Noble Gases Identify the Mechanisms of Fugitive Gas Contamination in Drinking-Water Wells Overlying the Marcellus and Barnett Shales

Horizontal drilling and hydraulic fracturing have enhanced energy production but raised concerns about drinking-water contamination and other environmental impacts. Identifying the sources and mechanisms of contamination can help improve the environmental and economic sustainability of shale-gas extraction. We analyzed 113 and 20 samples from drinking-water wells overlying the Marcellus and Barnett Shales, respectively, examining hydrocarbon abundance and isotopic compositions (e.g., C2H6/CH4, δ13C-CH4) and providing, to our knowledge, the first comprehensive analyses of noble gases and their isotopes (e.g., 4He, 20Ne, 36Ar) in groundwater near shale-gas wells. We addressed two questions. (i) Are elevated levels of hydrocarbon gases in drinking-water aquifers near gas wells natural or anthropogenic? (ii) If fugitive gas contamination exists, what mechanisms cause it? Against a backdrop of naturally occurring salt- and gas-rich groundwater, we identified eight discrete clusters of fugitive gas contamination, seven in Pennsylvania and one in Texas that showed increased contamination through time. Where fugitive gas contamination occurred, the relative proportions of thermogenic hydrocarbon gas (e.g., CH4, 4He) were significantly higher (P \u3c 0.01) and the proportions of atmospheric gases (air-saturated water; e.g., N2, 36Ar) were significantly lower (P \u3c 0.01) relative to background groundwater. Noble gas isotope and hydrocarbon data link four contamination clusters to gas leakage from intermediate-depth strata through failures of annulus cement, three to target production gases that seem to implicate faulty production casings, and one to an underground gas well failure. Noble gas data appear to rule out gas contamination by upward migration from depth through overlying geological strata triggered by horizontal drilling or hydraulic fracturing

Multi-Isotope Geochemical Baseline Study of the Carbon Management Canada Research Institutes CCS Field Research Station (Alberta, Canada), Prior to CO2 Injection

Carbon capture and storage (CCS) is an industrial scale mitigation strategy for reducing anthropogenic CO2 from entering the atmosphere. However, for CCS to be routinely deployed, it is critical that the security of the stored CO2 can be verified and that unplanned migration from a storage site can be identified. A number of geochemical monitoring tools have been developed for this purpose, however, their effectiveness critically depends on robust geochemical baselines being established prior to CO2 injection. Here we present the first multi-well gas and groundwater characterisation of the geochemical baseline at the Carbon Management Canada Research Institutes Field Research Station. We find that all gases exhibit CO2 concentrations that are below 1%, implying that bulk gas monitoring may be an effective first step to identify CO2 migration. However, we also find that predominantly biogenic CH4 (∼90%–99%) is pervasive in both groundwater and gases within the shallow succession, which contain numerous coal seams. Hence, it is probable that any upwardly migrating CO2 could be absorbed onto the coal seams, displacing CH4. Importantly, 4He concentrations in all gas samples lie on a mixing line between the atmosphere and the elevated 4He concentration present in a hydrocarbon well sampled from a reservoir located below the Field Research Station (FRS) implying a diffusive or advective crustal flux of 4He at the site. In contrast, the measured 4He concentrations in shallow groundwaters at the site are much lower and may be explained by gas loss from the system or in situ production generated by radioactive decay of U and Th within the host rocks. Additionally, the injected CO2 is low in He, Ne and Ar concentrations, yet enriched in 84Kr and 132Xe relative to 36Ar, highlighting that inherent noble gas isotopic fingerprints could be effective as a distinct geochemical tracer of injected CO2 at the FRS

Elevated levels of diesel range organic compounds in groundwater near Marcellus gas operations are derived from surface activities

Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of American 112 (2015): 13184-13189, doi: 10.1073/pnas.1511474112 .Hundreds of organic chemicals are utilized during natural gas extraction via high volume hydraulic fracturing (HVHF). However, it is unclear if these chemicals, injected into deep shale horizons, reach shallow groundwater aquifers and impact local water quality, either from deep underground injection sites or from the surface or shallow subsurface. Here, we report detectable levels of organic compounds in shallow groundwater samples from private residential wells overlying the Marcellus Shale in northeastern Pennsylvania. Analyses of purgeable and extractable organic compounds from 64 groundwater samples revealed trace levels of volatile organic compounds, well below the Environmental Protection Agency’s maximum contaminant levels, and low levels of both gasoline range (GRO; 0-8 ppb) and diesel range organic compounds (DRO; 0-157 ppb). A compound-specific analysis revealed the presence of bis(2-ethylhexyl)phthalate, which is a disclosed HVHF additive, that was notably absent in a representative geogenic water sample and field blanks. Pairing these analyses with 1) inorganic chemical fingerprinting of deep saline groundwater, 2) characteristic noble gas isotopes, and 3) spatial relationships between active shale gas extraction wells and wells with disclosed environmental health and safety (EHS) violations, we differentiate between a chemical signature associated with naturally occurring saline groundwater and a one associated with alternative anthropogenic routes from the surface (e.g., accidental spills or leaks). The data support a transport mechanism of DRO to groundwater via accidental release of fracturing fluid chemicals derived from the surface rather than subsurface flow of these fluids from the underlying shale formation.The authors thank Duke University’s Pratt School of Engineering and the National Science Foundation’s CBET Grant Number 1336702 and NSF EAGER (EAR-1249255) for financial support.2016-04-1

Stable isotopes of nitrate, sulfate, and carbonate in soils from the Transantarctic Mountains, Antarctica: A record of atmospheric deposition and chemical weathering

Soils in ice-free areas in Antarctica are recognized for their high salt concentrations and persistent arid conditions. While previous studies have investigated the distribution of salts and potential sources in the McMurdo Dry Valleys, logistical constraints have limited our investigation and understanding of salt dynamics within the Transantarctic Mountains. We focused on the Shackleton Glacier (85° S, 176° W), a major outlet glacier of the East Antarctic Ice Sheet located in the Central Transantarctic Mountains (CTAM), and collected surface soil samples from 10 ice-free areas. Concentrations of water-soluble nitrate (NO₃⁻) and sulfate (SO₄²⁻) ranged from <0.2 to ∼150 μmol g⁻¹ and <0.02 to ∼450 μmol g⁻¹, respectively. In general, salt concentrations increased with distance inland and with elevation. However, concentrations also increased with distance from current glacial ice position. To understand the source and formation of these salts, we measured the stable isotopes of dissolved water-soluble NO₃⁻ and SO₄²⁻, and soil carbonate (HCO₃ + CO₃). δ¹⁵N-NO₃ values ranged from −47.8 to 20.4‰ and, while all Δ¹⁷O-NO₃ values are positive, they ranged from 15.7 to 45.9‰. δ³⁴S-SO₄ and δ¹⁸O-SO₄ values ranged from 12.5 and 17.9‰ and −14.5 to −7.1‰, respectively. Total inorganic carbon isotopes in bulk soil samples ranged from 0.2 to 8.5‰ for δ¹³C and −38.8 to −9.6‰ for δ¹⁸O. A simple mixing model indicates that NO3⁻ is primarily derived from the troposphere (0–70%) and stratosphere (30–100%). SO₄²⁻ is primarily derived from secondary atmospheric sulfate (SAS) by the oxidation of reduced sulfur gases and compounds in the atmosphere by H₂O₂, carbonyl sulfide (COS), and ozone. Calcite and perhaps nahcolite (NaHCO₃) are formed through both slow and rapid freezing and/or the evaporation/sublimation of HCO₃ + CO₃-rich fluids. Our results indicate that the origins of salts from ice-free areas within the CTAM represent a complex interplay of atmospheric deposition, chemical weathering, and post-depositional processes related to glacial history and persistent arid conditions. These findings have important implications for the use of these salts in deciphering past climate and atmospheric conditions, biological habitat suitability, glacial history, and can possibly aid in our future collective understanding of salt dynamics on Mars

