The 500 million years ocean history

Brachiopod Paraspirifer bownockeri from the Middle Devonian of Ohio (USA); Width: 5.6 cm. Picture: U. Jansen, Senckenberg Museum, Frankfurt am Main.

GEOMAR coordinates European research and education project BASE-LiNE Earth
02.03.2015 / Kiel. As the history of the oceans can be reconstructed in the past 500 million based on calcareous shells of fossil marine life, busy to date with the research project BASE-LiNE Earth. At the same time it enables talented young scientists and scientists a doctorate in an international research environment. The European Union supports the at GEOMAR Helmholtz Centre for Ocean Research Kiel coordinated project with a total of 3.8 million euros.

Almost all life on earth would be extinct - and that at least five times in the past 500 million years. The environmental changes that have each led to the mass extinction, the oceans play an important role in almost all cases. How did it happen that was phased so hostile to life as a life-giving force sea? And why have some species still survive? These are fundamental questions that will be examined in the next three years as part of the European research project BASE-LiNE Earth with innovative technologies and methods. In addition to answering the research questions BASE LiNE Earth serves as the training of talented young scholars and scientists who are recruited by means of a demanding selection process from all over the world and doctorate within the scope of the project. 

The EU promotes the GEOMAR Helmholtz Centre for Ocean Research Kiel coordinated project under a Marie Skłodowska-Curie Action in Horizon2020-Pogramm with a total of 3.8 million euros. The challenge for the future BASE-LiNE Earth-doctoral students, is to provide information to gain from distant epochs of earth's history. "When historians want to know about events 100 or 200 years ago, they visit libraries or archives where there is written evidence from these times," says project coordinator Prof. Dr. Anton Eisenhauer from GEOMAR. "We also use archives. 
However, they see something different. It is, for example, the calcareous shells of fossil brachiopods in which the relevant data on the chemical history of ocean water are stored reliably, "explains the Kiel geochemist on. 

The information is in the calcite shells of course not writing before, but encrypted in the chemical and mineralogical composition. "If we precise the ratios of elements such as strontium, magnesium, boron, or measure of the isotopic to each other, we can decrypt the information," says Professor Eisenhauer.

This then the age of the shell, as well as the chemical composition of the previous ocean and prevailing environmental conditions such as water temperature and the acidity of the water can be reconstructed. We know, for example, know that during the greatest mass extinction 251 million years ago, the ocean contained no oxygen and was acidified to a large extent. 

"This is similar to some scenarios that we expect for the future of our ocean," explains Professor Eisenhauer. Model calculations are carried out within the framework of the project should show how far the former changes in the environment are transferable to the present day. The challenge is to gain this information and to make it usable. In collaboration with industry partners modern analytical methods for obtaining information in cooperation with business partners in this area in the context of BASE-LiNE Earth therefore be generated and developed. The project involves a total of 21 scientific institutions from eight European countries and partners from Canada, Israel, Palestine and Australia involved. 15 PhD positions will announce the project this spring, two of them for the GEOMAR in Kiel. 

The Integrated School of Ocean Sciences (ISOS) provides at the University of Kiel for a comprehensive training program in which the scholars not only pursue their academic goals, but also learn more professional qualifications, skills and interact with each other.  In the coming years, the parties want to do their topic also by means of exhibitions and school supplies to a wider audience. "Of course we also bind the doctoral students, which thus also learn to communicate their work understandable," says the project coordinator. For more information on the project website www.baseline-earth.eu.

Source: Geomar

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Drilling Reveals Fault Rock Architecture in New Zealand’s Central Alpine Fault

            Figure 1: Location map of study by Virginia Toy et al. Image Credit: GSA
Boulder, Colo., USA - Rocks within plate boundary scale fault zones become fragmented and altered over the earthquake cycle. They both record and influence the earthquake process. In this new open-access study published in Lithosphere on 4 Feb., Virginia Toy and colleagues document fault rocks surrounding New Zealand's active Alpine Fault, which has very high probability of generating a magnitude 8 or greater earthquake in the near future.

Descriptions already suggest that the complex fault rock sequence results from slip at varying rates during multiple past earthquakes, and even sometimes during aseismic slip. They also characterize this fault before rupture; Toy and colleagues anticipate that repeat observations after the next event will provide a previously undescribed link between changes in fault rocks and the ground shaking response. They write that in the future this sort of data might allow realistic ground shaking predictions based on observations of other "dormant" faults.

The first phase of the Deep Fault Drilling Project (DFDP-1) yielded a continuous lithological transect through fault rock surrounding the Alpine fault (South Island, New Zealand). This allowed micrometer- to decimeter-scale variations in fault rock lithology and structure to be delineated on either side of two principal slip zones intersected by DFDP-1A and DFDP-1B. Here, we provide a comprehensive analysis of fault rock lithologies within 70 m of the Alpine fault based on analysis of hand specimens and detailed petrographic and petrologic analysis. The sequence of fault rock lithologies is consistent with that inferred previously from outcrop observations, but the continuous section afforded by DFDP-1 permits new insight into the spatial and genetic relationships between different lithologies and structures. We identify principal slip zone gouge, and cataclasite-series rocks, formed by multiple increments of shear deformation at up to coseismic slip rates. A 20−30-m-thick package of these rocks (including the principal slip zone) forms the fault core, which has accommodated most of the brittle shear displacement. 

This deformation has overprinted ultramylonites deformed mostly by grain-size-insensitive dislocation creep. Outside the fault core, ultramylonites contain low-displacement brittle fractures that are part of the fault damage zone. Fault rocks presently found in the hanging wall of the Alpine fault are inferred to have been derived from protoliths on both sides of the present-day principal slip zone, specifically the hanging-wall Alpine Schist and footwall Greenland Group. This implies that, at seismogenic depths, the Alpine fault is either a single zone of focused brittle shear that moves laterally over time, or it consists of multiple strands. Ultramylonites, cataclasites, and fault gouge represent distinct zones into which deformation has localized, but within the brittle regime, particularly, it is not clear whether this localization accompanies reductions in pressure and temperature during exhumation or whether it occurs throughout the seismogenic regime. These two contrasting possibilities should be a focus of future studies of fault zone architecture.

Source:GSA

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A Long dry spell doomed Mexican city 1,000 years ago

Ruins of the city of Cantona in the Mexican state of Puebla, with the mountain Cerro Pizarro in the background. The city was abandoned almost 1,000 years ago, probably as a result of a prolonged dry spell. (Ines Urdaneta image courtesy of Wikimedia Commons.)

A UC Berkeley study sheds new light on this question, providing evidence that a prolonged period of below-average rainfall was partly responsible for the abandonment of one such city, Cantona, between A.D. 900 and A.D. 1050.

At its peak, Cantona, located in a dry, volcanic basin (La Cuenca Oriental) east of today’s Mexico City, was one of the largest cities in the New World, with 90,000 inhabitants. The area was a major source of obsidian, and the city may have played a military role alongside an important trade route from the Veracruz coast into the highlands.

