Trees Release Volatile Organic Compounds That Aid In Smog Production
April 26, 2013

Trees Release Volatile Organic Compounds That Aid In Smog Production

Brett Smith for - Your Universe Online

In 2004, a group of Princeton scientists found trees release the volatile organic compound (VOC) isoprene that reacts in the air to form particulate pollution, or smog.

However, the mechanism behind this process wasn't known until a new study from scientists at the University of North Carolina (UNC) was released this week showing how isoprene´s reaction to sunlight leads to the formation of harmful air pollution.

After isoprene is chemically altered by the sun, it reacts with man-made nitrogen oxide to create particulate matter, according to the study published in Proceedings of the National Academy of Sciences (PNAS). Nitrogen oxides are a part of the emissions generated by automobiles, aircrafts and coal plants.

"The work presents a dramatic new wrinkle in the arguments for reducing man-made pollutants worldwide," Jason Surratt, assistant professor of environmental sciences and engineering at UNC, said in a statement. "Isoprene evolved to protect trees and plants, but because of the presence of nitrogen oxides, it is involved in producing this negative effect on health and the environment."

"We certainly can't cut down all the trees," Surratt added, "but we can work on reducing these man-made emissions to cut down the production of fine particulate matter."

The researchers said their work will allow for the creation of better air pollution and climate change models. The predictions based on these models would enable researchers and environmental agencies to better understand and make policies that positively impact public health and climate change.

"We observe nature's quirks, but we must always consider that our actions do have repercussions," Surratt said. "It's the interaction between these natural and man-made emissions that produces this air pollution, smog and fine particulate matter — and now we know one reason for how it happens."

Drew Purves, the lead author of the Princeton study, noted at the time that his team´s findings severely undercut the notion of natural causes versus human causes of air pollution.

"You can't identify any of these processes as 'natural,'" said Purves. "The idea of natural versus human-caused is disappearing.”

“Ten years from now, woodlands may have more of one species than another, and you could call that natural change,” he added. “But here in New Jersey, the mix of trees is affected by the population of deer, and they are entirely under our control. In other parts of the country, it is the fire-suppression policies."

Other previous studies have shown some kinds or trees produce more isoprene than others.

The emerging research could seem as some kind of vindication for former President Ronald Reagan, who has long been derided for claiming in the 1980s that trees cause pollution.

"Approximately 80 percent of our air pollution stems from hydrocarbons released by vegetation,” Reagan said. "Trees cause more pollution than automobiles do."

The president was quickly mocked by his Democratic opponents who were likely eager to play a caricature of the former actor. White House aides quickly walked back Reagan´s statement, saying he had been misquoted and was referring only to certain pollutants.