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Effects of biofilm modification on polyethylene microplastics-associated sulfamethazine adsorption
Summary
A 28-day study found that biofilm colonization on polyethylene microplastics increased their adsorption of the antibiotic sulfamethazine by 2–2.6-fold, driven by hydrogen bonding, electrostatic, and CH/π interactions. This demonstrates that microplastics in aquatic environments become more dangerous over time as biofilms form on their surfaces, amplifying their ability to accumulate and transport harmful pollutants through ecosystems.
In aqueous environments, microplastics (MPs) are susceptible to biofilm colonization owing to their special carrier surface characteristics, which may enhance the adsorption of harmful pollutants. This study aimed to investigate the effect of biofilm colonization on the changes in the surface physicochemical properties of MPs and the adsorption of organic micropollutants. Polyethylene (PE; 200 μm) pellets, commercial PE film (5 mm × 5 mm), and agricultural (Bohu-collected) PE film (5 mm × 5 mm) were co-cultured with Chlamydomonas reinhardtii in BG-11 medium and natural water for 28 d, and the adsorption properties of different PE MPs before and after biofilm colonization for sulfamethazine (SMZ) adsorption was compared. Notably, biofilm colonization increased SMZ adsorption by all PE MPs by 2–2.6-fold compared with that by PE MPs without biofilm. SMZ adsorption by PE pellets, commercial PE film, and Bohu-collected PE film cultured in distilled water increased by 39.5%, 60.0%, and 62.7%, respectively. Moreover, the adsorption capacity of pollutants was increased by 1.6–2 times for micron-sized MPs compared to millimeter-sized MPs. Mainly, CH/π, electrostatic, and hydrogen bonding interactions were involved in SMZ adsorption by PE MPs. Overall, this study shows the enhancement in MP-associated pollutant adsorption due to biofilm colonization, providing insights into MP–pollutant interactions in natural waters and a theoretical basis for ecological risk assessment.