Oxygen-Loaded Porous Materials Inhibit Phosphorus Release at the Sediment-Water Interface in Eutrophic Waters
Dissolved oxygen (DO) is a critical factor controlling endogenous phosphorus (P) migration in eutrophic waters. Existing oxygenation technologies suffer from high energy consumption and sediment disturbance, necessitating low-disturbance, pH-stable strategies that avoid additional nitrogen and P loads. This study evaluated an oxygen-loaded porous material (OLPM) for inhibiting sediment P release using laboratory microcosms with natural eutrophic water samples. DO microprofiles across the sediment-water interface (SWI) were measured with microelectrodes; diffusive gradients in thin films (DGT) resolved Fe, S, and P distributions; and sequential extraction quantified sediment P fractions. Results showed that OLPM coverage increased surface sediment DO concentration by 6.58-fold and DO penetration depth by 1.33-fold (16.8 mm). Overlying water total phosphorus (TP) decreased by 93.79%, and sediment interstitial phosphate (PO4-P) decreased by up to 45.75%. The SWI TP exchange flux reversed from +0.0068 mg/(m2·d) to -0.014 mg/(m2·d), shifting the system from a P source to a P sink. Sediment P fractionation revealed a 5.22% increase in stable Res-P and a 4.48% decrease in labile NaHCO3-P. Mechanistically, OLPM enhanced iron oxidation (Fe2+ reduced by 59.62%) and suppressed sulfate reduction (S2- homogenized at low levels), promoting P immobilization via Fe-S coupling. The material effectively inhibits endogenous P release through interfacial DO regulation without altering pH, offering a promising approach for eutrophication management.