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Date Permissions Signed
Date of Award
Master of Science (MS)
Sofield, Ruth M.
Matthews, Robin A., 1952-
Abel, Troy D.
Semi-automated scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) can be used to determine the size and composition of filtered particulate matter (PM). This information is valuable for determining the identity and contribution of overlapping air emissions. One limitation of this method is the cost of filtering PM at enough locations to give meaningful spatial data. To address this limitation, I developed an exploratory method to collect PM using Ramalina farinacea for semi-automated SEM analysis as a component of lichen biomonitoring studies. I applied this method as a proof of concept in the Seattle area to better understand trends in regional urban dust. To do this, bags of lichen were transplanted to 9 locations in the Duwamish Valley and adjacent uplands for 3 months between September and December, 2017. Some of these locations were arranged close to major industrial sources of airborne metals, which we hypothesized would contribute to the PM observed on the lichens alongside the regional background signature of particulate emissions. Upon collection, PM deposition on the lichen was characterized using SEM with EDS. A total of 18,581 particles were identified and analyzed using the PACLA for Oxford two-stage classifier. My findings suggest that R. farinacea are an effective tool for collecting PM and show the greatest proportion of anthropogenic-specific particles on lichens adjacent to Interstate 5. Furthermore, the spatial trends of PM between locations suggest that fugitive dust controls such as green walls and green spaces may be more effective than point source controls at further reducing exposure to harmful dust in the Seattle area.
lichen biomonitoring, particulate matter, urban dust, source apportionment
Western Washington University
Subject – LCSH
Air quality--Washington (State)--Seattle--Measurement; Environmental monitoring--Washington (State)--Seattle; Ramalina; Scanning electron microscopy
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Guddal, Tor G. (Tor Gunnar), "Characterization of Particulate Matter Accumulated on Ramalina farinacea in the Seattle Area Using Semi-Automated Electron Microscopy" (2018). WWU Graduate School Collection. 806.