Distribution and diffusion thermodynamic characteristics of phosphorus at the interface between river sediment and water under the influence of artificial disturbance

Abstract

Abstract Artificial disturbance affects the migration of phosphorus (P) at the interface between river sediments and water. In the present research, we sampled three sections of the Yitong River in Changchun City, China, in order to obtain representative samples of city, town, and rural reaches. Overlying water and sediment samples were obtained in September 2021 during the dry period. In our experiments, we determined the distribution of different forms of P, diffusion flux of P at the interface, as well as P adsorption parameters. The results showed that concentrations of four P species in the sediments followed the order: Ca-P > Fe-P > Acid extracted phosphorus > Alkali extracted phosphorus. The diffusion flux of -P in each reach was positive, showing that sediments were an important P source for the overlying water. The -P content in the interstitial water of sediments was significantly correlated with that in the overlying water. This indicated that P diffused into the overlying water in the form of -P under most circumstances. The adsorption parameters gradually decreased from upstream to downstream. These data indicated that potential for phosphorus release from downstream sediments was higher than that from upstream sediments. This likely occurred because, downstream, a greater artificial disturbance intensity is observed.