First Advisor

Todd N. Rosenstiel

Term of Graduation

Summer 2022

Date of Publication


Document Type


Degree Name

Master of Science (M.S.) in Biology






Environmental monitoring, Heavy metals -- Bioaccumulation, Orthotrichum, Bryophytes, Air -- Pollution -- Measurement



Physical Description

1 online resource (vi, 167 pages)


The importance of monitoring and preventing pollution in the environment is a globally recognized issue. Of the criteria pollutants outlined by the United States Environmental Protection Agency, particulate matter is among these least understood in relation to toxicity and most wide-spread. Many governments have employed continuous air quality monitoring networks to track ambient levels of particulate matter, but are often too widespread to capture the heterogeneity of the urban environment, especially for heavy metal deposition. In Portland, OR, the epiphytic moss Orthotrichum lyellii was successfully used as a low-cost passive biomonitor to increase the spatial resolution of pollution around the city, identifying previously unknown heavy metal pollution "hotspots". Though informative, the relationship between environmental concentrations and metal accumulation in moss tissue is still poorly understood. As part of a larger calibration experiment, this study used O. lyellii as an active biomonitor deployed across eight experimental sites around Portland, OR along with co-located bulk deposition and PM10 monitors over a period of 48 weeks. In addition, an S. palustre clone, considered a "gold standard" as an active biomonitor moss, was installed alongside O. lyellii under matched conditions and exposed in eight-week intervals over the course of the study. Bulk deposition, PM10 and co-located moss tissue for both species were collected and analyzed for 24 elements: Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Si, Sr, Ti, V & Zn. Results indicate that O. lyellii can be successfully used as an active biomonitor and provide quantitative information about the surrounding environment. Significant enrichment of Zn was observed in O. lyellii in over 60% of the sites and a significant enrichment of Ni at some sites was identified, confirming the possibility of ongoing exposure at previously identified areas of concern within the city. Unsurprisingly, S. palustre showed a greater uptake capacity and greater sensitivity to almost all elements analyzed, especially heavy metals. Spearman correlations were used to compare both species relationship to bulk deposition and PM10, showing significant correlations for multiple metals with both measurements. Both species showed significant correlations with P and B in PM10 while O. lyellii uniquely correlated with Ca. S. palustre had additional significant correlations with K, S, Mn, Fe, Cu, Zn, B, V, Na, Ba, Al and Ti, suggesting a particular sensitivity to PM10 deposition on mosses derived from roadways and vehicular traffic. No correlations were seen in either species with heavy metal concentrations in PM10, although longer exposure times may result in better correlations with Cd. Both species showed significant correlations with Al and Co in bulk deposition while O. lyellii alone correlated with Cr. Additional correlations were seen in S. palustre for Ca, Mn, Fe, Ni, Cu, Zn, V, Sr, Ba and Pb. The results show that O. lyellii is uniquely suited to detect Cr in bulk deposition, highlighting species-specific difference in moss metal exchange dynamics. This thesis will further discuss the implications of these results and provide an in-depth analysis that can serve as an informational model for guiding future urban-focused active moss biomonitoring studies.


© 2022 Scott Bradley Kiel

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