Measurement and methods of assessing the impact of prevalent particulate matter.....

SEMINAR ORAL DEFENSE OFHarish Phuleria,
ENE Student"Measurement and methods of assessing the impact of prevalent particulate matter sources on air quality in Southern California".Abstract:Recent focus of studies on health effects of ambient particulate matter (PM) have suggested particle chemical composition in addition to particle size, shape and number concentration responsible for the observed health outcomes. However, chemical composition and size distribution of the atmospheric particles can be strongly affected by the differences in ambient temperature, relative humidity, photochemical activity and source contributions. This thesis is intended to demonstrate the importance of characterizing predominant PM sources from an exposure perspective and develop methods of assessing their impact on air quality in Southern California. A study of particle number concentration and size distribution showed seasonal and spatial variability in Southern California. While contribution of local vehicular emissions was most evident in winter, effects of long-range transport of particles and photochemical particle formation were enhanced during warmer periods. Ship emissions are found to be dominant source of lower accumulation and ultrafine particles near ports. Utilizing the "opportunistic" data from the air pollution studies during the October 2003 fires, the actual impact of the wildfires is studied on air quality in urban Los Angeles. The wildfires caused the greatest increases in PM10 levels while ozone concentrations dropped during the fire episode and these fire-borne particles were shown to effectively penetrate indoors. To characterize the emission profiles from on-road diesel and gasoline vehicle-fleets, size-segregated PM samples were collected inside the Caldecott tunnel in Orinda, CA and analyzed for vehicular organic tracers such as hopanes and steranes, and polycyclic aromatic hydrocarbons (PAHs). In a separate study, detailed information on the chemical characteristics of organic PM originating from a pure gasoline and a diesel dominated mixed-traffic freeway is obtained. While hopanes and steranes, and high molecular weight PAHs levels are found comparable near these freeways, elemental carbon and lighter molecular weight PAHs are found much elevated near diesel dominated mixed-fleet freeway. Remarkably good agreement is observed between the roadside measurements and the emission factors calculated from the tunnel measurements especially for hopanes and steranes. Our results indicate that the fleet composition as well as atmospheric dilution has strong impact on the ambient concentrations of these organic tracers.

Location: Kaprielian Hall (KAP) - rielilan Hall, Room 203

Audiences: Everyone Is Invited

Contact: Evangeline Reyes