Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 5 2008 10.5194/acpd-8-18531-2008 http://www.atmos-chem-phys-discuss.net/8/18531/2008/ http://www.atmos-chem-phys-discuss.net/8/18531/2008/acpd-8-18531-2008.html http://www.atmos-chem-phys-discuss.net/8/18531/2008/acpd-8-18531-2008.pdf 18531 18589 2008-10-28 Evidence for Asian dust effects from aerosol plume measurements during INTEX-B 2006 near Whistler, BC W. R. Leaitch richard.leaitch@ec.gc.ca A. M. Macdonald K. G. Anlauf P. S. K. Liu D. Toom-Sauntry S.-M. Li J. Liggio K. Hayden M. A. Wasey L. M. Russell S. Takahama S. Liu A. van Donkelaar T. Duck R. V. Martin Q. Zhang Y. Sun I. McKendry N. C. Shantz M. Cubison Science and Technology Branch, Environ. Canada, Toronto, Ontario, M3H 5T4, Canada Scripps Institution of Oceanography, University of California, San Diego, 92093, USA Dept. of Physics and Atmospheric Science, Dalhousie Univ., Halifax, NS M3J 1P3, Canada State University of New York at Albany, Albany, New York, USA University of British Columbia, Vancouver, BC, Canada V6T 1Z2, Canada Department of Chemistry, University of Toronto, Ontario, Canada University of Colorado, Boulder, Colorado, USA Several cases of aerosol plumes resulting from trans-Pacific transport were observed between 2 km and 5.3 km at Whistler, BC from 22 April 2006 to 15 May 2006. The fine particle (<1 μm) chemical composition of most of the plumes was dominated by sulphate that ranged from 1–5 μg m<sup>−3</sup> as measured with a Quadrapole Aerosol Mass Spectrometer (Q-AMS). Coarse particles (>1 μm) were enhanced in all sulphate plumes. Fine particle organic mass concentrations were relatively low in most plumes and anti-correlated with the increases in the coarse particles. The chemistry of coarse particles sampled at Whistler Peak was dominated by calcium, sodium, nitrate, sulphate and formate. Scanning transmission X-ray microscopy of coarse particles sampled from the NCAR C-130 aircraft relatively close to Whistler indicated carbonate, potassium and organic functional groups, in particular the carboxyl group. Asian plumes reaching Whistler, BC during the INTEX-B study were not only significantly reduced of fine particle organic material, but organic compounds were attached to coarse particles in significant quantities. Scavenging of organic aerosol precursors by dust near source regions is suggested, and any formation of secondary organic aerosol (SOA) during transport from Asian source regions across the Pacific was principally associated with the coarse particles. 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