Uptake and UV-photo-oxidation of gas phase PAHs on atmospheric water films

ENVR 24

Jing Chen, jchen6@lsu.edu and Kalliat T. Valsaraj, valsaraj@lsu.edu. Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA 70803
The processing of organic chemicals such as PAHs in fog can lead to more harmful oxy- and nitro-PAHs. Hence, the photo-transformation of gas phase PAHs (e.g., naphthalene and phenanthrene) is important to understand in the atmospheric environment. This work summarizes our work on the uptake and UV-photo-oxidation of these gas phase PAHs in thin water films such as occurring in fogs and aerosols. A flow tube reactor was used to carry out these reactions. The rate of photo-oxidation was substantially higher in a thin film as compared to a bulk phase reaction. Several products were identified in the water films and the mechanism of photo-oxidation was assessed. The presence of a natural surfactant in the water led to multiples on the rate of the reaction. These were characterized via a dual mechanism of self-sensitized and surfactant-sensitized pathways for the reaction. The atmospheric implications of these observations will be explored in this paper.