding of the transport and distribution of phosphorus in the riverbed and the contribution of transient flows such as flood to phosphorus dynamics in the hyporheic zone.