Geographic clustering of elevated blood heavy metal levels in pregnant women

Abstract Background Cadmium (Cd), lead (Pb), mercury (Hg), and arsenic (As) exposure is ubiquitous and has been associated with higher risk of growth restriction and cardiometabolic and neurodevelopmental disorders. However, cost-efficient strategies to identify at-risk populations and potential sources of exposure to inform mitigation efforts are limited. The objective of this study was to describe the spatial distribution and identify factors associated with Cd, Pb, Hg, and As concentrations in peripheral blood of pregnant women. Methods Heavy metals were measured in whole peripheral blood of 310 pregnant women obtained at gestational age ~12 weeks. Prenatal residential addresses were geocoded and geospatial analysis (Getis-Ord Gi* statistics) was used to determine if elevated blood concentrations were geographically clustered. Logistic regression models were used to identify factors associated with elevated blood metal levels and cluster membership. Results Geospatial clusters for Cd and Pb were identified with high confidence (p-value for Gi* statistic <0.01). The Cd and Pb clusters comprised 10.5 and 9.2 % of Durham County residents, respectively. Medians and interquartile ranges of blood concentrations (μg/dL) for all participants were Cd 0.02 (0.01–0.04), Hg 0.03 (0.01–0.07), Pb 0.34 (0.16–0.83), and As 0.04 (0.04–0.05). In the Cd cluster, medians and interquartile ranges of blood concentrations (μg/dL) were Cd 0.06 (0.02–0.16), Hg 0.02 (0.00–0.05), Pb 0.54 (0.23–1.23), and As 0.05 (0.04–0.05). In the Pb cluster, medians and interquartile ranges of blood concentrations (μg/dL) were Cd 0.03 (0.02–0.15), Hg 0.01 (0.01–0.05), Pb 0.39 (0.24–0.74), and As 0.04 (0.04–0.05). Co-exposure with Pb and Cd was also clustered, the p-values for the Gi* statistic for Pb and Cd was <0.01. Cluster membership was associated with lower education levels and higher pre-pregnancy BMI. Conclusions Our data support that elevated blood concentrations of Cd and Pb are spatially clustered in this urban environment compared to the surrounding areas. Spatial analysis of metals concentrations in peripheral blood or urine obtained routinely during prenatal care can be useful in surveillance of heavy metal exposure

Immunization with apical membrane antigen 1 confers sterile infection-blocking immunity against Plasmodium sporozoite challenge in a rodent model

Apical membrane antigen 1 (AMA-1) is a leading blood-stage malaria vaccine candidate. Consistent with a key role in erythrocytic invasion, AMA-1-specific antibodies have been implicated in AMA-1-induced protective immunity. AMA-1 is also expressed in sporozoites and in mature liver schizonts where it may be a target of protective cell-mediated immunity. Here, we demonstrate for the first time that immunization with AMA-1 can induce sterile infection-blocking immunity against Plasmodium sporozoite challenge in 80% of immunized mice. Significantly higher levels of gamma interferon (IFN-γ)/interleukin-2 (IL-2)/tumor necrosis factor (TNF) multifunctional T cells were noted in immunized mice than in control mice. We also report the first identification of minimal CD8 and CD4 T cell epitopes on Plasmodium yoelii AMA-1. These data establish AMA-1 as a target of both preerythrocytic- and erythrocytic-stage protective immune responses and validate vaccine approaches designed to induce both cellular and humoral immunity

COMPASS identifies T-cell subsets correlated with clinical outcomes.

