Adsorption of lead and cadmium by microplastics and their desorption behavior as vectors in the gastrointestinal environment

The behavior of microplastics (MPs) as vectors of environmental contaminants in aquatic systems can change the fate and transport of some toxic substances and promote their diffusion and bioenrichment. Therefore, our study investigated the adsorption of two kinds of metal ions [Pb(II) and Cd(II)] by polypropylene (PP) and polystyrene (PS) in aqueous solution and the desorption of metal ions in the gastrointestinal environment. Our findings indicated that pH, humic acid, and particle size are key factors affecting the adsorption of metal ions on MPs. The adsorption capacity of Pb(II) and Cd(II) on MPs increases as pH increases, and the presence of humic acid significantly inhibits the adsorption of metal ions on MPs. In a simulated gastrointestinal environment, the desorption rates of the two metal ions on MPs were high and controlled by the MP particle size, suggesting a possible toxicological risk for organisms after ingestion of metal-contaminated microplastics.