The Impact of Smoke on Aerosol Composition and Visibility in the U.S.

Sonia Kreidenweis

Colorado State University

Biomass burning, including forest fires, is a major global source for CO, aerosols and other pollutants. Much focus has been given to biomass burning in the tropics, but recent events have drawn attention to the role of wildfires in North and Central America in influencing aerosol concentrations in the U.S. This talk will present results from two studies examining impacts of fire on airborne particulate matter. In the first study, we examined IMPROVE aerosol data from national parks in the southeastern U.S. to look for impacts from long-range transport of smoke. Our analyses show that smoke from fires in Canada and Central America, in addition to smoke from U.S. fires, can be detected in about 10% of the aerosol samples from spring and summer over the last decade, with higher contributions in some years. Current work includes extension of the methodology to parks in the western U.S. The second study that will be described was a field project in Yosemite National Park in summer 2002. Observations of aerosol chemical and physical properties show several events in which the aerosol appears to be heavily impacted by smoke. The most likely sources of this smoke were the large fires in Oregon and Sequoia National Park that were burning during the study period, contributing to regional haze in areas of the western U.S.