L.; Amacher, Michael C.; and Monleon, Vicente J., "Using an epiphytic moss to identify previously unknown sources of atmospheric cadmium pollution" (2016
H I G H L I G H T S• Bio-indicators are a valid method for measuring atmospheric pollutants • We used moss to map atmospheric cadmium in Portland, Oregon • Using a spatial linear model, we identified two stained-glass manufacturers as the major sources of atmospheric cadmium in Portland • After both companies suspended cadmium use, atmospheric levels declined precipitously Urban networks of air-quality monitors are often too widely spaced to identify sources of air pollutants, especially if they do not disperse far from emission sources. The objectives of this study were to test the use of moss bioindicators to develop a fine-scale map of atmospherically-derived cadmium and to identify the sources of cadmium in a complex urban setting. We collected 346 samples of the moss Orthotrichum lyellii from deciduous trees in December, 2013 using a modified randomized grid-based sampling strategy across Portland, Oregon. We estimated a spatial linear model of moss cadmium levels and predicted cadmium on a 50 m grid across the city. Cadmium levels in moss were positively correlated with proximity to two stained-glass manufacturers, proximity to the Oregon-Washington border, and percent industrial land in a 500 m buffer, and negatively correlated with percent residential land in a 500 m buffer. The maps showed very high concentrations of cadmium around the two stainedglass manufacturers, neither of which were known to environmental regulators as cadmium emitters. In addition, in response to our findings, the Oregon Department of Environmental Quality placed an instrumental monitor 120 m from the larger stained-glass manufacturer in October, 2015. The monthly average atmospheric cadmium
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Contents lists available at ScienceDirectScience of the Total Environment j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / s c i t o t e n v This document is a U.S. government work and is not subject to copyright in the United States.concentration was 29.4 ng/m 3 , which is 49 times higher than Oregon's benchmark of 0.6 ng/m 3 , and high enough to pose a health risk from even short-term exposure. Both stained-glass manufacturers voluntarily stopped using cadmium after the monitoring results were made public, and the monthly average cadmium levels precipitously dropped to 1.1 ng/m 3 for stained-glass manufacturer #1 and 0.67 ng/m 3 for stained-glass manufacturer #2.Published by Elsevier B.V.