Dissolved gas ‘concentrations’ or ‘concentration estimates’ – A comment on “Origin, distribution and hydrogeochemical controls on methane occurrences in shallow aquifers, southwestern Ontario, Canada” by Jennifer C. McIntosh, Stephen E. Grasby, Stewart M. Hamilton, and Stephen G. Osborn

Ryan, M. Cathryn; Roy, James W.; Heagle, Dru J.

doi:10.1016/j.apgeochem.2015.08.015

Cited by 10 publications

(9 citation statements)

References 9 publications

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“…A key limitation in defining baseline characteristics and thus predicting fugitive gas sources in low K argillaceous sediments (representing two‐thirds of all sedimentary rocks on Earth) is the lack of knowledge on how to measure concentrations and isotope values of the gases dissolved in porewaters in these sediments. Collecting porewater gas samples that represent in situ dissolved concentrations using groundwater wells in aquifers can be challenging (cf McIntosh et al and Ryan et al ). Slow groundwater recharge rates further confound sampling and analyses of waters from wells installed in argillaceous sediments because they prohibit purging the standing water from these wells and can result in a mixed sample of altered and unaltered formation porewater (Wassenaar and Hendry ).…”

Section: Introductionmentioning

confidence: 99%

Measuring Concentrations of Dissolved Methane and Ethane and the ¹³C of Methane in Shale and Till

Hendry¹,

Barbour

Schmeling

et al. 2016

Groundwater

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Baseline characterization of concentrations and isotopic values of dissolved natural gases is needed to identify contamination caused by the leakage of fugitive gases from oil and gas activities. Methods to collect and analyze baseline concentration-depth profiles of dissolved CH and C H and δ C-CH in shales and Quaternary clayey tills were assessed at two sites in the Williston Basin, Canada. Core and cuttings samples were stored in Isojars in a low O headspace prior to analysis. Measurements and multiphase diffusion modeling show that the gas concentrations in core samples yield well-defined and reproducible depth profiles after 31-d equilibration. No measurable oxidative loss or production during core sample storage was observed. Concentrations from cuttings and mud gas logging (including IsoTubes ) were much lower than from cores, but correlated well. Simulations suggest the lower concentrations from cuttings can be attributed to drilling time, and therefore their use to define gas concentration profiles may have inherent limitations. Calculations based on mud gas logging show the method can provide estimates of core concentrations if operational parameters for the mud gas capture cylinder are quantified. The δ C-CH measured from mud gas, IsoTubes , cuttings, and core samples are consistent, exhibiting slight variations that should not alter the implications of the results in identifying the sources of the gases. This study shows core and mud gas techniques and, to a lesser extent, cuttings, can generate high-resolution depth profiles of dissolved hydrocarbon gas concentrations and their isotopes.

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Section: Introductionmentioning

confidence: 99%

Measuring Concentrations of Dissolved Methane and Ethane and the ¹³C of Methane in Shale and Till

Hendry¹,

Barbour

Schmeling

et al. 2016

Groundwater

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“…(2) deep, confined groundwater systems (Gardner and Solomon, 2009;Ryan et al, 2015); and (3) deep, crater lake systems containing submarine gas vents at depth, such as Lakes Monoun, and Nyos in Cameroon (Kling et al, 1987;Kusakabe and Sano, 1992). In both confined groundwater and deep, lake gas vent systems, increased hydrostatic pressure allows for greater gas saturation (i.e., increased concentration).…”

Section: Direct Measurement Of Dissolved Co 2 Principlesmentioning

confidence: 99%

“…As such, P TDG values may be several times that of atmospheric pressure if waters are gas saturated at these greater hydrostatic pressures. In practice, dual measurement of total dissolved gas pressure and dissolved CO 2 are recommended in environments where P TDG is suspected to be higher than atmospheric pressure to account for greater dissolved concentrations (Ryan et al, 2015). At abyssopelagic depths (> ∼4,000 m) in marine systems, changes in Henry's constant due to hydrostatic pressure must also be taken in account when calculating expected PCO 2 for a given dissolved CO 2 concentration or vice versa (Enns et al, 1965;Hamme et al, 2015).…”

Section: Direct Measurement Of Dissolved Co 2 Principlesmentioning

confidence: 99%

Monitoring Atmospheric, Soil, and Dissolved CO2 Using a Low-Cost, Arduino Monitoring Platform (CO2-LAMP): Theory, Fabrication, and Operation

