The emerging threat of hybrid microplastics: Impacts on per(poly)fluoroalkyl substance bioaccumulation and phytotoxicity in floating macrophytes

This study investigated how microplastic (MP) hybridization influence the environmental behavior of per(poly)fluoroalkyl substances (PFASs), with a focus on the bioaccumulation and phytotoxicity of Eichhornia crassipes, a macrophyte employed for phytoremediation. Perfluorooctanoic acid (PFOA) and perfluoro-2-methyl-3-oxahexanoic acid (GenX) were selected as the targeted PFASs, and polypropylene (PP), polyethylene (PE), and polystyrene (PS) were selected as the model MPs. Compared with previous co-exposure studies, this study considered the exposed polymer component, and innovatively introduced Simpson diversity (SDI) index to evaluate the component evenness and complexity, thereby quantifying the MP hybridization. Results revealed that at environmentally relevant concentrations, increased MP hybridization significantly enhanced the PFOA (k = 0.462) and GenX (k = 0.455) bioaccumulation in E. crassipes, with GenX exhibiting a greater sensitivity to colloidal interactions than PFOA. Although pure MPs initially promoted the PFOA/GenX removal by E. crassipes from the water column, this effect diminished with MP hybridization. This phenomenon is likely attributed to increased MP self-assembly and colloidal enlargement, thereby hindering PFOA/GenX adsorption onto the MPs. However, the enhanced rhizosphere filtration provided by MP hybridization led to a greater overall PFOA/GenX accumulation to E. crassipes. Furthermore, MP hybridization exacerbated lipid peroxidation and amplified the integrated toxicological responses in E. crassipes under coexposure to PFOA/GenX. Interestingly, despite the prevalence of antagonistic effects between MPs and PFOA/GenX, these effects decreased with increasing MP hybridization.