2006 News & Events

Scientists at ESRL's Chemical Sciences Division and Global Systems Division and their colleagues have shown that industry has successfully reduced pollutants emitted from U.S. electricity-generating power plants during the past decade, an accomplishment that should lead to improvements in air quality in the eastern U.S. The study, published online in Geophysical Research Letters on November 28, used modeling and measurements from satellites and aircraft of nitrogen oxide pollutants. The paper marks the first time space-based instruments have detected the regional impact of pollution controls implemented by coal-burning electric power plants in the 1990s.

Background: Pollutants from power plants and other fossil-fuel burning activities combine with other gases in the atmosphere in the sunlight-driven chemistry that makes ozone pollution, a key ingredient of "smog" and a primary cause of poor air quality. About one quarter of U.S. nitrogen oxides pollution (NOx) comes from electrical power generation by burning fossil fuels. Power plant NOx emissions can produce ozone in downwind urban areas hundreds of miles away, affecting these areas' compliance with the U.S. Environmental Protection Agency's ozone pollution standards. To mitigate this ozone formation, in the 1990s the EPA mandated reductions of stationary source of NOx emissions that focused primarily on eastern US coal-fired power plants. One of the key questions is: Can we verify that these power plant NOx pollution control regulations have led to measurable decreases in atmospheric NOx levels and, hence, improved ozone pollution? Lead author Si-Wan Kim is with the Cooperative Institute for Research in Environmental Sciences at CSD. Other ESRL scientists and scientists at the University of Bremen, Germany, coauthored the work.

Significance: As demonstrated in this paper, observations have shown that NOx emissions have indeed decreased precisely as reported by power companies. Satellite-observed NO2 levels in the Ohio River Valley region, with its high density of coal-fired plants targeted by pollution controls, showed a 40% decline over the past 10 years, a trend the model reproduced only when accounting for power plant NOx emission reductions. Much smaller decreases in satellite-observed NO2 levels were seen in the urban northeastern U.S. over the same time period, in agreement with the model-predicted pollution trend, because of the smaller contribution of power plant NOx pollution in that region. The study thus confirms that the response of the atmosphere was as expected. Future work will examine the effect of the NOx reductions on ozone pollution for the region. The work contributes to objectives in NOAA's Air Quality Program within the Weather and Water Goal.