To assess the climate in that area before and after Cantona’s collapse, UC Berkeley geographers analyzed sediment cores from a lake located 20 miles south of the former city. They found evidence of a 650-year period of frequent droughts that extended from around A.D. 500 to about A.D. 1150. This was part of a long-term drying trend in highland Mexico that started 2,200 years ago, around 200 B.C. The climate became wetter again in about A.D. 1300, just prior to the rise of the Aztec empire.

“The decline of Cantona occurred during this dry interval, and we conclude that climate change probably played a role, at least towards the end of the city’s existence,” said lead author Tripti Bhattacharya, a UC Berkeley graduate student.

Surprisingly, the population of Cantona increased during the early part of the dry period, perhaps because of political upheaval elsewhere that increased the importance of the heavily fortified city, she said. Teotihuacan, less than 100 miles to the west, was in decline at the time, also possibly because of more frequent droughts. 

Lake Aljojuca, Mexico
The maar lake Aljojuca, 20 miles south of Cantona, yielded sediments that recorded a lengthy series of droughts between A.D. 500 and 1150. (Tripti Bhattacharya photo)

“In a sense the area became important because of the increased frequency of drought,” said UC Berkeley associate professor of geography Roger Byrne. “But when the droughts continued on such a scale, the subsistence base for the whole area changed and people just had to leave. The city was abandoned.”

Bhattacharya, Byrne and their colleagues report their findings in an article appearing this week in the early edition of the journal Proceedings of the National Academy of Sciences. The UC Berkeley researchers analyzed lake cores provided by scientists at the National Autonomous University of Mexico in Juriquilla, Querétaro, Mexico and the German Research Centre for Geosciences in Potsdam, Germany.

Political upheaval and climate change

Byrne emphasized that the area’s typical monsoon weather with wet summers and dry winters did not stop, but was interrupted by frequent short-term droughts, no doubt affecting crops and water supplies. Today the area is close to the northern limit of maize production without irrigation, and would have been particularly vulnerable to drier conditions, he said.

Byrne, a member of the Berkeley Initiative on Global Change Biology (BiGCB) and curator of fossil pollen in the Museum of Paleontology, has studied sediment cores from many lakes in Mexico and California, and is particularly interested in possible links between climate change and human activities.

Nearly 20 years ago, he learned of Cantona and traveled with students to the areas three times to obtain cores from lakes near the site, most of which are maar lakes created by magma explosions. They are deep and often contain undisturbed and regularly layered sediments ideal for chronological studies.

Tripti Bhattacharya
Tripti Bhattacharya analyzed carbonates in lake sediments to explore the climate history of the Cuenca Oriental east of Mexico City. (Ellie Broadman photo)

German colleagues cored this particular lake, Aljojuca, in 2007, and Bhattacharya traveled to Potsdam to collect sediment samples. Oxygen isotope ratios in carbonate sediments are correlated with the ratio of precipitation to evaporation and thus indicate aridity. Organic material in the sediments was used for accelerator mass spectroscopy carbon-14 dating.

“We can show that both the growth and decline of the site took place during a time period of frequent drought, which forces us to think in more nuanced ways about how political and social factors interact with environmental factors to cause social and cultural change,” Bhattacharya said. “That makes the study particularly interesting.”

Bhattacharya noted that more studies are necessary to reconstruct the prehistoric climate of highland Mexico. Such studies could reveal the causes of prehistoric climatic change and whether they were similar to the factors that regulate the region’s climate today, such as the El Niño/Southern Oscillation.

Co-authors include Harald Böhnel and Kurt Wogau of UNAM, Juriquilla; Ulrike Kienel of the German Research Center for Geosciences in Potsdam; B. Lynn Ingram of UC Berkeley; and Susan Zimmerman of Lawrence Livermore National Laboratory. The work was funded by the National Science Foundation.

Source: UC Berkeley

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Switching to vehicles powered by electricity from renewables could save lives - Video

Use of corn ethanol or electricity from coal worse than gasoline for public health

Driving vehicles that use electricity from renewable energy instead of gasoline could reduce the resulting deaths due to air pollution by 70 percent. This finding comes from a new life cycle analysis of conventional and alternative vehicles and their air pollution-related public health impacts, published Monday, Dec. 15, 2014, in the Proceedings of the National Academy of Sciences.

The study also shows that switching to vehicles powered by electricity made using natural gas yields large health benefits. Conversely, vehicles running on corn ethanol or vehicles powered by coal-based or "grid average" electricity are worse for health; switching from gasoline to those fuels would increase the number of resulting deaths due to air pollution by 80 percent or more.

“These findings demonstrate the importance of clean electricity, such as from natural gas or renewables, in substantially reducing the negative health impacts of transportation,” said Chris Tessum, co-author on the study and a researcher in the Department of Civil, Environmental, and Geo- Engineering in the University of Minnesota’s College of Science and Engineering.

The University of Minnesota team estimated how concentrations of two important pollutants—particulate matter and ground-level ozone—change as a result of using various options for powering vehicles. Air pollution is the largest environmental health hazard in the U.S., in total killing more than 100,000 people per year. Air pollution increases rates of heart attack, stroke, and respiratory disease.

The authors looked at liquid biofuels, diesel, compressed natural gas, and electricity from a range of conventional and renewable sources. Their analysis included not only the pollution from vehicles, but also emissions generated during production of the fuels or electricity that power them. With ethanol, for example, air pollution is released from tractors on farms, from soils after fertilizers are applied, and to supply the energy for fermenting and distilling corn into ethanol.

“Our work highlights the importance of looking at the full life cycle of energy production and use, not just at what comes out of tailpipes,” said Bioproducts and Biosystems Engineering Assistant Professor Jason Hill, co-author of the study. “We greatly underestimate transportation’s impacts on air quality if we ignore the upstream emissions from producing fuels or electricity.”

The researchers also point out that whereas recent studies on life cycle environmental impacts of transportation have focused mainly on greenhouse gas emissions, it is also important to consider air pollution and health. Their study provides a unique look at where life cycle emissions occur, how they move in the environment, and where people breathe that pollution. Their results provide unprecedented detail on the air quality-related health impacts of transportation fuel production and use.

“Air pollution has enormous health impacts, including increasing death rates across the U.S.,” said Civil, Environmental and Geo- Engineering Associate Professor Julian Marshall, co-author on this study. “This study provides valuable new information on how some transportation options would improve or worsen those health impacts.”

The study’s authors are Marshall and Tessum (College of Science and Engineering) and Hill (College of Food, Agricultural and Natural Resource Sciences), at the University of Minnesota. Marshall and Hill are also Resident Fellows of the University’s Institute on the Environment. This research was supported by the University of Minnesota’s Initiative for Renewable Energy and the Environment (IREE), the Office of Energy Efficiency & Renewable Energy of the U.S. Dept. of Energy (EERE/DOE), and the Agricultural and Food Research Initiative of the U.S. Dept. of Agriculture (USDA/AFRI).

