Abstract
Although many studies have been focused on the photochemistry of antibiotics, the roles of reactive species in photolysis and the effects of dissolved substances on antibiotic photochemical behavior have been poorly examined. The photolytic behaviors of sulfamethazine (SMN) in pure water were investigated via adding different scavengers to quench the active species. Results showed that decomposition of the triplet-excited state of SMN (3SMN*) by direct photolysis was the main path of SMN photolysis in water. Moreover, self-sensitized SMN cannot be ignored during SMN photodegradation. The main photoproducts of SMN were identified by LC-MS/MS, which indicated that SMN could not be mineralized although the photolysis under UV was effective. The effects of Cl−, NO3−, and fulvic acid (FA) (common substances in natural water) on SMN photolytic behaviors were also studied. The triplet-induced halogenation of SMN increases the ionic strength and reduces the ground state SMN; these are the primary causes of promotion of SMN photolysis by Cl−. More ˙OH produced in the presence of NO3− could promote SMN photolysis. Competitive absorption of photons of FA with SMN and ROS scavenged by FA were the main reasons for the inhibition of SMN photolysis. The research findings are helpful for further studies on the environmental risks of ACs in natural waters and promoting the development of AC pollution treatment technology.
Highlights
In the last few decades, large amounts of veterinary antibiotics (ACs) have been used in animal husbandry as therapeutic medicine and feed additives for growth promotion
Paper previous research has reported that the solid phase extraction (SPE) technique can improve the sensitivity of the analytical methods by highperformance liquid chromatography (HPLC), the use of SPE for quanti cation of sulfonamides in aqueous samples has not been examined in detail.[36]
The results showed that UV irradiation was effective to degrade these drugs, and photolysis of ACs under simulated solar irradiation was caused by AC absorbing the UV light from sunlight
Summary
In the last few decades, large amounts of veterinary antibiotics (ACs) have been used in animal husbandry as therapeutic medicine and feed additives for growth promotion. In Europe, the output of SNs ranged from 11% to 23% of the total production of ACs.[4] SNs may be excreted from the body in their parent form without absorption and metabolism by animals. Because of their high stability and solubility, conventional sewage disposal technology used in livestock farming is not efficient for SN removal. The average removal ratio of SNs by activated sludge was found to be 24%,1 which meant that a mass of these drugs was introduced into the biosphere every year.[1,5] In this case, ACs were detected in rivers, lakes, estuarine, and coastal waters many years ago.[6,7,8] The highest concentration of sulfamethazine (SMN) in manure of swine farms in South China was up to 0.250 mg kgÀ1.9 The concentration of ACs in the aquatic environment was relatively low (ng LÀ1 to mg LÀ1),[10,11] whereas its
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