{"title":"火山气体中的氢和硫化氢:丰度、过程和大气通量","authors":"Alessandro Aiuppa, Yves Moussallam","doi":"10.5802/crgeos.235","DOIUrl":null,"url":null,"abstract":"Hydrogen (H 2 ) and hydrogen sulphide (H 2 S) are typically present at only minor to trace levels in volcanic gas emissions, and yet they occupy a key role in volcanic degassing research in view of the control they exert on volcanic gas reducing capacity (e.g., their ability to remove atmospheric O 2 ). In combination with other major compounds, H 2 and H 2 S are also key to extracting information on source magma conditions (temperature and redox) from observed magmatic gas compositions. Here, we use a catalogue, compiled by extracting from the geological literature a selection of representative analyses of magmatic to mixed (magmatic–hydrothermal) gases, to review the processes that control H 2 and H 2 S abundance in volcanic gases. We show that H 2 concentrations and H 2 /H 2 O ratios in volcanic gases both exhibit strong positive temperature dependences, while H 2 S concentrations and H 2 S/SO 2 ratios are temperature insensitive overall. The high H 2 concentrations (and low H 2 S/SO 2 compositions, of ∼0.1 on average) in high-temperature (>1000 °C) magmatic gases are overall consistent with those predicted thermodynamically assuming external redox buffering operated by the coexisting silicate melt, at oxygen fugacities ranging from ΔFMQ -1 to 0 (non-arc volcanoes) to ΔFMQ 0 to +2 (arc volcanoes) (where ΔFMQ is oxygen fugacity expresses as a log unit difference relative to the Fayalite–Magnetite–Quartz oxygen fugacity buffer). Lower temperature (<1000 °C) volcanic gases exhibit more oxidizing redox conditions (typically above the Nickel–Nickel Oxide buffer) that are caused by a combination of (i) gas re-equilibration during closed-system (gas-phase only) adiabatic cooling in a gas-buffered system, and (ii) heterogenous (gas–mineral) reactions. We show, in particular, that gas-phase equilibrium in the H 2 –H 2 S–H 2 O–SO 2 system is overall maintained upon cooling down to ∼600 °C, while quenching of higher temperature equilibria (at which Apparent Equilibrium Temperatures, AETs, largely exceed measured discharge temperatures) is more frequently observed for higher extents of cooling (e.g., at T<600 °C). In such lower temperature volcanic environments, gas–mineral reactions also become increasingly important, scavenging magmatic SO 2 and converting it into H 2 S and hydrothermal minerals (sulphates and sulphides). These heterogeneous reactions, when occurring, can also control the temperature dependence of the volcanic gas H 2 /H 2 O ratios. Finally, by using our volcanic gas dataset in tandem with recently published global volcanic SO 2 and CO 2 budgets, we provide refined estimates for total H 2 S (median, 1.4 Tg/yr; range, 0.9–8.8 Tg/yr) and H 2 (median, 0.23 Tg/yr; range, 0.06–1 Tg/yr) fluxes from global subaerial volcanism.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":2.0000,"publicationDate":"2023-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Hydrogen and hydrogen sulphide in volcanic gases: abundance, processes, and atmospheric fluxes\",\"authors\":\"Alessandro Aiuppa, Yves Moussallam\",\"doi\":\"10.5802/crgeos.235\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Hydrogen (H 2 ) and hydrogen sulphide (H 2 S) are typically present at only minor to trace levels in volcanic gas emissions, and yet they occupy a key role in volcanic degassing research in view of the control they exert on volcanic gas reducing capacity (e.g., their ability to remove atmospheric O 2 ). In combination with other major compounds, H 2 and H 2 S are also key to extracting information on source magma conditions (temperature and redox) from observed magmatic gas compositions. Here, we use a catalogue, compiled by extracting from the geological literature a selection of representative analyses of magmatic to mixed (magmatic–hydrothermal) gases, to review the processes that control H 2 and H 2 S abundance in volcanic gases. We show that H 2 concentrations and H 2 /H 2 O ratios in volcanic gases both exhibit strong positive temperature dependences, while H 2 S concentrations and H 2 S/SO 2 ratios are temperature insensitive overall. The high H 2 concentrations (and low H 2 S/SO 2 compositions, of ∼0.1 on average) in high-temperature (>1000 °C) magmatic gases are overall consistent with those predicted thermodynamically assuming external redox buffering operated by the coexisting silicate melt, at oxygen fugacities ranging from ΔFMQ -1 to 0 (non-arc volcanoes) to ΔFMQ 0 to +2 (arc volcanoes) (where ΔFMQ is oxygen fugacity expresses as a log unit difference relative to the Fayalite–Magnetite–Quartz oxygen fugacity buffer). Lower temperature (<1000 °C) volcanic gases exhibit more oxidizing redox conditions (typically above the Nickel–Nickel Oxide buffer) that are caused by a combination of (i) gas re-equilibration during closed-system (gas-phase only) adiabatic cooling in a gas-buffered system, and (ii) heterogenous (gas–mineral) reactions. We show, in particular, that gas-phase equilibrium in the H 2 –H 2 S–H 2 O–SO 2 system is overall maintained