Kooperativer Bibliotheksverbund

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

DOI: 10.1073/pnas.1809013115

URL: View this record in MEDLINE/PubMed

Language: English

In: Earth and Planetary Science Letters, August 1, 2013, Vol.375, p.372(11)

Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.epsl.2013.06.001 Byline: Rohit B. Warrier, M. Clara Castro, Chris M. Hall, Kyger C. Lohmann Abstract: Significant atmospheric noble gas excesses in aquifer systems have systematically been linked to increased hydrostatic pressure, either due to increased water table levels or due to the development of ice cover. Measured noble gases (Ne, Ar, Kr, and Xe) in the shallow Saginaw aquifer in the Michigan Basin display both moderate ([approximately equal to]20-60% Ne excess) and large ([approximately equal to]80-〉120% Ne excess) excesses of atmospheric noble gases with respect to air saturated water for modern recharge conditions. All large atmospheric noble gas excesses are located in the main discharge area of the Michigan Basin, in the Saginaw Lowlands region. Here, through a step-by-step analysis, we first show that large atmospheric noble gas excesses in the Saginaw aquifer do not result from increased hydrostatic pressure but, instead, are the result of vertical transport of atmospheric noble gases that are believed to have escaped from deep Michigan Basin brines following a past thermal event of mantle origin. Subsequently, we show that the atmospheric noble gas pattern of the entire Michigan Basin strata appears to result from two distinct end-members: (a) an end-member represented by the deepest, most depleted brines from which most of the atmospheric noble gases escaped; and (b) an end-member with excess atmospheric noble gas values above those displayed by the Saginaw samples. The latter is unconstrained due to the dilution effect exerted by recharge water. Using a Rayleigh distillation model we further show that the greater enrichment of lighter relative to heavier noble gases in the Saginaw aquifer in the Saginaw Lowlands area is compatible with either diffusion or solubility related mechanisms. These findings reinforce the notion that a past thermal event is indeed responsible for the atmospheric noble gas excesses found in the Saginaw aquifer in the Saginaw Lowlands area. They are also consistent with and reinforce previous findings with respect to the occurrence of a thermal event of mantle origin in the Michigan Basin. Author Affiliation: University of Michigan, Department of Earth and Environmental Sciences, 1100N. University Ave., Ann Arbor, MI 48109-1063, USA Article History: Received 2 July 2012; Revised 30 May 2013; Accepted 1 June 2013 Article Note: (miscellaneous) Editor: Y. Ricard

Keywords: Aquifers -- Analysis

ISSN: 0012-821X

Source: Cengage Learning, Inc.

In: Geophysical Research Letters, 16 November 2015, Vol.42(21), pp.9311-9318

Description: This study represents the first comprehensive noble gas study in glacial meltwater from the Greenland Ice Sheet. It shows that most samples are in disequilibrium with surface collection conditions. A preliminary Ne and Xe analysis suggests that about half of the samples equilibrated at a temperature of ~0°C and altitudes between 1000 m and 2000 m, with a few samples pointing to lower equilibration altitudes and temperatures between 2°C and 5°C. Two samples suggest an origin as melted ice and complete lack of equilibration with surface conditions. A helium component analysis suggests that this glacial meltwater was isolated from the atmosphere prior to the 1950s, with most samples yielding residence times ≤ 420 years. Most samples represent a mixture between a dominant atmospheric component originating as precipitation and basal meltwater or groundwater, which has accumulated crustal He over time. GrIS glacial meltwater residence times vary between 100 and 3600 years A lot of the GrIS glacial meltwater originates at altitudes between 1 and 2 km Most GrIS glacial meltwater is in disequilibrium with surface conditions

