Cooperative Institute for Research in Environmental Sciences
Monday, July 23, 2018

Why Winter Air Pollution Remains High in the East

University of Washington, CIRES researchers show why eastern U.S. air pollution levels are more stagnant in winter

snow on ground in fields by mountains

The air in the United States is much cleaner than even a decade ago. But those improvements have come mainly in summer, the season that used to be the poster child for haze-containing particles that cause asthma, lung cancer and other illnesses.         

A new study led by the University of Washington, with coauthors José Jiménez (CIRES) and Steven Brown (NOAA Boulder), shows why winter air pollution levels have remained high, despite overall lower levels of harmful emissions from power plants and vehicles throughout the year.

"The devil's in the chemistry details,” Jimenez said. "What we've learned is that wintertime chemistry can play some unanticipated tricks, making air-pollution-forming reactions more efficient even as the emissions behind that chemistry decrease.  Steeper future emissions reductions will be required to achieve winter air quality improvements."

"We could only figure this out by making a very comprehensive set of chemical measurements,” Brown added. "Our study was the first of its kind to include all of the major air pollutants that are relevant to understanding the winter from an aircraft.  This detailed knowledge of winter air composition has enabled more accurate predictions of future air quality in the Eastern United States." 

The study, to be published this week in the Proceedings of the National Academy of Sciences, shows that the particles follow different pathways in the winter.

Results came from analyzing observations collected during the 2015 Wintertime Investigation of Transport, Emissions and Reactivity (WINTER) campaign. During that UW-led effort, researchers spent six weeks in winter flying through pollution plumes over New York City, Baltimore, Cincinnati, Columbus, Pittsburgh, Washington, D.C., and along the coal-fired power plants of the Ohio River Valley.

The study was funded by the National Science Foundation, with in-kind support from NASA and the National Oceanic and Atmospheric Administration.

This story was written by University of Washington Communications. Continue reading the story here.