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Source: University of Minnesota

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Predicting the predator threatening a squirrel by analyzing its sounds and tail movements

Thaddeus McRae poses in the Gifford Arboretum with his remote-controlled cat, after being interviewed by WSVN. Credit: University of Miami College of Arts and Sciences

Everyone has watched squirrels playfully climbing trees, gracefully leaping from branch to branch, and scurrying across parks. Thaddeus McRae, Ph.D '12, adjunct assistant research professor of biology in the University of Miami College of Arts Sciences, has taken these observations to a scientific level.

McRae studied squirrel colonies on the Coral Gables campus to see how their sounds and tail movements differ in response to different kinds of threats. He is looking to discover why squirrels interact using both vocalizations and gestures.

"These multimodal signals, which simultaneously send information via two or more sensory modalities to communicate, are ubiquitous," McRae said, adding that people and other mammals, birds, insects and spiders -- and even some plants -- communicate in this manner.

The different sounds, expressions and gestures might "reinforce each other, or maybe they contain different information, or maybe they reach different audiences," he said.

To conduct his research -- the basis of his Ph.D. dissertation -- McRae designed a unique tool: a remote-controlled cat, which he used to chase squirrels while recording their reactions to ground-based predators. Gliders painted to resemble hawks showed the squirrels' responses to threats from the air.

McRae has become somewhat of a local celebrity scientist, with recent and upcoming stories about his study appearing on the Miami New Times "Riptide" blog, and WSVN. He sees three reasons for this media attention.

Squirrels "are often most abundant in the same places people are most abundant," McRae said, adding that they're "cute and fuzzy with a bushy tail, which for some people goes a long way toward earning goodwill."

He also conducted his research in a "very public setting, outdoors on UM's campus in the middle of the city." McRae believes that this helps to breakdown the "mysterious aura" of science, "putting scientific curiosity out there where passersby can see it and become curious themselves."

Finally, he admits that "there's something a little bit humorous" about his research process and his unusual tools.

"To me, this squirrel study isn't cool because I used remote control cats, although enjoying whatever tools you use is nice, it's cool because we learned something about squirrels that we didn't know before," McRae said.

Over two years of observation McRae, working closely with Professor of Biology Steven Green, found that he could quite accurately predict what type of predator was threatening a squirrel by analyzing its sounds and tail movements.

He measured the response of three distinct squirrel sounds: the "kuk" (a short bark), the "quaa" (a longer squeal) and the "moan" (a whistling sound).

He also looked for specific patterns for tail motions in combination with these noises. The "twitch" involves a controlled movement in an arc shape, while the "flag" can take the shape of an arc, figure eight, circle or squiggle.

McRae theorizes that the squirrels use the vocal and tail alarm calls for two purposes -- to let predators know that they have been spotted, and to warn other squirrels of danger in the area. To this end, he is now conducting follow-up research to determine how squirrels react to distress signals from their peers.

For both his current study and his dissertation research, McRae has worked extensively with undergraduate research assistants.

"I try to give them a taste of various steps in the process, from thinking about the organisms and asking questions, to collecting data, to the sometimes tedious task of converting those data into analyzable form, to drawing conclusions. I share with them the joy of discovery," he said.

"Even a small, fast research project can show us something we never knew before. It may not shake the earth, but it's another tiny piece of understanding. ... For a young student to be one of the first handful of people on Earth to share even a small discovery is, frankly, freaking awesome."

Source: University of Miami

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Magma pancakes beneath Indonesia's Lake Toba: Subsurface sources of mega-eruptions

Lake Toba, Indonesia

The tremendous amounts of lava that are emitted during super-eruptions accumulate over millions of years prior to the event in the Earth's crust. These reservoirs consist of magma that intrudes into the crust in the form of numerous horizontally oriented sheets resting on top of each other like a pile of pancakes.

A team of geoscientists from Novosibirsk, Paris and Potsdam presents these results in the current issue of Science. The scientists investigate the question on where the tremendous amounts of material that are ejected to from huge calderas during super-eruptions actually originate. Here we are not dealing with large volcanic eruptions of the size of Pinatubo of Mount St. Helens, here we are talking about extreme events: The Toba caldera in the Sumatra subduction zone in Indonesia originated from one of the largest volcanic eruption in recent Earth history, about 74,000 years ago. It emitted the enormous amount of 2,800 cubic kilometers of volcanic material with a dramatic global impact on climate and environment. Hereby, the 80 km long Lake Toba was formed.

Geoscientists were interested in finding out: How can the gigantic amounts of eruptible material required to form such a super volcano accumulate in the Earth's crust. Was this a singular event thousands of years ago or can it happen again?

Researchers from the GFZ German Research Centre for Geosciences successfully installed a seismometer network in the Toba area to investigate these questions and provided the data to all participating scientists via the GEOFON data archive. GFZ scientist, Christoph Sens-Schönfelder, a co-author of the study explains: "With a new seismological method we were able to investigate the internal structure of the magma reservoir beneath the Toba-caldera. We found that the middle crust below the Toba supervolcano is horizontally layered." The answer thus lies in the structure of the magma reservoir. Here, below 7 kilometers the crust consists of many, mostly horizontal, magmatic intrusions still containing molten material.

New seismological technique

It was already suspected that the large volume of magma ejected during the supervolcanic eruption had slowly accumulated over the last few millions of years in the form of consequently emplaced intrusions. This could now be confirmed with the results of field measurements. The GFZ scientists used a novel seismological method for this purpose. Over a six-month period they recorded the ambient seismic noise, the natural vibrations which usually are regarded as disturbing signals. With a statistical approach they analyzed the data and discovered that the velocity of seismic waves beneath Toba depends on the direction in which the waves shear the Earth's crust. Above 7 kilometers depth the deposits of the last eruption formed a zone of low velocities. Below this depth the seismic anisotropy is caused by horizontally layered intrusions that structure the reservoir like a pile of pancakes. This is reflected in the seismic data.

Supervolcanoes

Not only in Indonesia, but also in other parts of the world there are such supervoclcanoes, which erupt only every couple of hundred thousand years but then in gigantic eruptions. Because of their size those volcanoes do not build up mountains but manifest themselves with their huge carter formed during the eruption -- the caldera. Other known supervolcanoes include the area of the Yellow-Stone-Park, volcanoes in the Andes, and the caldera of Lake-Taupo in New Zealand. The present study helps to better understand the processes that lead to such super-eruptions.

Source: Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

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Re-thinking Southern California earthquake scenarios in Coachella Valley, San Andreas Fault

New 3D numerical modeling that captures more geometric complexity of an active fault segment in southern California than any other suggests that the overall earthquake hazard for towns on the west side of the Coachella Valley such as Palm Springs may be slightly lower than previously believed. Credit: Courtesy Google Earth and UMass Amherst

New three-dimensional (3D) numerical modeling that captures far more geometric complexity of an active fault segment in southern California than any other, suggests that the overall earthquake hazard for towns on the west side of the Coachella Valley such as Palm Springs and Palm Desert may be slightly lower than previously believed.

