Interactive effects of aquatic nitrogen and plant biomass on nitrous oxide emission from constructed wetlands

• Published in: Environmental research 2022-10, Vol.213, p.113716-113716, Article 113716
• Main Authors: Cai, Ze-Xiang, Li, Qu-Sheng, Bai, Heng, Zhu, Cong-Yun, Tang, Guan-Hui, Zhou, Huan-Zhan, Huang, Jia-Wei, Song, Xin-Shan, Wang, Jun-Feng
• Format: Article
• Language: English
• Subjects: Aquatic nitrogen form; Metabolomics; Nitrogen transformation genes; Nitrous oxide emission; Plant biomass accumulation
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2022.113716

Understanding of mechanisms in nitrous oxide (N2O) emission from constructed wetland (CW) is particularly important for the establishment of related strategies to reduce greenhouse gas (GHG) production during its wastewater treatment. However, plant biomass accumulation, microbial communities and nitrogen transformation genes distribution and their effects on N2O emission from CW as affected by different nitrogen forms in aquatic environment have not been reported. This study investigated the interactive effects of aquatic nitrogen and plant biomass on N2O emission from subsurface CW with NH4+-N (CW-A) or NO3−-N (CW–B) wastewater. The experimental results show that NH4+-N and NO3−-N removal efficiencies from CW mesocosms were 49.4% and 87.6%, which indirectly lead to N2O emission fluxes of CW-A and CW-B maintained at 213 ± 67 and 462 ± 71 μg-N/(m2·h), respectively. Correlation analysis of nitrogen conversion dynamic indicated that NO2−-N accumulation closely related to N2O emission from CW. Aquatic NH4+-N could up-regulate plant biomass accumulation by intensifying citric acid cycle, glycine-serine-threonine metabolism etc., resulting in more nitrogen uptake and lower N2O emission/total nitrogen (TN) removal ratio of CW-A compared to CW-B. Although the abundance of denitrifying bacteria and N2O reductase nosZ in CW-B were significantly higher than that of CW-A, after fed with mixed NH4+-N and NO3−-N influent, N2O fluxes and N2O emission/TN removal ratio in CW-A were extremely close to that of CW-B, suggesting that nitrogen form rather than nitrogen transformation microbial communities and N2O reductase nosZ determines N2O emission from CW. Hence, the selection of nitrate-loving plants will play an important role in inhibiting N2O emission from CW. [Display omitted] •N2O emitted from NO3−-N treatment was higher than that of NH4+-N treatment in CW.•NO2−-N accumulation closely related to N2O emission from subsurface CWs.•Plant biomass plays an important role in low ratio of N2O emission/TN removal.•N form rather than N2O reductase nosZ determines N2O fluxes of subsurface CWs.