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(searched for: doi:10.1007/s00024-013-0756-9)
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, Sarah Sherlock, Alison Halton, Kerry Reid, Hazel Rymer, Simon Kelley
Journal of Volcanology and Geothermal Research, Volume 414; https://doi.org/10.1016/j.jvolgeores.2021.107212

Abstract:
We provide evidence that noble gasses (NGs) trapped in Pele's hairs and tears can be used as a tool to monitor the degassing behaviour of persistently active volcanic systems. We investigated 4He, 36Ar, 40Ar abundances and 4He/40Ar* and 40Ar/36Ar isotopic ratios in samples collected in March 2015 and March 2016 from Masaya volcano (Nicaragua). The resurgence of a lava lake in December 2015 provided the opportunity to monitor NG variations during a specific volcanic event. The variations in the NG abundances of individual glass particles are here attributed to solubility-controlled NG fractionation between melt and bubbles, and consequently correlated with sample vesicularity and vesicle size. Inhomogeneous incorporation of 36Ar, along with kinetic mass fractionation during magma degassing, vesiculation and fast-quenching of the samples after eruption, are the mechanisms that control the variability of the 40Ar/36Ar ratios observed in the samples. From March 2015 to March 2016, our data indicate a general increase of mean 40Ar* abundances from 1.9E−8 ± 1.4E−8 cc/g to 9.3E−8 ± 8.9E−8 cc/g and decrease in mean 4He/40Ar* ratios from 0.37 ± 0.15 to 0.18 ± 0.13. We ascribe this to the upward migration of a gas-rich magma from depth that recharged the shallow magmatic reservoir of Masaya at some point between the two collection periods. Since this model agrees well with the physical volcanology of Masaya and with gas plume measurements spanning our collection period, we suggest that NG in Pele's hairs and tears can be further used as a valuable tool to monitor degassing processes at Masaya volcano and, when samples are available, at other persistently degassing systems (e.g. Etna, Hawaii).
Marco Camarda, , Giorgio Capasso, , Sergio Gurrieri, Vincenzo Prano
Published: 21 August 2019
Earth-Science Reviews, Volume 198; https://doi.org/10.1016/j.earscirev.2019.102928

Abstract:
Natural soil CO2 emissions constitute a substantial portion of the carbon emitted in the atmosphere, particularly in volcano-tectonic areas where deep CO2 supply is also present because of the Earth's degassing. Hence, these emissions are considered of fundamental importance in the study of global CO2 budget estimates. Furthermore, in recent years, soil CO2 emissions have played an important role in the realm of seismic and volcanic studies as well as in the mitigation of gas-hazard-related risks. Although many methods are available for monitoring soil CO2 emissions, the comprehension and use of monitoring data can be challenging. This is because soil CO2 emissions are influenced by numerous processes and as consequence exhibit high spatio-temporal variability. In this framework, understanding the processes behind the variability of soil CO2 emissions is instrumental in improving their investigations. In addition, more suitable management of the monitoring data series is another crucial aspect of soil CO2 emission studies. In this study, we provide a detailed description of the processes that determine soil CO2 emissions and outline their impacts as functions of different features of the measurement sites. In particular, we examine the processes driven by both exogenous and endogenous factors and explain the origin of the observed variations. This study is based on the data acquired via eight monitoring stations on the island of Vulcano (Italy) from 2009 to 2017. The monitoring sites exhibited different features and covered a wide range of the soil CO2 emission values, thereby allowing a broad application of the obtained results.
Journal of Volcanology and Geothermal Research, Volume 315, pp 65-78; https://doi.org/10.1016/j.jvolgeores.2016.02.004

