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  • MEDLINE/PubMed (NLM)  (57)
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  • 1
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 19 May 2015, Vol.112(20), pp.6325-30
    Description: High-volume hydraulic fracturing (HVHF) has revolutionized the oil and gas industry worldwide but has been accompanied by highly controversial incidents of reported water contamination. For example, groundwater contamination by stray natural gas and spillage of brine and other gas drilling-related fluids is known to occur. However, contamination of shallow potable aquifers by HVHF at depth has never been fully documented. We investigated a case where Marcellus Shale gas wells in Pennsylvania caused inundation of natural gas and foam in initially potable groundwater used by several households. With comprehensive 2D gas chromatography coupled to time-of-flight mass spectrometry (GCxGC-TOFMS), an unresolved complex mixture of organic compounds was identified in the aquifer. Similar signatures were also observed in flowback from Marcellus Shale gas wells. A compound identified in flowback, 2-n-Butoxyethanol, was also positively identified in one of the foaming drinking water wells at nanogram-per-liter concentrations. The most likely explanation of the incident is that stray natural gas and drilling or HF compounds were driven ∼ 1-3 km along shallow to intermediate depth fractures to the aquifer used as a potable water source. Part of the problem may have been wastewaters from a pit leak reported at the nearest gas well pad-the only nearby pad where wells were hydraulically fractured before the contamination incident. If samples of drilling, pit, and HVHF fluids had been available, GCxGC-TOFMS might have fingerprinted the contamination source. Such evaluations would contribute significantly to better management practices as the shale gas industry expands worldwide.
    Keywords: Marcellus Shale ; High-Volume Hydraulic Fracturing ; Natural Gas ; Shale Gas ; Water Quality ; Water Movements ; Extraction and Processing Industry -- Methods ; Groundwater -- Chemistry ; Natural Gas -- Adverse Effects ; Water Pollutants, Chemical -- Analysis ; Water Supply -- Analysis
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 2
    Language: English
    In: Physical review. E, Statistical, nonlinear, and soft matter physics, December 2015, Vol.92(6), pp.062114
    Description: The topography of a reactive surface contains information about the reactions that form or modify the surface and, therefore, it should be possible to characterize reactivity using topography parameters such as surface area, roughness, or fractal dimension. As a test of this idea, we consider a two-dimensional (2D) lattice model for crystal dissolution and examine a suite of topography parameters to determine which may be useful for predicting rates and mechanisms of dissolution. The model is based on the assumption that the reactivity of a surface site decreases with the number of nearest neighbors. We show that the steady-state surface topography in our model system is a function of, at most, two variables: the ratio of the rate of loss of sites with two neighbors versus three neighbors (d(2)/d(3)) and the ratio of the rate of loss of sites with one neighbor versus three neighbors (d(1)/d(3)). This means that relative rates can be determined from two parameters characterizing the topography of a surface provided that the two parameters are independent of one another. It also means that absolute rates cannot be determined from measurements of surface topography alone. To identify independent sets of topography parameters, we simulated surfaces from a broad range of d(1)/d(3) and d(2)/d(3) and computed a suite of common topography parameters for each surface. Our results indicate that the fractal dimension D and the average spacing between steps, E[s], can serve to uniquely determine d(1)/d(3) and d(2)/d(3) provided that sufficiently strong correlations exist between the steps. Sufficiently strong correlations exist in our model system when D〉1.5 (which corresponds to D〉2.5 for real 3D reactive surfaces). When steps are uncorrelated, surface topography becomes independent of step retreat rate and D is equal to 1.5. Under these conditions, measures of surface topography are not independent and any single topography parameter contains all of the available mechanistic information about the surface. Our results also indicate that root-mean-square roughness cannot be used to reliably characterize the surface topography of fractal surfaces because it is an inherently noisy parameter for such surfaces with the scale of the noise being independent of length scale.
