TY - JOUR

T1 - Comparing the photodegradation of typical antibiotics in ice and in water

T2 - Degradation kinetics, mechanisms, and effects of dissolved substances

AU - Ge, Linke

AU - Li, Xuanyan

AU - Zhang, Shuang

AU - Cao, Shengkai

AU - Zheng, Jinshuai

AU - Wang, Degao

AU - Zhang, Peng

PY - 2024/3/31

Y1 - 2024/3/31

N2 - New antibiotic contaminants have been detected in both surface waters and natural ice across cold regions. However, few studies have revealed distinctions between their ice and aqueous photochemistry. In this study, the photodegradation and effects of the main dissolved substances on the photolytic kinetics were investigated for sulfonamides (SAs) and fluoroquinolones (FQs) in ice/water under simulated sunlight. The results showed that the photolysis of sulfamethizole (SMT), sulfachloropyridazine (SCP), enrofloxacin (ENR) and difloxacin (DIF) in ice/water followed the pseudo-first-order kinetics with their quantum yields ranging from 4.93 × 10 −3 to 11.15 × 10 −2. The individual antibiotics experienced disparate photodegradation rates in ice and in water. This divergence was attributed to the concentration-enhancing effect and the solvent cage effect that occurred in the freezing process. Moreover, the main constituents (Cl −, HASS, NO 3 − and Fe(III)) exhibited varying degrees of promotion or inhibition on the photodegradation of SAs and FQs in the two phases (p < 0.05), and these effects were dependent on the individual antibiotics and the matrix. Extrapolation of the laboratory data to the field conditions provided a reasonable estimate of environmental photolytic half-lives (t 1/2,E) during midsummer and midwinter in cold regions. The estimated t 1/2,E values ranged from 0.02 h for ENR to 14 h for SCP, which depended on the reaction phases, latitudes and seasons. These results revealed the similarities and differences between the ice and aqueous photochemistry of antibiotics, which is important for the accurate assessment of the fate and risk of these new pollutants in cold environments.

AB - New antibiotic contaminants have been detected in both surface waters and natural ice across cold regions. However, few studies have revealed distinctions between their ice and aqueous photochemistry. In this study, the photodegradation and effects of the main dissolved substances on the photolytic kinetics were investigated for sulfonamides (SAs) and fluoroquinolones (FQs) in ice/water under simulated sunlight. The results showed that the photolysis of sulfamethizole (SMT), sulfachloropyridazine (SCP), enrofloxacin (ENR) and difloxacin (DIF) in ice/water followed the pseudo-first-order kinetics with their quantum yields ranging from 4.93 × 10 −3 to 11.15 × 10 −2. The individual antibiotics experienced disparate photodegradation rates in ice and in water. This divergence was attributed to the concentration-enhancing effect and the solvent cage effect that occurred in the freezing process. Moreover, the main constituents (Cl −, HASS, NO 3 − and Fe(III)) exhibited varying degrees of promotion or inhibition on the photodegradation of SAs and FQs in the two phases (p < 0.05), and these effects were dependent on the individual antibiotics and the matrix. Extrapolation of the laboratory data to the field conditions provided a reasonable estimate of environmental photolytic half-lives (t 1/2,E) during midsummer and midwinter in cold regions. The estimated t 1/2,E values ranged from 0.02 h for ENR to 14 h for SCP, which depended on the reaction phases, latitudes and seasons. These results revealed the similarities and differences between the ice and aqueous photochemistry of antibiotics, which is important for the accurate assessment of the fate and risk of these new pollutants in cold environments.

KW - Ice photochemistry

KW - Aqueous photochemistry

KW - Antibiotics

KW - Photodegradation kinetics

KW - Dissolved substances

KW - Environmental half-lives

U2 - 10.1016/j.chemosphere.2024.141489

DO - 10.1016/j.chemosphere.2024.141489

M3 - Journal article

VL - 352

JO - Chemosphere

JF - Chemosphere

SN - 0045-6535

M1 - 141489

ER -