Monday, December 2, 2013

Trees Capture Particulate Matter From Road Exhaust

Naomi Lubick, Chemical and Engineering News, November 22, 2013

Trees planted along a city street screen residents from sun and noise—and from tiny particles that pollute urban air. A new study shows that tree leaves can capture more than 50% of the particulate matter that’s a prime component of urban pollution and a trigger for disease (Environmental Science and Technology).

In urban settings, particulates come primarily from car exhaust, brake pad wear, and road dust and can contain metals, such as iron and lead. The Environmental Protection Agency classifies particulates in three size ranges: less than 1 μm (PM1), up to 2.5 μm (PM2.5), and up to 10 μm (PM10) in diameter. These particles are tiny enough for people to inhale and can exacerbate heart disease, asthma, and other health conditions.

By examining silver birch leaves with a scanning electron microscope, researchers confirmed that the hairy surfaces of the leaves trapped metallic particles. Like the particles measured inside homes, these metallic particles are most likely the product of combustion and brake wear from vehicles passing by. Previous work has indicated a strong correlation between the amount of material identified by magnetic remanence and benzo(a)pyrene, a carcinogenic polycyclic aromatic hydrocarbon found in particulates.

Read more here.

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