Evidence of impact of tire wear particles on a roadside plant community at environmentally relevant concentrations

Tire wear particles (TWPs) are recognized as a significant contributor of microplastic pollution, and recent research has shown their effects on plants using various types of crops. However, given the fact that abrasion of tire tread intensifies near roadways, roadside plant community should receive more attention. In this study, we established mono- and mixed-plant communities including four different species (, , , and ), and the effects of TWPs on each community were investigated across a range of concentrations (1 to 10,000 mg kg). We found the significant changes in the structure of mixed-plant community, which represented opposite growth patterns between two species ( and ), while there were no effects on each species in the mono-culture condition. Our results revealed that takes advantage in the mixed-culture condition, in terms of biomass, while experienced the negative effects on shoot mass. We measured electrical capacitances to understand plant-plant interactions in root system, and it aligned with the growth patterns ( and ) of TWP treatments. Soil pH varied depending on the cultivation of each species and TWP treatments. Consequently, we assumed that TWPs alter the soil process and plant-plant interactions. Roadside ecosystem provides ecological values, and the impacts of TWPs on roadside plant community might be crucial to sustain a wild range of environmental functions.