Research by a University of Iowa graduate student suggests gamma-ray spectroscopy may provide a more accurate measurement of radium in byproduct water produced by hydraulic fracturing, compared with other methods of analysis.
Hydraulic fracturing, or fracking, uses horizontal drilling to extract trapped natural gas from small crevices in rock formations. To free the gas, a mixture of water, sand, and chemicals is injected deep underground into wells vertically and then horizontally at extremely high pressure. The pressurized fluid mixture fractures the rock and allows the natural gas to rise to the surface through the recovered water—called flowback water (FBW).
Emanation
is a technique where radon-222 gas (the first decay product of radium-226) is bubbled out of fluids and counted for radioactivity. The radioactivity of radium-226 in a fluid can be estimated from the radioactivity of radon-222.
Gamma-ray spectroscopy is an analytical technique that can be used to identify various radioactive isotopes in a sample. In gamma-ray spectroscopy, the energy of striking gamma rays is measured by a detector. By comparing the measured energy to the known energy of gamma rays produced by radioisotopes, the identity of the emitter can be determined.
EPA method 903.0 covers the measurement of the total soluble radium radioisotopes in drinking water. This method provides for the separation of radium from other water-dissolved solids in the sample.
In a paper published online in Environmental Science & Technology Letters, first author Andrew Nelson, a doctoral student in the University of Iowa’s Interdisciplinary Graduate Program in Human Toxicology, and colleagues examined the effectiveness of several methods of measuring radium levels in FBW.
The study was conducted using a 55-gallon drum of FBW from the Marcellus Shale Region in northeastern Pennsylvania. The sample was extracted from a 2,100-meter deep, horizontally drilled well that was hydraulically fractured.
Nelson, a Presidential Graduate Research Fellow, and his team investigated the effectiveness of several types of common radium analysis methods, including gamma-ray spectroscopy, emanation techniques, and EPA method 903.0.
The researchers found that a high salt concentration in the FBW sample interferes with the EPA wet-chemistry method traditionally used for drinking water analysis. They also discovered that gamma-ray spectroscopy and emanation techniques are not as affected by the high salt concentration, allowing for more accurate radium readings.
“At the moment, in the literature, there are government agencies that are either using or proposing methods that we have found don’t work as well as gamma ray spectroscopy,” Nelson says. “We think it’s important that methods used most accurately assess the radioactivity of samples.”
Using gamma-ray spectroscopy, they identified levels of radium-226 (a radioactive metal produced by the radioactive decay of uranium) 1,000 times higher than would be allowed in drinking water, according to EPA regulations.
The authors say the research can help guide regulatory agencies in determining the best methods for analyzing FBW, establishing safeguards for fractural hydraulics operations, and safely disposing of byproducts from the process.
The U.S. Nuclear Regulatory Commission (NRC-HQ-12-G-38-0041) and Environmental Management Solutions (EMS FP 07-037-43) provided funding in support of the research.
In addition to Nelson, the research team included Michael Schultz, UI assistant professor of radiology and internal medicine and senior study author, Dustin May and Marinea Mehrhoff of the University of Iowa State Hygienic Laboratory; Andrew Knight and Eric Eitrheim, UI graduate students in chemistry; Robert Shannon of Quality Radioanalytical Support, LLC in Grand Marais, Minn.; and Robert Litman of Radiochemistry Laboratory Basics in The Villages, Fla.