Effects of Wheat Straw-Derived Biochar on Soil Microbial Communities Under Phenanthrene Stress

The potential of biochar to mediate shifts in soil microbial communities caused by polycyclic aromatic hydrocarbon (PAH) stress in farmland, thus assisting in the bioremediation of contaminated soil, remains uncertain. This study introduced wheat straw biochars generated at 300 °C (W300) and 500 °C (W500) at varying levels (1% and 2% w / w ) into agricultural soil contaminated with phenanthrene at 2.5 and 25 mg/kg. The aim was to investigate their effects on microbial community structure and phenanthrene degradation by indigenous microbes. Biochar application in both slightly (PLS) and heavily (PHS) contaminated soils increased overall microbial/bacterial biomass, preserved bacterial diversity, and selectively enriched certain bacterial genera, which were suppressed by phenanthrene stress, through sorption enhancement and biotoxicity alleviation. The abundances of PAH-degrading genera and nid A degradation gene were promoted by biochar, especially W300, in PHS due to soil nutrient improvement, enhancing phenanthrene biodegradation. However, in PLS, biochar, particularly W500, inhibited their abundance due to a reduction in phenanthrene bioavailability to specific degraders, thus hindering phenanthrene biodegradation. These findings suggest that applying wheat straw biochar produced at appropriate temperatures can benefit soil microbial ecology and facilitate PAH elimination, offering a sustainable strategy for utilizing straw resources and safeguarding soil health and agricultural product quality.