Photochemical Aging of Asian Particulate Matter: Formation of Oxygenated Polycyclic Aromatic Hydrocarbons

Oregon State University, Corvallis OR

Investigators

Abstract

This project is investigating the reactions that occur on polycyclic aromatic hydrocarbon (PAH) compounds that are transported over long distances. PAHs are emitted by many types of combustion, from sources such as automobiles, power plants, and wildfires. When these compounds undergo reactions with ozone and the hydroxyl radical in the atmosphere, they may become more toxic. As PAHs age and are transported over long distances, they may cause an increasing risk to human health. The specific goals of this research include: 1) predicting which oxygenated PAH are likely to form from the photochemical oxidation of higher molecular weight PAHs; 2) measuring the formation of oxygenated PAH products on Asian particulate matter using laboratory photochemical reactor studies and new analytical methods; and 3) measuring the oxygenated PAH composition of size fractionated particulate matter collected from Asia and the Pacific Northwestern U.S. Laboratory methods that will be used include 2D gas chromatography with time-of-flight mass spectrometry (GCxGC/ToF-MS) for analysis of the PAH, the OPAH fraction, and the hydroxy-PAH (OH-PAH) fraction, and gas chromatography with high resolution mass spectrometry (GC/HRMS) to confirm compound identities. Previously acquired samples from China, Japan, and Korea will be analyzed to represent particulate matter characteristic of Asian transport. Previously acquired samples from Washington and Oregon will be assessed for influence from Asian transport. A hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) 4.0 model will be used to calculate four-day forward and back trajectories for air masses sampled. Meteorological data and the concentrations of CO, O3, NO, SO2, and aerosol scattering will be used to aid in the interpretation of the data with respect to potential sources of PAH. The results will lead to a better understanding of the photochemical aging of Asian particulate matter and the potential formation of oxygenated PAH during trans-Pacific atmospheric transport to the U.S. West Coast.