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<p>Vehicle exhaust, as a major source of air pollutants in urban areas, contains a complex mixture of organic vapours including long-chain alkanes and aromatic hydrocarbons. The atmospheric oxidation of vehicle emissions is a highly complex system as inorganic gases (e.g. <span class="inline-formula">NO_<i>x</i></span> and <span class="inline-formula">SO₂</span>) from other urban sources coexist and therefore remains poorly understood. In this work, the photooxidation of <span class="inline-formula"><i>n</i></span>-dodecane, 1,3,5-trimethylbenzene, and their mixture is studied in the presence of <span class="inline-formula">NO_<i>x</i></span> and <span class="inline-formula">SO₂</span> to mimic the atmospheric oxidation of urban vehicle emissions (including diesel and gasoline vehicles), and the formation of ozone and secondary aerosols is investigated. It is found that ozone formation is enhanced by higher OH concentration and higher temperature, but is influenced little by <span class="inline-formula">SO₂</span> concentration. However, <span class="inline-formula">SO₂</span> can largely enhance the particle formation in both number and mass concentrations, likely due to the promoted new particle formation and acid-catalysed heterogeneous reactions from the formation of sulfuric acid. In addition, organo-sulfates and organo-nitrates are detected in the formed particles, and the presence of <span class="inline-formula">SO₂</span> can promote the formation of organo-sulfates. These results provide a scientific basis for systematically evaluating the effects of <span class="inline-formula">SO₂</span>, OH concentration, and temperature on the oxidation of mixed organic gases in the atmosphere that produce ozone and secondary particles.</p>