[Effects of Sediment Microenvironment on Sedimentary Phosphorus Release Under Capping]

Area of Science:

• Environmental Science
• Water Quality Management
• Geochemistry

Context:

• Endogenous phosphorus release from sediments significantly impacts aquatic ecosystems.
• In-situ sediment capping is a key strategy for controlling internal phosphorus loading.
• Understanding the sediment microenvironment's role is crucial for effective phosphorus management.

Purpose:

• To compare the effects of two in-situ covering materials, ACPM and Phoslock®, on the sediment microenvironment.
• To evaluate the control exerted by these materials on endogenous phosphorus release.
• To assess the phosphate adsorption capacity and impact on sediment phosphorus fractions.

Summary:

• ACPM coverage resulted in lower NH₄⁺-N and Fe²⁺ concentrations and higher microbial activity compared to Phoslock®, indicating a more aerobic microenvironment under ACPM.
• Phoslock® demonstrated superior phosphate adsorption capacity, as evidenced by lower dissolved inorganic phosphorus (DIP) concentrations in overlying and porewaters.
• Both materials facilitated phosphorus fixation, increasing Ca-P, but ACPM oxidation led to increased NH₄Cl-P and decreased Fe/Al-P, promoting active phosphorus release.

Impact:

• Phoslock® is more effective for direct phosphate adsorption, while ACPM may promote sediment remediation through controlled phosphorus release.
• Sediment microenvironment parameters (redox potential, microbial activity) are important but not the sole determinants of capping material efficacy.
• Findings guide the selection of sediment capping materials based on specific water quality objectives and sediment characteristics.