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  • American Chemical Society (CrossRef)  (12)
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  • 1
    Language: English
    In: Environmental science & technology, 20 March 2018, Vol.52(6), pp.3342-3343
    Description: Data define scientific research. While researchers in the past published data in print-only venues that were hard to find, nowadays data are mostly published online. In environmental science, the increase in data accessibility allows scientists to conduct...
    Keywords: Water Quality ; Data Analysis ; Big Data ; Environmental Science ; Information Management ; Regional Development ; Data Management ; Regional Analysis ; Quality Assessment ; Water Quality Standards ; Regional Planning ; Data Management ; Water Analysis ; Water Quality ; Water Quality Assessments ; Water Quality ; Regional Analysis;
    ISSN: 0013936X
    E-ISSN: 1520-5851
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  • 2
    Language: English
    In: Energy and Fuels, 24 February 2015, Vol.29(3)
    Description: The production of natural gas has become increasingly important in the United States because of the development of hydraulic fracturing techniques, which significantly increase the permeability and fracture network of black shales. The pore structure of shale is a controlling factor for hydrocarbon storage and gas migration. In this work, we investigated the porosity of the Union Springs (Shamokin) Member of the Marcellus Formation from a core drilled in Centre County, PA, USA, using ultrasmall-angle neutron scattering (USANS), small-angle neutron scattering (SANS), focused ion beam scanning electron microscopy (FIB-SEM), and nitrogen gas adsorption. The scattering of neutrons by Marcellus shale depends on the sample orientation: for thin sections cut in the plane of bedding, the scattering pattern is isotropic, while for thin sections cut perpendicular to the bedding, the scattering pattern is anisotropic. The FIB-SEM observations allow attribution of the anisotropic scattering patterns to elongated pores predominantly associated with clay. The apparent porosities calculated from scattering data from the bedding plane sections are lower than those calculated from sections cut perpendicular to the bedding. A preliminary method for estimating the total porosity from the measurements made on the two orientations is presented. This method is in good agreement with nitrogen adsorption for both porosity and specific surface area measurements. Neutron scattering combined with FIB-SEM reveals that the dominant nanosized pores in organic-poor, clay-rich shale samples are water-accessible sheetlike pores within clay aggregates. In contrast, bubblelike organophilic pores in kerogen dominate organic-rich samples. Developing a better understanding of the distribution of the water-accessible pores will promote more accurate models of water-mineral interactions during hydrofracturing.
    Keywords: Bio-Inspired, Mechanical Behavior, Carbon Sequestration ; Engineering ; Chemistry
    ISSN: 0887-0624
    E-ISSN: 1520-5029
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  • 3
    Language: English
    In: Energy and Fuels, 16 June 2016, Vol.30(6)
    Description: Pores within organic matter (OM) are a significant contributor to the total pore system in gas shales. These pores contribute most of the storage capacity in gas shales. Here we present a novel approach to characterize the OM pore structure (including the porosity, specific surface area, pore size distribution, and water accessibility) in Marcellus shale. By using ultrasmall and small-angle neutron scattering, and by exploiting the contrast matching of the shale matrix with suitable mixtures of deuterated and protonated water, both total and water-accessible porosity were measured on centimeter-sized samples from two boreholes from the nanometer to micrometer scale with good statistical coverage. Samples were also measured after combustion at 450 °C. Analysis of scattering data from these procedures allowed quantification of OM porosity and water accessibility. OM hosts 24–47% of the total porosity for both organic-rich and -poor samples. This porosity occupies as much as 29% of the OM volume. In contrast to the current paradigm in the literature that OM porosity is organophilic and therefore not likely to contain water, our results demonstrate that OM pores with widths 〉20 nm exhibit the characteristics of water accessibility. In conclusion, our approach reveals the complex structure and wetting behavior of the OM porosity at scales that are hard to interrogate using other techniques.
    Keywords: Bio-Inspired, Mechanical Behavior, Carbon Sequestration ; Engineering ; Chemistry
    ISSN: 0887-0624
    E-ISSN: 1520-5029
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  • 4
    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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  • 5
    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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  • 6
    Language: English
    In: Environmental science & technology, 19 June 2018, Vol.52(12), pp.7149-7159
    Description: Eleven thousand groundwater samples collected in the 2010s in an area of Marcellus shale-gas development are analyzed to assess spatial and temporal patterns of water quality. Using a new data mining technique, we confirm previous observations that methane concentrations in groundwater tend to be naturally elevated in valleys and near faults, but we also show that methane is also more concentrated near an anticline. Data mining also highlights waters with elevated methane that are not otherwise explained by geologic features. These slightly elevated concentrations occur near 7 out of the 1,385 shale-gas wells and near some conventional gas wells in the study area. For ten analytes for which uncensored data are abundant in this 3,000 km rural region, concentrations are unchanged or improved as compared to samples analyzed prior to 1990. Specifically, TDS, Fe, Mn, sulfate, and pH show small but statistically significant improvement, and As, Pb, Ba, Cl, and Na show no change. Evidence from this rural area could document improved groundwater quality caused by decreased acid rain (pH, sulfate) since the imposition of the Clean Air Act or decreased steel production (Fe, Mn). Such improvements have not been reported in groundwater in more developed areas of the U.S.