    Keywords: Physics;
    ISSN: 15393755
    E-ISSN: 1550-2376
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  • 3
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 04 December 2018, Vol.115(49), pp.12349-12358
    Description: Extensive development of shale gas has generated some concerns about environmental impacts such as the migration of natural gas into water resources. We studied high gas concentrations in waters at a site near Marcellus Shale gas wells to determine the geological explanations and geochemical implications. The local geology may explain why methane has discharged for 7 years into groundwater, a stream, and the atmosphere. Gas may migrate easily near the gas wells in this location where the Marcellus Shale dips significantly, is shallow (∼1 km), and is more fractured. Methane and ethane concentrations in local water wells increased after gas development compared with predrilling concentrations reported in the region. Noble gas and isotopic evidence are consistent with the upward migration of gas from the Marcellus Formation in a free-gas phase. This upflow results in microbially mediated oxidation near the surface. Iron concentrations also increased following the increase of natural gas concentrations in domestic water wells. After several months, both iron and SO concentrations dropped. These observations are attributed to iron and SO reduction associated with newly elevated concentrations of methane. These temporal trends, as well as data from other areas with reported leaks, document a way to distinguish newly migrated methane from preexisting sources of gas. This study thus documents both geologically risky areas and geochemical signatures of iron and SO that could distinguish newly leaked methane from older methane sources in aquifers.
    Keywords: Hydraulic Fracturing ; Methane ; Noble Gases ; Shale Gas ; Water Quality
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 4
    Language: English
    In: Science of the Total Environment, 15 May 2015, Vol.515-516, pp.49-59
    Description: Atmospheric emissions of metals from anthropogenic activities have led to deposition and contamination of soils worldwide. We quantified addition of manganese (Mn) to soils around the largest emitter of Mn in the United States (U.S.) using chemical analyses and atmospheric dispersion modeling (Second-Order Closure Integrated Puff (SCIPUFF)). Concentrations of soil-surface Mn were enriched by 9-fold relative to that of the parent material within 1 km of the facility. Elevated concentrations of Mn and chromium (Cr), another potentially toxic element that was emitted, document contamination only within 1 m of the soil surface. Total mass of Mn added per unit land area integrated over 1 m, , equals ~ 80 mg Mn cm near the facility. Values of remained above background up to tens of kilometers from the source. Air concentrations of Mn particles of 7.5-micron diameter simulated with SCIPUFF using available data for the emission rate and local meteorological conditions for 2006 were consistent with measured air concentrations. However, the Mn deposition calculated for 2006 with SCIPUFF yielded a cumulative value over the lifetime of the refinery (60 years) that is a factor of 15 lower than the Mn observed to have been added to the soils. This discrepancy can be easily explained if Mn deposition rates before 1988 were more than an order of magnitude greater than today. Such higher emissions are probable, given the changes in metal production with time and the installation of emission controls after the Clean Air Act (1970). This work shows that atmospheric dispersion models can be used with soil profiles to understand the changes in metal emissions over decadal timescales. In addition, the calculations are consistent with the Clean Air Act accounting for a 15-fold decrease in the Mn deposition to soils around the refinery per metric ton of Mn alloy produced.
    Keywords: Scipuff ; Metal Deposition ; Industrial Emissions ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 5
    Language: English
    In: Ground water, 2015, Vol.53(1), pp.21-3
    Description: The data provided by the PA DEP are incomplete because confidential data are not released. It is impossible to make firm conclusions about water quality impacts when data availability is limited. Nonetheless, the PA experience appears to be characterized by a low rate of problems per gas well or unit of gas produced. Only about 160 of the complaints from homeowners about groundwater to the PA DEP between 2008 and 2012 were problems attributed to oil and gas activity—and only half of these were caused by companies known to drill unconventional shale wells. These problematic wells in turn represent only 0.1 to 1% of the unconventional shale gas wells drilled in that time period (Brantley et al. 2014). Management practices appear to be improving as well; the rate of problems has decreased since 2010 (Figure 1). Apparently, however, the public responds not only to the number of problems per gas well or per unit of gas produced but rather to the number of problems per unit time and per unit area. Thus, even though the r ate of problems with shale gas wells has remained small on a per well basis, pushback has grown in areas of increasing density of drilling and fracking. This may be especially true when consequences are fearsome such as flaming tapwater, toxic contamination, or earthquakes. It is natural that the social license for shale gas development is influenced by short-term, local thinking. But, such thinking may not be helpful given that Marcellus Shale gas wells generate one third the waste per unit volume of gas as compared to conventional shallow gas wells (Vidic et al. 2013). In addition, the release of pollutants such as carbon dioxide, particulates, mercury, nitrogen, and sulfur generated per unit of heat energy is lower f or unconventional shale gas than for fuels such as coal (Heath et al. 2014). Public pushback could nonetheless be a blessing. After all, pushback represents intensified interest in environmental issues. This interest may be seen in the PA DEP data for the rate of well integrity issues in conventional oil and gas wells—the increase in problem rate from 2008 to 2012 (Figure 1) is more likely due to heightened public attention and inspector scrutiny rather than a sudden deterioration in the management practices of the drilling companies (Brantley et al. 2014) During the next decades, the rate of hydraulic fracturing in PA will eventually slow. At some point, the use of produced brines to hydrofracture new wells will cease. Once recycling of brine to frack new wells stops, hundreds of gallons of brine will accumulate as waste at each well per day (Rahm et al. 2013). Disposal of this slightly radioactive brine will then become increasingly problematic. Interest on the part of the public for such issues is warranted. Public engagement today is needed to develop sustainable waste management and sustainable energy practices for the future.