et al. 2019

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Variability of CO 2 concentrations within the Earth system occurs over a wide range of time and spatial scales. Resolving this variability and its drivers in terrestrial and aquatic environments ultimately requires high-resolution spatial and temporal monitoring; however, relatively high-cost gas analyzers and data loggers can present barriers in terms of cost and functionality. To overcome these barriers, we developed a low-cost Arduino monitoring platform (CO2-LAMP) for recording CO 2 variability in electronically harsh conditions: humid air, soil, and aquatic environments. A relatively inexpensive CO 2 gas analyzer was waterproofed using a semi-permeable, expanded polytetrafluoroethylene membrane. Using first principles, we derived a formulation of the theoretical operation and measurement of PCO 2(aq) by infrared gas analyzers submerged in aquatic environments. This analysis revealed that an IRGA should be able to measure PCO 2(aq) independent of corrections for hydrostatic pressure. CO2-LAMP theoretical operation and measurement were also verified by accompanying laboratory assessment measuring PCO 2(aq) at multiple water depths. The monitoring platform was also deployed at two sites within the Springfield Plateau province in northwest Arkansas, USA: Blowing Springs Cave and the Savoy Experimental Watershed. At Blowing Springs Cave, the CO2-LAMP operated alongside a relatively greater-cost CO 2 monitoring platform. Over the monitoring period, measured values between the two systems covaried linearly (r 2 = 0.97 and 0.99 for cave air and cave stream dissolved CO 2 , respectively). At the Savoy Experimental Watershed, measured soil CO 2 variability capturing sub-daily variation was consistent with previously documented studies in humid, temperate soils. Daily median values varied linearly with soil moisture content (r 2 = 0.84). Overall, the CO2-LAMP captured sub-daily variability of CO 2 in humid air, soil, and aquatic environments that, while out of the scope of the study, highlight both cyclical and complex CO 2 behavior. At present, long-term assessment of platform design is ongoing. Considering cost-savings, CO2-LAMP presents a working base design for continuous, accurate, low-power, and low-cost CO 2 monitoring for remote locations.

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“…If the groundwater pressure, P g.w. (bar), is reduced below the sum of p vapor ( T 0 ) and the hypothetical in situ partial pressures (∑ i p i , in situ ), bubbles emerge from the groundwater (Pankow ; Roy and Ryan ), neglecting any contribution from capillary pressure (Ryan et al ). Therefore, the groundwater pressure at which bubbles appear, P critical (bar), is

P_{critical} = \sum p_{i, in situ} + p_{vapor} ((), T_{0})

…”

Section: Relationship Of Partial Pressures In a Bubble To In Situ Parmentioning

confidence: 99%

“…The dissolved gas concentrations in groundwater are important for monitoring environmental contaminants (e.g., U.S. Environmental Protection Agency ; Nadim et al ), revealing redox conditions (e.g., Lovley and Goodwin ; Jakobsen and Cold ), and estimating the age of groundwater (Ekwurzel et al ; Plummer et al ). However, bubble formation decreases the dissolved gas concentrations (Roy and Ryan ; Ryan et al ), meaning that most methods (Hirsche and Mayer ) misrepresent the in situ concentrations. To circumvent this problem, groundwater and its dissolved gases must be trapped in situ (i.e., before bubble formation) using special techniques such as sealing the collected groundwater in a sampler at depth (e.g., Simpkins and Parkin ; Yager and Fountain ; Britt et al ), collecting dissolved gases with a passive gas diffusion sampler (e.g., McLeish et al ; Spalding and Watson ; Gardner and Solomon ) and collecting groundwater in a pre‐evacuated vial (e.g., Miyakawa et al ).…”

Section: Introductionmentioning

confidence: 99%

A Proposed Method to Estimate In Situ Dissolved Gas Concentrations in Gas‐Saturated Groundwater

Tamamura¹,

Miyakawa

Aramaki

et al. 2017

Groundwater

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Gas-saturated groundwater forms bubbles when brought to atmospheric pressure, preventing precise determination of its in situ dissolved gas concentrations. To overcome this problem, a modeling approach called the atmospheric sampling method is suggested here to recover the in situ dissolved gas concentrations of groundwater collected ex situ under atmospheric conditions at the Horonobe Underground Research Laboratory, Japan. The results from this method were compared with results measured at the same locations using two special techniques, the sealed sampler and pre-evacuated vial methods, that have been developed to collect groundwater under its in situ conditions. In gas-saturated groundwater cases, dissolved methane and inorganic carbon concentrations derived using the atmospheric sampling method were mostly within ±4 and ±10%, respectively, of values from the sealed sampler and pre-evacuated vial methods. In gas-unsaturated groundwater, however, the atmospheric sampling method overestimated the in situ dissolved methane concentrations, because the groundwater pressure at which bubbles appear (P critical ) was overestimated. The atmospheric sampling method is recommended for use where gas-saturated groundwater can be collected only ex situ under atmospheric conditions.

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Cited by 10 publications

References 9 publications

Measuring Concentrations of Dissolved Methane and Ethane and the ¹³C of Methane in Shale and Till

Measuring Concentrations of Dissolved Methane and Ethane and the ¹³C of Methane in Shale and Till

Monitoring Atmospheric, Soil, and Dissolved CO2 Using a Low-Cost, Arduino Monitoring Platform (CO2-LAMP): Theory, Fabrication, and Operation

A Proposed Method to Estimate In Situ Dissolved Gas Concentrations in Gas‐Saturated Groundwater

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Cited by 10 publications

References 9 publications

Measuring Concentrations of Dissolved Methane and Ethane and the 13C of Methane in Shale and Till

Measuring Concentrations of Dissolved Methane and Ethane and the 13C of Methane in Shale and Till

Monitoring Atmospheric, Soil, and Dissolved CO2 Using a Low-Cost, Arduino Monitoring Platform (CO2-LAMP): Theory, Fabrication, and Operation

A Proposed Method to Estimate In Situ Dissolved Gas Concentrations in Gas‐Saturated Groundwater

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Product

Resources

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Measuring Concentrations of Dissolved Methane and Ethane and the ¹³C of Methane in Shale and Till

Measuring Concentrations of Dissolved Methane and Ethane and the ¹³C of Methane in Shale and Till