CU-Boulder technique finds major class of fracking chemicals no more toxic than common household substances; “fingerprinting”
The surfactant chemicals found in samples of fracking fluid collected in five states were no more toxic than substances commonly found in homes, according to a first-of-its-kind analysis by researchers at the University of Colorado Boulder. Imma Ferrer, chief scientist at the mass spectrometry laboratory and co-author of a paper in Analytical Chemistry describing the work said, “Our unique instrumentation with accurate mass and intimate knowledge of ion chemistry was used to identify these chemicals.”
Two series of ethylene oxide (EO) surfactants, polyethylene glycols (PEGs from EO3 to EO33) and linear alkyl ethoxylates (LAEs C-9 to C-15 with EO3−EO28), were identified in hydraulic fracturing flowback and produced water using a new application of the Kendrick mass defect and liquid chromatography/ quadrupole-time-of-flight mass spectrometry.
The Kendrick mass defect differentiates the proton, ammonium, and sodium adducts in both singly and doubly charged forms. A structural model of adduct formation is presented, and binding constants are calculated, which is based on a spherical cagelike conformation, where the central cation (NH4+ or Na+) is coordinated with ether oxygens.
A major purpose of the study was the identification of the ethylene oxide (EO) surfactants and the construction of a database with accurate masses and retention times in order to unravel the mass spectral complexity of surfactant mixtures used in hydraulic fracturing fluids. For example, over 500 accurate mass assignments are made in a few seconds of computer time, which then is used as a fingerprint chromatogram of the water samples. This technique is applied to a series of flowback and produced water samples to illustrate the usefulness of ethoxylate “fingerprinting”, in a first application to monitor water quality that results from fluids used in hydraulic fracturing.—Thurman et al.
Fracking fluid is largely composed of water and sand, but oil and gas companies also add a variety of other chemicals, including anti-bacterial agents, corrosion inhibitors and surfactants. Surfactants reduce the surface tension between water and oil, allowing for more oil to be extracted from porous rock underground.
Among the concerns raised by the fracking boom is that the chemicals used in the fracking fluid might contaminate ground and surface water supplies. But determining the risk of contamination—or proving that any contamination has occurred in the past—has been difficult because oil and gas companies have been reluctant to share exactly what’s in their proprietary fluid mixtures, citing stiff competition within the industry.
Recent state and federal regulations require companies to disclose what is being used in their fracking fluids, but the resulting lists typically use broad chemical categories to describe the actual ingredients.
The CU-Boulder research team identified the surfactants found in fracking fluid samples from Colorado, Louisiana, Nevada, Pennsylvania and Texas. The results showed that the chemicals found in the fluid samples were also commonly found in everyday products, from toothpaste to laxatives to detergent to ice cream.
The results of the new CU-Boulder study not only give a picture of the possible toxicity of the fluid but also enable a detailed list of the ingredients to be used as a “fingerprint” to trace whether suspected contamination of water supplies actually originated from a fracking operation.
This is the first published paper that identifies some of the organic fracking chemicals going down the well that companies use. We found chemicals in the samples we were running that most of us are putting down our drains at home.—Michael Thurman, lead author
The fluid samples analyzed for the study were provided through partnerships with Colorado State University and colleagues at CU-Boulder.
The authors caution that their results may not be applicable to all wells. Individual well operators use unique fracking fluid mixtures that may be modified depending on the underlying geology. Ferrer and Thurman are now working to analyze more water samples collected from other wells as part of a larger study at CU-Boulder exploring the impacts of natural gas development.
Thurman notes that there are other concerns about fracking—including air pollution, the antimicrobial biocides used in fracking fluids, wastewater disposal triggering earthquakes and the large amount of water used—that are important to investigate and ameliorate. But water pollution from surfactants in fracking fluid may not be as big a concern as previously thought.
E. Michael Thurman, Imma Ferrer, Jens Blotevogel, and Thomas Borch (2014) “Analysis of Hydraulic Fracturing Flowback and Produced Waters Using Accurate Mass: Identification of Ethoxylated Surfactants” Analytical Chemistry 86 (19), 9653-9661 doi: 10.1021/ac502163k