Remediation of contaminated intertidal sediment by increasing permeability using active capping material

Area of Science:

• Environmental Engineering
• Soil Science
• Marine Science

Background:

• Intertidal zones often suffer from contaminated clayey sediments.
• Remediation of these sediments is crucial for ecosystem health.
• Existing methods may have limitations in effectiveness or environmental impact.

Purpose of the Study:

• To introduce a novel active capping agent for clayey sediment remediation.
• To evaluate the efficacy of granulated coal ash (GCA) in improving sediment properties.
• To assess the impact of GCA on nutrient loads and oxidation levels in intertidal sediments.

Main Methods:

• Development of granulated coal ash (GCA) from coal fly ash.
• Application of GCA as an active capping agent to clayey sediment.
• Measurement of sediment permeability coefficient, soil classification, and ion exchange.
• Analysis of pore water nutrient concentrations (PO4-P, NH4-N), dissolved oxygen, and redox potential.

Main Results:

• GCA increased sediment permeability sevenfold, altering classification from clayey silt to silt.
• Permeability increase was linked to Ca2+ ions, reducing the sodium adsorption ratio.
• Nutrient loads decreased significantly: 55% for PO4-P and 44% for NH4-N.
• Dissolved oxygen increased by 1.8 mg/L, and redox potential rose from -370 to -306 mV.

Conclusions:

• Active capping with GCA is a novel and effective technology for intertidal sediment remediation.
• GCA successfully enhances soil permeability, reduces nutrient pollution, and increases sediment oxidation.
• This approach presents a promising strategy for managing contaminated clayey sediments in coastal environments.