Responding to nitrogen removal of constructed wetlands with modified basalt fiber bio-nest under different chain-lengths perfluorocarboxylic acids exposure: Decontamination and metabolism

Modified basalt fiber bio-nest could enhance the decontamination performance of constructed wetlands (CWs), though influence of different chain-lengths perfluorocarboxylic acids (PFCAs) were awaited to be investigated. This study explored different chain-length FPCAs that generated the influence on nitrogen removal in CWs amended with modified basalt fiber bio-nest (CW-BF). Results demonstrated a significant decrease of ammonium (NH4+-N) by 20.65-24.79 % in later stages and a higher nitrate (NO3--N) removal by 3.02-5.21 % during April to August were observed with perfluorooctanoic acid (PFOA) stress. In contrast, there were slighter impacts on both NH4+-N and NO3--N removal by perfluorobutanoic acid (PFBA). PFOA suppressed the activity of ammonia monooxygenase and nitrite oxidoreductase, while stimulated nitrate reductase and nitrite reductase. For functional microorganisms, the relative abundance of Ellin6067 decreased by 24.97 % with PFOA treatment, aligned with lower nitrifying enzyme activities and higher effluent NH4+-N concentration. Besides, both PFCAs caused the enrichment of denitrifying bacteria like Plasticicumulans, Denitratisoma, Hassallia, and Azoarcus, according with higher expression of functional genes. Nevertheless, an increase of NH4+-N in the effluent of the PFOA group might result from the up-regulation of genes related to dissimilatory nitrate reduction to ammonium with PFCAs exposure.