AbstractsChemistry

Ambient air pollution, and more specifically particulate matter (PM), is a major concern for public health, causing 5% of all cardiopulmonary deaths worldwide. Research has demonstrated that the chemical composition of particulate matter plays a role in its toxicity. Polycyclic aromatic hydrocarbons (PAHs), some of which have known carcinogenic and toxic effects, and their oxygenated derivatives, are among the organic species found in particulate matter. Meteorological factors as well as sources of emission affect the chemical composition. This leads to variability in the composition of particulate matter by geographic region and by season. The cities of Tijuana, Baja California, Mexico and San Diego, California, USA are a part of the vast border region that deals with many environmental and public health concerns, one of which is air pollution. This study sought to investigate particulate matter in the region and obtain an initial fingerprint of the organic content. Specifically, the objectives of this study were to identify and characterize PAHs and related chemical contaminants using nontargeted analysis and select compounds for targeted and semi-targeted analysis, as well as identify interesting compounds for future study. Between July 2013 and February 2014, thirteen PM???.??? high-volume air samples were collected in Tijuana, Baja California, Mexico using a Tisch TE-6001 PM10 High-Vol Air Sampler. Samples were extracted with acetone and hexane in a MARS Xpress microwave system and eluted through silica gel columns with solvents of increasing polarity. Twodimensional gas chromatography coupled to time-of-flight mass spectrometry (GCxGC/TOFMS) was used to characterize PAHs and related compounds in the organic content of particulate matter samples from four sampling locations in Tijuana. A non-targeted approach was utilized to identify PAHs and other compounds of interest from two initial samples. Based on these results, targeted and semi-targeted methods were employed to quantify specific compounds in eleven samples. Average total PAH concentrations ranged from 0.658 ng/m3 (coastal site) to 6.44 ng/m3 (inland site). Winter total PAH levels detected at inland sampling sites were greater than winter concentrations observed in Southern California. In addition, benzo[a]pyrene, fluoranthene, benzo[a]anthracene, benzo[ghi]perylene, and chrysene were detected at higher levels than those observed in many Southern California cities. Total oxygenated polycyclic aromatic hydrocarbon (OPAH) concentrations averaged 0.326 ng/m3 at the coastal site and 0.938 ng/m3 at the site the furthest inland. The most prevalent OPAHs were 9,10-anthracenedione, naphthalic anhydride and 6H-benz[de]anthracen-6-one. A number of compounds not previously detected in PM were identified and quantified, including 6H-benz[de]anthracen-6-one, 4,4'- dichlorodiphenylsulfone, and podocarpa-8,11,13-trien-19-oic acid methyl ester. Further analysis is required in order to confirm trends between sites and compare levels in different seasons.