FGD and DeNOx
NEWSLETTER       

                                                                                                         March 2005
                                                                                                             No. 323

Study Shows Power Plant Contribution to Air Quality Greater than Estimated

When 100 power plants in northeastern North America shut down in the blackout of August 2003, the University of Maryland research team used the opportunity to study the impact power plants have on air quality. The team sent two light aircraft aloft on August 15, 2003, a day after the start of the blackout, when most power plants remained shut down. One flight made its measurements outside the blackout area—over Cumberland, Maryland, and nearby parts of Virginia—and the other over Selinsgrove, Pennsylvania, in the heart of the blackout region. The rural sites were chosen to minimize the contribution from urban, non-power plant sources, such as automobiles. The planes flew in vertical spirals to sample various altitudes and measured ozone, carbon monoxide, sulfur dioxide, light scattered by suspended particles, and particle counts.

“What surprised us was the extent and speed with which the pollution levels fell,” says Lackson Marufu, team leader of the university’s Department of Meteorology. Over Selinsgrove, SO2 dropped by 92 percent, ozone by more than 50 percent, and light scattered by particles by more than 70 percent. Visual range increased from 25 km to a crystal-clear 65 km. In contrast, the pollution levels over Cumberland were essentially the same as the 2002 readings from Selinsgrove. The team confirmed that the reduction resulted entirely from the power plant shutoff and not from any fall in contributions from cars.

EPA estimates that power plants produce 69 percent of the SO2 pollution and 22 percent of NOx. Marufu says, “Clearly the blackout measurements show that, at least in the Northeast, this is an understatement.” Although some plants upwind of Selinsgrove (about a quarter of normal) were still operating on August 15, the measurements indicated that power plants contribute more towards air quality than EPA estimates. “The good news is that pollution cleared up in 24 hours,” points out Marufu. (Geophys. Res. Lett. 2004, 31, L13106)

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