Plastic particles affect N2O release via altering core microbial metabolisms in constructed wetlands.

• Plastic particles affect nitrogen removal while mitigating the release of N 2 O. • Large plastics reduce N 2 O release by impeding CO 2 assimilation and NH 2 OH reduction. • Nanoplastics affect N metabolism by disrupting N-ion transmembrane transport. • Nanoplastics block the key N-removing enzyme activity, hindering N 2 O production. Constructed wetlands (CWs) have been proven to effectively immobilize plastic particles. However, little is known about the differences in the impact of varying sized plastic particles on nitrous oxide (N 2 O) release, as well as the intervention mechanisms in CWs. Here, we built a lab-scale wetland model and introduced plastic particles of macro-, micro-, and nano-size at 100 μg/L for 370 days. The results showed that plastic particles of all sizes reduced N 2 O release in CWs, with the degrees being the strongest for the Nano group, followed by Micro and Macro groups. Meanwhile, 15N- and 18O-tracing experiment revealed that the ammoxidation process contributed the most N 2 O production, followed by denitrification. While for every N 2 O-releasing process, the contributing proportion of N 2 O in nitrification-coupled denitrification were most significantly cut down under exposing to macro-sized plastics and had an obvious increase in nitrifier denitrification in all groups, respectively. Finally, we revealed the three mechanism pathways of N 2 O release reduction with macro-, micro-, and nano-sized plastics by impacting carbon assimilation (RubisCO activity), ammonia oxidation (gene amo abundance and HAO activity), and N-ion transmembrane and reductase activities, respectively. Our findings thus provided novel insights into the potential effects of plastic particles in CWs as an eco-technology. [Display omitted] [ABSTRACT FROM AUTHOR]