Microplastic aging alters the adsorption-desorption behaviors of sulfamethoxazole in marine animals: A study in simulated biological liquids

Antibiotics and microplastics (MPs) coexisting as unique environmental contaminants may cause unintended environmental issues. In this study, the adsorption-desorption behaviors of sulfamethoxazole (SMX) on both original and UV-aged MPs were examined. Polyhydroxyalkanoates (PHA) and polyethylene (PE), which repre-sent degradable and refractory MPs, respectively, were chosen as two distinct types of MPs. Furthermore, simulated fish intestinal fluids (SFIF) and simulated mammalian stomach fluids (SMGF) were employed to evaluate the desorption behaviors of SMX from aged MPs. Our findings demonstrate that UV-aging altered the polarity, hydrophilicity, and structure of the MPs. Aged MPs showed a higher adsorption capacity than the original MPs and they have a higher desorption capacity than original MPs in simulated body fluids. PE has a higher SMX desorption capacity in SFIF and the opposite happened in SMGF. Our results highlight the impor-tance of considering the different adsorption-desorption behaviors of antibiotics on MPs when evaluating their environmental impact.