刊物名称：ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
卷： 23 页码: 24166-24177
Many coastal rivers have a system of cascade reser-voirs, but the role of these reservoirs in regulating nutrient trans-port from watershed to coast is still unknown. In this study, phosphorus (P) in surface water and top sediment was investi-gated along the North Jiulong River (southeast China) under three hydrological conditions (high flow, medium flow and low flow) in 2012–2013, and P dynamics inacascade reservoir (Xipi Reservoir) were studied on a monthly scale. Results showed that the concentrations of dissolved reactive phosphorus (DRP) consistently decreased long itudinally in the upper river with the lowest values observed in the section of cascade reservoirs, likely due to tributary inputs and in situ uptakes. The decrease was most rapid during base flow when DRP was highest in the free-flowing river section and lowest in cascade reservoirs. Results from monthly monitoring on the Xipi Reservoir showed general downriver decreases in DRP, total particulate phosphorus (TPP) and total phosphorus (TP) in the riverine zone and transition zone. Mass balance results on an annual basis suggest that the Xipi Reservoir (lacustrinezone) was an overall sink for TPP (6% retention) but somewhat a source of DRP (−0.3 %) with TPretention (1 %). Even scaled up to the whole cascade reservoir system, P retention was low compared with worldwide reser-voirs, which weascribe to the high P loading and short hydraulic residence time. Nevertheless, major processes controlling P re-tention in coastal rivers with cascade reservoirs varied from sed-imentation in the dry-cold season to biotic transformation in the wet-warm season, thereby affecting loading and composition of P from watershed to the coast. This study highlights the hydro-logical controls on the role of cascade reservoirs in regulating Pretention and downriver fluxes in different seasons.
Fig. 7. A schematic showing hydrological controls on the role of cascade reservoirs in regulating phosphorus retention and downriver fluxes under an Asian monsoon climate.