JUL 08, 2015

Scrubbers Installed In Oregon Coal Plant To Decrease Mercury Pollution End Up Reducing Other Pollutants As Well

WRITTEN BY: Andrew J. Dunlop

Oregon's environmental regulatory agency, the Environmental Quality Commission, is heavily regulating the state's coal-fired power plants. In fact, in 2010, the EQC slated one of the state's largest and most polluting, the Boardman plant, for closure by 2020. But even with that deadline in place, the EQC wanted to severely limit the pollutants, especially mercury, the Boardman plant would emit in the time between 2010 and the plant's closure. In that vein, in 2011, air pollution controls in the form of scrubbers were installed at Boardman. A year-long study of the pollutants the plant was emitting was conducted, and a new analysis of this study has shown some surprising results. Though the scrubbers were installed with the intention of controlling the emission of mercury, recent analysis of the study's data have shown that the scrubbers reduce another class of harmful emissions as well.

When it was announced that scrubbers were going to be installed at the Boardman plant, a team of Oregon State University scientists took the opportunity to record measure emissions from the Boardman plant before the scrubbers were installed and after they were installed. The team tracked concentrations of airborne pollutants during 2010 and 2011 at two locations: Cabbage Hill, Oregon (at an elevation of 3,130 feet), which is about 60 miles east of the Boardman plant, and at the summit of Mount Bachelor (at an elevation of 9,065 feet) located about 200 miles southwest of Boardman.

The team took samples weekly from March through October of 2010, and again from March through September of 2011. These measurements revealed that mercury emissions were down, by about ninety percent. But they also by found that concentrations of two major groups of air pollutants went down by 40 and 72 percent, respectively. The results of this new analysis of the data
were recently published in the journal Environmental Science & Technology.

 
Staci Simonich, an environmental chemist in OSU's College of Agricultural Sciences is the leader of the team that did the study on The Boardman plant says, "PGE put control measures in to reduce mercury emissions, and as a side benefit, these other pollutants were also reduced."

The pollutants which were unexpectedly reduced are from a family of chemicals called polycyclic aromatic hydrocarbons (PAHs). They are formed when fossil fuels and organic matter are incompletely combusted. PAHs are all toxic, but some chemicals in this group are of additional concern because they trigger cell mutations which lead to cancer and other ailments.

But, after the scrubbers were installed, some of these compounds were drastically reduced. In fact, Simonich says that some of the individual PAH chemicals were reduced so much after the installation of the scrubbers that the research team couldn't discern from the data whether the plant was running or not.
"The upgrades reduced the PAH emissions to the point where we could hardly distinguish between air we sampled along the Gorge and at the top of Mount Bachelor. ... Boardman used to be a major source of PAH pollution in the Columbia River Gorge, and now it's not," Simonich says. "That's a good thing for PGE and a good thing for the people living in the Gorge."

(Source: phys.org)