Mingchen Xu, Xiaoxuan Wang, Yifei Li, Hua Zou
We propose that aeration-induced changes in the rhizosphere environment are essential for enhancing the pharmaceutical removal in surface freshwater ecosystems. However, the mechanisms by which rhizospheric microorganisms degrade pharmaceuticals under aeration in phytoremediation systems are poorly understood. This study examined the effects of aeration on the biodegradation of pharmaceutical mixtures (diclofenac, ibuprofen, ketoprofen, trimethoprim, roxithromycin, propranolol, and valsartan) in surface water from the vegetative to bolting stages of Phragmites australis in aerated wetlands over a 12-week experimental period in batch constructed wetland microcosms. It was found that the removal efficiencies of most pharmaceuticals except for diclofenac were apparently enhanced under aeration conditions in wetlands compared to the non-aerated wetlands at concentrations of 150 ng/L and 1000 ng/L, reaching the best performance (removal efficiencies: 44% ibuprofen, 25% ketoprofen, 50% trimethoprim, 60% roxithromycin, 43% propranolol, and 24% valsartan). Aeration also synergistically improved the elimination of roxithromycin, ibuprofen, NH 4 + -N, and TP in wetlands compared to non-aerated and pure aeration systems. During wetland phytoremediation of pharmaceuticals under aeration conditions, there was a significant increase in the secretion rates of four sugars, three organic acids, and three amino acids from Phragmites australis roots at the bolting stage compared to non-aerated wetlands. This change was accompanied by a higher abundance of dominant rhizosphere bacteria from five phyla (Proteobacteria, Actinobacteria, Chloroflexi, Patescibacteria, and Bdellovibrionota), suggesting that aeration-associated shifts in root exudates might modulate the rhizosphere microbiome and contribute to pharmaceutical degradation. These findings highlight aeration's potential to optimize wetland systems for pharmaceutical removal and improved water quality.