New research co-led by UW Biology professor Jeff Riffell and UW Atmospheric Sciences professor Joel Thornton shows that air pollution – coming primarily from car exhaust and power plant emissions – is responsible for a major drop in nighttime pollinator activity. The lead author on the paper is Jeremy Chan, a postdoctoral researcher at the University of Copenhagen who conducted this study as a UW doctoral student in biology. They discovered that nitrate radicals in the air degrade the scent chemicals released by a common wildflower, drastically reducing the scent-based cues that its chief pollinators rely on to locate the flower. The findings, published Feb. 9 in Science, are the first to show how nighttime pollution creates a chain of chemical reactions that degrades scent cues, leaving flowers undetectable by smell. This research was featured in an article in UW News.
The researchers found that nitrate radicals (NO3) in the air degrade the scent chemicals released by a common wildflower, drastically reducing the scent-based cues that nighttime pollinators rely on to locate the flower. In the atmosphere, NO3 is produced by chemical reactions among other nitrogen oxides, which are themselves released by the combustion of gas and coal from cars, power plants and other sources.
The team — co-led by Jeff Riffell, a UW professor of biology, and Joel Thornton, a UW professor of atmospheric sciences — studied the pale evening primrose (Oenothera pallida). This wildflower grows in arid environments across the western U.S. They chose this species because its white flowers emit a scent that attracts a diverse group of pollinators, including nocturnal moths, which are one of its most important pollinators.
At field sites in eastern Washington, the researchers collected scent samples from pale evening primrose flowers. Back in the laboratory, they used chemical analysis techniques to identify the dozens of individual chemicals that make up the wildflower’s scent.
“When you smell a rose, you’re smelling a diverse bouquet composed of different types of chemicals,” said Riffell. “The same is true for almost any flower. Each has its own scent made up of a specific chemical recipe.”
Once they had identified the individual chemicals that make up the wildflower’s scent, the team used a more advanced technique called mass spectrometry to observe how each chemical within the scent reacted to NO3. They found that reacting with NO3 nearly eliminated certain scent chemicals. In particular, the pollutant decimated levels of monoterpene scent compounds, which in separate experiments moths found most attractive.
Read the full article in UW News and the paper published in Science.