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Transpacific and regional atmospheric transport of anthropogenic semivolatile organic compounds to Cheeka Peak Observatory during the spring of 2002



[1] Ambient high-volume (hi-vol) air samples were collected between 15 March and 30 May 2002, at Cheeka Peak Observatory (CPO), located on the tip of the Olympic Peninsula, Washington State. This sampling campaign was in conjunction with the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) campaign and the Photochemical Ozone Budget of the Eastern North Pacific Atmosphere 2 (PHOEBA2) experiment. The anthropogenic semivolatile organic compounds (SOCs) measured during this time period included polycyclic aromatic hydrocarbons (PAHs) and various U.S. current-use and historical-use pesticides. The total PAH concentration ranged from 0.480 to 4.49 ng/m3, which is comparable to other remote sites throughout the globe. Ten pesticides (hexachlorobenzene, dacthal, chlorothalonil, heptachlor, trans-nonachlor, cis-nonachlor, endosulfan I, triallate, trifluralin, and mirex) were also measured, and their concentrations (0.104–57.0 pg/m3) were comparable to other remote sites and less than agricultural areas. Gas-phase/particle-phase partitioning was explored, with significant correlation to temperature found with endosulfan I and retene and the possible relationship at CPO of low TSP concentration and the concentration of nonexchangeable compounds in the particle phase. Principal component analysis, as well as a t-test, showed that there were elevated concentrations of anthropogenic SOCs measured during possible transpacific events on 15–16 March, 27–28 March, and 22–23 April 2002 that were identified using the GEOS-CHEM model. The potential sources of these compounds at CPO were determined using diagnostic ratios of their concentrations, back trajectories calculated using Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT4), local meteorological conditions, and U.S. pesticide use data. Additional data are needed to confirm the sources of anthropogenic SOCs at CPO during regional and transpacific atmospheric transport events.

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