OnAir@AAAR: Ironing out Trace Metal Measurements

Michelle Oakes has developed a new instrument to more accurately measure a dangerous air pollutant: Iron (II).
Oakes, an EPA STAR grantee and scientist at the Georgia Institute of Technology, presented the new instrument Monday at the 2010 AAAR conference on air pollution and health.

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Iron (II) is commonly emitted by sources like biomass burning and coal-fired power plants and is associated with the production of harmful reactive oxygen species in the body. Oakes’ device, called a Particle-to-Liquid Sampler, measures the dangerous trace metal significantly better than previous methods ever have.

“People usually use a filter that works over 24 hours to measure Iron (II),” Oakes explained.
“But what we found is that the filters underestimate Iron (II) by a lot.”

She reported that in some cases, the Particle-to-Liquid Sampler measured Iron (II) levels twice as high as those measured by the filters—a very significant difference.

Because the Sampler conducts automated measurements every 12 minutes, it does a better job than 24-hour filters at capturing changes in Iron (II) levels throughout the day.

As wind speeds change, it is common for Iron (II) levels to fluctuate, producing what Oakes calls “transient events,” or periods of time where iron levels oscillate strongly from high to low.

The average daily Iron (II) measurements produced from the filters tend to mask these fluctuations.
Oakes explained that her device and its ability to more accurately reflect Iron (II) variations over time could significantly benefit the public health community.

“From a health standpoint,” Oakes said, “you need something that’s reliable…you want to be able to see the times of day when it’s most dangerous for people to be outdoors.”

But there are additional advantages to the “totally new” device.
“Not only does it do a better job measuring variations, but it’s also much less labor intensive than using filters which require lots of hours and work,” Oakes pointed out.

Once adapted to become more easily deployable, the sampler could potentially help States measure trace metals more easily.
Oakes presented the work during Monday’s AAAR poster session and seemed pleased to share the new technology.
“I really enjoy working on this,” Oakes said smiling, “it’s a way to do chemistry, be outdoors, and make an impact.”


About the Author: Becky Fried is a science writer with EPA’s National Center for Environmental Research. Her OnAir posts are a regular “Science Wednesday” feature.

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