Assessment of Microplastic Degradation in Bottom Sediments Using Raman Microspectroscopy and Atomic Force Microscopy

Abstract

The assessed degradation of microplastics from bottom sediments of the Laptev Sea, the Weddell Sea, the Chukchi Sea and Peter the Great Bay, Sea of Japan, was studied using Raman microspectroscopy and atomic force microscopy (AFM). The degree of amorphous-crystallinity of polyethylene terephthalate (PET) was determined by the ratio of Raman mode intensities (I1095 cm–1 / I1115 cm–1). Changes in the topography and mechanical properties of the surface of polymer fragments were studied by AFM methods. It has been shown that the degradation of PET found in the bottom sediments of the Laptev Sea affects mainly its crystalline phase. The amorphous phase of PET is affected to a much lesser extent or not at all. The same changes in the phase composition of the PET surface have been shown after plastic exposure in a marine aquarium in silty sand from the Amur Bay (Peter the Great Bay, Sea of Japan). AFM data show an increase in PET surface roughness and a decrease in elasticу modulus (Young’s modulus) in bottom sediment samples. Raman microspectroscopy also shows signs of degradation of cellophane fragments from the Weddell Sea, polyvinyl chloride (PVC) from the Laptev Sea, and polyethylene (PE) from the Amur Bay.