Phosphorus speciation in the hyporheic zone and its response to sediment-water quality-biological activity coupling...

Different speciation of phosphorus in the hyporheic zone exhibit various release potentials, so as to control the phosphorus content in the overlying water. The process of phosphorus release under the multi-factor coupling of rivers is crucial for understanding the element cycle in complex environments. In this paper, the Weihe River in China was used as a case study to analyze the phosphorus speciation and distribution of overlying water and sediments in the hyporheic zone, and the phosphorus release process of sediments under the coupling of multiple factors. The results showed that the sediment acted as a phosphorus ' sink ' to accept the input of exogenous industrial and agricultural production. Microorganisms could produce complexes through their own metabolism, related enzyme expression, and sulfur reduction process to promote the transformation of phosphorus in sediments to soluble forms. The direct effect of phytoplankton on promoting phosphorus release from sediments is obvious. Water quality and sediment can indirectly promote the release of biological available phosphorus by promoting the proliferation of phytoplankton. As the demand for available phosphorus by phytoplankton increases, phosphorus-related bacterial communities show a stronger ability to decompose phosphorus. The functional genes of microorganisms involved in the phosphorous cycle are also coupled in this system, thus forming a sediment-water quality-biological activity coupling system that plays an important role in promoting sediment phosphorus release. The results of this study provide a theoretical reference for further research on the transformation and circulation of nutrient elements in the complex environment of rivers.