Bioavailability evaluation of naphthalene in soil using persulfate oxidation and ultrasonic extraction method

Area of Science:

• Environmental Chemistry
• Soil Science
• Microbial Ecology

Background:

• Bioavailability quantifies the fraction of soil contaminants accessible for microbial breakdown.
• Conventional exhaustive extraction methods often overestimate contaminant bioavailability, including naphthalene.
• Accurate bioavailability assessment is crucial for understanding contaminant fate and remediation strategies.

Purpose of the Study:

• To develop and optimize a novel method, persulfate oxidation ultrasonic extraction (POUSE), for estimating naphthalene bioavailability in soil.
• To compare the POUSE method with conventional exhaustive extraction techniques (sonicator, SFE, SE) and biodegradation tests.
• To determine the optimal operating conditions for the POUSE method.

Main Methods:

• Developed the persulfate oxidation ultrasonic extraction (POUSE) method.
• Investigated the impact of temperature, persulfate oxidation duration, and persulfate to soil organic matter ratio (S2O8^2-/SOM) on POUSE.
• Compared naphthalene bioavailability estimates from POUSE with sonicator, supercritical fluid extraction (SFE), and soxhlet extraction (SE) against biodegradation data.

Main Results:

• Optimal POUSE conditions were identified as 70°C, 3 hours, and an S2O8^2-/SOM ratio of 11.6 g g⁻¹.
• POUSE-estimated naphthalene bioavailability correlated well with biodegradation tests for both freshly spiked and aged soils.
• Sonicator, SFE, and SE methods overestimated naphthalene bioavailability compared to biodegradation assessments.

Conclusions:

• The POUSE method provides a more precise estimation of naphthalene bioavailability in soil than conventional exhaustive extraction techniques.
• POUSE's accuracy stems from its better alignment with microbial degradation processes.
• This novel method offers a valuable tool for environmental risk assessment and soil remediation planning.