Experimental study of radon production and transport in an analogue for the Martian regolith

Meslin, Pierre‐Yves; Sabroux, J. C.; Bassot, S.; Chassefière, Éric

doi:10.1016/j.gca.2011.01.028

Cited by 18 publications

(4 citation statements)

References 59 publications

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“…It has been proposed that molecules of CO 2 gas, transported rapidly through soils to the atmosphere, might be able to entrain and disperse the small size soil particles associated with higher radium concentration [ Greeman and Rose , ; Breitner et al , ]. Alternatively, although such effects are poorly known in soils, CO 2 might affect radon adsorption: CO 2 is known to decrease the adsorption potential for radon on activated charcoals and silica gels [ Meslin et al , ]. Also, the presence of dissolved CO 2 in water might increase radium dissolution and hence transport in solution.…”

Section: Discussionmentioning

confidence: 99%

The Syabru‐Bensi hydrothermal system in central Nepal: 1. Characterization of carbon dioxide and radon fluxes

et al. 2014

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The Syabru-Bensi hydrothermal system (SBHS), located at the Main Central Thrust zone in central Nepal, is characterized by hot (30-62°C) water springs and cold (<35°C) carbon dioxide (CO 2 ) degassing areas. From 2007 to 2011, five gas zones (GZ1-GZ5) were studied, with more than 1600 CO 2 and 850 radon flux measurements, with complementary self-potential data, thermal infrared imaging, and effective radium concentration of soils. Measurement uncertainties were evaluated in the field. CO 2 and radon fluxes vary over 5 to 6 orders of magnitude, reaching exceptional maximum values of 236 ± 50 kg m À2 d À1 and 38.5 ± 8.0 Bq m À2 s À1 , with estimated integrated discharges over all gas zones of 5.9 ± 1.6 t d À1 and 140 ± 30 MBq d À1 , respectively. Soil-gas radon concentration is 40 × 10 3 Bq m À3 in GZ1-GZ2 and 70 × 10 3 Bq m À3 in GZ3-GZ4. Strong relationships between CO 2 and radon fluxes in all gas zones (correlation coefficient R = 0.86 ± 0.02) indicate related gas transport mechanisms and demonstrate that radon can be considered as a relevant proxy for CO 2 . CO 2 carbon isotopic ratios (δ 13 C from À1.7 ± 0.1 to À0.5 ± 0.1‰), with the absence of mantle signature (helium isotopic ratios R/R A < 0.05), suggest metamorphic decarbonation at depth. Thus, the SBHS emerges as a unique geosystem with significant deep origin CO 2 discharge located in a seismically active region, where we can test methodological issues and our understanding of transport properties and fluid circulations in the subsurface.

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Section: Discussionmentioning

confidence: 99%

The Syabru‐Bensi hydrothermal system in central Nepal: 1. Characterization of carbon dioxide and radon fluxes

et al. 2014

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“…Indeed, what we measured is the apparent emanation, which includes a small contribution from radon adsorption on mineral surfaces (Meslin et al, 2011). Adsorption decreases when temperature increases, resulting in an increased apparent emanation.…”

Section: Discussionmentioning

confidence: 77%

“…Moreover, the temperature effect on the radon sorption coefficient may be more precisely reproduced using an exponential trend (Schery and Whittlestone, 1989), which may be a method to isolate this contribution. However, adsorption is expected to be important only for particular minerals and only for small water content (Meslin et al, 2011) and, therefore, it is not straightforward that the temperature sensitivity of adsorption is sufficient to account for the observed values of TS. Finally, another parameter can affect E: the intercrystalline diffusion of radon in the mineral lattices (Bossus, 1984).…”

Section: Discussionmentioning

confidence: 99%

Heterogeneous temperature sensitivity of effective radium concentration from various rock and soil samples

Girault

Perrier

2011

Nat. Hazards Earth Syst. Sci.

