ARB Research Division
Natural and anthropogenic aerosols and ozone clouds have been sporadically detected in transport across the northern Pacific Ocean during the last decade. Persistent organic pollutants such as dioxins and PCBs have been found in surface waters in remote sites in sub-arctic Canada; occasional ozone clouds have been detected at Cheeka Peak on the Washington coast; soil aerosol from Asian “yellow sand” dust and accompanying combustion products have been regularly observed in Hawaii. Asian dust has been seen in North America for a few very large events, most notably in April 1998 and again in April 2001. Systematic assessment of the temporal and spatial distributions of Asian pollutants in the U.S. and Canada have not been undertaken before now. We report here our recent work using chemical signatures from extreme events to probe aerosol data bases for unrecognized low-concentration dust events. Data from IMPROVE and IMPROVE-compatible sites were analyzed to characterize the April 1998 very large dust event and to explore the distribution of Asian dust over the decade of the 1990s. The results present a pattern of consistent, frequent transport that contradicts the anecdotal “infrequent-episodic” characterization of transpacific transport. Our results indicate that Asian dust is a regular component of the troposphere over most of North America throughout spring, summer, and fall in a “transport layer” that extends from below 1000 m to about 3000 m altitude, and typically contains fine (<2.5 um diameter) Asian mineral dust in concentrations of 0.5 to 1.5 ug/m3. This research lays the groundwork for assessment of pollutants accompanying the dust as well as providing a basis for correcting dust aerosol representation in General Circulation Models used to study climate processes. Tony VanCuren – is an Air Pollution Research Specialist in the Research Division in Sacramento. With an academic background is in climatology and satellite sensing systems, he began studying pollutant aerosols while employed by the U.S. Navy at China Lake, CA. He came to the Research Division in 1985, where he has specialized in aerosols and visibility. While in the division he has worked on all aspects of particulate matter pollution, ranging from exposure calculation for epidemiology to developing new PM measurement methods for visibility and particle characterization. The work described in this seminar is an outgrowth of ongoing cooperative research with the DELTA Group (Detection and Evaluation of Long Range Transport of Aerosols) at the University of California, Davis, focusing on smoke, dust, and long range transport of combustion products as they impact PM air quality in California.