摘要
This study revealed the dual roles of Cu(Ⅱ)on the β-lactam antibiotics degradation in Suwannee River fulvic acid(SRFA)solution during day and night cycle.Amoxicillin(AMX)and ampicillin(AMP)were selected as the representative β-lactam antibiotics.Cu(Ⅱ)played a key role in the dark degradation of AMX and AMP via catalytic hydrolysis and oxidation.However,Cu(Ⅱ)mainly exhibited an inhibitory effect on SRFA-involved photochemical degradation of AMX and AMP.In the presence of 500 nM of Cu(Ⅱ),the degradation rate of AMX and AMP in the light condition were around 5 times higher than that in the dark condition,suggesting the photodegradation of β-lactam antibiotics was much more pronounced than catalyzed hydrolysis and oxidation.The triplet excited state of SRFA(^(3)SRFA*)primarily contributed to AMX and AMP photodegradation.Hydroxyl radicals(·OH)and singlet oxygen(^(1)O_(2))exhibited limit impacts.The redox cycle of Cu(Ⅱ)/Cu(Ⅰ)restricted the electron transfer pathway of ^(3)SRFA* with AMX and AMP.During the day and night cycles for 48 h,Cu(Ⅱ)served as a stronger inhibitor rather than a promotor.These findings highlight the interactions between Cu(Ⅱ)and SRFA are distinct under day and night conditions,which could further affect the fate of β-lactam antibiotics in natural environments.
基金
China’s National Key Research and Development Program(grant 2017YFE0133200)
National Science Foundation of China(grants 51708562 and 21577178)
Characteristic Innovation Projects of Universities in Guangdong province(grant 2018KTSCX001)
Guangdong Basic and Applied Basic Research Foundation(2019A1515011664)
the Fundamental Research Funds for the Central Universities(20lgzd22)for their financial support of this study.
