7 research outputs found
Sources of Radium Accumulation in Stream Sediments near Disposal Sites in Pennsylvania: Implications for Disposal of Conventional Oil and Gas Wastewater
In
Pennsylvania, Appalachian oil and gas wastewaters (OGW) are
permitted for release to surface waters after some treatment by centralized
waste treatment (CWT) facilities. While this practice was largely
discontinued in 2011 for unconventional Marcellus OGW at facilities
permitted to release high salinity effluents, it continues for conventional
OGW. This study aimed to evaluate the environmental implications of
the policy allowing the disposal of conventional OGW. We collected
stream sediments from three disposal sites receiving treated OGW between
2014 and 2017 and measured <sup>228</sup>Ra, <sup>226</sup>Ra, and
their decay products, <sup>228</sup>Th and <sup>210</sup>Pb, respectively.
We consistently found elevated activities of <sup>228</sup>Ra and <sup>226</sup>Ra in stream sediments in the vicinity of the outfall (total
Ra = 90–25,000 Bq/kg) compared to upstream sediments (20–80
Bq/kg). In 2015 and 2017, <sup>228</sup>Th/<sup>228</sup>Ra activity
ratios in sediments from two disposal sites were relatively low (0.2–0.7),
indicating that a portion of the Ra has accumulated in the sediments
in recent (<3) years, when no unconventional Marcellus OGW was
reportedly discharged. <sup>228</sup>Ra/<sup>226</sup>Ra activity
ratios were also higher than what would be expected solely from disposal
of low <sup>228</sup>Ra/<sup>226</sup>Ra Marcellus OGW. Based on these
variations, we concluded that recent disposal of treated conventional
OGW is the source of high Ra in stream sediments at CWT facility disposal
sites. Consequently, policies pertaining to the disposal of only unconventional
fluids are not adequate in preventing radioactive contamination in
sediments at disposal sites, and the permission to release treated
Ra-rich conventional OGW through CWT facilities should be reconsidered
Radium and Barium Removal through Blending Hydraulic Fracturing Fluids with Acid Mine Drainage
Wastewaters
generated during hydraulic fracturing of the Marcellus
Shale typically contain high concentrations of salts, naturally occurring
radioactive material (NORM), and metals, such as barium, that pose
environmental and public health risks upon inadequate treatment and
disposal. In addition, fresh water scarcity in dry regions or during
periods of drought could limit shale gas development. This paper explores
the possibility of using alternative water sources and their impact
on NORM levels through blending acid mine drainage (AMD) effluent
with recycled hydraulic fracturing flowback fluids (HFFFs). We conducted
a series of laboratory experiments in which the chemistry and NORM
of different mix proportions of AMD and HFFF were examined after reacting
for 48 h. The experimental data combined with geochemical modeling
and X-ray diffraction analysis suggest that several ions, including
sulfate, iron, barium, strontium, and a large portion of radium (60–100%),
precipitated into newly formed solids composed mainly of Sr barite
within the first ∼10 h of mixing. The results imply that blending
AMD and HFFF could be an effective management practice for both remediation
of the high NORM in the Marcellus HFFF wastewater and beneficial utilization
of AMD that is currently contaminating waterways in northeastern U.S.A
Impacts of Shale Gas Wastewater Disposal on Water Quality in Western Pennsylvania
The
safe disposal of liquid wastes associated with oil and gas
production in the United States is a major challenge given their large
volumes and typically high levels of contaminants. In Pennsylvania,
oil and gas wastewater is sometimes treated at brine treatment facilities
and discharged to local streams. This study examined the water quality
and isotopic compositions of discharged effluents, surface waters,
and stream sediments associated with a treatment facility site in
western Pennsylvania. The elevated levels of chloride and bromide,
combined with the strontium, radium, oxygen, and hydrogen isotopic
compositions of the effluents reflect the composition of Marcellus
Shale produced waters. The discharge of the effluent from the treatment
facility increased downstream concentrations of chloride and bromide
above background levels. Barium and radium were substantially (>90%)
reduced in the treated effluents compared to concentrations in Marcellus
Shale produced waters. Nonetheless, <sup>226</sup>Ra levels in stream
sediments (544–8759 Bq/kg) at the point of discharge were ∼200
times greater than upstream and background sediments (22–44
Bq/kg) and above radioactive waste disposal threshold regulations,
posing potential environmental risks of radium bioaccumulation in
localized areas of shale gas wastewater disposal
Iodide, Bromide, and Ammonium in Hydraulic Fracturing and Oil and Gas Wastewaters: Environmental Implications
The
expansion of unconventional shale gas and hydraulic fracturing
has increased the volume of the oil and gas wastewater (OGW) generated
in the U.S. Here we demonstrate that OGW from Marcellus and Fayetteville
hydraulic fracturing flowback fluids and Appalachian conventional
produced waters is characterized by high chloride, bromide, iodide
(up to 56 mg/L), and ammonium (up to 420 mg/L). Br/Cl ratios were
consistent for all Appalachian brines, which reflect an origin from
a common parent brine, while the I/Cl and NH<sub>4</sub>/Cl ratios
varied among brines from different geological formations, reflecting
geogenic processes. There were no differences in halides and ammonium
concentrations between OGW originating from hydraulic fracturing and
conventional oil and gas operations. Analysis of discharged effluents
from three brine treatment sites in Pennsylvania and a spill site
in West Virginia show elevated levels of halides (iodide up to 28
mg/L) and ammonium (12 to 106 mg/L) that mimic the composition of
OGW and mix conservatively in downstream surface waters. Bromide,
iodide, and ammonium in surface waters can impact stream ecosystems
and promote the formation of toxic brominated-, iodinated-, and nitrogen
disinfection byproducts during chlorination at downstream drinking
water treatment plants. Our findings indicate that discharge and accidental
spills of OGW to waterways pose risks to both human health and the
environment
Isotopic Imprints of Mountaintop Mining Contaminants
Mountaintop
mining (MTM) is the primary procedure for surface coal
exploration within the central Appalachian region of the eastern United
States, and it is known to contaminate streams in local watersheds.
