A Review of Mechanism of Constructed Wetland Plants, Substrates, and Microorganisms Influencing Nitrous Oxide Production

Nitrous oxide (N2O), as a critical greenhouse gas, has emerged as a significant contributor to global climate change. Constructed wetlands (CWs), while serving as an ecological wastewater treatment technology, generate substantial N2O emissions during the operation. Therefore, this article aims to offer mechanisms of N2O production through nitrogen cycling processes in the CWs. A comprehensive and systematic analysis was conducted on the regulatory mechanisms of wetland plants in controlling N2O emissions, focusing on five core perspectives: rhizosphere effects and plant diversity, substrate properties, functional microbial communities, substrate–plant interactions, and microbial community–plant interactions. Notably, this review is the first to explicitly describe the process by which the interactions between plants and substrates, as well as between plants and microorganisms, synergistically regulate N2O emissions in CWs. Furthermore, strategies and methodologies for N2O emission reduction in CW systems were proposed, offering practical insights for the application of CW systems. Particular attention should be directed toward elucidating the synergistic regulatory relationships between nutrient removal processes and greenhouse gas mitigation in the engineered wetland ecosystems.