Bridging the gap: Environmentally relevant aging of microplastics under laboratory conditions

Microplastics (MPs) are characterized by a great diversity in terms of size, shape and chemical composition. In addition, environmental plastics undergo the processes of aging, altering their composition and properties. Many studies have focused on simulating the environmental aging of MPs mainly using accelerated aging by UV radiation. MPs also undergo biotic aging in the aquatic environment and biofilm are likely to develop on their surface. This type of aging, however, is not yet well understood. Some studies use well-defined algal/bacterial cultures under controlled conditions, while others age them in the natural environment where conditions are not controlled at all. In response to the need to produce biotically aged MPs for laboratory research, we have developed a method of aging MPs in natural stream water under controlled conditions that combines the best of the latter two approaches – aging is driven by natural microbial consortia in stream water but under controlled laboratory conditions. We have been using this method in laboratory research for the last six years. This method, in combination with innovative assessments of biofilm development, enable us to observe the growth phase of biofilms on microplastics, to compare biofilm development in terms of their structural and functional properties on different polymers, to evaluate how biofilms affect the toxicity and bioavailability of MPs to aquatic organisms, and to show how the shape of MPs influences biofilm growth and how biotic aging affects different properties of MPs such as shape, morphology, density, and adsorption properties. The results obtained contribute significantly to the understanding of the biotic aging of MPs and their effects, behavior, and fate in the environment. Also see: https://micro2024.sciencesconf.org/558700/document