Magnetite-mediated microbial functional restructuring and electron transfer pathways for enhanced PAHs degradation in...

Area of Science:

• Environmental Science
• Environmental Chemistry
• Environmental Microbiology

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants in sediments, posing risks to aquatic ecosystems and human health.
• Effective remediation strategies are needed to mitigate the toxicity and environmental persistence of PAHs.

Purpose of the Study:

• To investigate the efficacy of nano-Fe₃O₄ (magnetite) in enhancing the biodegradation of PAHs in contaminated river sediments.
• To elucidate the underlying mechanisms of nano-Fe₃O₄-mediated PAH remediation, including microbial community shifts and electron transfer processes.

Main Methods:

• Incubation of contaminated river sediments with varying concentrations of nano-Fe₃O₄ (0.5-5%) under simulated aquatic conditions for 210 days.
• Quantification of PAH degradation efficiencies using gas chromatography-mass spectrometry (GC-MS).
• Assessment of microbial activity via electron transfer system (ETS) assays, microbial community analysis (16S rRNA gene sequencing), and bioavailability assays.

Main Results:

• Nano-Fe₃O₄ addition significantly enhanced PAH biodegradation, with notable reductions in both low-molecular-weight (LMW) and high-molecular-weight (HMW) PAHs.
• Specific dosages (3.5-5% Fe₃O₄) rapidly reduced HMW-PAHs and sustained LMW-PAH removal.
• Microbial analysis revealed enrichment of sulfate- and iron-reducing bacteria, increased ETS activity, and enhanced extracellular electron transfer, driven by nano-Fe₃O₄-mediated conductivity.
• PAH bioavailability increased due to nano-Fe₃O₄-induced desorption from sediment matrices.

Conclusions:

• Nano-Fe₃O₄ acts as a potent enhancer for microbial PAH biodegradation in contaminated sediments.
• The remediation mechanism involves fostering microbial cooperation, improving metabolic efficiency, and promoting synergistic electron transfer processes.
• Nano-Fe₃O₄ presents a promising and sustainable solution for the remediation of PAH-contaminated aquatic environments.