Fracking: how isotope hydrology can support environmental assessments to help protect groundwater (French Edition)

Any industrial activity near water reserves could, in principle, cause contamination. Isotope hydrology offers a unique combination of methods to monitor water quality and trace the source of pollution if any is identified. Increasingly, countries are making use of this technology to protect surface and ground water near sites used for oil extension with a technique known as fracking. Hydraulic fracturing, or fracking, has opened up previously inaccessible oil and natural gas resources for production. It accounts for about half of the total oil output of the United States, and many developing countries are considering using it for the first time. Fracking is a wellstimulation technique in which rock is fractured by injecting fluid at high pressure. This fluid consists of water, sand and other chemical additives. Injected through a well, fracking creates cracks in deep-rock formations, through which natural gas and oil can flow more freely. This method allows access to oil and gas that are trapped in tight formations and are not accessible using conventional drill and pump methods. Surface water may be contaminated through spillage during fracking, or accidental release from the waste pit in which the fracking fluid is recovered after extraction; groundwater can be contaminated if the fluid escapes through, for example, abandoned or leaking wells; and drinking water may also be contaminated if natural gas leaks into shallow aquifers. In many cases where contamination is suspected, identifying the source and extent of the contamination is difficult due to a lack of baseline data, said Jennifer McIntosh, Professor of Hydrology and Atmospheric Sciences at the University of Arizona in the US. "There is an opportunity for the scientific community to provide guidance on the best analytical methods for evaluating fugitive gas leakage and fracking fluid or water contamination of groundwater," she said. A recent paper by McIntosh and 14 other authors from leading universities around the world explained how various isotope hydrology techniques can be used to monitor the impact of fracking on ground and surface water. It also provided recommendations on which method to use under a diverse set of circumstances and environmental conditions. The initial ideas for the paper entitled A Critical Review of State-of-the-Art and Emerging Approaches to Identify FrackingDerived Gases and Associated Contaminants in Aquifers, which appeared in the journal Environmental Science and Technology in December 2018, were developed at an IAEA technical meeting two years earlier