Spatial Distribution and Compartmental Allocation of Microplastics in Belowground Systems of Mulched Phyllostachys...

Intensive management practices promote microplastic (MP) accumulation in Phyllostachys violascens forests, posing potential threats to ecosystem stability and the edibility safety of bamboo shoots. However, how urbanization and mulching duration jointly regulate MP distribution, transfer, and associated food safety risks remains unclear. We investigated MP dynamics across urban-rural gradients (suburban vs. exurban) under different mulching durations (no mulching, short-term mulching, and long-term mulching), focusing on the rhizome-root-soil system and bamboo shoots. MP abundance was significantly higher in suburban forests, with maxima under long-term mulching, whereas in exurban forests, peaks occurred under long-term mulching. Urbanization also altered MP allocation patterns, with enrichment in rhizome roots and rhizomes in suburban forests but greater accumulation in bamboo shoots in exurban forests. Long-term mulching markedly enhanced MP accumulation across all components, particularly in clump roots, where abundance was three times higher than that in exurban forests. MPs were predominantly small (20-50 μm), mainly composed of acrylates (ACRs), polyvinyl chloride (PVC), polypropylene (PP), polyethylene terephthalate (PET), polyurethane (PU), and polyethylene (PE). Along the "soil-root-rhizome" continuum, contrasting transfer patterns emerged between suburban and exurban forests, with soil total potassium identified as the key driver regulating MP migration and redistribution. Although the pollution load index indicated moderate contamination without significant accumulation in bamboo shoots, the ecological risk index revealed a high ecological risk, highlighting potential food safety concerns. Overall, MP accumulation and migration in Ph. violascens systems are jointly shaped by urban-rural gradients and mulching duration, with implications for belowground processes and the safety of edible bamboo shoots.