Work

Microbial mechanisms underlying the reduction of N2O emissions from submerged plant covered system

Year: 2025

Type: article

Abstract: • Submerged plant-covered system reduced N 2 O flux. • Lower N 2 O emission attributed to submerged plant-attached biofilm. • Denitrification drive N 2 O emission from attached biofilm. • Dark conditions reduced N 2 O emission from submerged plant attached biofilm. • Counter-diffusion of dissolved oxygen and nutrients reduced N 2 O emission. Submerged plant (SP) restoration is a crucial strategy for restoring aquatic ecosystem. However, the effect of SP on nitrous oxide (N 2 O) emissions remains controversial, and the impact of SP-attached biofilms on N 2 O emissions is often overlooked. In this study, SP and non-submerged plant (NSP) systems were set up and operated continuously for 189 days, revealing that SP reduced N 2 O flux by 42.4 %. By comparing the N 2 O net emission rates from water, sediment, and biofilms, we identified biofilms as the primary medium responsible for the reduction in N 2 O emissions in both SP and NSP systems. Further analysis of N 2 O metabolic rates from nitrification, denitrification, and abiotic processes under light and dark conditions confirmed that counter-diffusion of dissolved oxygen and nutrients in SP biofilms plays a key role in reducing denitrification-driven N 2 O emissions. Additionally, SP-attached biofilms increased nosZII -type denitrifiers (e.g., Bacillus ) and reduced N 2 O production potential (( nirS + nirK )/( nosZI + nosZII )). Notably, the establishment of a SP restoration project in a typical eutrophic freshwater lake demonstrated that SP could reduce N 2 O fluxes by 61.5 %. This study provides significant insights for strategies aimed at mitigating N 2 O emissions.

Source: Water Research X

DOI: 10.1016/j.wroa.2025.100314