Unexpectedly rapid SO(2) heterogeneous reaction on the surface of vehicular brake wear particles.

Brake wear particles exhibit an exceptionally high SO2 oxidation rate, with uptake coefficients up to 2.87 × 10^-5, vastly surpassing mineral dust and soot under dark conditions.

• Why it matters: Understanding sulfate formation in polluted air is crucial for air quality and climate models, yet the role of urban aerosols like brake wear particles has been underestimated.
• What they did: The study analyzed the catalytic activity of brake wear particles, revealing a synergy between α-Fe2O3 and carbonaceous components that drives rapid SO2 oxidation through cyclic catalysis.
• The result: This discovery highlights brake wear particles as a significant, previously overlooked source of atmospheric sulfate, impacting future atmospheric chemistry research and pollution mitigation strategies.