The aim of this thesis is to enhance the knowledge on exposure to size fractions of airborne particulate matter and their components and to find more intensive information on sources of indoor and outdoor size fractionated particles. In the first part of the study, the physical and chemical characteristics of indoor, outdoor, and personal quasi-ultrafine (<0.25μm), accumulation (0.25-2.5 μm), and coarse (2.5-10 μm) mode particles and gaseous pollutant were measured at two phases (warmer and colder phase) of four different retirement communities in Southern California in 2005-2007. Overall, the magnitude of indoor and outdoor measurements was similar, due to high influence of outdoor sources on indoor particle and gas levels. Secondary organic aerosol showed to be able to comprise a major fraction of organic carbon (more than 40% were estimated at some phases). Outdoor and indoor concentrations of gaseous pollutant were more positively correlated to personal quasi-UF particles than larger size fractions. Indoor sources were not significant contributors to personal exposure of PM, which is predominantly influenced by primary emitted pollutants of outdoor origin. Vehicular sources had the highest contribution to PM0.25 among the apportioned sources for both indoor and outdoor particles at all sites. The contribution of mobile sources to indoor levels was similar to their corresponding outdoor estimates, thus even if people generally spend most of their time indoors, a major portion of the submicron particles to which they are exposed to, comes from outdoor mobile sources.
In the following, we characterized the physicochemical properties and sources of size fractionated PM and their spatial and seasonal variability at the Los Angeles-Long Beach harbor community, which is the busiest harbor in the US and the fifth in the world. The major mass contributions in the quasi-UF fraction were particulate organic matter, non-sea salt sulfate and elemental carbon; in the accumulation mode fraction were non-sea salt sulfate, sea salt, particulate organic matter and nitrate; and in the coarse fraction were sea salt and insoluble soil. In general, PM and its components in accumulation mode showed relatively lower spatial variability compare to the quasi-UF and the coarse modes. The vehicular sources accounted for almost all of quasi-ultrafine PM and more than 50% fine PM, whereas ship contribution was lower than 5% of total PM mass. Our results clearly indicate that, although ship emissions can be significant, PM emissions in the area of the largest US harbor are dominated by vehicular sources.
The results obtained in this study have been/will be used to examine the relationships between outdoor (or ambient), indoor and personal measurements of atmospheric particulate air pollution and health outcomes and to link health effects to certain sources of particulate matter. Such information would be highly valuable for targeting control strategies that protect human health and life.
|Commitee:||Henry, Ronald C., Phares, Denis J.|
|School:||University of Southern California|
|School Location:||United States -- California|
|Source:||DAI-B 70/05, Dissertation Abstracts International|
|Subjects:||Civil engineering, Environmental engineering|
|Keywords:||Air pollution, Exposure, Los Angeles, Particulate matter, Size fractions, Source apportionment|
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