Gas- and Particle-Phase Products from the Chlorine-InitiatedOxidation of Polycyclic Aromatic Hydrocarbons.

The chlorine atom (Cl)-initiatedoxidation of three polycyclicaromatic hydrocarbons (PAHs; namely, naphthalene, acenaphthylene,and acenaphthene) was investigated. Experiments were performed inan atmospheric simulation chamber using a proton transfer reactiontime-of-flight mass spectrometer (TOF-MS) and an aerosol TOF-MS tocharacterize the oxidation products in the gas and particle phases,respectively. The major products identified from the reaction of Clatoms with naphthalene were phthalic anhydride and chloronaphthalene,indicating that H atom abstraction and Cl addition reaction pathwaysare both important. Acenaphthenone was the principal product arisingfrom reaction of Cl with acenaphthene, while 1,8-naphthalic anhydride,acenaphthenone, acenaphthenequinone, and chloroacenaphthenone wereall identified as products of acenaphthylene oxidation, confirmingthat the cylcopenta-fused ring controls the reactivity of these PAHstoward Cl atoms. Possible reaction mechanisms are proposed for theformation of these products, and favored pathways have been suggested.Large yields of secondary organic aerosol (SOA) were also observedin all experiments, and the major products were found to undergo significantpartitioning to the particle-phase. This work suggests that Cl-initiatedoxidation could play an important role in SOA formation from PAHsunder specific atmospheric conditions where the Cl atom concentrationis high, such as the marine boundary layer. [ABSTRACT FROM AUTHOR]