The production of hazardous wastewater in hydraulic fracturing is assumed to be partly due to chemicals introduced into injected freshwater when it mixes with highly saline brine naturally present in the rock. But a Dartmouth study investigating the toxic metal barium in fracking wastewater finds that chemical reactions between injected freshwater and the fractured shale itself could play a major role.
The findings, which are published in the journal Applied Geochemistry, show that transformation of freshwater used for fracking to a highly saline liquid with abundant toxic metals is a natural consequence of water-rock reactions occurring at depth during or following fracking. Fracking wastewater poses a hazard to drinking water supplies if improperly disposed. A PDF is available on request.