Arsenic in fumarolic gases of Vulcano(Aeolian Islands, Italy) from 1978 to 1993: Geochemical evidence from multivariate analysis.

Signorelli, S.; Buccianti, Antonella; Martini, M.; Piccardi, Giovanni

doi:10.2343/geochemj.32.367

Cited by 16 publications

(9 citation statements)

References 48 publications

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“…The ability of a degassing melt to supply significant quantities of As and Au to the superjacent magmatic-hydrothermal environment via a magmatic volatile phase can be inferred from the high concentrations of As and Au in volcanic gas emissions (Symonds et al, 1987(Symonds et al, , 1990Quisefit et al, 1989;Mambo et al, 1991;Mambo and Yoshida, 1993;Hedenquist, 1995;Taran et al, 1995;Barnes and Seward, 1997;Fulignati and Sbrana, 1998;Signorelli et al, 1998;Yudovskaya et al, 2006). This is corroborated by in situ measurements of As distribution coefficients between melt and exsolving aqueous fluids from co-existing melt and fluid inclusion assemblages (Audétat et al, 2000;Audétat and Pettke, 2003).…”

Section: Introductionmentioning

confidence: 66%

The partitioning behavior of As and Au in S-free and S-bearing magmatic assemblages

Simon

Pettke

Candela

et al. 2007

Geochimica et Cosmochimica Acta

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Section: Introductionmentioning

confidence: 66%

The partitioning behavior of As and Au in S-free and S-bearing magmatic assemblages

Simon

Pettke

Candela

et al. 2007

Geochimica et Cosmochimica Acta

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“…In this phase the environment was characterized by conditions favoring the mobilization phenomena of chemical elements (i.e. As abundance increased from 10 to 25 ppm from 1983 to 1993 as reported by Signorelli et al (1998)). The second perturbation vector, given by p A!B ; indicates that an important relative increase in CO 2 and SO 2 characterized the approach to the crisis period which started in 1978; the passage was signed also by the relative increase of HF, HCl and H 2 O.…”

Section: Hierarchical Cluster Analysis In the Simplex: Results And DImentioning

confidence: 75%

Statistical evaluation of compositional changes in volcanic gas chemistry: a case study

Buccianti

Pawlowsky‐Glahn

2006

Stoch Environ Res Ris Assess

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The geochemical analysis of fumarolic gases collected at quiescent and active volcanic systems over time is one of the main tools to understand changes in the state of activity for surveillance and risk assessment. The continuous output of chemical species through fumarolic activity, which characterizes the inter-eruptive intervals, has also a major and general influence on the environment. The mobilization of chemical species due to weathering of volcanic rocks, or the input of gaseous components from fumarolic activity, results in some kind of modification of the environment affecting, in particular, water, soils, and the consequent growth of the plants present in these areas. In this paper, an investigation on the chemical composition of fumarolic gases collected at Vulcano island (Sicily, southern Italy) is performed, with the aim to discover how data changes during the monitored period of time, and to design a strategy for the environmental surveillance of volcanic systems taking into account the nature of the analyzed data. In order to summarize the contribution of all the components that can affect the chemical composition of volcanic gases, a multivariate statistical approach appears to be suitable. Since many of those methods assume independent observations, the possible presence of time-dependent structures should be carefully verified. In this framework, given the compositional nature of geochemical data, we have applied recent theoretical and practical developments in the field of compositional data analysis to work in the correct sample space and to isolate groups of parts responsible for significant changes in the gas chemistry. The proposed approach can be generalized to the investigation of complex environmental systems.

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“…Given the relationships between As, HF, and H 2 S, the sub-composition was analyzed in order to obtain a simpler model for the behavior of arsenic concentrations. First results evidence a two-group structure of the analyzed sub-composition, not clearly pointed out in the preceding multivariate investigation by Signorelli et al (1998), which can be interpreted as a consequence of events that occur in time and/or of changes in temperature. In this context the interpretation of relative changes in the analyzed sub-composition has required an accurate process of geochemical hypotheses validation.…”

Section: Introductionmentioning

confidence: 86%

“…Thus, the distribution of heavy metals showing significant mobility in hydrothermal conditions has been recently considered as an important step in monitoring programs of well-known toxicity elements (Signorelli 1997). In this framework, the significant As mobility in high temperature fumarolic fluids and its presence in low temperature fumarolic products, has been evaluated for Vulcano Island by taking into account its concentrations in the gas condensates of a fumarole, which appeared inside the crater in 1978 and has been continuously monitored since then (Signorelli et al 1998). Results in previous investigations of the relationships between the evolution with time of the whole fluid chemical composition and As abundance indicate that the element appears to be positively related to temperature and to chemical variables given by the log ratios (HF/H 2 O) and (H 2 S/H 2 O), which are generally interpreted as associated to an intense hydrothermal circulation.…”

Section: Introductionmentioning

confidence: 99%

Visualization and modeling of sub-populations of compositional data: statistical methods illustrated by means of geochemical data from fumarolic fluids

Pawlowsky‐Glahn

Buccianti

2002

International Journal of Earth Sciences

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In the investigation of fluid samples of a volcanic system, collected during a given period of time, one of the main goals is to discover cause-effect relationships that allow us to explain changes in the chemical composition. They might be caused by physicochemical factors, such as temperature, pressure, or non-conservative behavior of some chemical constituents (addition or subtraction of material), among others. The presence of subgroups of observations showing different behavior is evidence of unusually complex situations, which might render even more difficult the analysis and interpretation of observed phenomena. These cases require appropriate statistical techniques as well as sound a priori hypothesis concerning underlying geological processes. The purpose of this article is to present the state of the art in the methodology for a better visualization of compositional data, as well as for detecting statistically significant sub-populations. The scheme of this article is to present first the application, and then the underlying methodology, with the aim of the first motivating the second. Thus, the first part has the goal to illustrate how to understand and interpret results, whereas the second is devoted to expose how to perform a study of this kind. The case study is related to the chemical composition of a fumarole of Vulcano Island (southern Italy), called F14. The volcanic activity at Vulcano Island is subject to a continuous program of geochemical surveillance from 1978 up to now and the large data set of observations contains the main chemical composition of volcanic gases as well as trace element concentrations in the condensates of fumarolic gases. Out of the complete set of measured components, the variables H 2 S, HF and As, determined in samples collected from 1978 to 1993 (As is not available in recent samples) are used to characterize two groups in the original population, which proved to be statistically distinct. The choice of the variables is motivated by the importance of investigating the behavior of well-known toxicity elements, which show, like As, a significant mobility under hydrothermal conditions. The statistical methodology used for this study is based on models devised for compositional data. They include (1) the perturbation approach for a better visualization; (2) cluster analysis to detect groups; (3) confidence regions for the center of the groups to obtain graphical evidence of differences between groups; and (4) tests of hypothesis about centers and covariance structures to obtain statistical evidence about differences between groups. The fact that only three components are used allows us to illustrate the results using ternary diagrams.

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Arsenic in fumarolic gases of Vulcano(Aeolian Islands, Italy) from 1978 to 1993: Geochemical evidence from multivariate analysis.

Cited by 16 publications

References 48 publications

The partitioning behavior of As and Au in S-free and S-bearing magmatic assemblages

The partitioning behavior of As and Au in S-free and S-bearing magmatic assemblages

Statistical evaluation of compositional changes in volcanic gas chemistry: a case study

Visualization and modeling of sub-populations of compositional data: statistical methods illustrated by means of geochemical data from fumarolic fluids

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