When people talk about pollution, mostly they think of nasty stuff from giant smokestacks that kills nearby plants. What they don't know is that those plants are releasing the same chemicals.

Allen Goldstein is on the cutting-edge of research into plant-released volatile organic compounds (VOCs). VOCs are a family of noxious chemicals associated with air pollution (think of solvents and paint thinners). They are also the compounds that make pine trees smell so fresh. Plants release millions of tons per year that quickly turn into aerosol haze (like the haze for which the Smokey Mountains are named). Although it's not technically pollution, no one knows how many of these chemicals are out there or exactly how they affect the atmosphere or climate. So Goldstein's team goes to California's Sierra Nevada mountains to hunt for new chemicals and try to guess how existing ones might be interacting. Using a number of techniques (including sealing off tree branches to tinker with surrounding air and temperature) they are also trying to understand how VOCs might change with global warming. One student even found a new chemical feeding the aerosols—the same chemical that makes fennel smell like licorice.

A view of the tower in Blodgett Forest that Goldstein's lab uses to sample volatile compounds put off by the trees.