Researchers have found that wastewater spills from unconventional oil production has caused widespread water and soil contamination in North Dakota.
A Duke University study has found high levels of ammonium, selenium, and lead among other toxic contaminants as well as high salts in the brine-laden waste-water. It is believed that these contaminants have predominantly come from hydraulically fractured oil wells in the Bakken region.
Avner Vengosh, professor of geochemistry and water quality at Duke’s Nicholas School of the Environment, said in a statement:
“Until now, research in many regions of the nation has shown that contamination from fracking has been fairly sporadic and inconsistent.
“In North Dakota, however, we find it is widespread and persistent, with clear evidence of direct water contamination from fracking. The magnitude of oil drilling in North Dakota is overwhelming.”
Streams that have been polluted by the waste-water have been found to contain levels of contaminants that have frequently exceeded the federal guidelines for safe drinking water or aquatic health.
At spill sites the soil is contaminated with radium, which is a naturally occurring radioactive element found in brines that chemically attach to the soil after the spill water was released, according to a statement from Duke University.
At one particular site, researchers were able to detect high levels of contaminants in spill water that had occurred four years earlier, Vengosh said:
“More than 9,700 wells have been drilled there in the past decade. This massive development has led to more than 3,900 brine spills, mostly coming from faulty pipes built to transport fracked wells’ flowback water from on-site holding containers to nearby injection wells where it will be disposed underground.”
To show how the spill sites were associated with the intensity of the oil drilling, the team mapped out the distribution of the 3,900 spill sites. Unconventional oil production in North Dakota has risen from around 100,000 barrels a day in 2007 to over 1 million barrels a day in 2014.
This expansion has increased economic growth, particularly on tribal lands, however it has also raised concerns about drinking water contamination. Nancy Lauer, a Ph.D. student of Vengosh’s and the lead author of the study, said it was:
“Unlike spilled oil, which starts to break down in soil, these spilled brines consist of inorganic chemicals, metals, and salts that are resistant to biodegradation. They don’t go away; they stay. This has created a legacy of radioactivity at spill sites.”
The researchers noted that samples of soil collected downstream had contained higher levels of radioactivity than at the spill sites themselves, suggesting that the radium is building up in the soil as the spilled brine travels through the environment.
The study, which was published in the journal Environmental Science & Technology, consisted of collecting samples of brine-laden spill waters from four sites, two of which were large spills and two were smaller ones.
The samples were then measured and analyzed for inorganic contaminants and to identify the unique isotopic signature of Bakken region brines.
By matching the signature to the geochemical and isotopic profiles of 29 background surface water samples that have been collected across the region, the team is able to conclude from where and to what extent contamination associated with brine spills had occurred, and also rule out that it had been caused by other sources. Vengosh said:
“These isotopic tracers give scientists powerful forensic tools for tracking the presence of spill waters in the environment.
“Given that spills can occur upstream from drinking water sources, long-term monitoring of downstream waters is necessary to assess impacts on water quality.
“Many smaller spills have also occurred on tribal lands, and as far as we know, no one is monitoring them. People who live on the reservations are being left to wonder how it might affect their land, water, health, and way of life.”