Occurrence and characterization of microplastics in the Chili River (Arequipa, Perú) based on FTIR-ATR and SEM-EDS analysis

Abstract

Microplastic contamination in fluvial systems has emerged as a growing environmental concern linked to urban expansion and inadequate plastic waste management. This study, we assessed the abundance, morphology, color, and polymeric composition of microplastics in the surface waters of the Chili River (Arequipa, Peru). Particles were identified using stereoscopic microscopy and classified according to shape and color, while chemical characterization was performed through FTIR-ATR spectroscopy. Detailed morphological analysis was conducted using scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS). The analysis showed revealed a predominance of fibers of various colors (60–80%), followed by foams and fragments. Chromatic distribution varied across sampling sites, with bluish green being the most prevalent color, particularly at TB, where it accounted for 30% of the fibers. FTIR analysis enabled the identification of widely used conventional polymers, including polyethylene (44.4%), polypropylene, polyethylene terephthalate (25.9%), ethylene-vinyl acetate, and polyurethane. SEM micrographs exhibited irregular surfaces, cracks, delamination, and cavities, consistent with progressive physical degradation. EDS analysis also indicated a polymeric nature of the particles by the predominance of carbon and oxygen. These findings indicate that the microplastics present in the Chili River are predominantly secondary particles subjected to environmental aging processes, reflecting the influence of urban activities on fluvial contamination dynamics.