Satellite‐observed U.S. power plant NOx emission reductions and their impact on air quality

Nitrogen oxide (NO x ) emissions resulting from fossil fuel combustion lead to unhealthy levels of near‐surface ozone (O 3 ). One of the largest U.S. sources, electric power generation, represented about 25% of the U.S. anthropogenic NO x emissions in 1999. Here we show that space‐based instruments observed declining regional NO x levels between 1999 and 2005 in response to the recent implementation of pollution controls by utility companies in the eastern U.S. Satellite‐retrieved summertime nitrogen dioxide (NO 2 ) columns and bottom‐up emission estimates show larger decreases in the Ohio River Valley, where power plants dominate NO x emissions, than in the northeast U.S. urban corridor. Model simulations predict lower O 3 across much of the eastern U.S. in response to these emission reductions.