Atrazine disrupts nitrogen removal performance and greenhouse gas abatement in bioretention systems: Unraveling microbiotas and macrophytes responses.

The potential impact of stormwater runoff-induced loss of triazine herbicides, like atrazine (ATZ), on soil nitrogen cycling remains poorly understood. Bioretention systems (BRS) represent effective stormwater control measures (SCM) now understood to serve as important ATZ accumulation zones. However, the effects of ATZ exposure on nitrogen removal and greenhouse gas (GHG) abatement within BRS remain unclear. In the present study, bioretention columns were established and exposed to ATZ (0-25 mg kg) for 200 days. The results demonstrated that the accumulation of ATZ led to a reduction in total nitrogen removal efficiency (by 7.7-49.3 %) while simultaneously causing an increase in GHG emission fluxes (by 11.2 %-25.1 %). Moreover, ATZ significantly altered microbial activities, including nitrogen metabolism enzymes (hydroxylamine oxidoreductase, nitrate reductase, and nitrite reductase) and the electron transport system (ETSA). Microbial community analysis showed that ATZ reduced the relative abundance of nitrifying bacteria (Nitrospira and Nitrosomonas), along with certain denitrifying bacteria (Thauera, Terrimonas, and Dechloromona). Besides, the compromised function of leaves and roots diminished plant nitrogen uptake, and the application of structural equation modeling (SEM) revealed an increased contribution of plants to nitrogen removal. These findings collectively suggest that the widespread presence of triazine herbicides in urban areas could potentially impact the performance of SCMs.