In a study published Monday, the six scientists write that they are the first to describe the tracer method, which can pinpoint highly diluted remnants of the industrial fluids in waterways and other drinking water sources.
The study, appearing in Environmental Science and Technology, is entitled “New Tracers Identify Hydraulic Fracturing Fluids and Accidental Release from Oil and Gas Operations.”
Its authors have been researching water contamination from shale gas drilling for several years. In the interim several have left Duke, including the paper’s lead author, Nathaniel Warner, now a post-doctoral fellow at Dartmouth College’s Department of Earth Sciences.
Warner said the methodology could be used as a forensic tool to identify illegal spills and accidental contamination.
The study tracks the presence of “flowback” water, also known as “produced” water, which is a mixture of water and chemicals used in fracking and the underground salines and metals that flush out of the ground when drillers strike gas.
The Duke researchers say this mixture can be identified by boron and lithium isotopes found in flowback water. They tested the theory on 39 samples in Pennsylvania and Arkansas, and at a spill site in West Virginia.
One of the test samples was flowback water that had been treated at a municipal water treatment plant. The fingerprints were detected in the treated water coming out of the facility’s clean discharge pipe, Warner said.
The samples of flowback water were taken between 2010 and 2012.
The tracers occur naturally between 1 mile and 2 miles underground, where fracking takes place, and where high-pressure blasts of water dislodge elements such as boron and lithium.
These tracer technology cannot identify flowback water by drill site; it is designed to distinguish between fracking flowback water and water produced from other oil and gas operations.
Warner said the boron and lithium deep underground have a different weight, and a distinct fingerprint, from those elements found in conventional drilling waters.
Co-author Avner Vengosh, a Duke professor of Earth and Ocean Sciences, said the study was funded with a $100,000 grant from the National Science Foundation.
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