Are aromatic hydrocarbons generated from the atmospheric oxidation of biogenic hydrocarbons?

Anthropogenic sources release into the troposphere a wide range of VOCs including aromatic hydrocarbons, whose major sources are believed to be combustion and evaporation of fossil fuels. The goal of the present study was to determine whether aromatic hydrocarbons can be directly generated from reactions in air. The oxidations of isoprene, α-pinene and limonene by O₃, NO₃ and OH have been studied at 1 atm in air and 298 K at both low and high RH in a Teflon reaction chamber. To probe for the possibility of acid-catalyzed reactions on the walls of the chamber, some experiments were carried out after exposing the chamber to low volatility H₂SO₄. The product search was made using GC-MS and PTR-MS. p-cymene was observed from the oxidation of α-pinene and limonene, but not isoprene. Possible mechanisms and the atmospheric implications will be discussed.