I'm promoting the idea of solving one environmental problem and utilizing the waste from that to avoid causing another.

Carl Kirby

For years, Carl Kirby's deep orange Vanagon was a mobile landmark around Lewisburg. The vehicle got its unique color from a paint he created from "yellow boy," a pollutant that can smother creeks downstream of old mines. The geology professor has since traded the Vanagon for a more recent Eurovan, but his research on acid mine drainage continues.

Modern mines are required by law to treat their runoff, but thousands of abandoned mines across the country continue to contaminate streams as the subsurface rock exposed by mining is weathered by air and water. For example, pyrite, or iron-sulfide, is associated with coal. Long after the coal has been removed and the mine has closed, the pyrite continues to oxidize, producing sulfuric acid and dissolved iron ions. As these pollutants are washed downstream, if the water becomes less acidic, the iron precipitates out as iron hydroxide, or yellow boy. This by-product of acid mine drainage treatment systems is usually considered a waste product, but Kirby has found several potential commercial applications for it, including pigment, sewage treatment, and others. Replacing the chemicals currently used in these applications, which have to be mined themselves, could reduce the need for more mines.

"I'm promoting the idea of solving one environmental problem and utilizing the waste from that to avoid causing another," Kirby says. || Learn about Kirby's newest research area -- Ask the Experts: Carl Kirby on Marcellus Shale

Much of Kirby's research has focused on the speed at which iron oxidizes under different conditions. This chemical reaction is the limiting step in treatment systems. "How fast you can do the oxidation limits how fast you can do anything else," he says. Knowing the oxidation rates under different pH levels and different microbial communities allows one to size treatment facilities appropriately.

Acid also finds its way into streams from rain and other forms of precipitation that carry emissions from coal-burning power plants. The ability of a stream to neutralize acid depends in part on the surrounding geology. Kirby and his students have discovered that some sandstone formations are better at neutralizing acid than others. In areas that are more susceptible to acidification, the team gathers water chemistry data and documents the presence or absence of brook trout and other fish. "Where the chemistry looked bad, there were no fish," Kirby says. The project has catalogued a number of streams that state officials have not yet registered as impaired.

Just as mining and burning coal have left their imprint on Pennsylvania's streams, modern methods of tapping deep reserves of natural gas are leaving another legacy. Hydrofracturing involves shooting large quantities of salty water mixed with organic chemicals deep into gas wells. Kirby is studying the geochemical behavior of the water as it makes its way back to the surface, information that will be vital for formulating treatment techniques. Using what he is finding in the field, Kirby and his students are discovering that environmental problems sometimes hold their solutions.

Posted Aug. 31, 2009

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