This project addresses questions regarding the chemical processing in fog of polynuclear aromatic hydrocarbons (PAHs), some of which are known to be toxic. Specifically: Is there a possibility that fog processing of PAHs could transform them to oxidized compounds (oxy-PAHs) or particles? Might some of the oxy-PAHs be toxic? If so, these compounds might also represent a potential health threat if they are inhaled in a foggy environment. The approach consists of field determination of phase distributions of PAHs and oxy-PAHs throughout smog-fog-smog (SFS) cycles near Fresno, CA and/or at Louisiana State University.
Broader impacts include new perspectives on the cycling of PAHs in atmospheric waters, which are of interest to a broad range of scientists. Graduate students from underrepresented groups are being trained through their participation in the project. Also participating is a faculty member from Prairie View A&M University, a Historically Black College-University institution. Research results are being incorporated into undergraduate courses taught by the principal investigator.
This project was to understand the effects of a common atmospheric process such as the fog formation and dissipation on the overall atmospheric quality. In particular, we investigated the effects of fog on the composition of existing particles in the atmosphere. Specifically, we studied the presence and concentrations of anthropogenically-generated polycyclic aromatic compounds (PAC) and their transformation products. The primary observation was that most of the PAC transformed to their respective oxygenated PACs (oxy-PAC) during fog and were left behind on the particles. Oxy-PAC are significatly more toxic than the parent PAC. This has signifcant implications with respect to the atmospheric quality. The existing theory is that particles are simply washed out of air by fog. However, our observation suggests that the particle phase composition is changed to one in which more toxic by-products such as oxy-PACs are left behind in the atmosphere after a fog event. We also observed that the oxy-PAC were sigficantly concentrated in the collected fog water as well. We believe that further research as to the health effects ( via inhalation exposure) of the post-fog atmosphere has to be undertaken in the future. The compositional changes on the particles are also useful in studying broadly how the aerosol effects global climate change via effecting both the hygroscopicity and heat radiative properties of atmospheric aerosols. This study helps in understanding the overall aerosol behavior in an urban environment and how it impacts human health and climate.