New simulations of deformation on three alternative fault configurations for the Coachella Valley segment of the San Andreas Fault conducted by geoscientists Michele Cooke and Laura Fattaruso of the University of Massachusetts Amherst, with Rebecca Dorsey of the University of Oregon, appear in the December issue of Geosphere.

The Coachella Valley segment is the southernmost section of the San Andreas Fault in California. It has a high likelihood for a large rupture in the near future, since it has a recurrence interval of about 180 years but has not ruptured in over 300 years, the authors point out.

The researchers acknowledge that their new modeling offers "a pretty controversial interpretation" of the data. Many geoscientists do not accept a dipping active fault geometry to the San Andreas Fault in the Coachella Valley, they say. Some argue that the data do not confirm the dipping structure. "Our contribution to this debate is that we add an uplift pattern to the data that support a dipping active fault and it rejects the other models," say Cooke and colleagues.

Their new model yields an estimated 10 percent increase in shaking overall for the Coachella segment. But for the towns to the west of the fault where most people live, it yields decreased shaking due to the dipping geometry. It yields a doubling of shaking in mostly unpopulated areas east of the fault. "This isn't a direct outcome of our work but an implication," they add.

Cooke says, "Others have used a dipping San Andreas in their models but they didn't include the degree of complexity that we did. By including the secondary faults within the Mecca Hills we more accurately capture the uplift pattern of the region."

Fattaruso adds, "Others were comparing to different data sets, such as geodesy, and since we were comparing to uplift it is important that we have this complexity." In this case, geodesy is the science of measuring and representing the Earth and its crustal motion, taking into account the competition of geological processes in 3D over time.

Most other models of deformation, stress, rupture and ground shaking have assumed that the southern San Andreas Fault is vertical, say Cooke and colleagues. However, seismic, imaging, aerial magnetometric surveys and GPS-based strain observations suggest that the fault dips 60 to 70 degrees toward the northeast, a hypothesis they set out to investigate.

Specifically, they explored three alternative geometric models of the fault's Coachella Valley segment with added complexity such as including smaller faults in the nearby Indio and Mecca Hills. "We use localized uplift patterns in the Mecca Hills to assess the most plausible geometry for the San Andreas Fault in the Coachella Valley and better understand the interplay of fault geometry and deformation," they write.

Cooke and colleagues say the fault structures in their favored model agree with distributions of local seismicity, and are consistent with geodetic observations of recent strain. "Crustal deformation models that neglect the northeast dip of the San Andreas Fault in the Coachella Valley will not replicate the ground shaking in the region and therefore inaccurately estimate seismic hazard," they note.

This work was supported by the National Science Foundation.

Source:  University of Massachusetts at Amherst

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Hydraulic fracturing linked to earthquakes in Ohio

Seismograph (stock image). Hydraulic fracturing triggered a series of small earthquakes in 2013 on a previously unmapped fault in Harrison County, Ohio, according to a study. Credit: © hakandogu / Fotolia

Hydraulic fracturing triggered a series of small earthquakes in 2013 on a previously unmapped fault in Harrison County, Ohio, according to a study published in the journal Seismological Research Letters (SRL).

Nearly 400 small earthquakes occurred between Oct. 1 and Dec. 13, 2013, including 10 "positive" magnitude earthquake, none of which were reported felt by the public. The 10 positive magnitude earthquakes, which ranged from magnitude 1.7 to 2.2, occurred between Oct. 2 and 19, coinciding with hydraulic fracturing operations at nearby wells.

This series of earthquakes is the first known instance of seismicity in the area.
Hydraulic fracturing, or fracking, is a method for extracting gas and oil from shale rock by injecting a high-pressure water mixture directed at the rock to release the gas inside. The process of hydraulic fracturing involves injecting water, sand and chemicals into the rock under high pressure to create cracks. The process of cracking rocks results in micro-earthquakes. Hydraulic fracturing usually creates only small earthquakes, ones that have magnitude in the range of negative 3 (−3) to negative 1 (-1).

"Hydraulic fracturing has the potential to trigger earthquakes, and in this case, small ones that could not be felt, however the earthquakes were three orders of magnitude larger than normally expected," said Paul Friberg, a seismologist with Instrumental Software Technologies, Inc. (ISTI) and a co-author of the study.

The earthquakes revealed an east-west trending fault that lies in the basement formation at approximately two miles deep and directly below the three horizontal gas wells. The EarthScope Transportable Array Network Facility identified the first earthquakes on Oct. 2, 2013, locating them south of Clendening Lake near the town of Uhrichsville, Ohio. A subsequent analysis identified 190 earthquakes during a 39-hour period on Oct. 1 and 2, just hours after hydraulic fracturing began on one of the wells.

The micro-seismicity varied, corresponding with the fracturing activity at the wells. The timing of the earthquakes, along with their tight linear clustering and similar waveform signals, suggest a unique source for the cause of the earthquakes -- the hydraulic fracturing operation. The fracturing likely triggered slip on a pre-existing fault, though one that is located below the formation expected to confine the fracturing, according to the authors.

"As hydraulic fracturing operations explore new regions, more seismic monitoring will be needed since many faults remain unmapped." Friberg co-authored the paper with Ilya Dricker, also with ISTI, and Glenda Besana-Ostman originally with Ohio Department of Natural Resources, and now with the Bureau of Reclamation at the U.S. Department of Interior.

Source: Seismological Society of America

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Fracking: Gas leaks from faulty wells linked to contamination in some groundwater

As researchers study hydraulic fracturing, a team led by Thomas Darrah at The Ohio State University has identified a key source of groundwater contamination (labeled 5, center right) caused by faulty well casings.
Credit: Image courtesy of Thomas Darrah, The Ohio State University

A study has pinpointed the likely source of most natural gas contamination in drinking-water wells associated with hydraulic fracturing, and it's not the source many people may have feared.

What's more, the problem may be fixable: improved construction standards for cement well linings and casings at hydraulic fracturing sites.

A team led by a researcher at The Ohio State University and composed of researchers at Duke, Stanford, Dartmouth, and the University of Rochester devised a new method of geochemical forensics to trace how methane migrates under the earth. The study identified eight clusters of contaminated drinking-water wells in Pennsylvania and Texas.

Most important among their findings, published this week in the Proceedings of the National Academy of Sciences, is that neither horizontal drilling nor hydraulic fracturing of shale deposits seems to have caused any of the natural gas contamination.

"There is no question that in many instances elevated levels of natural gas are naturally occurring, but in a subset of cases, there is also clear evidence that there were human causes for the contamination," said study leader Thomas Darrah, assistant professor of earth sciences at Ohio State. "However our data suggests that where contamination occurs, it was caused by poor casing and cementing in the wells," Darrah said.

