Hydrolysis of sulfamethoxazole in the hyporheic zone: kinetics, factors and pathways

Yan Cheng; Wenxuan Li; Dan Zhang; Jianping Zhang; Fanfan Zhang; Hongwei Liu; Mengya Luo; Shengke Yang

doi:10.1080/09593330.2023.2283402

Hydrolysis of sulfamethoxazole in the hyporheic zone: kinetics, factors and pathways

Environ Technol. 2023 Nov 28:1-14. doi: 10.1080/09593330.2023.2283402. Online ahead of print.

Authors

Yan Cheng^{1

2

3}, Wenxuan Li^{1

2

3}, Dan Zhang^{1

2

3}, Jianping Zhang^{1

2

3}, Fanfan Zhang^{1

2

3}, Hongwei Liu⁴, Mengya Luo^{1

2

3}, Shengke Yang^{1

2

3}

Affiliations

¹ Key Laboratory of Subsurface Hydrology and Ecology in Arid Areas, Ministry of Education, Chang' an University, Xi'an, People's Republic of China.
² School of Water and Environment, Chang' an University, Xi'an, People's Republic of China.
³ Key Laboratory of Eco-hydrology and Water Security in Arid and Semi-arid Regions of Ministry of Water Resources, Chang'an University, Xi'an, People's Republic of China.
⁴ Zhongsheng Environmental Technology Development Co. Ltd, Xi'an, People's Republic of China.

PMID: 37970958
DOI: 10.1080/09593330.2023.2283402

Abstract

ABSTRACTIt is unknown how antibiotics would behave after entering the hyporheic zone (HZ), which is an area where groundwater and surface water alternate continuously. In this study, the hydrolysis process in the HZ was investigated based on the intermediates identified by HPLC-Q-TOF-MS and FTIR, and the active sites of sulfamethoxazole (SMX) were predicted by density functional theory (DFT). The results showed that the hydrolysis rate of SMX during surface water recharged groundwater reached 38.94%, and the contribution rate of hydroxyl radicals reached 48.35%. In neutral and alkaline environments, SMX hydrolysed more quickly. This is due to the fact that ·OH, as the main precursor of OH^-, is much higher in quantity under alkaline conditions. Inorganic anions such as NO₃^-, HCO₃^- and ${CO}_{3}^{2 -}$ may inhibit the hydrolysis of SMX by eliminating the reactive oxygen species generated in the HZ. In the process of groundwater recharging to surface water, the concentration of dissolved oxygen (DO) and the rate of SMX hydrolysis gradually reduced. Nitrification, hydroxylation and polymerisation are the main hydrolysis pathways of SMX. The hydrolysis products of SMX in the HZ are more plentiful and have a higher hydrolysis rate compared to the single oxygen environment. The study on the hydrolysis mechanism of SMX in this paper will provide a theoretical basis for the treatment of antibiotic pollution.

Keywords: DFT; Sulfamethoxazole; hydrolysis pathways; hyporheic zone; kinetics.