    Keywords: Groundwater ; Water Pollutants, Chemical
    ISSN: 0013936X
    E-ISSN: 1520-5851
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  • 7
    Language: English
    In: Environmental science & technology, 07 April 2015, Vol.49(7), pp.4057-65
    Description: The environmental impacts of shale-gas development on water resources, including methane migration to shallow groundwater, have been difficult to assess. Monitoring around gas wells is generally limited to domestic water-supply wells, which often are not situated along predominant groundwater flow paths. A new concept is tested here: combining stream hydrocarbon and noble-gas measurements with reach mass-balance modeling to estimate thermogenic methane concentrations and fluxes in groundwater discharging to streams and to constrain methane sources. In the Marcellus Formation shale-gas play of northern Pennsylvania (U.S.A.), we sampled methane in 15 streams as a reconnaissance tool to locate methane-laden groundwater discharge: concentrations up to 69 μg L(-1) were observed, with four streams ≥ 5 μg L(-1). Geochemical analyses of water from one stream with high methane (Sugar Run, Lycoming County) were consistent with Middle Devonian gases. After sampling was completed, we learned of a state regulator investigation of stray-gas migration from a nearby Marcellus Formation gas well. Modeling indicates a groundwater thermogenic methane flux of about 0.5 kg d(-1) discharging into Sugar Run, possibly from this fugitive gas source. Since flow paths often coalesce into gaining streams, stream methane monitoring provides the first watershed-scale method to assess groundwater contamination from shale-gas development.
    Keywords: Environmental Monitoring ; Oil and Gas Industry ; Groundwater -- Analysis ; Methane -- Analysis ; Water Pollutants, Chemical -- Analysis
    ISSN: 0013936X
    E-ISSN: 1520-5851
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  • 8
    Language: English
    In: Environmental science & technology, 2013, Vol.47(23), pp.13220-1
    Keywords: Natural Gas ; Extraction and Processing Industry -- Methods ; Waste Water -- Analysis
    ISSN: 0013936X
    E-ISSN: 1520-5851
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  • 9
    Language: English
    In: Journal of Proteome Research, 04 October 2013, Vol.12(10)
    Description: The bioavailability of terminal electron acceptors (TEAs) and other substrates affects the efficiency of subsurface bioremediation. While it is often argued that microorganisms exist under "feast or famine", in the laboratory most organisms are studied under "feast" conditions, whereas they typically encounter "famine" in nature. The work described here aims to understand the survival strategies of the anaerobe Geobacter sulfurreduces under TEA-starvation conditions. Cultures were starved for TEA and at various times sampled to perform global comparative proteomic analysis using iTRAQ to obtain insight into the dynamics of change in proteins/enzymes expression associated with change in nutrient availability/environmental stress. Proteins varying in abundance with a high level of statistical significance (p 〈 0.05) were identified to understand how cells change from midlog to (i) stationary phase and (ii) conditions of prolonged starvation (survival phase). The most highly represented and significantly up-regulated proteins in the survival phase cells are involved in energy metabolism, cell envelope, and transport and binding functional categories. The majority of the proteins were predicted to be localized in the cell membranes. These results document that changes in the outer and cytoplasmic membranes are needed for survival of Geobacter under starvation conditions. The cell shuts down anabolic processes and becomes poised, through changes in its membrane proteins, to sense nutrients in the environment, to transport nutrients into the cell, and to detect or utilize TEAs that are encountered. Under TEA-limiting conditions, the cells turned from translucent white to red in color, indicating higher heme content. The increase in heme content supported proteomics results showing an increase in the number of cytochromes involved in membrane electron transport during the survival phase. The cell is also highly reduced with minimal change in energy charge (ATP to total adenine nucleotide ratio). Nonetheless, these proteomic and biochemical results indicate that even under TEA starvation cells remain poised for bioremediation.
    Keywords: Chemistry
    ISSN: 1535-3893
    E-ISSN: 1535-3907
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  • 10
    Language: English
    In: Environmental Science & Technology, 02/15/2009, Vol.43(4), pp.1086-1090
    Description: The pH-dependent dissolution flux of FeO (wstite, a ferrous oxide) was measured in this study; flux = k{H+}n (mol/m2/s), where k = 10-4.95 and n = 0.64. This flux was consistent with theoretical predictions based on the rate of water exchange of hexaaquo Fe2+. Interestingly, when compared to published data, the pH-dependent dissolution flux of FeO defined an upper limit for the reductive dissolution fluxes of iron(III) (oxyhydr)oxides, including bacterial dissimilatory iron reduction (DIR). A wide range of dissolution fluxes across several orders of magnitude has been reported for iron(III) (oxyhydr)oxides in the literature and the fluxes were affected by various experimental variables, e.g., pH, ligands, chemical reductants, and bacteria. We concluded that (i) the reductive dissolution fluxes of iron(III) (oxyhydr)oxides, including bacterial DIR, are ultimately bracketed by the detachment rate of reduced Fe(II) from the surface and (ii) the maximum flux can be approached when the mole fraction of reduced Fe(II) at the surface is close to unity.
    Keywords: Water Exchange ; Ligands ; Ferric Oxide ; Water Exchange ; Data Processing ; Oxides ; Dissolution ; Iron ; Ph Effects ; Water Exchange ; Iron ; Ph ; Prediction ; Bacteria ; Water Exchange ; Hydrogen Ion Concentration ; Iron ; Fluctuations ; Oxides ; Prediction ; Bacteria ; Water Exchange ; Hydrogen Ion Concentration ; Iron ; Fluctuations ; Oxides ; Environmental Pollution & Waste Treatment ; General ; Data Acquisition ; Water Resources and Supplies ; Characteristics, Behavior and Fate;
    ISSN: 0013-936X
    E-ISSN: 1520-5851
    Source: American Chemical Society (via CrossRef)
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