spea magazine

In the Lab

Projects and People

What's happening in Phil Stevens lab?

The OH radical measurement project. The OH radical is the Pac-Man of the atmosphere. It reacts with pollutants in the air, transforming them into the more mundane water and carbon dioxide. OH radicals are also a contributing factor in the formation of smog and acid rain.

Because this radical is so unstable, it’s hard to know exactly how much of it is in the atmosphere. Stevens’ goal is to understand which factors determine how reactive the radicals are. His findings will help refine government pollution regulation models.

Phil Stevens What makes this project so unique to SPEA?
Stevens has one of the few instruments designed to measure OH radicals in the environment. There are only four in the country, ten worldwide. Stevens actually built his himself, a handy skill he acquired while doing post-doctoral work at Penn State University. A half-million dollar National Science Foundation grant funded the parts and Stevens took a sabbatical so he could build it. The machine now tests atmospheric conditions in southern Indiana as it sits at an open window in a SPEA lab.

So is the machine going to sit at SPEA?
Not always. First this device is making its way to Purdue, where it will be paired with that school’s atmospheric simulator. Stevens hopes that a controlled environment will yield new information about the ways in which the OH radicals operate. He also plans to set it up in forests in Indiana, Michigan, and California to see how emissions from trees may be involved in pollution by reacting to OH radicals.

Wait. Trees cause pollution?
In a way. President Ronald Reagan once said “Trees cause more pollution than automobiles,” which isn’t totally accurate, but trees are, in fact, more reactive than one might think. Emissions from trees, known as isoprene emissions, are eaten by the Pac-Man particles and could be one of the reasons government models for estimated pollution standards may be different from actual measurements. In fact, eastern states may have more problems with smog than the West because of the larger amounts of vegetation contributing to OH radical chemistry.

Why is this project good for SPEA students?
“They get to see a real measure of atmospheric chemistry,” Stevens says. “It’s a real opportunity for them to use state-of-the-art equipment.” It also gives students the chance to work on a machine that very few others have access to. In fact, some of the students helped build the machine and calibrate it to make the measurements more accurate. Stevens even believes they may know more about his creation now than he does.

So what’s going to become of all this?
As with most projects, Stevens hopes this one will be used to solve real-life problems. “This will improve our understanding of the chemical reactions in the atmosphere,” he says, noting that it will hopefully lead to changes in our regulatory models to make them more refined. Because we don’t fully understand the extent of OH radicals and how they react, Stevens’ work could lead to profound regulatory changes as he continues to unlock more of the radicals’ secrets.


Phil Stevens is an assistant professor at SPEA, IUB. His focus is on the characterization of the chemical mechanisms that influence regional air quality and global climate change. Professor Stevens received his Ph.D. in chemistry from Harvard University in 1990.