Bioavailability gating in bamboo-microbe-biochar systems for petroleum hydrocarbon remediation: An emerging conceptual framework and critical evidence gaps

Abstract

Globally, soil contamination with petroleum hydrocarbons (PHs) remains a persistent environmental issue. Contaminant aging and reduced bioavailability can restrict microbial access, while microbial inhibition and the formation of potentially persistent transformation products may further limit biodegradation. Existing strategies independently enhance either microbial degradation or contaminant immobilization but rarely resolve the trade-off between substrate accessibility and toxicity reduction. This review proposes a bioavailability-regulated framework in which bamboo-microbe systems are considered potential soil bioreactors that integrate rhizosphere priming, endophytic processes, and pyrolyzed bamboo-derived biochar as an exogenous soil amendment. The proposed framework links the remediating bamboo with a biochar derived from its own biomass, creating a plant-biomass-to-amendment connection that is generally absent from conventional plant-biochar remediation systems based on unrelated plant and biochar feedstocks. Within this framework, biochar is proposed to regulate PHs bioavailability through sorption-desorption processes that may reduce toxicity while retaining sufficient microbial accessibility for transformation and degradation. This review synthesized emerging evidence linking bamboo-driven shifts in soil physicochemical properties, rhizosphere processes, microbial functional traits, and metabolic pathways with PHs transformation, while distinguishing direct bamboo evidence from analogous and mechanistic evidence. For bamboo-based systems, available evidence reveals a critical gap between conceptual potential and field-scale validation. Overall, this work reframes bamboo as a potential regulator of contaminant bioavailability instead of a passive phytoremediator. This framework provides a testable basis for designing and evaluating integrated bamboo-microbe-biochar systems for hydrocarbon-contaminated soils, while highlighting the experimental evidence required before field-scale application.