Impact of Pristine\nand Aged Tire Wear Particles on Ipomoea aquatica and Rhizospheric Microbial Communities:\nInsights from a Long-Term Exposure Study

Tire wear particles (TWPs), generated from tire abrasion,\ncontribute\nsignificantly to environmental contamination. The toxicity of TWPs\nto organisms has raised significant concerns, yet their effects on\nterrestrial plants remain unclear. Here, we investigated the long-term\nimpact of pristine and naturally aged TWPs on water spinach (Ipomoea aquatica) and its rhizospheric soil. The\nresults indicated that natural aging reduced the toxicity of TWPs,\nas evidenced by decreased levels of polycyclic aromatic hydrocarbons\n(PAHs) in soil and TWPs themselves. Consequently, aged TWPs were found\nto enhance the plant growth and chlorophyll content, whereas pristine\nTWPs increased the plant stress. Furthermore, aged TWPs improved soil\norganic matter (SOM) and total organic carbon (TOC), thereby boosting\nthe microbial enzymes involved in nitrogen cycling. Metabolomic analysis\nrevealed that aged TWPs upregulated key pathways related to carbon\nand nitrogen metabolism, enhancing plant growth and stress responses.\nAdditionally, rhizosphere bacterial diversity was higher under aged\nTWPs, favoring nutrient-cycling taxa such as <i>Acidobacteriota</i> and <i>Nitrospirota</i>. Pristine TWPs may lead to overproliferation\nof certain dominant species, thereby reducing microbial diversity\nin soil, which could ultimately compromise the soil health. These\nfindings contribute to a deeper understanding of the mechanisms underlying\nTWP toxicity in plants and highlight the necessity for further research\non the impact of aged TWPs across various plant species over different\nexposure durations for comprehensive risk assessment.