Dissolved Organic Matter Chemistry Modulates Biochar Effects on Phenanthrene Biodegradation in Agricultural Soil:...

Area of Science:

• Environmental Chemistry
• Soil Science
• Microbiology

Background:

• Biochar application in agriculture is rising, impacting soil contaminants like polycyclic aromatic hydrocarbons (PAHs).
• Dissolved organic matter (DOM) co-exists with biochar and influences the bioavailability and degradation of PAHs.
• Understanding these interactions is crucial for assessing food safety and environmental risks.

Purpose of the Study:

• To investigate how different types of DOM (citric acid, oxalic acid, humic acid) affect the fate of phenanthrene (a model PAH) in soil amended with wheat-straw biochar.
• To link PAH biodegradation to changes in bioavailable pools and microbial community responses.
• To determine if biochar and DOM combinations promote bioremediation or stabilization of PAHs.

Main Methods:

• Agricultural soil was spiked with phenanthrene and amended with wheat-straw biochar and three DOM types.
• PAH biodegradation was quantified by measuring removal percentages.
• Bioavailable PAH fractions and microbial responses, including the abundance of nidA gene copies, were analyzed.

Main Results:

• Citric and oxalic acids increased phenanthrene bioavailability and microbial removal rates.
• Humic acid decreased phenanthrene bioavailability and reduced its removal.
• Biochar alone enhanced removal, but its combination with citric/oxalic acids yielded the highest removal rates by enriching key degraders.
• Biochar combined with humic acid resulted in the lowest phenanthrene removal, indicating sequestration.

Conclusions:

• DOM chemistry critically modulates the effects of biochar on PAH fate in soil.
• Biochar can enhance PAH bioremediation when paired with specific DOM types that increase bioavailability.
• Conversely, biochar may promote PAH stabilization when combined with DOM types that reduce bioavailability.