Advances in flow cytometry and other single-cell technologies have enabled high-dimensional, high-throughput measurements of individual cells as well as the interrogation of cell population heterogeneity. However, in many instances, computational tools to analyze the wealth of data generated by these technologies are lacking. Here, we present a computational framework for unbiased combinatorial polyfunctionality analysis of antigen-specific T-cell subsets (COMPASS). COMPASS uses a Bayesian hierarchical framework to model all observed cell subsets and select those most likely to have antigen-specific responses. Cell-subset responses are quantified by posterior probabilities, and human subject-level responses are quantified by two summary statistics that describe the quality of an individual's polyfunctional response and can be correlated directly with clinical outcome. Using three clinical data sets of cytokine production, we demonstrate how COMPASS improves characterization of antigen-specific T cells and reveals cellular 'correlates of protection/immunity' in the RV144 HIV vaccine efficacy trial that are missed by other methods. COMPASS is available as open-source software

Resident Memory T Cells (TRM) Are Abundant in Human Lung: Diversity, Function, and Antigen Specificity

Recent studies have shown that tissue resident memory T cells (TRM) are critical to antiviral host defense in peripheral tissues. This new appreciation of TRM that reside in epithelial tissues and mediate host defense has been studied most extensively in skin: adult human skin contains large numbers of functional TRM that express skin specific markers. Indeed, more than twice as many T cells reside in skin as in peripheral blood. This T cell population has a diverse T cell receptor repertoire, and can produce a broad array of cytokines. More recently, we have begun to examine other epithelial tissues for the presence of resident T cells. In the present study, we asked whether analogous populations of resident T cells could be found in human lung. We were able to demonstrate abundant resident T cells in human lung-more than 10 billion T cells were present. Lung T cells were largely of the effector memory T cell (TEM) phenotype, though small numbers of central memory T cells (TCM) and T regulatory cells (Treg) could be identified. Lung T cells had a diverse T cell receptor repertoire and subsets produced IL-17, IL-4, IFNγ, as well as TNFα. A significant number of lung TRM CD4+Th cells produced more than one cytokine, identifying them as “multifunctional” Th1 type cells. Finally, lung TRM, but not TRM resident to skin or T cells from blood, proliferated in response to influenza virus. This work suggests that normal human lung contains large numbers of TRM cells, and these cells are poised to respond to recall antigens previously encountered through lung mucosa. This population of T cells may contribute to the pathogenesis of asthma and other T cell mediated lung diseases

Members of Marinobacter and Arcobacter Influence System Biogeochemistry During Early Production of Hydraulically Fractured Natural Gas Wells in the Appalachian Basin

Hydraulic fracturing is the prevailing method for enhancing recovery of hydrocarbon resources from unconventional shale formations, yet little is understood regarding the microbial impact on biogeochemical cycling in natural-gas wells. Although the metabolisms of certain fermentative bacteria and methanogenic archaea that dominate in later produced fluids have been well studied, few details have been reported on microorganisms prevelant during the early flowback period, when oxygen and other surface-derived oxyanions and nutrients become depleted. Here, we report the isolation, genomic and phenotypic characterization of Marinobacter and Arcobacter bacterial species from natural-gas wells in the Utica-Point Pleasant and Marcellus Formations coupled to supporting geochemical and metagenomic analyses of produced fluid samples. These unconventional hydrocarbon system-derived Marinobacter sp. are capable of utilizing a diversity of organic carbon sources including aliphatic and aromatic hydrocarbons, amino acids, and carboxylic acids. Marinobacter and Arcobacter can metabolize organic nitrogen sources and have the capacity for denitrification and dissimilatory nitrate reduction to ammonia (DNRA) respectively; with DNRA and ammonification processes partially explaining high concentrations of ammonia measured in produced fluids. Arcobacter is capable of chemosynthetic sulfur oxidation, which could fuel metabolic processes for other heterotrophic, fermentative, or sulfate-reducing community members. Our analysis revealed mechanisms for growth of these taxa across a broad range of salinities (up to 15% salt), which explains their enrichment during early natural-gas production. These results demonstrate the prevalence of Marinobacter and Arcobacter during a key maturation phase of hydraulically fractured natural-gas wells, and highlight the significant role these genera play in biogeochemical cycling for this economically important energy system