Comparison of the effects of tire wear particles on the freshwater macrophyte under different exposure scenarios

Tire wear particles (TWPs) are a specific type of microplastic and behave differently due to their complex composition, comprising both natural and synthetic rubber along with numerous additives and fillers. They are generated by the friction between the tire tread and the road surface and are then washed from the roads into the environment. Although they widespread in the environment, their fate and interactions with aquatic organisms are not yet fully understood. In this context, the aim of the study was to investigate how TWPs interact with and affect the floating macrophyte Lemna minor under different exposure scenario. Pristine TWPs, hydrated TWPs (incubated for 24 hours in Steinberg medium on a rotary shaker) and aged TWPs (incubated for 14 days in freshwater from a local stream) were prepared and used in ecotoxicity test with L. minor. During the 9-day exposure, all three types of TWPs adhered to the plant biomass. The maximum number of adhered pristine TWPs was reached after 7 days, while for hydrated and aged TWPs maximum adhesion occurred already after 2 days. All three types of TWPs had a significant effect on the specific growth rate and root length of L. minor, but the amount of chlorophyll a was significantly reduced only when the plant was exposed to the aged TWPs. The negative effect can be related to the presence of algae that were transferred from the biofilm on aged TWPs, leading to their overgrowth in test vessels and consequently causing a reduction in space and nutrient availability in the medium. This indicates that TWPs can also have indirect effects on the environment, such as the transfer of microorganisms to other environments, which can possibly endanger native species and thereby disrupt the natural balance in the ecosystem. Also see: https://micro2024.sciencesconf.org/557622/document