Keywords: Noble Gases ; Greenland ; Glacial Meltwater ; Water Residence Times

ISSN: 0094-8276

E-ISSN: 1944-8007

DOI: 10.1002/2015GL065778

Language: English

In: Journal of Hydrology, May 2015, Vol.524, pp.1-14

Description: Noble gases, in particular He/ He ( ) ratios, were measured together with tritium activity in groundwater from eskers and moraines of the Abitibi-Temiscamingue region of northwestern Quebec (eastern Canada). These high-latitude glaciofluvial landforms contain precious freshwater resources that need to be quantified. Here we provide estimates of residence time for groundwater in glaciofluvial sediments forming the Saint-Mathieu–Berry (SMB) and Barraute eskers, the Harricana moraine and in the underlying fractured bedrock aquifer. The He/ He ratios range from 0.224 ± 0.012 to 1.849 ± 0.036Ra, where Ra is the atmospheric He/ He ratio (1.386 × 10 ). These results suggest the occurrence of He produced by decay of tritium and terrigenic He produced by decay of U and Th. Calculated H/ He apparent ages of groundwater from the SMB esker and the Harricana moraine range from 6.6 ± 1.1 a to 32 ± 7.4 a. Terrigenic He ( He ) was found in the deeper wells of the SMB esker and in the wells tapping water from the deeper fractured aquifer located below the eskers and moraines and confined by postglacial clays. The amount of He ranges from 3.4 × 10 to 2.2 × 10 cm STP g and shows a clear gradient with depth, suggesting addition of a He flux entering the bottom of the eskers. Modeled He fluxes range from 2.0 × 10 cm STP cm yr at the Harricana moraine to 6.6 × 10 cm STP cm yr in the southern section of the SMB esker. Calculated fluxes are highly variable and 5–165 times lower than the helium continental crustal flux, suggesting local helium sources, with helium being driven upward through preferential pathways such as local faults. Maximum U–Th/ He ages obtained for the groundwater in the fractured bedrock range from 1473 ± 300 a to 137 ± 28 ka, suggesting the occurrence of several generations of fossil meltwater trapped under the clay plain after the last two glaciations.

Keywords: Esker ; Groundwater Age ; 3h/3he ; U–Th/4he ; Helium Flux ; Abitibi-Temiscamingue ; Geography

ISSN: 0022-1694

E-ISSN: 1879-2707

DOI: 10.1016/j.jhydrol.2015.01.072

URL: View record in ScienceDirect (Access to full text may be restricted)

Language: English

In: Chemical Geology, 06 December 2015, Vol.417, pp.356-370

Description: This study uses stable noble gases' (He, Ne, Ar, Kr, Xe) volume fractions and isotopic ratios from Antrim Shale natural gas to assess compositional variability and vertical fluid migration within this reservoir, in addition to distinguishing between the presence of thermogenic versus biogenic methane. R/Ra values, where R is the measured He/ He ratio and Ra is the atmospheric value of 1.384 ± 0.013 × 10 , vary from 0.01 to 0.34 suggesting a largely dominant crustal He component with minor atmospheric and mantle contributions. Crustal Ne, Ar and Xe contributions are also present but the atmospheric component is largely dominant for these gases. Crustal contributions for Ne, Ar and Xe vary between 1.1% and 12.5%, between 0.7% and 19% and between 0.1% and 2.7%, respectively. A few samples present higher than atmospheric Ne/ Ne ratios pointing to the presence of a small mantle Ne component. High horizontal and vertical variability of noble gas signatures in the Antrim Shale are observed. These are mainly due to variable noble gas input from deep brines and, to a smaller extent, variable in-situ production within different layers of the Antrim Shale, in particular, the Lachine and Norwood members. Estimated He ages, considering external He input for Antrim Shale water, vary between 0.9 ka and 238.2 ka and match well for most samples with the timing of the major Wisconsin glaciation, suggesting that Antrim Shale water was influenced by glaciation-induced recharge. Consistency between measured and predicted Ar/ Ar ratios assuming Ar release temperatures ≥ 250 °C supports a thermogenic origin for most of the methane in these samples. This thermogenic methane is likely to originate at greater depths, either from the deeper portion of the Antrim Shale in the central portion of the Michigan Basin or from deeper formations given that the thermal maturity of the Antrim Shale in the study area is rather low.

Keywords: Antrim Shale Gas ; Noble Gases ; Groundwater Recharge ; Biogenic Methane ; Thermogenic Methane ; Sedimentary Basins ; Geology

ISSN: 0009-2541

E-ISSN: 1872-6836

DOI: 10.1016/j.chemgeo.2015.10.029

URL: View record in ScienceDirect (Access to full text may be restricted)

