U. BUFFALO (US) — Disputes over drilling Marcellus shale for natural gas have focused on the environmental effects of pumping millions of gallons of water and chemicals deep underground.
Hydraulic fracturing—or “fracking”—to release natural gas also causes uranium that is naturally trapped inside Marcellus shale to be released, according to new research, raising additional environmental concerns.
Marcellus shale is a massive rock formation that stretches from New York through Pennsylvania, Ohio, and West Virginia, and is often described as the nation’s largest source of natural gas.
“Marcellus shale naturally traps metals such as uranium and at levels higher than usually found naturally, but lower than manmade contamination levels,” says Tracy Bank, assistant professor of geology at the University at Buffalo.
“My question was, if they start drilling and pumping millions of gallons of water into these underground rocks, will that force the uranium into the soluble phase and mobilize it? Will uranium then show up in groundwater?”
To find out, Bank scanned the surfaces of Marcellus shale samples from Western New York and Pennsylvania.
Using sensitive chemical instruments, they created a chemical map of the surfaces to determine the precise location in the shale of the hydrocarbons, the organic compounds containing natural gas.
“We found that the uranium and the hydrocarbons are in the same physical space,” says Bank, and “are not just physically, but also chemically, bound.
“That led me to believe that uranium in solution could be more of an issue because the process of drilling to extract the hydrocarbons could start mobilizing the metals as well, forcing them into the soluble phase and causing them to move around.”
When samples were reacted in the lab with surrogate drilling fluids, uranium was indeed found to be solubilized.
Also, when the millions of gallons of water used in hydraulic fracturing come back to the surface, it can contain uranium contaminants, potentially polluting streams and other ecosystems and generating hazardous waste.
“Even though at these levels, uranium is not a radioactive risk, it is still a toxic, deadly metal,” Bank says.
“We need a fundamental understanding of how uranium exists in shale. The more we understand about how it exists, the more we can better predict how it will react to ‘fracking.'”
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