The gauzy mists of the United States Great Smoky Mountains have inspired writers and painters for centuries. But the source of these mists is less than poetic. “The Smoky Mountains are called smoky because of chemical emissions from trees,” said Jonathan Abbatt, a professor at the University of Toronto. Trees are often considered the lungs of the Earth, inhaling the greenhouse gas carbon dioxide (CO2), and exhaling harmless chemicals like water vapor and oxygen (O2). Trees give off other particles, however, that may not be so benign. Once in the atmosphere, these fine particles can transform into aerosols, a component of air pollution.
In large amounts, these chemicals create a visible haze, when light is reflected off the tiny particles. However, it is not the mysterious appearance that causes concern, but the chemistry behind it. Although this haze may include chemicals from other sources, scientists have not yet been able to tell exactly how much. “There’s been a question about how much of those aerosol-forming chemicals are from trees, or biogenic, and how much are from people, or anthropogenic,” Abbatt said. Trees are supposed to clean the air, but might they be contributing to the amount of aerosols in the atmosphere, too?