    Keywords: Oil and Gas Fields ; Groundwater -- Chemistry ; Water Pollutants, Chemical -- Analysis ; Water Pollution, Chemical -- Prevention & Control
    E-ISSN: 1745-6584
    Source: MEDLINE/PubMed (U.S. National Library of Medicine)
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  • 6
    Language: English
    In: 2014, Vol.9(8), p.e104336
    Description: When Geobacter sulfurreducens utilizes an electrode as its electron acceptor, cells embed themselves in a conductive biofilm tens of microns thick. While environmental conditions such as pH or redox potential have been shown to change close to the electrode, less is known about the response of G. sulfurreducens to growth in this biofilm environment. To investigate whether respiratory protein abundance varies with distance from the electrode, antibodies against an outer membrane multiheme cytochrome (OmcB) and cytoplasmic acetate kinase (AckA) were used to determine protein localization in slices spanning ∼25 µm-thick G. sulfurreducens biofilms growing on polished electrodes poised at +0.24 V (vs. Standard Hydrogen Electrode). Slices were immunogold labeled post-fixing, imaged via transmission electron microscopy, and digitally reassembled to create continuous images allowing subcellular location and abundance per cell to be quantified across an entire biofilm. OmcB was predominantly localized on cell membranes, and 3.6-fold more OmcB was detected on cells 10–20 µm distant from the electrode surface compared to inner layers (0–10 µm). In contrast, acetate kinase remained constant throughout the biofilm, and was always associated with the cell interior. This method for detecting proteins in intact conductive biofilms supports a model where the utilization of redox proteins changes with depth.
    Keywords: Research Article ; Biology And Life Sciences ; Engineering And Technology ; Physical Sciences ; Research And Analysis Methods
    E-ISSN: 1932-6203
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  • 7
    Language: English
    In: Environmental science & technology, 20 March 2018, Vol.52(6), pp.3342-3343
    ISSN: 0013936X
    E-ISSN: 1520-5851
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  • 8
    Language: English
    In: Environmental science & technology, 01 January 2011, Vol.45(1), pp.241-7
    Description: It is well-known that metals are emitted to the air by human activities and subsequently deposited to the land surface; however, we have not adequately evaluated the geographic extent and ecosystem impacts of industrial metal loading to soils. Here, we demonstrate that atmospheric inputs have widely contaminated soils with Mn in industrialized regions. Soils record elemental fluxes impacting the Earth's surface and can be analyzed to quantify inputs and outputs during pedogenesis. We use a mass balance model to interpret details of Mn enrichment by examining soil, bedrock, precipitation, and porefluid chemistry in a first-order watershed in central Pennsylvania, USA. This reveals that ∼ 53% of Mn in ridge soils can be attributed to atmospheric deposition from anthropogenic sources. An analysis of published data sets indicates that over half of the soils surveyed in Pennsylvania (70%), North America (60%), and Europe (51%) are similarly enriched in Mn. We conclude that soil Mn enrichment due to industrial inputs is extensive, yet patchy in distribution due to source location, heterogeneity of lithology, vegetation, and other attributes of the land surface. These results indicate that atmospheric transport must be considered a potentially critical component of the global Mn cycle during the Anthropocene.
