Magnetization of pine needles

The Salt Lake Valley experiences atmospheric temperature inversions during the winter. During these inversions particulate matter becomes trapped within the valley and causes “bad air days.” There are many adverse health effects to prolonged exposure to the particulate-rich air including respiratory, cardiovascular, and neurodegenerative diseases. After reading several papers describing how plants can passively collect particulate matter, and that these plants can acquire a magnetization from the iron-bearing minerals within particulate matter, we formed a team of graduate students to test whether we could track the inversion events in Salt Lake using magnetic measurements. As part of this ongoing project, we collect real and artificial evergreen needles and measure their magnetization as a function of distance from major roadways during times of non-inversion and inversion events. We characterize the size and spatial distribution of particulates on the surfaces of the needles through electron microscopy. Using inductively coupled plasma mass spectrometry we are able to determine metal concentrations both on and within the needles. Low-temperature magnetic measurements help us predict the concentration and sizes of the magnetic particles near major roadways. Our work shows that magnetic measurements are a low-cost way to monitor these inversion events.


Rea-Downing, G., B. Quirk, C. L. Wagner, P.C. Lippert, 2020. Evergreen needle magnetization as a proxy for particulate matter pollution in urban environments. GeoHealth,

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Contact information:

Courtney Wagner, Ph.D.

Peter Buck Postdoctoral Fellow

Smithsonian Institution, NMNH

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