Exploring the Interaction between Microplastics, Polycyclic Aromatic Hydrocarbons and Biofilms in Freshwater

Water pollution by non-biodegradable materials such as plastics is a major source of concern. Here, we investigated the ability of polyethylene terephthalate (PET), high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) microplastics (MPs-4 mm) to adsorb benzo(a)pyrene (BaP) and pyrene (Pyr) in freshwater after 3 and 30 days. BaP was more adsorbed than Pyr with PP and PS being the most and least efficient adsorbents of BaP, respectively. In mixed solutions, the differences in PAHs adsorption are smoother than in pure solutions, and an increase in adsorbed PAHs half-life has been observed. In parallel, the ability of bacterial species isolated from freshwater responsible for infections in humans (Escherichia coli, Klebsiella pneumoniae and Aeromonas sobria) to assemble biofilms on plastics was evaluated. Biofilm assembly increased with time (1 to 3 months) being possible to observe biofilms on LDPE, HDPE and PS. For PET and PP only after 3 months on fragments of the original MPs was possible to observe attached bacteria. Exposure to 100 µg/mL PAHs (either isolated or mixed) during 1 month significantly decreased bacterial persistence (p < .01) compared to unexposed bacteria.