In hydraulic fracturing, water is pumped underground to break up shale at a depth far below the water table, he explained. The long vertical pipes that carry the resulting gas upward are encircled in cement to keep the natural gas from leaking out along the well. The study suggests that natural gas that has leaked into aquifers is the result of failures in the cement used in the well.

"Many of the leaks probably occur when natural gas travels up the outside of the borehole, potentially even thousands of feet, and is released directly into drinking-water aquifers" said Robert Poreda, professor of geochemistry at the University of Rochester.

"These results appear to rule out the migration of methane up into drinking water aquifers from depth because of horizontal drilling or hydraulic fracturing, as some people feared," said Avner Vengosh, professor of geochemistry and water quality at Duke.

"This is relatively good news because it means that most of the issues we have identified can potentially be avoided by future improvements in well integrity," Darrah said.

"In some cases homeowner's water has been harmed by drilling," said Robert B. Jackson, professor of environmental and earth sciences at Stanford and Duke. "In Texas, we even saw two homes go from clean to contaminated after our sampling began."

The method that the researchers used to track the source of methane contamination relies on the basic physics of the noble gases (which happen to leak out along with the methane). Noble gases such as helium and neon are so called because they don't react much with other chemicals, although they mix with natural gas and can be transported with it.

That means that when they are released underground, they can flow long distances without getting waylaid by microbial activity or chemical reactions along the way. The only important variable is the atomic mass, which determines how the ratios of noble gases change as they tag along with migrating natural gas. These properties allow the researchers to determine the source of fugitive methane and the mechanism by which it was transported into drinking water aquifers.

The researchers were able to distinguish between the signatures of naturally occurring methane and stray gas contamination from shale gas drill sites overlying the Marcellus shale in Pennsylvania and the Barnett shale in Texas.

The researchers sampled water from the sites in 2012 and 2013. Sampling sites included wells where contamination had been debated previously; wells known to have naturally high level of methane and salts, which tend to co-occur in areas overlying shale gas deposits; and wells located both within and beyond a one-kilometer distance from drill sites.

As hydraulic fracturing starts to develop around the globe, including countries South Africa, Argentina, China, Poland, Scotland, and Ireland, Darrah and his colleagues are continuing their work in the United States and internationally. And, since the method that the researchers employed relies on the basic physics of the noble gases, it can be employed anywhere. Their hope is that their findings can help highlight the necessity to improve well integrity.

Source: Ohio State University

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Environmental costs, health risks, and benefits of fracking examined

This is a fracking operations at a well pad near a farm over the Marcellus shale formation in Pennsylvania.
Credit: Robert Jackson, Stanford University

A strange thing happened on the way to dealing with climate change: Advances in hydraulic fracturing put trillions of dollars' worth of previously unreachable oil and natural gas within humanity's grasp.

The environmental costs -- and benefits -- from "fracking," which requires blasting huge amounts of water, sand and chemicals deep into underground rock formations, are the subject of new research that synthesizes 165 academic studies and government databases. The survey covers not only greenhouse gas impacts but also fracking's influence on local air pollution, earthquakes and, especially, supplies of clean water.

The authors are seven environmental scientists who underscore the real consequences of policy decisions on people who live near the wells, as well as some important remaining questions.
"Society is certain to extract more gas and oil due to fracking," said Stanford environmental scientist Robert Jackson, who led the new study. "The key is to reduce the environmental costs as much as possible, while making the most of the environmental benefits."

Fracking's consumption of water is rising quickly at a time when much of the United States is suffering from drought, but extracting natural gas with hydraulic fracturing and horizontal drilling compares well with conventional energy sources, the study finds. Fracking requires more water than conventional gas drilling; but when natural gas is used in place of coal or nuclear fuel to generate electricity, it saves water. From mining to generation, coal power consumes more than twice the water per megawatt-hour generated than unconventional gas does.

Unconventional drilling's water demand can be better or worse than alternative energy sources, the study finds. Photovoltaic solar and wind power use almost no water and emit no greenhouse gas, but cheap, abundant natural gas may limit their deployment as new sources of electricity. On the other hand, fracked gas requires less than a hundredth the water of corn ethanol per unit of energy.

Fracking's impact on both climate change and local air pollution is similar to its impact on water, finds the study "The Environmental Costs and Benefits of Fracking," published in the Annual Review of Environment and Resources.

Getting a fractured well going is more intense than for conventional oil and gas drilling, with potential health threats arising from increases in volatile organic compounds and air toxics.

But when natural gas replaces coal as a fuel for generating electricity, the benefits to air quality include lower carbon dioxide emissions than coal and almost none of the mercury, sulfur dioxide or ash.

Globally, though, relief to climate change is uncertain, the study finds. "While the increased gas supply reduces air pollution in U.S. cities downwind from coal-fired power plants, we still don't know whether methane losses from well pads and pipelines outweigh the lower carbon dioxide emissions," said Jackson.

In the eastern United States, fears of contaminated drinking water have raised more concerns than fracking's water consumption. Gas and chemicals from humanmade fractures thousands of meters underground very rarely seep upward to drinking-water aquifers, the study says. The real threats are failures in the steel and cement casings of wells nearer to the surface and the disposal of wastewater, the study finds. Numerous previous studies have shown that casings fail between 1 percent and 10 percent of the time, depending on geology and well construction.

Cases of groundwater contamination have been hotly debated, but the new study finds that the overwhelming evidence suggests it has happened, albeit not commonly. Is the methane contamination observed in drinking water a precursor to other toxins -- arsenic, various salts, radioactive radium and other metals -- making their way up slowly? The researchers do not yet know. A few recent studies suggest the answer could be "yes" in rare cases.

How oil and gas companies handle wastewater -- fluid used to fracture the shale that flows back up the well and water unleashed with the oil and gas -- shows the importance of state policies. "Wastewater disposal is one of the biggest issues associated with fracking," said co-author Avner Vengosh, a professor of geochemistry at Duke University.

Most fracking wastewater in the United States is injected deep underground, and an increasing amount is recycled for subsequent drilling or sent to advanced water treatment facilities. However, a handful of states still allow the wastewater to be used for watering cattle, sprayed onto roads for dust control or sent to municipal water-treatment plants not equipped to handle the chemicals involved.

All bad ideas, according to the authors of the new survey, who work at Duke University, MIT, Ohio State University, Newcastle University, Los Alamos National Laboratory, the National Oceanic and Atmospheric Administration and Stanford. One study they cite found that the agricultural use of fracking wastewater killed more than half of nearby trees within two years.

Injection of wastewater deep underground presents its own problems, the study finds. The practice occasionally has caused earthquakes strong enough to be felt by human beings, while the fracturing of shale miles below the surface rarely has done so. The dangers of seismicity can be reduced, however, if energy companies follow basic guidelines and undertake careful monitoring.

