Residual plastic film debris induced the reconstruction of soil microbial communities: Potential mechanisms affecting the natural attenuation of PAHs

The coexistence of plastic film residues and organic pollutants like polycyclic aromatic hydrocarbons (PAHs) in agricultural soils is a rising concern, but microbial effects and contaminant attenuation linkages remain unclear. This study used soil microcosms, 16S rDNA quantification, metagenomics, and PAHs degradation assays to explore how bacterial communities and PAHs attenuation in contaminated soils were influenced by residual plastic films (non-biodegradable LDPE and biodegradable PBAT/PLA composite) in 45 d. Both plastic types restructured bacterial communities without altering richness, but biodegradable films reduced alpha-diversity. Beta-diversity varied significantly between bacteria on plastic surfaces and soil microbiota, differing across plastic types. Co-occurrence networks showed enhanced bacterial synergy and reduced modularity under plastic residues, with higher complexity and stability in biodegradable film-treated group. Plastic residues reduced total bacterial abundance by 1.9 × 10⁸–2.7 × 10⁸ copies/g, yet enriched plastic-PAHs dual-functional degraders in soil and on films (1.3–2.2 times the control). Metagenomic analysis identified these degraders carrying genes for plastic (e.g., K01046) and PAHs degradation (e.g., K01055) and their PAHs-degrading capability was confirmed by PAHs degradation assays. Natural attenuation of PAHs was accelerated in film-treated systems, with 0.5–0.6 mg/kg residue reduction compared to the control by day 45. Plastic film debris promoted PAHs dissipation by shaping “plastic-PAHs dual-degrading” bacterial consortia. The biodegradable film-enriched consortia had superior PAHs-degrading efficiency, coupled with higher KO abundance, leading to slightly stronger PAHs attenuation. These results improve understanding of plastic-film environmental impacts, PAHs biogeochemical processes, and co-pollution risk management in agroecosystems.