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Abstract. Temporal variations of radon concentration, or spatial variations around geothermal systems, are partly driven by the effect of temperature on the radon source term, the effective radium concentration (EC Ra ). EC Ra from 12 crushed rock and 12 soil samples from Nepal was measured in the laboratory using the radon accumulation method and Lucas scintillation flasks at three temperatures: 7, 22 and 37 • C. For each sample and at each temperature, 5 or 6 measurements were carried out, representing a total of 360 measurements, with an EC Ra average varying from 1.1 to 75 Bq kg −1 . While the effect is small, EC Ra was observed to increase with temperature in a significant and sufficiently reproducible manner. The increase was approximately linear with a slope (temperature sensitivity, TS) expressed in % • C −1 . We observed a large heterogeneity of TS with average values (range min-max) of 0.79 ± 0.05 (0.16-2.0) % • C −1 and 0.61 ± 0.05 (0.10-2.0) % • C −1 , for rock and soil samples, respectively. While this range overlaps with the results of previous studies, our values of TS tend to be smaller. The observed heterogeneity implies that the TS, rather poorly understood, needs to be assessed by dedicated experiments in every case where it is of consequence for the interpretation.

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“… 58 ). Here, for given layer i, we introduce empirical relations for porosity- and water-saturation-dependent effective diffusion coefficients 75 ( and ), temperature-dependent water/air partition 58 and adsorption coefficients 76 ( and with and ) and water-saturation- and temperature-dependent radon source terms 73 , 77 ( ) and ). For both sites, we fix parameters according to field and laboratory data-sets, such as soil thickness (1 m), soil and rock porosity and water saturation (deep rock is assumed saturated), gas temperature, and radon source term; we calculate water–air partition and adsorption coefficients; and we correct radon source term.…”

Section: Methodsmentioning

confidence: 99%

Radon signature of CO2 flux constrains the depth of degassing: Furnas volcano (Azores, Portugal) versus Syabru-Bensi (Nepal Himalayas)

Girault

Viveiros

Silva

et al. 2022

Sci Rep

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Substantial terrestrial gas emissions, such as carbon dioxide (CO2), are associated with active volcanoes and hydrothermal systems. However, while fundamental for the prediction of future activity, it remains difficult so far to determine the depth of the gas sources. Here we show how the combined measurement of CO2 and radon-222 fluxes at the surface constrains the depth of degassing at two hydrothermal systems in geodynamically active contexts: Furnas Lake Fumarolic Field (FLFF, Azores, Portugal) with mantellic and volcano-magmatic CO2, and Syabru-Bensi Hydrothermal System (SBHS, Central Nepal) with metamorphic CO2. At both sites, radon fluxes reach exceptionally high values (> 10 Bq m−2 s−1) systematically associated with large CO2 fluxes (> 10 kg m−2 day−1). The significant radon‒CO2 fluxes correlation is well reproduced by an advective–diffusive model of radon transport, constrained by a thorough characterisation of radon sources. Estimates of degassing depth, 2580 ± 180 m at FLFF and 380 ± 20 m at SBHS, are compatible with known structures of both systems. Our approach demonstrates that radon‒CO2 coupling is a powerful tool to ascertain gas sources and monitor active sites. The exceptionally high radon discharge from FLFF during quiescence (≈ 9 GBq day−1) suggests significant radon output from volcanoes worldwide, potentially affecting atmosphere ionisation and climate.

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Experimental study of radon production and transport in an analogue for the Martian regolith

Cited by 18 publications

References 59 publications

The Syabru‐Bensi hydrothermal system in central Nepal: 1. Characterization of carbon dioxide and radon fluxes

The Syabru‐Bensi hydrothermal system in central Nepal: 1. Characterization of carbon dioxide and radon fluxes

Heterogeneous temperature sensitivity of effective radium concentration from various rock and soil samples

Radon signature of CO2 flux constrains the depth of degassing: Furnas volcano (Azores, Portugal) versus Syabru-Bensi (Nepal Himalayas)

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