Single and Combined Effects of Aged Polyethylene Microplastics and Cadmium on Nitrogen Species in Stormwater Filtration Systems: Perspectives from Treatment Efficiency, Key Microbial Communities, and Nitrogen Cycling Functional Genes

• Published in: Molecules (Basel, Switzerland) Vol. 30; no. 7; p. 1464
• Main Authors: Men, Cong, Pan, Zixin, Liu, Jiayao, Miao, Sun, Yuan, Xin, Zhang, Yanyan, Yang, Nina, Cheng, Shikun, Li, Zifu, Zuo, Jiane
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 26.03.2025
• Subjects: Adsorption; Analysis; Cadmium; Cadmium - chemistry; Chemical reactions; Constructed wetlands; Denitrification; Efficiency; Enzymes; Filtration; functional genes; Genes; Hydraulics; Metabolism; microbial community; Microbiota; Microbiota - drug effects; microplastics; Microplastics - chemistry; Nitrates; Nitrogen; Nitrogen cycle; Nitrogen Cycle - drug effects; Nitrogen Cycle - genetics; nitrogen removal; Nonpoint source pollution; Plastic pollution; Pollutants; Polyethylene; Polyethylene - chemistry; Rain; Runoff; stormwater filtration system; Stormwater management; Water Pollutants, Chemical; Water Purification - methods; China; Prince Edward Island; functional genes; microbial community; microplastics; stormwater filtration system; nitrogen removal
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules30071464

Microplastics and heavy metal contamination frequently co-occur in stormwater filtration systems, where their interactions may potentially compromise nitrogen removal. Current research on microplastics and Cd contamination predominantly focuses on soils and constructed wetlands, with limited attention given to stormwater filtration systems. In this study, the single and synergistic effects of aged polyethylene microplastics (PE) and cadmium (Cd) contamination in stormwater infiltration systems were investigated from perspectives of nitrogen removal, microbial community structures, and predicted functional genes in nitrogen cycling. Results showed that PE single contamination demonstrated stronger inhibition on NO3−–N removal than Cd. Low-level PE contamination (PE content: 0.1% w/w) in Cd-contaminated systems showed stronger inhibitory effect than high-level PE contamination (PE content: 5% w/w). The mean NO3−–N removal efficiency under combined Cd50 (Cd concentration: 50 μg/L) and PE5 contamination during the sixth rainstorm event was 1.04 to 34.68 times that under other contamination scenarios. Metagenomic analysis identified keystone genera (Saccharimonadales, Enterobacter, Aeromonas, etc.), and critical nitrogen transformation pathways (nitrate reduction to ammonium, denitrification, nitrogen fixation, and nitrification) govern system performance. PE and Cd contamination effects were most pronounced on nitrification/denitrification enzymes beyond nitrite oxidase and nitrate reductase. These mechanistic findings advance our understanding of co-contaminant interactions in stormwater filtration systems.