Aging Process of Microplastics in the Environment

The presence of plastics in various ecosystems is an emerging worldwide environmental concern. Researchers have studied the interaction of microplastics (MPs) with other pollutants that are also present in the environment and have concluded that they act as vectors for pollution dispersion, transporting pollutants to different ecosystems, and being taken up by living organisms. The effects of natural processes that MPs undergo in the environment (UV radiation, physical abrasion, chemical reactions, and biodegradation) cause changes in their external surface, morphology, and chemical alterations that increase their ability to interact with other pollutants and transport them. Researchers have developed laboratory techniques to simulate the aging process of polymers and predict the behavior of MPs in real ecosystems. These reports highlight permanent physical and chemical changes in different properties of MPs, such as color, morphology, particle size, specific surface area, hydrophobicity, crystallinity, melting and glass transition temperature, surface groups, carbonyl index, and oxygen/carbon ratio. These properties have been measured using standard techniques (e.g., optical, fluorescence, and scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy); however, emerging techniques are being explored (two-dimensional correlation spectroscopy and excitation–emission matrix-parallel factor analysis), where it is possible to detect the release products of the aging process.