Effect of capping-temperature control coupled with electroosmotic adsorption on sediment phosphorus forms and release characteristics

With external phosphorus input gradually controlled, inhibiting internal phosphorus release is pivotal for water eutrophication management. However, existing technologies mostly adopt a "passive sequestration" approach, which fails to eliminate the potential risk and exhibits unstable long-term performance. For the first time, this study proposes the concept of “induced release, directional driving and in-situ capture”, aiming to achieve the dual goals of reducing sediment phosphorus content and inhibiting phosphorus release. Based on this concept, five experimental treatments were designed, including blank control, capping alone, capping-temperature control, capping-temperature control combined with adsorption and capping-temperature control combined with electroosmotic-adsorption(CTCEA). Phosphorus content dynamics in the overlying water, sediment pore water and sediments were analyzed before and after treatment. Phosphorus release flux variations at the sediment-water interface under different treatments were quantified to characterize their patterns, and the internal mechanism underlying the “induced release and controlled release” of sediment phosphorus was elucidated. Results showed CTCEA performed optimally. With one month, the phosphorus release amounts from sediments and pore water increased by 24.3% and 42.2%, respectively. Correspondingly, the total phosphorus and unstable phosphorus in sediments and the phosphorus concentration in overlying water decreased by 29.7%, 51.2% and 72.4%, respectively. Under the elevated phosphorus release risk in summer-autumn, sediment phosphorus release flux dropped by 84.23%, with overlying water phosphorus stabilized at 0.2~0.4 mg/L.These findings indicated that CTCEA achieved the dual goals of “efficient removal and long-term controlled release” of sediment phosphorus, thereby providing an innovative and practical strategy for the targeted remediation of internal phosphorus pollution. ● Elevated sediment-water interface temperature promotes sediment phosphorus (P) release. ● Electroosmosis-adsorption accelerates efficient P removal from sediment pore water. ● Sediment P content reduction and P form remolding enable long-term P release control.