Tire Wear Particles\nExposure Enhances Denitrification\nin Soil by Enriching Labile DOM and Shaping the Microbial Community

Tire wear particles (TWP) are emerging contaminants in\nthe soil\nenvironment due to their widespread occurrence and potential threat\nto soil health. However, their impacts on soil biogeochemical processes\nremain unclear. Here, we investigated the effects of TWP at various\ndoses and their leachate on soil respiration and denitrification using\na robotized continuous-flow incubation system in upland soil. Fourier\ntransform ion cyclotron resonance mass spectrometry and high-throughput\nsequencing were employed to elucidate the mechanisms underpinning\nthe TWP effects. We show that TWP increased soil CO<sub>2</sub>, N<sub>2</sub>, and N<sub>2</sub>O emissions, which were attributed to the\nchanges in content and composition of soil dissolved organic matter\n(DOM) induced by TWP and their leachate. Specifically, the labile\nDOM components (H/C ≥ 1.5 and transformation >10), which\nwere\ncrucial in shaping the denitrifying community, were significantly\nenriched by TWP exposure. Furthermore, the abundances of denitrification\ngenes (<i>nirK</i>/<i>S</i> and <i>nosZ</i>-I) and the specific denitrifying genera Pseudomonas were increased following TWP exposure. Our findings provide new\ninsights into impacts of TWP on carbon and nitrogen cycling in soil,\nhighlighting that TWP exposure may exacerbate greenhouse gas emissions\nand fertilizer N loss, posing adverse effects on soil fertility in\nperi-urban areas and climate change mitigation.