A new software tool for the analysis of noble gas data sets from (ground)water

Jung, M.; Aeschbach–Hertig, Werner

doi:10.1016/j.envsoft.2018.02.004

Cited by 30 publications

(36 citation statements)

References 28 publications

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“…If P R and S R and the concentration of at least three noble gases are known, then T R , A e and F can be identified inversely using one of the available noble gas algorithms (Aeschbach‐Hertig & Solomon, 2013; Brennwald, 2014; Jung & Aeschbach‐Hertig, 2018). However, the GE‐MIMS is only capable of measuring He and 40 Ar at sufficient accuracy for the small concentrations typically encountered in young GW.…”

Section: Methodsmentioning

confidence: 99%

Quantifying Groundwater Recharge Dynamics and Unsaturated Zone Processes in Snow‐Dominated Catchments via On‐Site Dissolved Gas Analysis

Schilling

Parajuli

Otis

et al. 2021

Water Resources Research

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Snowmelt contributes a significant fraction of groundwater recharge in snow‐dominated regions, making its accurate quantification crucial for sustainable water resources management. While several components of the hydrological cycle can be measured directly, catchment‐scale recharge can only be quantified indirectly. Stable water isotopes are often used as tracers to estimate snowmelt recharge, even though estimates based on stable water isotopes are biased due to the large variations of δ2H and δ18O in snow and the difficulty to measure snowmelt directly. To overcome this gap, a new tracer method based on on‐site measurements of dissolved He, 40Ar, 84Kr, N2, O2, and CO2 is presented. The new method was developed alongside classical tracer methods (stable water isotopes, 222Rn, 3H/3He) in a highly instrumented boreal catchment. By revealing (noble gas) recharge temperatures and excess air, dissolved gases allow (i) the contribution of snowmelt to recharge, (ii) the temporal recharge dynamics, and (iii) the primary recharge pathways to be identified. In contrast to stable water isotopes, which produced highly inconsistent snowmelt recharge estimates for the experimental catchment, dissolved gases produced consistent estimates even when the temperature of snowmelt during recharge was not precisely known. As dissolved gases are not controlled by the same processes as stable water isotopes, they are not prone to the same biases and represent a highly complementary tracer method for the quantification of snowmelt recharge dynamics in snow‐dominated regions. Furthermore, an observed systematic depletion of N2 in groundwater provides new evidence for the pathways of biological N‐fixation in boreal forest soils.

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Section: Methodsmentioning

confidence: 99%

Quantifying Groundwater Recharge Dynamics and Unsaturated Zone Processes in Snow‐Dominated Catchments via On‐Site Dissolved Gas Analysis

Schilling

Parajuli

Otis

et al. 2021

Water Resources Research

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“…Specifically, A e is the initial concentration of trapped air and F describes the degree of gas fractionation during subsequent dissolution, which depends on the fraction of trapped air that dissolves (Aeschbach-Hertig et al, 2000;Kipfer et al, 2002). Recharge parameters were derived using a computer code that employs standard inverse techniques to minimize the error-weighted misfit (χ 2 ) between measured and modeled gas concentrations, similar to that described by Aeschbach-Hertig et al (1999) and Jung and Aeschbach (2018). Excess air levels are indicated by ΔNe, the excess-air component of Ne expressed as a percentage of the solubility component.…”

Section: Recharge Parameter and Groundwater Age Calculationsmentioning

confidence: 99%

Direct Observation of the Depth of Active Groundwater Circulation in an Alpine Watershed

Manning

Ball

Wanty

et al. 2021

Water Resources Research

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The depth of active groundwater circulation is a fundamental control on stream flows and chemistry in mountain watersheds, yet it remains challenging to characterize and is rarely well constrained. We collected hydraulic conductivity, hydraulic head, temperature, chemical, noble gas, and 3H/3He groundwater age data from discrete levels in two boreholes 46 and 81 m deep in an alpine watershed, in combination with chemical and age data from shallow groundwater discharge, to discern groundwater flow rates at different depths and directly observe active and inactive groundwater. Vertical head gradients are steep (average of 0.4) and thermal profiles are consistent with typical linear conductive continental geotherms. Groundwater deeper than ∼20 m is distinct from shallow groundwater and creek water in its chemistry, noble gas signature, and age (dominantly >65 years compared to <9 years). Together these results suggest low vertical groundwater flow velocities and a relatively shallow active circulation depth of ∼20 m. This hypothesis is tested with a simple 2‐D numerical fluid flow and heat transport model representing a hillslope transect through the two boreholes. The modeling indicates that the subhorizontally bedded sedimentary rocks underlying the basin are highly anisotropic with low vertical hydraulic conductivity, and at most ∼10% of bedrock recharge (equivalent to <2% of stream baseflow) flows below a depth of 20 m. The study demonstrates the considerable value of discrete‐depth hydrogeologic, chemical, and age data for determining active circulation depth, and illustrates an approach for maximizing the utility of individual boreholes drilled for mountain bedrock aquifer characterization.

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“…Excess air (Heaton and Vogel ; Aeschbach‐Hertig et al ; Klump et al ; Solomon et al ) in groundwater was formed either by fluctuating water levels at the recharge pressurizing gas in the pore space or through vorticity in rapidly descending waters in fractured or karstified formations. Dissolved gas analysis is commonly used to calculate temperature at recharge by assuming that the saturation level of atmogenic gas is temperature driven; however, excess air is shown as a pressure phenomenon related to the depth of free gas entrapment in porous media (Holocher et al ; Jung and Aeschbach ). By measuring ebullated gas, gas flux, and dissolved phase gas concentrations, the total gas saturation per unit mass of the discharge water (hydropneumograph) can be obtained and used to evaluate the likelihood of a temperature or a pressure driving force for the excess dissolved gas.…”

Section: Discussion and Summarymentioning

confidence: 99%

An Instrument for the Determination of a Hydropneumograph in a Bubbling Spring

Agnew¹,

Halihan

Holtzhower

et al. 2019

Groundwater

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In order to enable greater accuracy in the determination of the mass discharge of gas and water‐gas ratios (WGR) in groundwater from springs, we have developed a field‐deployable instrument using commercially available components to independently measure the gas and water mass flow rates in springs with bubbling mixed‐phase flow. Collecting and measuring the free gas phase will allow for further compositional analysis that may be useful in improving gas‐derived parameters such as recharge temperature and age, as well as quantification of methanogenesis and flux of crustal/mantle gasses. By installing a phase separator at the spring discharge, a thermal mass flow sensor is utilized to measure the gas flow rate (ebullition + flux) generated from a spring. The water flow rate is determined by a standard weir. Field performance of the device was tested on a spring discharging from the Arbuckle‐Simpson aquifer near the town of Connerville in south‐central Oklahoma, USA.

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A new software tool for the analysis of noble gas data sets from (ground)water

Cited by 30 publications

References 28 publications

Quantifying Groundwater Recharge Dynamics and Unsaturated Zone Processes in Snow‐Dominated Catchments via On‐Site Dissolved Gas Analysis

Quantifying Groundwater Recharge Dynamics and Unsaturated Zone Processes in Snow‐Dominated Catchments via On‐Site Dissolved Gas Analysis

Direct Observation of the Depth of Active Groundwater Circulation in an Alpine Watershed

An Instrument for the Determination of a Hydropneumograph in a Bubbling Spring

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