Abstract

Sulfamethoxazole (SMX) is a popular active substance, which is extensively applied to treat bacterial infections in humans and animals. Due to its widespread use, SMX enters the natural environment, where it can undergo degradation. Similarly to other emerging contaminants, SMX photodegradation and the use of oxidants in wastewater treatment processes can lead to the formation of potentially adverse transformation products for ecosystems. This study investigated the efficiency of SMX photodegradation in the presence of oxidizing agents (H₂O₂ and Fenton reagent). The potential environmental consequences of degradation product formation were analyzed based on experimental toxicity characterization. Standardized tests employing diverse organisms were utilized: Alivibrio fischeri (Microtox®), Daphnia magna (Daphtoxkit F®), and Lemna minor (Lemna sp. GIT). The potential environmental impact of the products identified in the reaction mixtures was evaluated using parameters describing aqueous solubility, hydrophobicity, toxicity, bioconcentration, persistence, and mobility. The analysis revealed that photodegradation produces transformation products with higher toxicity than SMX, as confirmed by in vitro tests of the reaction mixtures. Most of the detected compounds were found to have low mobility potential. The formation rates of key environmentally relevant transformation products, such as 1,4-benzoquinone, aniline, and phenol, were also discussed. The changes in total organic carbon (TOC) affected by photodegradation under the influence of the considered oxidizing agents were characterized.

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Authors (4)