Alteration in the potential of sediment phosphorus release along series of rubber dams in a typical urban landscape river

Rubber dams are widely used for landscaping in urban rivers and they retain large amounts of sediments. The sediments are rich in phosphorus (P) which can cause river eutrophication. Little is known about P release in rubber dams. We investigated the potential of sediment P release by isotherm experiment in an urban river with 30 rubber dams of northern China. We found that the potential of sediment P release (percentage saturation of zero equilibrium P concentration, EPCsat) was 76% at natural river part above dams, and then decreased to 67% at the 4th dam because of high deposition of fine sediments within the upper 4 dams. Between the 5th and the 30th dams, EPCsat increased to 90% because of the decrease of fine sediments and water soluble reactive P. EPCsat was also significantly higher (p < 0.05) in April and August than in November. The results suggest that the potential of sediment P release in this dammed river was mainly controlled by sediment grain size and biological effects. Therefore, management strategies for dammed rivers should focus on reducing P inputs and improving the hydraulic conditions.