Indirect photodegradation of sulfadimidine and sulfapyridine: Influence of CDOM components and main seawater factors

Mingyan Xiao; Xinyu Tang; Xiaoyong Shi; Chuansong Zhang

doi:10.1016/j.chemosphere.2023.138821

Indirect photodegradation of sulfadimidine and sulfapyridine: Influence of CDOM components and main seawater factors

Chemosphere. 2023 Aug:333:138821. doi: 10.1016/j.chemosphere.2023.138821. Epub 2023 May 4.

Authors

Mingyan Xiao¹, Xinyu Tang¹, Xiaoyong Shi², Chuansong Zhang³

Affiliations

¹ Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, 238 Songling Road, Qingdao, 266100, PR China.
² Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, 238 Songling Road, Qingdao, 266100, PR China; National Marine Hazard Mitigation Service, Beijing, 100194, China. Electronic address: shixy@ouc.edu.cn.
³ Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, 238 Songling Road, Qingdao, 266100, PR China. Electronic address: zcsong@ouc.edu.cn.

PMID: 37149098
DOI: 10.1016/j.chemosphere.2023.138821

Abstract

This study investigated the indirect photodegradation of sulfadimidine (SM₂) and sulfapyridine (SP) in the presence of chromophoric dissolved organic matter (CDOM), and studied the influences of main marine factors (salinity, pH, NO₃^- and HCO₃^-). Reactive intermediate (RI) trapping experiments demonstrated that triplet CDOM (³CDOM*) played a major role in the photodegradation of SM₂ with a 58% photolysis contribution, and the contributions to the photolysis of SP were 32%, 34% and 34% for ³CDOM*, hydroxyl radical (HO·) and singlet oxygen (¹O₂), respectively. Among the four CDOMs, JKHA, with the highest fluorescence efficiency, exhibited the fastest rate of SM₂ and SP photolysis. The CDOMs were composed of one autochthonous humus (C1) and two allochthonous humus (C2 and C3). C3, with the strongest fluorescence intensity, had the strongest capacity to generate RIs and accounted for approximately 22%, 11%, 9% and 38% of the total fluorescence intensity of SRHA, SRFA, SRNOM and JKHA, respectively, indicating the predominance of CDOM fluorescent components in the indirect photodegradation of SM₂ and SP. These results demonstrated the photolysis mechanism: The photosensitization of CDOM occurred after its fluorescence intensity decreased, and a large number of RIs (³CDOM*, HO· and ¹O₂, etc.) were generated by energy and electron transfer, then these RIs reacted with SM₂ and SP to cause photolysis. The increase in salinity stimulated the photolysis of SM₂ and SP consecutively. The photodegradation rate of SM₂ first increased and then decreased with increasing pH, whereas the photolysis of SP was remarkably promoted by high pH but remained stable at low pH. NO₃^- and HCO₃^- had little effect on the indirect photodegradation of SM₂ and SP. This research may contribute to a better understanding of the fate of SM₂ and SP in the ocean and provide new insights into the transformation of other sulfonamides (SAs) in marine ecological environments.

Keywords: Chromophoric dissolved organic matter; Indirect photodegradation; Reactive intermediates; Sulfadimidine; Sulfapyridine.

MeSH terms

Dissolved Organic Matter*
Photolysis
Seawater
Soil
Sulfamethazine
Sulfapyridine
Water Pollutants, Chemical*

Substances

Dissolved Organic Matter
Sulfapyridine
Sulfamethazine
Soil
Water Pollutants, Chemical