A report in the 27 April issue of the journal Science suggests that current U.S. Environmental Protection Agency (EPA) programs to reduce harmful ozone produced by electric utility power plants could be significantly improved by additionally considering power plant emission rates and geographic location.
"We think that our research represents an opportunity to build on current efforts to improve air quality," says Science lead author T.B. Ryerson of the National Oceanic and Atmospheric Administration (NOAA) in Boulder, Colorado.
Ryerson and colleagues analyzed ozone production in chemical plumes emitted by coal-fired power plants in the rural United States, and found that ozone production depends in large part on the plant's emission rate and location. Current emission reduction programs "implicitly value all emissions equally, regardless of emission density or location," according to the study.
Tropospheric ozone (not to be confused with stratospheric ozone, which shields the Earth from ultraviolet radiation) is found in the atmospheric layer nearest to Earth's surface and is a prominent pollutant, especially during the summer months when elevated concentrations of ozone can harm human health and vegetation.
Ozone is formed in an atmospheric reaction involving NOx and volatile organic compounds (VOCs). Electric utility power plants are a key source of NOx emissions in the U.S., accounting for 25 percent of the nation's total human-produced NOx emissions each year. As part of the Clean Air Act, the EPA has proposed emission reductions at 392 NOx sources, primarily rural coal-fired power plants in the eastern and midwestern United States.
VOCs can come from anthropogenic sources such as car exhaust and petrochemical refining, but they are also emitted in large amounts by natural vegetation. In the Eastern U.S., for instance, the hydrocarbon isoprene fro
Contact: Cherita Gonzales
American Association for the Advancement of Science