[Chemical Component of Particulate Matters and VOCs Characteristics During Vehicle Brake Processes]

Six sets of brake systems were tested using a brake dynamometer, and the brake wear particles (BWPs) and volatile organic compounds (VOCs) were collected during the braking process. In total, 39 elements, 12 water-soluble ions, 7 carbon components, and 18 polycyclic aromatic hydrocarbons (PAHs) in BWPs were extracted and detected, and 74 VOCs in gas samples were analyzed. The average mass fractions of 12 inorganic elements (i.e., Sb, Mg, Cu, Zn, Ti, Ca, Si, Zr, K, Ba, Al, and Fe) with higher contents in PM_2.5 and PM₁₀ were 43.4% and 40.3%, respectively, and the average mass fraction of Fe was the highest, accounting for 16.6% and 13.1% of PM_2.5 and PM₁₀, respectively. The average mass fractions of the 12 water-soluble ions in PM_2.5 and PM₁₀ were 16.5% and 12.6%, respectively, and NO₃^-, SO₄^2-, and Ca²⁺ were the ions with high contents. The average mass fraction of total carbon (TC) in PM_2.5 and PM₁₀ were 21.9% and 18.1%, respectively, and the average mass fraction of organic carbon (OC) was approximately five times that of elemental carbon (EC). There were six types of PAHs with a detection rate greater than 50%, among which naphthalene (Nap) was the most abundant. The average mass concentration of 74 VOCs was 316.04 μg·m^-3, of which the aromatic hydrocarbon had the highest mass concentration. The compositions of BWPs and VOCs emitted by the six sets of brake systems were quite different, which was mainly determined by the brand and raw materials of the brake pads.