Influence of Asian and Western United States urban areas and fires on the atmospheric transport of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and fluorotelomer alcohols in the Western United States.

Atmospheric measurements of semivolatile organic compounds (SOCs) were made at Mt Bachelor Observatory (MBO), located in Oregon's Cascade Range, to understand the trans-Pacific and regional transport of SOCs from urban areas. High volume air sampling (approximately 644 m3 for 24 h periods) of both the gas and particulate phases was conducted from April 19, 2004 to May 13, 2006 (n = 69); including NASA's INTEX-B campaign in spring 2006 (n = 34 of 69). Air mass back trajectories were calculated and were used to calculate source region impact factors (SRIFs), the percentage of time the sampled air mass resided in a given source region. Particulate-phase polycyclic aromatic hydrocarbon (PAH) concentrations at MBO increased with the percentage of air mass time in Asia and, in conjunction with other data, provided strong evidence that particulate-phase PAHs are emitted from Asia and undergo trans-Pacific atmospheric transport to North America. Gas-phase PAH and fluorotelomer alcohol (FTOH) concentrations significantly increased with the percentage of air mass time in California's urban areas, whereas retene and polychlorinated biphenyl (PCB) concentrations increased with the percentage of air mass time in Oregon and during regional fire events. In addition, sigma(gas-phase) PAH, retene, and levoglucosan concentrations were significantly correlated (p-value < 0.001) with sigma(PCB) concentrations, suggesting that increased atmospheric PCB concentrations were associated with fires due to the volatilization of stored PCBs from soil and vegetation.

Semivolatile fluorinated organic compounds in Asian and western U.S. air masses.

Semivolatile fluorinated organic compounds (FOCs) were measured in archived air sample extracts collected from Hedo Station Observatory (HSO) on Okinawa, Japan and Mount Bachelor Observatory (MBO), Oregon U.S. during the springs of 2004 (MBO and HSO) and 2006 (MBO). Fluorotelomer alcohols (FTOHs) were measured in both Asian and western U.S. air masses, though western U.S. air masses had significantly higher concentrations. Concentrations of fluorotelomer olefins in Asian air masses and 8:2 fluorotelomer acrylate in U.S. air masses were reported for the first time. N-ethyl perfluorooctane sulfonamide, N-methyl perfluorooctane sulfonamido ethanol, and N-ethyl perfluorooctane sulfonamido ethanol were also measured in Asian and western U.S. air masses but less frequently than FTOHs. The atmospheric sources and fate of FTOHs were investigated by estimating their atmospheric residence times, calculating FTOH concentration ratios, investigating FTOH correlations with nonfluorinated semivolatile organic compound concentrations, and determining air mass back trajectories. Estimated atmospheric residence times for 6:2 FTOH, 8:2 FTOH, and 10:2 FTOH were 50, 80, and 70 d, respectively, and the average concentration ratio of 6:2 FTOH to 8:2 FTOH to 10:2 FTOH at MBO in 2006 was 1.0 to 5.0 to 2.5. The relative order of these atmospheric residence times may explain the observed enhancement of 8:2 FTOH and 10:2 FTOH (relative to 6:2 FTOH) at MBO compared to North American indoor air (FTOH average ratio of 1.0 to 2.0 to 1.0). FTOH concentrations in western U.S. air masses were positively correlated (p < 0.05) with gas-phase polycyclic aromatic hydrocarbon and polychlorinated biphenyl concentrations and negatively correlated (p < 0.05) with agricultural pesticide concentrations. In comparison to western U.S. air masses, trans-Pacific air masses did not contain elevated concentrations of these compounds, whereas lower boundary layer air masses that passed over urban areas of the western U.S. did. This suggests that semivolatile FOCs are emitted from urban areas in the western U.S.