Effect of polystyrene micro/nanoplastics on PCBs removal in constructed wetlands planted with Myriophyllum aquaticum

The co-occurrence of microplastics (MPs) and nanoplastics (NPs) with polychlorinated biphenyls (PCBs) is an emerging environmental concern. Wetland plants, with their unique anaerobic-aerobic environments, offer a promising approach for PCBs removal. However, the impact of MPs and NPs on PCBs dynamics in constructed wetlands is not well understood. This study examined the influence of polystyrene MPs and NPs of two different sizes on PCBs fate in constructed wetlands featuring Myriophyllum aquaticum. Results showed that although there was no significant difference in overall PCBs removal rates, the presence of MPs increased residues of highly chlorinated PCBs from 331 μg/kg to 379 μg/kg, while the presence of NPs increased residues of lightly chlorinated PCBs from 125 μg/kg to 153 μg/kg. Additionally, MPs and NPs increased plant uptake of PCBs from 0.08% to 0.10-0.14%, despite potential inhibition of plant growth. While MPs/NPs elevated microorganism counts, they did not affect microbial diversity or community structure. Importantly, MPs significantly inhibited the main PCB-dechlorinating bacteria (Dehalococcoidia) and had a greater impact on PCB-degrading enzymes (dioxygenase, K03381) compared to NPs. This study highlights the complex interactions between MPs/NPs and PCBs in wetland environments and their implications for bioremediation strategies.