The study highlights several policies and practices that could optimize fracking's environmental cost-benefit balance, and it highlights the need for further research. For example, the direct impact on the health of nearby residents is virtually unknown. "Almost no comprehensive research has been done on health effects," said Jackson, "but decisions about drilling -- both approvals and bans on fracking -are made all the time based on assumptions about health risks."

Source: Stanford University

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Residual hydraulic fracturing water not a risk to groundwater

Sixty-one minutes of imbibition and evaporation of a 154 microliter bead of tap water on a 2.3 gram chip of the Union Springs Member of the Marcellus Formation. The drop disappeared in approximately 100 minutes. The photograph labeled 0 min was taken about 10 seconds after the bead was dropped on the Marcellus chip. Counter-current imbibition is indicated by methane bubbles floating up into the water bead from the Marcellus chip, starting on the left side of the bead at time = 0 min. This experiment was started 5 days after receiving fresh cuttings of the Union Springs from a horizontal well in PA.
Credit: Engelder, Penn State

Hydraulic fracturing -- fracking or hydrofracturing -- raises many concerns about potential environmental impacts, especially water contamination. Currently, data show that the majority of water injected into wells stays underground, triggering fears that it might find its way into groundwater. New research by a team of scientists should help allay those fears.

In a paper published in the current issue of the Journal of Unconventional Oil and Gas Resources, Terry Engelder, professor of geosciences, Penn State; Lawrence Cathles, professor of earth and atmospheric sciences, Cornell University; and Taras Bryndzia, geologist, Shell International Exploration and Production Inc., report that injected water that remains underground is sequestered in the rock formation and therefore does not pose a serious risk to water supplies.

Hydraulic fracturing is a drilling technique commonly used to extract gas from previously inaccessible "tight" gas reserves, including gas trapped in shale formations such as the Marcellus. During this technique between 1.2 and 5 million gallons of water mixed with sand and chemical additives are injected at high pressure into each well to fracture the rock and release the gas.

Typically less than half of the injected water returns to the surface as "flowback" or, later, production brine, and in many cases recovery is less than 30 percent. In addition to the chemical additives, flowback water contains natural components of the gas shale including salt, some metals, and radionuclides and could impair water quality if released without proper treatment. While flowback water can be managed and treated at the surface, the fate of the water left in place, called residual treatment water or RTW, was previously uncertain.

Some have suggested that RTW may be able to flow upward along natural pathways, mainly fractures and faults, and contaminate overlying groundwater. Others have proposed that natural leakage of the Marcellus is occurring without human assistance through high-permeability fractures connecting the Marcellus directly to the water table and that hydraulic fracturing could worsen this situation.

The researchers report that ground water contamination is not likely because contaminant delivery rate would be too small even if leakage were possible, but more importantly, upward migration of RTW is not plausible due to capillary and osmotic forces that propel RTW into, not out of, the shale. Their study indicates that RTW will be stably retained within the shale formation due to multiphase capillary phenomena.

"Capillary forces and coupled diffusion-osmosis processes are the reasons the brines and the RTW are not free to escape from gas shale," said Engelder. "The most direct evidence of these forces is the observation that more than half the treatment waters are not recovered. Introducing treatment water causes gas shale to act like a sponge based on the principles of imbibition.

"Imbibition into gas shale is made possible by the high capillary suction that a fine-grained, water-wet shale matrix can exert on water. As water is wicked into gas shale, the natural gas in the shale is pushed out. The capillary forces that suck the RTW into the gas shale keep it there."

Estimating imbibition is complicated, but simple experiments conducted by the researchers show that water can be readily imbibed into gas shale in quantities fully capable of sequestering RTW. The researchers demonstrated this process in a series of experiments on cuttings recovered from the Union Springs Member of the Marcellus gas shale in Pennsylvania and on core plugs of Haynesville gas shale from NW Louisiana.

"The hydraulic fracturing fluid consists mostly of very low-salinity surface water, while the shale contains high concentrations of water soluble inorganic cations and anions," said Engelder. "During hydraulic fracturing water is lost to the formation while inorganic cations and anions are transferred from the formation to the hydraulic fracture. Diffusion osmosis assists the rapid imbibition of water by the shale and diffusion of ions into the treatment water causing the high salinities observed in flowback fluids. The point to be emphasized here is that this osmotic pressure pushes the hydraulic fracture fluids into the shale matrix, expelling gas and cations to make high-salinity flowback in the process."

The researchers believe that in addition to there not being enough water in the shale to contaminate groundwater, the most important point of their work is that multiphase capillary phenomena must be considered in cases where a non-aqueous fluid is present in the subsurface pore space. The vadose zone -- the area from the surface to the groundwater -- and oil and gas migration cannot be understood using single-phase, porous-media flow methods, and any policy insights or prescriptions based on single-phase considerations will be fatally flawed, they argue.

"The practical implication is that hydrofracture fluids will be locked into the same 'permeability jail' that sequestered overpressured gas for over 200 million years," said Engelder. "If one wants to dispose of fracking waters, one could probably not choose a safer way to do so than to inject them into a gas shale."

Source: Penn State

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Nanoparticle research could enhance oil recovery, tracing of fracking fluid

William Sanford and Vivian Li.
Credit: Image courtesy of Colorado State University

Two Colorado State University researchers are examining how nanoparticles move underground, knowledge that could eventually help improve recovery in oil fields and discover where hydraulic fracking chemicals travel.

Vivian Li, assistant professor in the Department of Design and Merchandising, and William Sanford, associate professor in the Department of Geosciences, are trying to find patterns in how certain nanoparticles move underground. If successful, they could train the nanoparticles to indicate when specific chemicals are present in the subsurface, including those found in underground water deposits. These modified "smart" nanoparticles, known as tracers, could sense high pH levels or the presence of hydraulic fracking chemicals.

In the initial phase of their research, funded through a grant from the CSU Water Center, Li and Sanford are testing their specially engineered carbon nanoparticle to see how it moves through the ground. Once they understand how the particle travels through a number of subsurface environments, it could eventually be used to search for chemicals in some of Earth's most hostile underground environments.

"We also want to see how nanoparticles affect the composition of the natural environment and how certain elements found in the ground alter the composition of the nanoparticle," explained Li.
Temperature, water saturation, and the physical and chemical composition of the soil are the primary factors that can alter the movement of nanoparticles.

Hydraulic fracturing of wells has caused a political firestorm in recent years, as Colorado residents have questioned the health and safety risks of injecting chemicals into the ground to free oil and natural gas. There is still debate about whether these chemicals are harming the environment, and some question where the chemicals go after injection, fearing they may be contaminating groundwater supplies.

Using tracers, Li and Sanford theorize they could inject the particles into the earth near fracking sites and allow them to follow subsurface water flow paths to a distance away from the injection site. If the recovered tracers are fluorescent, they are reacting to the fracking chemical they were engineered to detect, demonstrating the path those chemicals traveled.