upon cooling down to ∼600 °C, while quenching of higher temperature equilibria (at which Apparent Equilibrium Temperatures, AETs, largely exceed measured discharge temperatures) is more frequently observed for higher extents of cooling (e.g., at T<600 °C). In such lower temperature volcanic environments, gas–mineral reactions also become increasingly important, scavenging magmatic SO 2 and converting it into H 2 S and hydrothermal minerals (sulphates and sulphides). These heterogeneous reactions, when occurring, can also control the temperature dependence of the volcanic gas H 2 /H 2 O ratios. Finally, by using our volcanic gas dataset in tandem with recently published global volcanic SO 2 and CO 2 budgets, we provide refined estimates for total H 2 S (median, 1.4 Tg/yr; range, 0.9–8.8 Tg/yr) and H 2 (median, 0.23 Tg/yr; range, 0.06–1 Tg/yr) fluxes from global subaerial volcanism.\",\"PeriodicalId\":50651,\"journal\":{\"name\":\"Comptes Rendus Geoscience\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":2.0000,\"publicationDate\":\"2023-09-26\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Comptes Rendus Geoscience\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.5802/crgeos.235\",\"RegionNum\":4,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"GEOSCIENCES, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Comptes Rendus Geoscience","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.5802/crgeos.235","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
Hydrogen and hydrogen sulphide in volcanic gases: abundance, processes, and atmospheric fluxes
Hydrogen (H 2 ) and hydrogen sulphide (H 2 S) are typically present at only minor to trace levels in volcanic gas emissions, and yet they occupy a key role in volcanic degassing research in view of the control they exert on volcanic gas reducing capacity (e.g., their ability to remove atmospheric O 2 ). In combination with other major compounds, H 2 and H 2 S are also key to extracting information on source magma conditions (temperature and redox) from observed magmatic gas compositions. Here, we use a catalogue, compiled by extracting from the geological literature a selection of representative analyses of magmatic to mixed (magmatic–hydrothermal) gases, to review the processes that control H 2 and H 2 S abundance in volcanic gases. We show that H 2 concentrations and H 2 /H 2 O ratios in volcanic gases both exhibit strong positive temperature dependences, while H 2 S concentrations and H 2 S/SO 2 ratios are temperature insensitive overall. The high H 2 concentrations (and low H 2 S/SO 2 compositions, of ∼0.1 on average) in high-temperature (>1000 °C) magmatic gases are overall consistent with those predicted thermodynamically assuming external redox buffering operated by the coexisting silicate melt, at oxygen fugacities ranging from ΔFMQ -1 to 0 (non-arc volcanoes) to ΔFMQ 0 to +2 (arc volcanoes) (where ΔFMQ is oxygen fugacity expresses as a log unit difference relative to the Fayalite–Magnetite–Quartz oxygen fugacity buffer). Lower temperature (<1000 °C) volcanic gases exhibit more oxidizing redox conditions (typically above the Nickel–Nickel Oxide buffer) that are caused by a combination of (i) gas re-equilibration during closed-system (gas-phase only) adiabatic cooling in a gas-buffered system, and (ii) heterogenous (gas–mineral) reactions. We show, in particular, that gas-phase equilibrium in the H 2 –H 2 S–H 2 O–SO 2 system is overall maintained upon cooling down to ∼600 °C, while quenching of higher temperature equilibria (at which Apparent Equilibrium Temperatures, AETs, largely exceed measured discharge temperatures) is more frequently observed for higher extents of cooling (e.g., at T<600 °C). In such lower temperature volcanic environments, gas–mineral reactions also become increasingly important, scavenging magmatic SO 2 and converting it into H 2 S and hydrothermal minerals (sulphates and sulphides). These heterogeneous reactions, when occurring, can also control the temperature dependence of the volcanic gas H 2 /H 2 O ratios. Finally, by using our volcanic gas dataset in tandem with recently published global volcanic SO 2 and CO 2 budgets, we provide refined estimates for total H 2 S (median, 1.4 Tg/yr; range, 0.9–8.8 Tg/yr) and H 2 (median, 0.23 Tg/yr; range, 0.06–1 Tg/yr) fluxes from global subaerial volcanism.
期刊介绍:
Created in 1835 by physicist François Arago, then Permanent Secretary, the journal Comptes Rendus de l''Académie des sciences allows researchers to quickly make their work known to the international scientific community.
It is divided into seven titles covering the range of scientific research fields: Mathematics, Mechanics, Chemistry, Biology, Geoscience, Physics and Palevol. Each series is led by an editor-in-chief assisted by an editorial committee. Submitted articles are reviewed by two scientists with recognized competence in the field concerned. They can be notes, announcing significant new results, as well as review articles, allowing for a fine-tuning, or even proceedings of symposia and other thematic issues, under the direction of invited editors, French or foreign.