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Master of Science (MS)
Housen, Bernard Arthur
Abel, Troy D.
Although transportation is a large source of air particulate pollution in the U.S., air quality is currently not routinely monitored on the street level or using methods that could routinely determine particulate composition. In this study, we will use biomonitoring- using biological organisms (in this case tree leaves) as sample collectors- and magnetic characterization of particulate matter (PM) to provide a simple and inexpensive alternative air quality monitoring apparatus that is at the human spatial level, can collect micron-sized particles, and can be found in closely-spaced locations, so that there is a dense area collection network. Magnetic methods such as SIRM and magnetic susceptibility have been used to gauge PM concentrations on the street level (Hoffman et al 2014, Kardel et al 2011, Lehndorff & Schwark 2004, Maher et al 2008) using biomonitors such as tree leaves. Total PM concentrations correlate well with measured magnetic values on leaf surfaces because PM contains magnetic particles sourced from iron impurities in fossil fuel vehicle exhaust, brake dust, and other vehicle sources (Sagnotti et al 2009). The geographic focus of this study is the Seattle area because it has the most traffic in the Pacific Northwest (Seattle Department of Transportation) and because a mix of residential and community activities are located near sites of industry that include manufacturing, warehousing, commercial, container shipping and support activities, concentrated in the south Seattle Duwamish Valley (Abel et al 2015). This study uses rock-magnetic methods (SIRM, magnetic hysteresis) and imaging (SEM) to characterize types of particulates, and map the spatial variation of Seattle’s air pollution. Magnetic saturation and susceptibility values for Duwamish Valley samples were higher than those of Capitol Hill samples. Coniferous leaves and deciduous leaves had similar magnetic values. The magnetic intensity of samples in a 300 mT field did not change when the field was 1 T, meaning the magnetic particles are composed of one magnetic mineral. Morphology and chemical makeup of magnetic particles varied within leaf samples, ranging from ~5-40 microns in diameter and from 0-93% Fe content. Cluster analyses determined that there are three sets of sources, but are not conclusive on whether some leaf samples have a mixture of source material on their surfaces.
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Asefa, Saba, "Biomonitoring in Seattle: Spatial Variation and Source-Determining of Airborne Pollutants in High-Traffic Areas" (2018). WWU Graduate School Collection. 690.