Effects of norfloxacin on nitrate reduction and dynamic denitrifying enzymes activities in groundwater

Linpeng Chen; Fuyang Huang; Chong Zhang; Jia Zhang; Fei Liu; Xiangyu Guan

doi:10.1016/j.envpol.2021.116492

Effects of norfloxacin on nitrate reduction and dynamic denitrifying enzymes activities in groundwater

Environ Pollut. 2021 Jan 13:273:116492. doi: 10.1016/j.envpol.2021.116492. Online ahead of print.

Authors

Linpeng Chen¹, Fuyang Huang¹, Chong Zhang¹, Jia Zhang¹, Fei Liu², Xiangyu Guan³

Affiliations

¹ MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing, 100083, PR China; Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing, 100083, PR China.
² MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing, 100083, PR China; Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing, 100083, PR China. Electronic address: feiliu@cugb.edu.cn.
³ Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing, 100083, PR China; School of Ocean Sciences, China University of Geosciences (Beijing), Beijing, 100083, PR China.

PMID: 33493764
DOI: 10.1016/j.envpol.2021.116492

Abstract

The impact of antibiotics on denitrification has attracted widespread attention recently. Norfloxacin, as a representative of fluoroquinolone antibiotics, is extensively detected in groundwater. However, whether the release of norfloxacin into the groundwater poses potential risks to denitrification remains unclear. In this study, effect of norfloxacin on denitrification was investigated. The results showed that increasing norfloxacin from 0 to 100 μg/L decreased nitrate removal rate from 0.68 to 0.44 mg/L/h, but enhanced N₂O emission by 177 folds. Additionally, 100 μg/L of norfloxacin decreased nitrite accumulation by 50.6%. Corresponding inhibition of norfloxacin on bacterial growth, carbon source utilization, electron transport system activity and genes expression was revealed. Furthermore, denitrifying enzyme dynamic monitoring results showed that norfloxacin inhibited nitrate reductase activity, and enhanced nitrite reductase activity to some extent in denitrification process, which was consistent with the variations of nitrate and nitrite. Meanwhile, sensitivity analysis demonstrated that nitrate reductase was more easily affected by norfloxacin than nitrite reductase. Overall, this study suggests that multiple regulation of denitrifying enzyme activity contributes to evaluating the comprehensive effects of antibiotics on groundwater denitrification.

Keywords: Denitrification; Enzyme; Groundwater; Norfloxacin.