Abstract:
Soil CO2 flux and 222Rn activity measurements may positively contribute to the geochemical monitoring of active volcanoes. The influence of several environmental parameters on the gas signals has been substantially demonstrated. Therefore, the implementation of tools capable of removing (or minimizing) the contribution of the atmospheric effects from the acquired timeseries is a challenge in volcano surveillance. Here, we present four years-long continuous monitoring (from April 2007 to September 2011) of radon activity and soil CO2 flux collected on the NE flank of Stromboli volcano. Both gases record higher emissions during fall–winter (up to 2700 Bq*m− 3 for radon and 750 g m− 2 day− 1 for CO2) than during spring–summer seasons. Short-time variations on 222Rn activity are modulated by changes in soil humidity (rainfall), and changes in soil CO2 flux that may be ascribed to variations in wind speed and direction. The spectral analyses reveal diurnal and semi-diurnal cycles on both gases, outlining that atmospheric variations are capable to modify the gas release rate from the soil. The long-term soil CO2 flux shows a slow decreasing trend, not visible in 222Rn activity, suggesting a possible difference in the source depth of the of the gases, CO2 being deeper and likely related to degassing at depth of the magma batch involved in the February–April 2007 effusive eruption. To minimize the effect of the environmental parameters on the 222Rn concentrations and soil CO2 fluxes, two different statistical treatments were applied: the Multiple Linear Regression (MLR) and the Principal Component Regression (PCR). These approaches allow to quantify the weight of each environmental factor on the two gas species and show a strong influence of some parameters on the gas transfer processes through soils. The residual values of radon and CO2 flux, i.e. the values obtained after correction for the environmental influence, were then compared with the eruptive episodes that occurred at Stromboli during the analysed time span (2007–2011) but no clear correlations emerge between soil gas release and volcanic activity. This is probably due to i) the distal location of the monitoring stations with respect to the active craters and to ii) the fact that during the investigated period no major eruptive phenomena (paroxysmal explosion, flank eruption) occurred. Comparison of MLR and PCR methods in time-series analysis indicates that MLR can be more easily applied to real time data processing in monitoring of open conduit active volcanoes (like Stromboli) where the transition to an eruptive phase may occur in relatively short times.
, Nemesio M Pérez, , , , , , Jose Barrrancos, Germán D Padilla, Paulo Fernandes, et al.
Published: 10 April 2015
Earth, Planets and Space, Volume 67; https://doi.org/10.1186/s40623-015-0219-x

Abstract:
Diffuse CO2 emission surveys were carried out at São Vicente, Brava, and Fogo islands, Cape Verde, archipelago to investigate the relationship between diffuse CO2 degassing and volcanic activity. Total amounts of diffuse CO2 discharged through the surface environment of the islands of São Vicente, Brava, and Fogo were estimated in 226, 50, and 828 t d−1, respectively. The highest CO2 efflux values of the three volcanic islands systems were observed at the summit crater of Pico do Fogo (up to 15.7 kg m−2 d−1). Statistical graphical analysis of the data suggests two geochemical populations for the diffuse CO2 emission surveys. The geometric mean of the peak population, expressed as a multiple of the geometric mean of the background population, seems to be the best diffuse CO2 emission geochemical parameter to correlate with the volcanic activity (age of the volcanism) for these three island volcanic systems at Cape Verde. This observation is also supported by helium isotopic signature observed in the Cape Verde’s fluids, fumaroles, and ground waters. This study provides useful information about the relationship between diffuse CO2 degassing and volcanic activity at Cape Verde enhancing the use of diffuse CO2 emission as a good geochemical tool, for volcanic monitoring at Cape Verde as well as other similar volcanic systems.
Published: 7 March 2015
Bulletin of Volcanology, Volume 77, pp 1-15; https://doi.org/10.1007/s00445-015-0914-2

Abstract:
We report herein the results of 13 soil CO2 efflux surveys at Cumbre Vieja volcano, La Palma Island, the most active basaltic volcano in the Canary Islands. The CO2 efflux measurements were undertaken using the accumulation chamber method between 2001 and 2013 to constrain the total CO2 output from the studied area and to evaluate occasional CO2 efflux surveys as a volcanic surveillance tool for Cumbre Vieja. Soil CO2 efflux values ranged from non-detectable up to 2442 g m−2 days−1, with the highest values observed in the south, where the last volcanic eruption took place (Teneguía, 1971). Isotopic analyses of soil gas carbon dioxide suggest an organic origin as the main contribution to the CO2 efflux, with a very small magmatic gas component observed at the southern part of the volcano. Total biogenic and magmatic combined CO2 emission rates showed a high temporal variability, ranging between 320 and 1544 t days−1 and averaging 1147 t days−1 over the 220-km2 region. Two significant increases in the CO2 emission observed in 2011 and 2013 were likely caused by an enhanced magmatic endogenous contribution revealed by significant changes in the 3He/4He ratio in a CO2-rich cold spring. The relatively stable emission rate presented in this work defines the background CO2 emission range for Cumbre Vieja during a volcanic quiescence period.
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