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DATE IMPORTED:September 23, 2009Floodwaters engulf parts of the R.M. Clayton Sewage Treatment Plant in Atlanta, Georgia, in this aerial view taken September 23, 2009. Constant rains for nearly a week have saturated the metro Atlanta area, bringing Chattahoochee River basin flood waters to residents' doors and closing businesses. Flooding in north Georgia that killed nine people caused $250 million worth of damage to property and tens of millions of dollars more damage to infrastructure, the state insurance commissioner said on Wednesday. REUTERS/David Tulis

Scientists studying the environmental effects of the controversial drilling technique known as fracking have found radioactive waste water from such an operation in a Pennsylvania's Marcellus Shale region.

The Marcellus Shale is one of the largest zones of its kind and stretches from Upstate New York to West Virginia. To extract the gas from the shale rock, millions of gallons of water and chemicals are used to fracture the formations deep beneath the surface. The drilling technique has been heavily criticized, and some environmentalists have long contended it poisons groundwater.

The two-year Duke University study collected water samples at Josephine Brine Treatment Facility, on Blacklick Creek in Indiana County, one of the 74 treatment facilities that treat fracking wastewater in the state.

Scientists found concentrations of the highly radioactive element radium as well as chloride and bromide, which were two to 10 times higher than normal.

“The treatment removes a substantial portion of the radioactivity, but it does not remove many of the other salts, including bromide," Avner Vengosh, professor of geochemistry and water quality at Duke University’s Nicholas School of the Environment, said. "When the high-bromide effluents are discharged to the stream, it increases the concentrations of bromide above the original background levels.” Avner added that bromide can increase the risk of highly toxic disinfection byproducts in drinking water.

Map of hydrological system
Map of the hydrological system of Pennsylvania and the locations of 74 facilities permitted in 2010 to accept and treat Marcellus Shale produced and flowback waters (red squares), the majority of which are located in the Ohio River Basin (light blue shading). This study focused on the Josephine Brine Treatment Facility (black square), a centralized waste treatment facility in western Pennsylvania where treated wastewater is discharged to Blacklick Creek (See SI Figure S1 for details). Background measurements (yellow circles) were collected in 2011 at locations upstream of any permitted facilities or >1 km downstream of permitted facilities. Cidney A. Christie, Robert B. Jackson, and Avner Vengosh

Blacklick Creek is an arm of the Conemaugh River, which flows into the Allegheny River and provides water for several Pennsylvania cities, including Pittsburgh.