Microplastics in river water: occurrence, weathering, and adsorption behaviour

Abstract

Microplastics (MPs) are emerging contaminants of concern due to their ubiquitous presence in aquatic environments and their ability to adsorb and transport other contaminants. In this study, the presence of MPs was determined in river water samples, reflecting their potential impact on the transport of other emerging contaminants in aqueous matrices. This study investigates the adsorption behavior of atrazine (ATZ), a widely used herbicide, onto pristine and UV-aged polyethylene (PE) and polypropylene (PP) MPs. The study revealed that UV aging enhances adsorption by increasing surface roughness and oxygen-containing functional groups. Batch adsorption experiments were conducted under varying environmental conditions, including pH, salinity, and dissolved organic matter changes. Adsorption kinetics were evaluated using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models, with PSO providing a better fit, as indicated by lower p-values and higher R² values. The interparticle diffusion model showed that during the first stage of adsorption, surface adsorption was dominant, while pore diffusion was predominant at later stages. Desorption experiments indicated that aged MPs retain ATZ more effectively, reducing its potential for remobilization in aquatic systems. These findings provide insight into the environmental risks associated with MPs as carriers of pesticides and their implications for water quality and ecosystem health.