Insights into Plastic Degradation Processes in Marine Environment by X-ray Photoelectron Spectroscopy Study

Area of Science:

• Environmental Chemistry
• Materials Science
• Spectroscopy

Background:

• Plastic pollution is a significant environmental concern, with degradation processes contributing to fragmentation.
• Understanding the chemical mechanisms of plastic degradation is essential for developing mitigation strategies.

Purpose of the Study:

• To investigate the chemical processes and fragmentation mechanisms of plastics under simulated environmental conditions.
• To identify and quantify chemical changes on plastic surfaces resulting from UV weathering and hydrodynamic exposure.
• To compare surface chemistry changes in experimentally weathered plastics with microplastics from marine environments.

Main Methods:

• X-ray photoelectron spectroscopy (XPS) was used to analyze polystyrene (PS) and polyethylene (PE) samples.
• Samples were subjected to artificial UV radiation-triggered weathering under simulated hydrodynamic conditions in fresh and marine water.
• Raman and Fourier-transform infrared (FT-IR) spectroscopy were employed for comparative analysis.

Main Results:

• XPS detected an increase in hydroxyl, carbonyl, and carboxyl functionalities on weathered plastic surfaces.
• These chemical modifications correlate with degradation processes and macroplastic fragmentation.
• Raman and FT-IR spectroscopy showed no significant surface modifications, highlighting the sensitivity of XPS for surface analysis.

Conclusions:

• XPS is a powerful tool for investigating surface chemistry changes in plastics undergoing degradation.
• Hydrolysis and oxidation reactions on the plastic surface are key drivers of macroplastic fragmentation.
• The study provides insights into degradation pathways relevant to both macroplastic fragmentation and microplastic formation.