Fracking Flowback May Lead to Contaminated Groundwater

New research has revealed that flowback fluid, or wastewater, from "hydrofracking" causes the release of particles in soil that bind to pollutants, which have the potential to contaminate groundwater.

The particles in question are colloids - microscopic in size but larger than a molecule - which are naturally bound to sand and soil due to their electric charge.

Fracking involves injecting a water and chemical solution mixture into deep rock strata at high pressures. Previous research has shown that 10 to 40 percent of this mixture surges back to the surface during well development. But, Cornell researchers found that this "flowback fluid," while effective at extracting natural gas from shale, also causes associated pollutants, like heavy metals, to leach out of the soil and into groundwater.

Scientists at the College of Agriculture and Life Sciences published their findings in the American Chemical Society's journal, Environmental Science & Technology.

The study attempts to understand the prevalence of colloids in groundwater from soils exposed to flowback fluid via accidental "hydrofracking" spills. Researchers filled tubes with synthetic colloids, and then flushed each with two different fluids - deionized water and flowback fluid from a drilling site at the Marcellus Shale.

Visible as red spheres under a bright light microscope, they found that fewer than five percent of colloids were released when they poured deionized water into the tubes. But 32 to 36 percent of the colloids seeped out with the flowback fluid.

The authors believe the fluid's chemical composition weakens the bind between colloids and the soil. This makes groundwater susceptible to contamination when these particles leach out of the soil, bringing bound pollutants and heavy metals with it.

"This is a first step into discovering the effects of flowback fluid on colloid transport in soils," co-author Cathelijne Stoof said in a statement.

Authors note that understanding the mechanisms behind this phenomenon can lead to better strategies to help prevent its damaging impact.

"Sustainable development of any resource requires facts about its potential impacts, so legislators can make informed decisions about whether and where it can and cannot be allowed, and to develop guidelines in case it goes wrong. In case of spills, you want to know what happens when the fluid moves through the soil," Stoof added.