Category Archives: Application example

In-situ monitoring of noble gases in groundwater during rock fracking

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Clement Roques and his colleagues published a paper in Nature Scientific Reports, where they used a miniRUEDI to study changes of dissolved-gas concentrations in groundwater in response to hydraulic stimulation and fracturing of the reservoir rocks (Nature Scientific Reports, 10, 6949, 2020). The miniRUEDI was installed on-site to continuously analyse the dissolved-gas concentrations of the groundwater. The high-frequency He and Ar measurements indicate that trapped fluids were mobilized from the rocks in response to the fracking. The miniRUEDI revealed the nature and evolution of the fracture network and flow paths, and showed the effect of the fracking procedures on groundwater quality.

Full paper: “In situ observation of helium and argon release during fluid-pressure-triggered rock deformation.” Sci Rep 10, 6949 (2020). https://doi.org/10.1038/s41598-020-63458-x

Eawag News article: https://www.eawag.ch/en/news-agenda/news-portal/news-detail/observing-how-fissure-systems-are-formed-thanks-to-the-gas-sniffer/

miniRUEDI goes sailing

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Researchers from the Max Planck Institute for Chemistry (Germany) installed a miniRUEDI on the Eugen Seibold, the world’s greenest research vessel. Since May of 2019, the innovative yacht has been sailing the high seas, and the miniRUEDI is set up to continuously analyse the dissolved gas concnetration in the surface water. By gradually gathering data on the various marine provinces, the climate geochemists at the Max Planck Institute for Chemistry in Mainz will be able to chart a detailed description of the world’s oceans, characterising their current properties and even reconstructing how they change over time.

A New in Situ Method for Tracing Denitrification in Riparian Groundwater

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Andrea Popp and her colleagues used a miniRUEDI to study the dynamics of the biogeochemical N2 turnover in a river/groundwater system over a six-month period (Environ. Sci. Technol. 2020, 54). In addition to N2, they analysed He, Ar and Kr concentrations in the water in order to quantify the air-derived N2 component in the groundwater. These miniRUEDI data allowed them to rigorously quantify the N2 excess produced by denitrification, and to unravel the spatio-temporal dynamics of N2 denitrification in the riparian groundwater system. The results show that denitrification is highly variable in space and time, emphasizing the need for spatially and temporally resolved data to accurately account for denitrification dynamics in groundwater.

Full paper: “A New in Situ Method for Tracing Denitrification in Riparian Groundwater”, Environ. Sci. Technol. 2020, 54, 3, 1562-1572, DOI: 10.1021/acs.est.9b05393

Using a miniRUEDI to identify and quantify groundwater mixing

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In their recent paper “Integrating Bayesian Groundwater Mixing Modeling With On‐Site Helium Analysis to Identify Unknown Water Sources“, Andrea Popp and her Eawag colleagues studied a groundwater system used for drinking water production. The drinking water field needs to be protected from several potential sources of contamination by artificially controlling the groundwater flow. In view of these problems, the Eawag team identified the origins of the different groundwater components in the drinking water field and quantified their mixing ratios using a miniRUEDI by analysing He and other dissolved gases as natural tracers for the different groundwater components.

miniRUEDI used to quantify air-water gas exchange in surface waters – without adding tracer gases!

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In their recent paper “A Novel Approach To Quantify Air–Water Gas Exchange in Shallow Surface Waters Using High-Resolution Time Series of Dissolved Atmospheric Gases“, Uli Weber and his colleagues developed a new method to study and quantify the air-water gas exchange in a shallow surface waters. The method uses a miniRUEDI to quantify the natural variations of dissolved atmospheric gases in the water. The resulting high-resolution time series of dissolved gas concentrations in the water yield accurate gas exchange rates without adding artificial tracers.

miniRUEDI used for gas monitoring in a full-scale experiment targeted at underground radioactive waste disposal

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In their recent paper “On-line monitoring of the gas composition in the full-scale emplacement experiment at Mont Terri (Switzerland)“, Yama Tomonaga and his colleagues at Nagra, Eawag and ETH Zurich used a miniRUEDI to study the dynamics and the fate of the gas species in a tunnel of a full-scale experiment targeted at radioactive waste disposal in Switzerland.

Highlights:

  • An on-line gas monitoring has been implemented for the FE experiment at Mont Terri underground rock laboratory.
  • The monitoring of gas species was performed successfully over several months.
  • Rapid gas exchange occurs between drift backfilling and FE niche/host rock.
  • Terrigenic gases (e.g., 4He, 40Ar, CH4, CO2) accumulated in the backfill pore space.
  • Fast gas exchange partly explains the O2 removal from the backfill pore space.

Use of miniRUEDI Instruments in Air/Water Exchange Studies in Small Streams

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In their recent paper “In-situ mass spectrometry improves the estimation of stream reaeration from gas-tracer tests“, Julia Knapp and her colleagues at Uni Tübingen and Eawag used two miniRUEDI instruments to study air/water exchange in small streams.

Highlights:

  • Determination of gas-exchange rates in streams from gas-tracer testsQuantification of gas tracers using a portable gas-equilibrium mass spectrometer
  • Reliable estimation of reaeration rates from krypton and propane injections
  • In-situ analysis avoids gas loss and improves the determination of reaeration rates