Phosphorus adsorption by sediment considering mineral composition and environmental factors

Sediment, composed of a complex assemblage of minerals, controls the fate and behaviour of P in aqueous environments and affects trophic status. In this study, P adsorption was studied on minerals including quartz, hematite, potassium feldspar, montmorillonite, kaolin, and calcite (i.e., the main components of sediment) and sediment from the Guanting Reservoir. A general formula for P adsorption was proposed that considers mineral composition through the component additivity method, also incorporating the effects of environmental factors, including the aqueous P concentration (C_e), pH, sediment concentration (S), and ionic strength (IS). The P adsorption capacity gradually decreased with increasing particle size, and the contributions from kaolin and montmorillonite to P adsorption were significant despite representing only a small fraction of sediment (with a maximum amount of P adsorption of 0.92 and 0.36 mg/g, respectively). The content of quartz accounted for approximately 40-60% of sediment; however, its P adsorption capacity was only 0.13 mg/g. These minerals exhibited different adsorption characteristics due to their different surface morphologies and lattice structures. Multivariable regression analysis was used to show that the amount of P adsorption was strongly correlated with C_e, followed by S, IS, and pH.