First Advisor

Olyssa Starry

Date of Award


Document Type


Degree Name

Bachelor of Science (B.S.) in Liberal Studies and University Honors


Liberal Studies


Polycyclic aromatic hydrocarbons -- Environmental aspects -- Oregon -- Portland, Indicators (Biology), Mosses -- Effect of Polycyclic aromatic hydrocarbons on, Trees -- Effect of Polycyclic aromatic hydrocarbons on, Air -- Pollution -- Oregon -- Portland




This study is a spatial analysis of Polycyclic Aromatic Hydrocarbons (PAH) across the Portland Metro area using data collected from samples of moss tissue (Orthotrichum spp.), and an exploration of the relationship between PAH deposition and urban tree canopy in Portland Oregon. PAH are a class of common environmental pollutants created by the incomplete combustion of organic materials; largely via anthropocentric activity. Species of lichens and mosses have been shown to be suitable bioindicators of air pollutants (including PAH contamination) in other studies. Urban tree canopy is known to mitigate other environmental pollutants, as well as provide numerous environmental services to urban populations. In this study ArcGIS was used to create a raster of PAH across Portland. A raster of tree canopy volume across Portland was used with the PAH raster in a zonal analysis to calculate mean levels of PAH concentrations and tree canopy volume in each census block laying within the extent of the PAH raster. Two maps were created of the Portland census blocks within the extent of the PAH/moss study, and Excel was used to create scatter plots and a regression analysis of the correlation between tree canopy volume and PAH concentration. A statistically relevant correlation was found between greater urban tree canopy and lower PAH, but the data is variable and the relationship is demonstrated to be complex. More research is needed to determine if the correlation has to do with land use and industry or a physiological function of the tree canopy.


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