A new study of 100 private water wells in and near the Barnett Shale showed elevated levels of potential contaminants such as arsenic and selenium closest to natural gas extraction sites, according to a team of researchers that was led by UT Arlington associate professor of chemistry and biochemistry Kevin Schug.
Brian Fontenot, who earned his Ph.D. in quantitative biology from UT Arlington, worked with Kevin Schug, UT Arlington
associate professor of chemistry and biochemistry, and a team of researchers to analyze samples from 100 private water wells.
The results of the
North Texas well study were published online by the journal Environmental Science & TechnologyThursday.
The peer-reviewed paper focuses on the presence of metals such as arsenic,
barium, selenium and strontium in water samples. Many of these heavy metals occur naturally at low levels in
groundwater, but disturbances from natural gas extraction activities could cause
them to occur at elevated levels.
“This study alone can’t
conclusively identify the exact causes of elevated levels of contaminants in
areas near natural gas drilling, but it does provide a powerful argument for
continued research,” said Brian Fontenot, a UT Arlington graduate with a
doctorate in quantitative biology and lead author on the new paper.
He added: “We expect this to be
the first of multiple projects that will ultimately help the
scientific community, the natural gas industry, and most importantly, the
public, understand the effects of natural gas drilling on water
Researchers believe the increased presence of metals could be due to a
variety of factors including: industrial accidents such as faulty gas
well casings; mechanical vibrations from natural gas drilling activity
disturbing particles in neglected water well equipment; or the lowering
of water tables through drought or the removal of water used for the
hydraulic fracturing process. Any of these scenarios could release
dangerous compounds into shallow groundwater.
Researchers gathered samples from privatewater
wells of varying depth within a 13 county area in or near the Barnett
Shale in North Texas over four months in the summer and fall of 2011.
Ninety-one samples were drawn from what they termed “active extraction
areas,” or areas that had one or more gas wells within a five kilometer
radius. Another nine samples were taken from sites either inside the
Barnett Shale and more than 14 kilometers from a natural gas drilling
site, or from sites outside the Barnett Shale altogether. The locations
of those sites were referred to as “non-active/reference areas” in the
Researchers accepted no outside funding to ensure the
integrity of the study. They compared the samples to historical data on
water wells in these counties from the Texas Water Development Board
groundwater database for 1989-1999, prior to the proliferation of
natural gas drilling.
In addition to standard water quality tests,
the researchers used gas chromatography – mass spectrometry (GC-MS),
headspace gas chromatography (HS-GC) and inductively coupled plasma-mass
spectrometry (ICP-MS). Many of the tests were conducted in the Shimadzu Center for Advanced Analytical Chemistry on the UT Arlington campus.
gas drilling is one of the most talked about issues in North Texas and
throughout the country. This study was an opportunity for us to use our
knowledge of chemistry and statistical analysis to put people’s concerns
to the test and find out whether they would be backed by scientific
data,” said Schug, who is also the Shimadzu Distinguished Professor of
Analytical Chemistry in the UT Arlington College of Science.
average, researchers detected the highest levels of these contaminants
within 3 kilometers of natural gas wells, including several samples that
had arsenic and selenium above levels considered safe by the
Environmental Protection Agency. For example, 29 wells that were within
the study’s active natural gas drilling area exceeded the EPA’s Maximum
Contaminant Limit of 10 micrograms per liter for arsenic, a potentially
The areas lying outside of active drilling
areas or outside the Barnett Shale did not show the same elevated levels
for most of the metals.
Other leaders of the Texas Gas Wells team
were Laura Hunt, who conducted her post-doctoral research in biology at
UT Arlington, and Zacariah Hildenbrand, who earned his doctorate in
biochemistry from the University of Texas at El Paso and performed
post-doctoral research at UT Southwestern Medical Center. Hildenbrand is
also the founder of Inform Environmental,
LLC. Fontenot and Hunt work for the EPA regional office in Dallas, but
the study is unaffiliated with the EPA and both received permission to
work on this project outside the agency.
Scientists note in the
paper that they did not find uniformity among the contamination in the
active natural gas drilling areas. In other words, not all gas well
sites were associated with higher levels of the metals in well water.
Some of the most notable results were on the following heavy metals:
Arsenic occurs naturally in the region’s water and was detected in
99 of the 100 samples. But, the concentrations of arsenic were
significantly higher in the active extraction areas compared to
non-extraction areas and historical data. The maximum concentration from
an extraction area sample was 161 micrograms per liter, or 16 times the
EPA safety standard set for drinking water. According to the EPA,
people who drink water containing arsenic well in excess of the safety
standard for many years “could experience skin damage or problems with
their circulatory system, and may have an increased risk of getting
Selenium was found in 10 samples near extraction sites, and all of
those samples showed selenium levels were higher than the historical
average. Two samples exceeded the standard for selenium set by
the EPA. Circulation problems as well as hair or fingernail loss are
some possible consequences of long-term exposure to high levels of
selenium, according to the EPA.
Strontium was also found in almost all the samples, with
concentrations significantly higher than historical levels in the areas
of active gas extraction. A toxicological profile by the federal
government’s Agency for Toxic Substances and Disease Registry recommends
no more than 4,000 micrograms of strontium per liter in drinking water.
Seventeen samples from the active extraction area and one from the
non-active areas exceeded that recommended limit. Exposure to high
levels of stable strontium can result in impaired bone growth in
children, according to the toxic substances agency.
“After we put the word out about the study, we received numerous
calls from landowner volunteers and their opinions about the natural
gas drilling in their communities varied,” Hildenbrand said. “By
participating in the study, they were able to get valuable data about
their water, whether it be for household or land use.
participation has been incredibly important to this study and has helped
us bring to light some of the important environmental questions
surrounding this highly contentious issue.”
The paper also
recommends further research on levels of methanol and ethanol in water
wells. Twenty-nine private water wells in the study contained methanol,
with the highest concentrations in the active extraction areas. Twelve
samples, four of which were from the non-active extraction sites,
contained measurable ethanol. Both ethanol and methanol can occur
naturally or as a result of industrial contamination. Historical data on
methanol and ethanol was not available, researchers said in the paper.
paper is called “An evaluation of water quality in private drinking
water wells near natural gas extraction sites in the Barnett Shale
formation.” A Just Accepted version is available here on the journal
Other co-authors include: Qinhong “Max” Hu, associate
professor of earth and environmental sciences at UT Arlington; Doug D.
Carlton Jr., a Ph.D. student in the chemistry and biochemistry
department at UT Arlington; Hyppolite Oka, a recent graduate of the
environmental and earth sciences master’s program at UT Arlington; Jayme
L. Walton, a recent graduate of the biology master’s program at UT
Arlington; and Dan Hopkins, of Carrollton-based Geotech Environmental
Alexandria Osorio and Bryan Bjorndal of Assure Controls,
Inc. in Vista, Calif., also are co-authors. The team used Assure’s
Qwiklite™ system to test for toxicity in well samples and those results
are being prepared for a separate publication.
Many from the
research team are now conducting well water sampling in the Permian
Basin region of Texas, establishing a baseline set of data prior to gas
well drilling activities there. That baseline will be used for a direct
comparison to samples that will be collected during and after upcoming
natural gas extraction. The team hopes that these efforts will shed
further light on the relationship between natural gas extraction and
ground water quality.
The research published this week is
representative of the important work going on at The University of Texas
at Arlington, a comprehensive research institution with about 33,800
students and more than 2,200 faculty members in the heart of North
Texas. For more information, please visit www.uta.edu.