In continuation of Li's post-doctorate work, these tracers could also be used to improve the recovery of oil from reserves deep within the earth, which would allow scientists to increase the amount of oil that can be pumped, saving time and money on drilling new wells.

"Only about 50 percent of the Earth's oil reservoirs are being tapped," Li said. "With the potential to quickly drain the current oil reserves, the need to improve oil recovery and find the other hidden 50 percent becomes extremely important."

However, these reservoirs are often very deep in the ground and can be home to extreme conditions that make it difficult for nanoparticles to survive. Many nanoparticles that have been developed cannot withstand the high salinity of the oil reserve and deteriorate in the process of finding the oil. However, Li and Sanford believe they have engineered a nanoparticle that can both survive in the harsh environment and keep its smart abilities for a long period of time.

"The uses of these nanoparticles are potentially quite extensive," explained Sanford. "By creating smart particles we can see how contaminants are distributed in the subsurface, the recovery of economic minerals in water can be done, and the uses in the oil industry are many-fold."
Still in the early stages of the research, Li and Sanford are patenting their new nanoparticle and continue to test it in preparation for studies in the field.

The Department of Design and Merchandising is in CSU's College of Health and Human Sciences. The Department of Geosciences is part of the Warner College of Natural Resources.

Source: Colorado State University

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A new look at what's in 'fracking' fluids raises red flags: Some compounds toxic to mammals

Scientists are getting to the bottom of what’s in fracking fluids — with some troubling results.
Credit: Doug Duncan/U.S. Geological Survey

As the and gas drilling technique called hydraulic fracturing (or "fracking") proliferates, a new study on the contents of the fluids involved in the process raises concerns about several ingredients. The scientists presenting the work today at the 248th National Meeting & Exposition of the American Chemical Society (ACS) say that out of nearly 200 commonly used compounds, there's very little known about the potential health risks of about one-third, and eight are toxic to mammals.

William Stringfellow, Ph.D., says he conducted the review of fracking contents to help resolve the public debate over the controversial drilling practice. Fracking involves injecting water with a mix of chemical additives into rock formations deep underground to promote the release of oil and gas. It has led to a natural gas boom in the U.S., but it has also stimulated major opposition and troubling reports of contaminated well water, as well as increased air pollution near drill sites.

"The industrial side was saying, 'We're just using food additives, basically making ice cream here,'" Stringfellow says. "On the other side, there's talk about the injection of thousands of toxic chemicals.

As scientists, we looked at the debate and asked, 'What's the real story?'"
To find out, Stringfellow's team at Lawrence Berkeley National Laboratory and University of the Pacific scoured databases and reports to compile a list of substances commonly used in fracking. They include gelling agents to thicken the fluids, biocides to keep microbes from growing, sand to prop open tiny cracks in the rocks and compounds to prevent pipe corrosion.

What their analysis revealed was a little truth to both sides' stories -- with big caveats. Fracking fluids do contain many nontoxic and food-grade materials, as the industry asserts. But if something is edible or biodegradable, it doesn't automatically mean it can be easily disposed of, Stringfellow notes.
"You can't take a truckload of ice cream and dump it down the storm drain," he says, building on the industry's analogy. "Even ice cream manufacturers have to treat dairy wastes, which are natural and biodegradable. They must break them down rather than releasing them directly into the environment."
His team found that most fracking compounds will require treatment before being released. And, although not in the thousands as some critics suggest, the scientists identified eight substances, including biocides, that raised red flags. These eight compounds were identified as being particularly toxic to mammals.

"There are a number of chemicals, like corrosion inhibitors and biocides in particular, that are being used in reasonably high concentrations that potentially could have adverse effects," Stringfellow says. "Biocides, for example, are designed to kill bacteria -- it's not a benign material."

They're also looking at the environmental impact of the fracking fluids, and they are finding that some have toxic effects on aquatic life.

In addition, for about one-third of the approximately 190 compounds the scientists identified as ingredients in various fracking formulas, the scientists found very little information about toxicity and physical and chemical properties.

"It should be a priority to try to close that data gap," Stringfellow says.
He acknowledges funding from the University of the Pacific, the Bureau of Land Management and the state of California.

Source: American Chemical Society (ACS)

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Are ants the answer to carbon dioxide sequestration?

A 25-year-long study provides the first quantitative measurement of in situ calcium-magnesium silicate mineral dissolution by ants, termites, tree roots, and bare ground.

A 25-year-long study published in Geology on 14 July provides the first quantitative measurement of in situ calcium-magnesium silicate mineral dissolution by ants, termites, tree roots, and bare ground. This study reveals that ants are one of the most powerful biological agents of mineral decay yet observed. It may be that an understanding of the geobiology of ant-mineral interactions might offer a line of research on how to "geoengineer" accelerated CO2 consumption by Ca-Mg silicates.

Researcher Ronald Dorn of Arizona State University writes that over geological timescales, the dissolution of calcium (Ca) and magnesium (Mg) bearing silicates has led to the graduate drawdown of atmospheric carbon dioxide (CO2) through the accumulation of limestone and dolomite. Many contemporary efforts to sequester CO2 involve burial, with some negative environmental consequences.

Dorn suggests that, given that ant nests as a whole enhance abiotic rates of Ca-Mg dissolution by two orders of magnitude (via biologically enhanced weathering), future research leading to the isolation of ant-based enhancement process could lead to further acceleration. If ant-based enhancement could reach 100 times or greater, he writes, this process might be able to geo-engineer sequestration of CO2 from the atmosphere. Similarly, ants might also provide clues on geoengineering efficient pathways of calcium carbonate precipitation to sequester atmospheric CO2.

Earth's climate has cooled significantly over the past 65 m.y., likely from hydrologic regulation, vegetation change, and interactions related to tectonism, in part mediated by Ca-Mg silicate mineral dissolution that draws down CO2. Although speculative, says Dorn, the timing of the expansion in the variety and number of ants in the Paleogene and the Neogene suggests that biologically enhanced weathering by ants could potentially be a part of the puzzle of Cenozoic cooling.

Source: Geological Society of America

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Acid mine drainage reduces radioactivity in fracking waste

“Fracking wastewater and acid mine drainage each pose well-documented environmental and public health risks. But in laboratory tests, we found that by blending them in the right proportions we can bind some of the fracking contaminants into solids that can be removed before the water is discharged back into streams and rivers,” said Avner Vengosh.
 Credit: Duke University

Much of the naturally occurring radioactivity in fracking wastewater might be removed by blending it with another wastewater from acid mine drainage, according to a Duke University-led study.

"Fracking wastewater and acid mine drainage each pose well-documented environmental and public health risks. But in laboratory tests, we found that by blending them in the right proportions we can bind some of the fracking contaminants into solids that can be removed before the water is discharged back into streams and rivers," said Avner Vengosh, professor of geochemistry and water quality at Duke's Nicholas School of the Environment.

