Seeing the City Through the Trees

Cities are often thought of as forests of metal and concrete, but what if the trees can tell us something about the "forest"?

Saba Asefa, a graduate student in the Geology Department at Western Washington University, is using tree leaves to determine pollution levels in two neighborhoods in Seattle: Duwamish Valley and Capitol Hill. Particle pollutants can be harmful to human health and her work gives us a better idea of what types of areas in a city see the most pollution. Saba’s work also informs cities on how to reduce particle pollution in their neighborhoods.

Saba Asefa, a graduate student in the Geology Department at Western Washington University

How big is the particulate matter we are talking about? REALLY, really small. The EPA is concerned with particles that are less than 10 microns (PM10 in the image above, blue) and less than 2.5 microns (PM2.5 in the image above, pink). These particles are so small, the can be breathed into the lungs and eventually end up in the bloodstream, which can lead to asthma, lung disease, and even heart attack.

The pollution Saba examines is very tiny (1/3 – 1/4 the width of a human hair) but the particles are magnetic and collect on the surfaces of leaves. Where pollution is greater, more of these particles stick on the leaves surfaces and Saba can detect how much pollution is on the leaves (and in the air) by measuring the magnetism of her leaf samples.

In addition to applications to pollution reduction and health, Saba is also using her research to encourage and empower students by including them in her research efforts. Saba will be working with high school students, who will help her collect samples in the Duwamish neighborhood, to teach them about their own neighborhood and empower the next generation of scientists.

I talked with Saba last week about her research and I really enjoyed speaking with her. Listen to the podcast above for our whole conversation!


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