A direct evidence for high carbon dioxide and radon-222 discharge in Central Nepal

Perrier, Frédéric; Richon, Patrick; Byrdina, Svetlana; France‐Lanord, Christian; Rajaure, Sudhir; Koirala, Bharat Prasad; Shrestha, Prabin; Gautam, Umesh; Tiwari, Dilli Ram; Revil, A.; Bollinger, Laurent; Contraires, Simon; Bureau, Sarah; Sapkota, Soma Nath

doi:10.1016/j.epsl.2008.12.008

Cited by 51 publications

(84 citation statements)

References 46 publications

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“…SSA code written by the authors in Scilab was used for this investigation. (Perrier et al, 2009b). In each case, non-stationary features are clearly visible in the data, some having magnitudes exceeding those of the stationary features under investigation.…”

Section: Singular Spectrum Analysismentioning

confidence: 83%

“…The soil was assumed to be always saturated at that location. The second time series, of 336 days duration, has been obtained in the soil of a river terrace, at a depth of 30 cm, in Syabru-Bensi, Nepal, in the vicinity of a geothermal zone (Perrier et al, 2009b). This site is characterised by a dry winter season and a summer season dominated by heavy monsoon rains.…”

Section: Introductionmentioning

confidence: 99%

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Spectral-decomposition techniques for the identification of periodic and anomalous phenomena in radon time-series

Crockett

Perrier

Richon

2010

Nat. Hazards Earth Syst. Sci.

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Abstract. Two hourly-sampled time-series of soil-gas radon concentrations of durations of the order of a year have been investigated for periodic and anomalous phenomena. These time-series have been recorded in locations having little or no routine human behaviour and thus are effectively free of significant anthropogenic influences. One measurement site, Sur-Frêtes, is located in the French Alps, with saturated soil conditions; the second site, Syabru-Bensi, is located in Nepal, in a river terrace with unsaturated soil conditions. In such conditions, periodic components with periods ranging from 8 h to 7 days are often weak and intermittent and therefore, even in the presence of stationary forcing, difficult to identify.Two spectral decomposition techniques, Empirical Mode Decomposition (EMD) and Singular Spectrum Analysis (SSA), have been applied to these time series and yield similar results. For Sur-Frêtes, weak diurnal and semi-diurnal components are observed with EMD, while SSA reveals only a diurnal component. In Syabru-Bensi, both EMD and SSA reveal a strong diurnal component and a weaker semi-diurnal component. Tidal components M1 and M2 are also suggested by EMD in Sur-Frêtes, while these frequencies are not observed in Syabru-Bensi. The development of such analytical techniques can help in characterising the multiple physical processes contributing to the surface and subsurface dynamics of soil gases.

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Section: Singular Spectrum Analysismentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Spectral-decomposition techniques for the identification of periodic and anomalous phenomena in radon time-series

Crockett

Perrier

Richon

2010

Nat. Hazards Earth Syst. Sci.

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“…The MCT thus provides a possible percolation path for metamorphic fluids to reach the surface. Geochemical modelling (Becker et al, 2008;Evans et al, 2008) further suggested massive degassing, which was actually observed in Syabru-Bensi, in the Langtang range north of Kathmandu (Perrier et al, 2009a). Carbon dioxide fluxes at that location reach spectacular values, larger than 10 kg m À2 d À1 , comparable with values observed in active volcanoes (Finizola et al, 2006).…”

Section: Introductionmentioning

confidence: 57%

“…Gas discharge can actually be identified up to 100 m around GZ1 and GZ2. Measurements repeated after several months also indicated that the gas fluxes are rather stable over a one-year period (Perrier et al, 2009a). These gas discharges are also associated with an extended dipolar self-potential anomaly (Byrdina et al, 2009), whose spatial structure and magnitude are compatible with hydroelectric coupling associated with water circulation driven by the gas discharges.…”

Section: The Syabru-bensi Geothermal Systemmentioning

confidence: 93%

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Temporal signatures of advective versus diffusive radon transport at a geothermal zone in Central Nepal

Richon¹,

Perrier²,

Koirala³

et al. 2011

Journal of Environmental Radioactivity

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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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A direct evidence for high carbon dioxide and radon-222 discharge in Central Nepal

Cited by 51 publications

References 46 publications

Spectral-decomposition techniques for the identification of periodic and anomalous phenomena in radon time-series

Spectral-decomposition techniques for the identification of periodic and anomalous phenomena in radon time-series

Temporal signatures of advective versus diffusive radon transport at a geothermal zone in Central Nepal

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

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