Language: English

In: Chemical Geology, 20 April 2018, Vol.483, pp.275-285

Description: Noble gas concentrations in water are ideal probes to study surface and groundwater dynamics by providing indications of flow paths, connectivity between aquifers, and water residence times. Recent studies have pointed out anomalies in noble gas concentrations derived from groundwater in fractured systems, likely due to the presence of rapid infiltration and preferential flow paths. It has been suggested that such anomalies originate from conditions at high altitude when rainwater has had insufficient time to equilibrate with surface conditions. Potential sources also include snow, never previously investigated for its noble gas composition. In order to document the noble gas signature in snow, noble gas concentrations and isotopic ratios were measured in samples collected between 2013 and 2016. Here, we outline a methodology for measuring noble gases in collected snow samples that involves a two-step procedure where He and Ne are measured independently from Ar, Kr and Xe. Our results show that snow has elevated He concentrations with depleted concentrations of other noble gases with respect to air-saturated water (ASW). However, samples collected in 2013 show significant He and Ne depletion compared to those collected in 2014, 2015 and 2016. We suspect that, despite the well-controlled conditions of storage, the 2013 batch sample might have significantly re-crystalized, leading to a reduction in the characteristic diffusion length scale of the snow crystal structure. In addition, He and Ne concentrations display relatively low variability among all measured samples (〈14%), while Ar, Kr and Xe show large variability in their concentrations (〉40%). Our results confirm that He and Ne, which have small atomic radii, are likely dissolved within the ice/snow crystal lattice itself while the heavy noble gases (Ar, Kr and Xe) are likely accommodated by fluid inclusions, including air and quenched liquid water inclusions. Consequently, the smaller variability recorded in light noble gases may be due to the fact that He and Ne are hosted within plentiful host sites within the snow crystal lattice structure, whereas heavy noble gases rely on the presence of comparatively rare fluid inclusions.

Keywords: Noble Gas ; Snow Structure ; Noble Gas Solubility in Ice ; Geology

ISSN: 0009-2541

E-ISSN: 1872-6836

DOI: 10.1016/j.chemgeo.2018.02.022

URL: View record in ScienceDirect (Access to full text may be restricted)

DOI: 10.15784/600389

Source: DataCite

URL: View record in DataCite

URL: View full text (Access may be restricted)

In: Water Resources Research, April 2012, Vol.48(4), pp.n/a-n/a

Description: We report the results of a yearlong noble gas study conducted in 2008–2009 together with continuous physical and chemical measurements collected in a monitoring well in an aquifer in southern Michigan. Conditions near the water table are correlated with noble gas concentrations, corresponding noble gas temperatures (NGTs), and precipitation events. This yearlong study is the first noble gas field test that has employed natural recharge and in situ monitored conditions, with minimal disturbance of the unsaturated zone. This detailed study demonstrates that significant changes in conditions near the water table can occur over a year that can greatly affect NGTs. Results show that precipitation events are detected within hours at the water table, but a lag in pressure response argues for a long time constant for gas transport within the unsaturated zone. There is strong evidence for the depletion of oxygen near the water table, which affects the noble gas air‐saturated water component. During reducing conditions there is evidence for significant noble gas degassing. Rain from the passage of Hurricane Ike caused a significant shift in stable isotope ratios and injection of a large quantity of excess air and likely led to a much more oxygen‐rich environment in the soil gas. Although individual models can account for NGTs over portions of the record, no single NGT model can account for all features observed over the entire study. It is likely that the NGT temperature proxy must be viewed as an average of recharge conditions over several years. Soil air conditions can change during the year and this can affect NGTs No single NGT model can account for the entire dataset NGT models must average conditions over years

Keywords: Dissolved Oxygen ; Noble Gas Temperatures ; Noble Gases ; Precipitation ; Recharge ; Water Table