"This could be an effective way to treat Marcellus Shale hydraulic fracturing wastewater, while providing a beneficial use for acid mine drainage that currently is contaminating waterways in much of the northeastern United States," Vengosh said. "It's a win-win for the industry and the environment."
Blending fracking wastewater with acid mine drainage also could help reduce the depletion of local freshwater resources by giving drillers a source of usable recycled water for the hydraulic fracturing process, he added.

"Scarcity of fresh water in dry regions or during periods of drought can severely limit shale gas development in many areas of the United States and in other regions of the world where fracking is about to begin," Vengosh said. "Using acid mine drainage or other sources of recycled or marginal water may help solve this problem and prevent freshwater depletion."

The peer-reviewed study was published in late December 2013 in the journal Environmental Science & Technology.

In hydraulic fracturing -- or fracking, as it is sometimes called -- millions of tons of water are injected at high pressure down wells to crack open shale deposits buried deep underground and extract natural gas trapped within the rock. Some of the water flows back up through the well, along with natural brines and the natural gas. This "flowback fluid" typically contains high levels of salts, naturally occurring radioactive materials such as radium, and metals such as barium and strontium.

A study last year by the Duke team showed that standard treatment processes only partially remove these potentially harmful contaminants from Marcellus Shale wastewater before it is discharged back into streams and waterways, causing radioactivity to accumulate in stream sediments near the disposal site.

Acid mine drainage flows out of abandoned coal mines into many streams in the Appalachian Basin. It can be highly toxic to animals, plants and humans, and affects the quality of hundreds of waterways in Pennsylvania and West Virginia.

Because much of the current Marcellus shale gas development is taking place in regions where large amounts of historic coal mining occurred, some experts have suggested that acid mine drainage could be used to frack shale gas wells in place of fresh water.

To test that hypothesis, Vengosh and his team blended different mixtures of Marcellus Shale fracking wastewater and acid mine drainage, all of which were collected from sites in western Pennsylvania and provided to the scientists by the industry.

After 48 hours, the scientists examined the chemical and radiological contents of 26 different mixtures. Geochemical modeling was used to simulate the chemical and physical reactions that had occurred after the blending; the results of the modeling were then verified using x-ray diffraction and by measuring the radioactivity of the newly formed solids.

"Our analysis suggested that several ions, including sulfate, iron, barium and strontium, as well as between 60 and 100 percent of the radium, had precipitated within the first 10 hours into newly formed solids composed mainly of strontium barite," Vengosh said. These radioactive solids could be removed from the mixtures and safely disposed of at licensed hazardous-waste facilities, he said. The overall salinity of the blended fluids was also reduced, making the treated water suitable for re-use at fracking sites.

"The next step is to test this in the field. While our laboratory tests show that is it technically possible to generate recycled, treated water suitable for hydraulic fracturing, field-scale tests are still necessary to confirm its feasibility under operational conditions," Vengosh said.

Source: Duke University

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Natural gas saves water, even when factoring in water lost to hydraulic fracturing

For every gallon of water used to produce natural gas through hydraulic fracturing, Texas saved 33 gallons of water by generating electricity with that natural gas instead of coal (in 2011).

A new study finds that in Texas, the U.S. state that annually generates the most electricity, the transition from coal to natural gas for electricity generation is saving water and making the state less vulnerable to drought.

Even though exploration for natural gas through hydraulic fracturing requires significant water consumption in Texas, the new consumption is easily offset by the overall water efficiencies of shifting electricity generation from coal to natural gas. The researchers estimate that water saved by shifting a power plant from coal to natural gas is 25 to 50 times as great as the amount of water used in hydraulic fracturing to extract the natural gas. Natural gas also enhances drought resilience by providing so-called peaking plants to complement increasing wind generation, which doesn't consume water.

The results of The University of Texas at Austin study are published this week in the journal Environmental Research Letters.

The researchers estimate that in 2011 alone, Texas would have consumed an additional 32 billion gallons of water -- enough to supply 870,000 average residents -- if all its natural gas-fired power plants were instead coal-fired plants, even after factoring in the additional consumption of water for hydraulic fracturing to extract the natural gas.

Hydraulic fracturing is a process in which water, sand and chemicals are pumped at high pressure into a well to fracture surrounding rocks and allow oil or gas to more easily flow. Hydraulic fracturing and horizontal drilling are the main drivers behind the current boom in U.S. natural gas production.
Environmentalists and others have raised concerns about the amount of water that is consumed. In Texas, concerns are heightened because the use of hydraulic fracturing is expanding rapidly while water supplies are dwindling as the third year of a devastating drought grinds on. Because most electric power plants rely on water for cooling, the electric power supply might be particularly vulnerable to drought.

"The bottom line is that hydraulic fracturing, by boosting natural gas production and moving the state from water-intensive coal technologies, makes our electric power system more drought resilient," says Bridget Scanlon, senior research scientist at the university's Bureau of Economic Geology, who led the study.

To study the drought resilience of Texas power plants, Scanlon and her colleagues collected water use data for all 423 of the state's power plants from the Energy Information Administration and from state agencies including the Texas Commission on Environmental Quality and the Texas Water Development Board, as well as other data.

Since the 1990s, the primary type of power plant built in Texas has been the natural gas combined cycle (NGCC) plant with cooling towers, which uses fuel and cooling water more efficiently than older steam turbine technologies. About a third of Texas power plants are NGCC. NGCC plants consume about a third as much water as coal steam turbine (CST) plants.

The other major type of natural gas plant in the state is a natural gas combustion turbine (NGCT) plant. NGCT plants can also help reduce the state's water consumption for electricity generation by providing "peaking power" to support expansion of wind energy. Wind turbines don't require water for cooling; yet wind doesn't always blow when you need electricity. NGCT generators can be brought online in a matter of seconds to smooth out swings in electricity demand. By combining NGCT generation with wind generation, total water use can be lowered even further compared with coal-fired power generation.

The study focused exclusively on Texas, but the authors believe the results should be applicable to other regions of the U.S., where water consumption rates for the key technologies evaluated -- hydraulic fracturing, NGCC plants with cooling towers and traditional coal steam turbine plants -- are generally the same.

The Electric Reliability Council of Texas, manager of the state's electricity grid, projects that if current market conditions continue through 2029, 65 percent of new power generation in the state will come from NGCC plants and 35 percent from natural gas combustion turbine plants, which use no water for cooling, but are less energy efficient than NGCC plants.

"Statewide, we're on track to continue reducing our water intensity of electricity generation," says Scanlon.

Hydraulic fracturing accounts for less than 1 percent of the water consumed in Texas. But in some areas where its use is heavily concentrated, it strains local water supplies, as documented in a 2011 study by Jean-Philippe Nicot of the Bureau of Economic Geology. Because natural gas is often used far from where it is originally produced, water savings from shifting to natural gas for electricity generation might not benefit the areas that use more water for hydraulic fracturing.


Source: University of Texas at Austin.

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