Vibrational analysis of polystyrene photodegradation and its implications for microplastic formation in arid zones

Abstract

This study examines the photodegradation of polystyrene as a potential source of microplastics (and nanoplastics) in arid soils. For this purpose, polystyrene pellets were exposed to UV-C radiation for different periods by placing them directly on soil collected from an arid region. The progressive degradation of the material was monitored weekly using Raman microscopy, Fourier transform infrared spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). Spectroscopic analyses revealed chemical transformations associated with the photoinduced oxidation of polystyrene. Characteristic Raman peaks at 877 and 1732 cm⁻¹ indicate the presence of hydroperoxide and ketone groups, respectively. The presence of an FTIR band at ∼3400 cm⁻¹ further confirmed the formation of hydroperoxides. After the UV-C exposure period ended, the soil samples were processed to extract particles generated from the degraded polymer. Dynamic Light Scattering analysis indicated an average hydrodynamic size of 2388.88 ± 988.42 nm. Raman spectra of these particles confirmed the presence of polystyrene, while particles with an average size of 182.01 ± 34.58 nm were identified as common soil minerals (quartz, anatase, calcite, albite, and hematite). These findings enhance our understanding of the mechanisms driving microplastics formation under extreme environmental conditions and highlight key analytical tools for their detection and characterization in complex soil matrices.