In this study, we measured the chemical and isotopic compositions
of water samples from MTM-impacted tributaries and streams in the
Mud River watershed in West Virginia. We systematically document the
isotopic compositions of three major constituents: sulfur isotopes
in sulfate (δ<sup>34</sup>S<sub>SO4</sub>), carbon isotopes
in dissolved inorganic carbon (δ<sup>13</sup>C<sub>DIC</sub>), and strontium isotopes (<sup>87</sup>Sr/<sup>86</sup>Sr). The
data show that δ<sup>34</sup>S<sub>SO4</sub>, δ<sup>13</sup>C<sub>DIC</sub>, Sr/Ca, and <sup>87</sup>Sr/<sup>86</sup>Sr measured
in saline- and selenium-rich MTM impacted tributaries are distinguishable
from those of the surface water upstream of mining impacts. These
tracers can therefore be used to delineate and quantify the impact
of MTM in watersheds. High Sr/Ca and low <sup>87</sup>Sr/<sup>86</sup>Sr characterize tributaries that originated from active MTM areas,
while tributaries from reclaimed MTM areas had low Sr/Ca and high <sup>87</sup>Sr/<sup>86</sup>Sr. Leaching experiments of rocks from the
watershed show that pyrite oxidation and carbonate dissolution control
the solute chemistry with distinct <sup>87</sup>Sr/<sup>86</sup>Sr
ratios characterizing different rock sources. We propose that MTM
operations that access the deeper Kanawha Formation generate residual
mined rocks in valley fills from which effluents with distinctive <sup>87</sup>Sr/<sup>86</sup>Sr and Sr/Ca imprints affect the quality
of the Appalachian watersheds
Isotopic Imprints of Mountaintop Mining Contaminants
Mountaintop
mining (MTM) is the primary procedure for surface coal
exploration within the central Appalachian region of the eastern United
States, and it is known to contaminate streams in local watersheds.
In this study, we measured the chemical and isotopic compositions
of water samples from MTM-impacted tributaries and streams in the
Mud River watershed in West Virginia. We systematically document the
isotopic compositions of three major constituents: sulfur isotopes
in sulfate (δ<sup>34</sup>S<sub>SO4</sub>), carbon isotopes
in dissolved inorganic carbon (δ<sup>13</sup>C<sub>DIC</sub>), and strontium isotopes (<sup>87</sup>Sr/<sup>86</sup>Sr). The
data show that δ<sup>34</sup>S<sub>SO4</sub>, δ<sup>13</sup>C<sub>DIC</sub>, Sr/Ca, and <sup>87</sup>Sr/<sup>86</sup>Sr measured
in saline- and selenium-rich MTM impacted tributaries are distinguishable
from those of the surface water upstream of mining impacts. These
tracers can therefore be used to delineate and quantify the impact
of MTM in watersheds. High Sr/Ca and low <sup>87</sup>Sr/<sup>86</sup>Sr characterize tributaries that originated from active MTM areas,
while tributaries from reclaimed MTM areas had low Sr/Ca and high <sup>87</sup>Sr/<sup>86</sup>Sr. Leaching experiments of rocks from the
watershed show that pyrite oxidation and carbonate dissolution control
the solute chemistry with distinct <sup>87</sup>Sr/<sup>86</sup>Sr
ratios characterizing different rock sources. We propose that MTM
operations that access the deeper Kanawha Formation generate residual
mined rocks in valley fills from which effluents with distinctive <sup>87</sup>Sr/<sup>86</sup>Sr and Sr/Ca imprints affect the quality
of the Appalachian watersheds
Watershed-Scale Impacts from Surface Water Disposal of Oil and Gas Wastewater in Western Pennsylvania
Combining horizontal
drilling with high volume hydraulic fracturing
has increased extraction of hydrocarbons from low-permeability oil
and gas (O&G) formations across the United States; accompanied
by increased wastewater production. Surface water discharges of O&G
wastewater by centralized waste treatment (CWT) plants pose risks
to aquatic and human health. We evaluated the impact of surface water
disposal of O&G wastewater from CWT plants upstream of the Conemaugh
River Lake (dam controlled reservoir) in western Pennsylvania. Regulatory
compliance data were collected to calculate annual contaminant loads
(Ba, Cl, total dissolved solids (TDS)) to document historical industrial
activity. In this study, two CWT plants 10 and 19 km upstream of a
reservoir left geochemical signatures in sediments and porewaters
corresponding to peak industrial activity that occurred 5 to 10 years
earlier. Sediment cores were sectioned for the collection of paired
samples of sediment and porewater, and analyzed for analytes to identify
unconventional O&G wastewater disposal. Sediment layers corresponding
to the years of maximum O&G wastewater disposal contained higher
concentrations of salts, alkaline earth metals, and organic chemicals.
Isotopic ratios of <sup>226</sup>Ra<sup>/228</sup>Ra and <sup>87</sup>Sr<sup>/86</sup>Sr identified that peak concentrations of Ra and
Sr were likely sourced from wastewaters that originated from the Marcellus
Shale formation