    Keywords: Air Pollutants -- Analysis ; Manganese -- Analysis ; Soil -- Chemistry ; Soil Pollutants -- Analysis
    ISSN: 0013936X
    E-ISSN: 1520-5851
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  • 9
    Language: English
    In: The journal of physical chemistry. A, 12 January 2006, Vol.110(1), pp.198-206
    Description: Molecular orbital energy minimizations were performed with the B3LYP/6-31G(d) method on a [((OH)3SiO)3SiOH-(H3O+).4(H2O)] cluster to follow the reaction path for hydrolysis of an Si-O-Si linkage via proton catalysis in a partially solvated system. The Q3 molecule was chosen (rather than Q2 or Q1) to estimate the maximum activation energy for a fully relaxed cluster representing the surface of an Al-depleted acid-etched alkali feldspar. Water molecules were included in the cluster to investigate the influence of explicit solvation on proton-transfer reactions and on the energy associated with hydroxylating the bridging oxygen atom (Obr). Single-point energy calculations were performed with the B3LYP/6-311+G(d,p) method. Proton transfer from the hydronium cation to an Obr requires sufficient energy to suggest that the Si-(OH)-Si species will occur only in trace quantities on a silica surface. Protonation of the Obr lengthens the Si-Obr bond and allows for the formation of a pentacoordinate Si intermediate ([5]Si). The energy required to form this species is the dominant component of the activation energy barrier to hydrolysis. After formation of the pentacoordinate intermediate, hydrolysis occurs via breaking the [5]Si-(OH)-Si linkage with a minimal activation energy barrier. A concerted mechanism involving stretching of the [5]Si-(OH) bond, proton transfer from the Si-(OH2)+ back to form H3O+, and a reversion of [5]Si to tetrahedral coordination was predicted. The activation energy for Q3Si hydrolysis calculated here was found to be less than that reported for Q3Si using a constrained cluster in the literature but significantly greater than the measured activation energies for the hydrolysis of Si-Obr bonds in silicate minerals. These results suggest that the rate-limiting step in silicate dissolution is not the hydrolysis of Q3Si-Obr bonds but rather the breakage of Q2 or Q1Si-Obr bonds.
    Keywords: Chemistry;
    ISSN: 1089-5639
    E-ISSN: 15205215
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  • 10
    In: Archaea, 2012, Vol.2012, 12 pages
    Description: To date, no experimental data has been reported for the metallome of hyperthermophilic microorganisms although their metal requirements for growth are known to be unique. Here, experiments were conducted to determine (i) cellular trace metal concentrations of the hyperthermophilic Archaea and , and (ii) a first estimate of the metallome for these hyperthermophilic species via ICP-MS. The metal contents of these cells were compared to parallel experiments using the mesophilic bacterium grown under aerobic and anaerobic conditions. Fe and Zn were typically the most abundant metals in cells. Metal concentrations for grown aerobically decreased in the order Fe 〉 Zn 〉 Cu 〉 Mo 〉 Ni 〉 W 〉 Co. In contrast, and show almost the reverse pattern with elevated Ni, Co, and W concentrations. Of the three organisms, a biosignature is potentially demonstrated for the methanogen that may, in part, be related to the metallome requirements of methanogenesis. The bioavailability of trace metals more than likely has varied through time. If hyperthermophiles are very ancient, then the trace metal patterns observed here may begin to provide some insights regarding Earth's earliest cells and in turn, early Earth chemistry.
    Keywords: Bioavailability ; Growth ; Anoxic Conditions ; Heavy Metals ; Microorganisms ; Methanogenesis ; Metal Concentration ; Trace Metals ; Data Processing ; Zinc ; Microorganisms ; Hyperthermophiles ; Copper ; Methanogenic Bacteria ; Anaerobic Conditions ; Methanogenesis ; Trace Metals ; Hyperthermophilic Archaea ; Methanococcus ; Archaea ; Escherichia Coli ; Pyrococcus Furiosus ; Genetics and Evolution ; Pollution - Organisms/Ecology/Toxicology ; Cell Biology;
    ISSN: 1472-3646
    E-ISSN: 1472-3654
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