Analysis of plastics exposed to seabird stomach conditions, using Raman, mid- and near-infrared spectroscopy

Plastic pollution in the ocean is increasing each year and it is estimated that 8 million tonnes of plastic waste enter the oceans each year with rivers being the main source of transportation. This number could triple by 2025 if nothing is done. Plastics are usually accompanied by additives and persistent organic pollutants (POPs). Additives are introduced during plastic production in their matrix to modify their properties. They can take on different roles such as flame retardants, catalysts, antioxidants, or antimicrobials. POPs, on the other hand, are persistent chemical substances that have the potential to be transported for long distances, biomagnifying and bioaccumulating in ecosystems. They are contaminants released by industries into the ocean that adsorb to the surface of the plastic due to their hydrophobic properties. Plastic ingestion by seabirds happens deliberately or accidentally and causes mechanical and chemical damage. Plastic can remain stuck in the stomach of the birds for extended periods. The environment in the stomach enhances the release of plastic-associated chemicals which, for the most part, are known as endocrine-disrupting chemicals. To study this release, simulated digestive treatments have been applied to high-density polyethylene (HDPE) samples supplemented with 1 % of an additive (PBDE-209) and having adsorbed two POPs (PCB-28 and PCB-138) at its surface. This master thesis aims at determining if the plastic samples have been impacted by those treatments with the use of Raman spectroscopy, Fourier transform mid-infrared spectroscopy (FT-MIR) and Fourier transform near-infrared spectroscopy (FT-NIR). FT-MIR has proved to be the most successful technique for identifying the different contaminants. Raman spectroscopy detected contaminants less accurately, whereas FT-NIR did not detect them at all. Both may, however, detect structural modifications of plastic samples resulting from the digestive treatments. FT-MIR and Raman spectroscopy have confirmed the leaching of additives and POPs from the HDPE samples following the digestive treatments. These results support the use of these spectroscopic techniques for future analyses of contaminated plastic samples.