Application of stochastic simulation to CO₂ flux from soil: Mapping and quantification of gas release

Abstract

[1] Conditional sequential Gaussian simulations (sGs) have been applied for the first time to the study of soil diffuse degassing from different volcanic and nonvolcanic systems. The application regards five data sets of soil CO 2 fluxes measured with the accumulation chamber methodology at the volcanic areas of Solfatara of Pozzuoli (Italy), Vesuvio cone (Italy), Nisyros (Greece), and Horseshoe Lake (California) and at the nonvolcanic degassing area of Poggio dell'Olivo (Italy). The sGs algorithm was used to generate 100 realizations of CO 2 flux for each area. Probabilistic summaries of these simulations, together with the information given by probability plots, were used (1) to draw maps of the probability that CO 2 fluxes exceed thresholds specific for a background flux, i.e., to define the probable extension of the degassing structures, (2) to calculate the total CO 2 output, and (3) to quantify the uncertainty of the estimation. The results show that the sGs is a suitable tool to model soil diffuse degassing, producing realistic images of the distribution of the CO 2 fluxes that honor the histogram and variogram of the original data. Moreover, the relation between the sample design and the uncertainty of estimation was investigated leading to an empirical relation between uncertainty and the sampling density that can be useful for the planning of future CO 2 flux surveys. Citation: Cardellini, C., G. Chiodini, and F. Frondini, Application of stochastic simulation to CO 2 flux from soil: Mapping and quantification of gas release,

Relationship between Diffuse CO2 Degassing and Volcanic Activity. Case Study of the Poás, Irazú, and Turrialba Volcanoes, Costa Rica

“…However, sGs appear to be the most suitable methodology for this purpose according to Cardellini et al (2003) and Lewicki et al (2005). sGs consist of the generation of a large number of possible and equally probable spatial distributions of the variable under consideration with respect to the histogram (Cardellini et al, 2003). Furthermore, the generation of a large number of variable events allows statistical uncertainty to be calculated (typically the mean plus or minus two standard deviations which contain 95.4% of the events).…”

“…Many geostatistical interpolation methods-such as, ordinary krigingare reliable and were used, for example, by Chiodini et al (2001). However, sGs appear to be the most suitable methodology for this purpose according to Cardellini et al (2003) and Lewicki et al (2005). sGs consist of the generation of a large number of possible and equally probable spatial distributions of the variable under consideration with respect to the histogram (Cardellini et al, 2003).…”

“…The diffuse degassing data for volcanoes is known to be lognormally distributed and to exhibit a frequently overlapping polymodal distribution indicating different degassing sources (Chiodini et al, 1998(Chiodini et al, , 2001Cardellini et al, 2003). Basically, these sources are generally a background and endogenous sources and the data are assigned to those sources using a graphical statistical approach (Chiodini et al, 1998(Chiodini et al, , 2001Cardellini et al, 2003).…”

“…Basically, these sources are generally a background and endogenous sources and the data are assigned to those sources using a graphical statistical approach (Chiodini et al, 1998(Chiodini et al, , 2001Cardellini et al, 2003). The partitioning of these sources provides important information about the volcano's dynamic and volcanic activity.…”

Tunable diode laser measurements of hydrothermal/volcanic CO<sub>2</sub> and implications for the global CO<sub>2</sub> budget

“…The volcanic/hydrothermal CO 2 flux sustained by diffuse soil degassing can be measured relatively easily during surveys (Chiodini et al, 1996(Chiodini et al, , 2005Favara at al., 2001;Hernán-dez, 2001;Cardellini et al, 2003;Inguaggiato et al, 2005Inguaggiato et al, , 2012Pecoraino et al, 2005;Mazot et al, 2011) or with permanent installations Carapezza et al, 2004;Werner and Cardellini, 2006;Inguaggiato et al, 2011). In contrast, the volcanic CO 2 flux contributed by open vents and/or fumarolic fields is more difficult to measure, since the volcanic CO 2 gas signal is diluted -upon atmospheric transport -into the overwhelming background air CO 2 signal.…”