ISSN: 0043-1397

E-ISSN: 1944-7973

DOI: 10.1029/2011WR010951

Language: English

In: Earth and Planetary Science Letters, 01 August 2013, Vol.375, pp.372-382

Description: Significant atmospheric noble gas excesses in aquifer systems have systematically been linked to increased hydrostatic pressure, either due to increased water table levels or due to the development of ice cover. Measured noble gases (Ne, Ar, Kr, and Xe) in the shallow Saginaw aquifer in the Michigan Basin display both moderate (∼20–60% Ne excess) and large (∼80−〉120% Ne excess) excesses of atmospheric noble gases with respect to air saturated water for modern recharge conditions. All large atmospheric noble gas excesses are located in the main discharge area of the Michigan Basin, in the Saginaw Lowlands region. Here, through a step-by-step analysis, we first show that large atmospheric noble gas excesses in the Saginaw aquifer do not result from increased hydrostatic pressure but, instead, are the result of vertical transport of atmospheric noble gases that are believed to have escaped from deep Michigan Basin brines following a past thermal event of mantle origin. Subsequently, we show that the atmospheric noble gas pattern of the entire Michigan Basin strata appears to result from two distinct end-members: (a) an end-member represented by the deepest, most depleted brines from which most of the atmospheric noble gases escaped; and (b) an end-member with excess atmospheric noble gas values above those displayed by the Saginaw samples. The latter is unconstrained due to the dilution effect exerted by recharge water. Using a Rayleigh distillation model we further show that the greater enrichment of lighter relative to heavier noble gases in the Saginaw aquifer in the Saginaw Lowlands area is compatible with either diffusion or solubility related mechanisms. These findings reinforce the notion that a past thermal event is indeed responsible for the atmospheric noble gas excesses found in the Saginaw aquifer in the Saginaw Lowlands area. They are also consistent with and reinforce previous findings with respect to the occurrence of a thermal event of mantle origin in the Michigan Basin.

Keywords: Atmospheric Noble Gas Excesses ; Mantle Thermal Event ; Vertical Transport ; Rayleigh Distillation ; Saginaw Aquifer ; Michigan Basin ; Geology ; Physics

ISSN: 0012-821X

E-ISSN: 1385-013X

DOI: 10.1016/j.epsl.2013.06.001

URL: View record in ScienceDirect (Access to full text may be restricted)

Language: English

In: Applied Geochemistry, February 2016, Vol.65, pp.36-53

Description: Major and trace elements, noble gases, and stable (δD, δ O) and cosmogenic ( H, C) isotopes were measured from geothermal fluids in two adjacent geothermal areas in NW-Mexico, Las Tres Vírgenes (LTV) and Cerro Prieto (CP). The goal is to trace the origin of reservoir fluids and to place paleoclimate and structural-volcanic constraints in the region. Measured He/ He (R) ratios normalized to the atmospheric value (R  = 1.386 × 10 ) vary between 2.73 and 4.77 and are compatible with mixing between a mantle component varying between 42 and 77% of mantle helium and a crustal, radiogenic He component with contributions varying between 23% and 58%. Apparent U–Th/ He ages for CP fluids (0.7–7 Ma) suggest the presence of a sustained He flux from a granitic basement or from mixing with connate brines, deposited during the Colorado River delta formation (1.5–3 Ma). Radiogenic He production age modeling at LTV, combined with the presence of radiogenic carbon (1.89 ± 0.11 pmC – 35.61 ± 0.28 pmC) and the absence of tritium strongly suggest the Quaternary infiltration of meteoric water into the LTV geothermal reservoir, ranging between 4 and 31 ka BP. The present geochemical heterogeneity of LTV fluids can be reconstructed by mixing Late Pleistocene – Early Holocene meteoric water (58–75%) with a fossil seawater component (25–42%), as evidenced by Br/Cl and stable isotope trends. CP geothermal water is composed of infiltrated Colorado River water with a minor impact by halite dissolution, whereas a vapor-dominated sample is composed of Colorado River water and vapor from deeper levels. δD values for the LTV meteoric end-member, which are 20‰–44‰ depleted with respect to present-day precipitation, as well as calculated annual paleotemperatures 6.9–13.6 °C lower than present average temperatures in Baja California point to the presence of humid and cooler climatic conditions in the Baja California peninsula during the final stage of the Last Glacial Pluvial period. Quaternary recharge of the LTV geothermal reservoir is related to elevated precipitation rates during cooler-humid climate intervals in the Late Pleistocene and Early Holocene. The probable replacement of connate water or pore fluids by infiltrating surface water might have been triggered by enhanced fracture and fault permeability through contemporaneous tectonic–volcanic activity in the Las Tres Vírgenes region. Fast hydrothermal alteration processes caused a secondary, positive δ O-shift from 4‰ to 6‰ for LTV and from 2‰ to 4‰ for CP geothermal fluids since the Late Glacial infiltration.

Keywords: Las Tres Vírgenes ; Cerro Prieto ; Geothermal Reservoir ; Fluid Provenance ; Residence Time ; Noble Gases ; Environmental Isotopes ; Paleotemperature ; Co-Genetic Volcanic Activity ; Geology

ISSN: 0883-2927

E-ISSN: 1872-9134

DOI: 10.1016/j.apgeochem.2015.10.009

URL: View record in ScienceDirect (Access to full text may be restricted)