Invasive Plant Poisons Our Air

It's not only invading more landscapes with the help of global warming, but invasive kudzu vines might also someday increase ozone pollution by more than a third, say soil researchers.

"It's an impressive and dramatic plant," said Jonathan Hickman of The Earth Institute at Columbia University. "But there a lot of things you can't see. ... Air pollution hasn't really been a part of the conversation when it comes to invasion."

Hickman is the lead author on a study, which appears in the May 17 issue of the Proceedings of the National Academy of Sciences, looking at what could happen to both urban and rural air quality if the kudzu invasion continues unabated.

Kudzu's contribution to ozone levels works like this: Like other members of the pea family, or legumes, Kudzu grabs nitrogen from the air and puts it into the soil. There microbes convert nitrogen into nitrous oxide, one of the pollutants that also comes from automobile exhaust. That gas escapes from the soil and into the air, and undergoes reactions that lead to the creation of ozone.

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Normally there aren't enough legumes around to have any massive impact on air quality. But with kudzu now commanding 7,000,000 acres of land in the United States -- including New York -- Hickman thought it was time to take a closer look.

What he and his colleagues found was that in some areas kudzu could lead to a 35 percent increase in ozone on extra hot, smoggy days. That means 10 smoggy days with ozone in excess of EPA standards could someday be 17 days, thanks to a plant that won't stop spreading.

This isn't the first time a plant has been suspected of abetting human air pollution.

Some trees have been investigated for emitting volatile organic compounds, says ecosystem ecologist Sharon Hall at Arizona State University. But although air quality officials are aware of nitrous oxide emissions from soils, no one had really looked specifically at how kudzu might lead to air quality effects.

"It was such a great question to ask," said Hall of Hickman's research."As we know more about how it works, we'll have a better road map."

Ozone is a short-lived pollutant made of three oxygen atoms -- O3. It's very unstable and tends to react with whatever it touches in order to get rid of an oxygen atom and revert to 02, or normal oxygen gas.

What makes it hurtful is that act of getting rid of an oxygen atom. That reaction can happen in your lungs, damaging sensitive tissues, or even break down plastic parts of your car or house that are exposed to the outside air.