Volcanic Gases Research Articles

The Independent Volcanic Eruption Source Parameter Archive (IVESPA, version 1.0): A new observational database to support explosive eruptive column model validation and development

Eruptive column models are powerful tools for investigating the transport of volcanic gas and ash, reconstructing past explosive eruptions, and simulating future hazards. However, the evaluation of these models is challenging as it requires independent estimates of the main model inputs (e.g. mass eruption rate) and outputs (e.g. column height). There exists no database of independently estimated eruption source parameters (ESPs) that is extensive, standardized, maintained, and consensus-based. This paper introduces the Independent Volcanic Eruption Source Parameter Archive (IVESPA, ivespa.co.uk), a community effort endorsed by the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) Commission on Tephra Hazard Modelling. We compiled data for 134 explosive eruptive events, spanning the 1902-2016 period, with independent estimates of: i) total erupted mass of fall deposits; ii) duration; iii) eruption column height; and iv) atmospheric conditions. Crucially, we distinguish plume top versus umbrella spreading height, and the height of ash versus sulphur dioxide injection. All parameter values provided have been vetted independently by at least two experts. Uncertainties are quantified systematically, including flags to describe the degree of interpretation of the literature required for each estimate. IVESPA also includes a range of additional parameters such as total grain size distribution, eruption style, morphology of the plume (weak versus strong), and mass contribution from pyroclastic density currents, where available. We discuss the future developments and potential applications of IVESPA and make recommendations for reporting ESPs to maximize their usability across different applications. IVESPA covers an unprecedented range of ESPs and can therefore be used to evaluate and develop eruptive column models across a wide range of conditions using a standardized dataset.

On the use of plume models to estimate the flux in volcanic gas plumes

Many of the standard volcanic gas flux measurement approaches involve absorption spectroscopy in combination with wind speed measurements. Here, we present a new method using video images of volcanic plumes to measure the speed of convective structures combined with classical plume theory to estimate volcanic fluxes. We apply the method to a nearly vertical gas plume at Villarrica Volcano, Chile, and a wind-blown gas plume at Mount Etna, Italy. Our estimates of the gas fluxes are consistent in magnitude with previous reported fluxes obtained by spectroscopy and electrochemical sensors for these volcanoes. Compared to conventional gas flux measurement techniques focusing on SO2, our new model also has the potential to be used for sulfur-poor plumes in hydrothermal systems because it estimates the H2O flux.

Sealing mechanisms in volcanic faulted reservoirs in Xujiaweizi extension, northern Songliao Basin, northeastern China

Distribution of volcanic reservoirs in Xujiaweizi half graben is controlled by both faults and sealing layers where their integrity could have been compromised. This paper documents the distribution of sealing units of the Denglouku and Yingcheng Formations based on seismic and well-log data to delineate all of the reservoirs with proper cap rocks within the volcanic Yincheng Formation via the relationship between the fault system and reservoir rocks. Based on the regional sealing effect of Denglouku Formation, two hydrocarbon traps are identified: the lower primary and upper secondary gas reservoirs where the formation with a mudstone percentage of more than 50% within the second member seals the primary reservoirs. The upper secondary trap is controlled by faults that have been activated during the structural reversal phase, causing the regional sealing layers in the Denglouku Formation to get displaced with a cap rock juxtaposition thickness of less than 35 m. This has created a series of fault-seal, dual-control reservoirs. The local seals within the Yingcheng Formation consist of mudstone, tight volcanic rock, and clayey breccia covering each volcanic eruption cycle. These local seals separate the volcanic gas reservoirs with a minimum thickness of 20 m. The local top seals in this tectonically active zone were placed on the hanging wall via the juxtaposition of the reservoir and overlying mudstone and/or clayey breccia. It was concluded that gas has migrated vertically through the faults and accumulated in the fault-controlled traps where sharp changes in the lithology (juxtaposition) form the seal, whereas the gas-water contact is controlled by the depth of the reservoir rock. Finally, this study concludes that the primary reservoirs are distributed in a sinusoidal configuration around the fault zone because of the dolphin effect of the Xuzhong strike-slip fault system that has connected the source and reservoir rocks.

Integration of Medical and Graduate Education with the USAT Secure SSPOC Instructional Model

Emergence of the 2019 Coronavirus pandemic posed new challenges for the delivery of medical and graduate education by Institutions throughout most of the world, as travel restrictions and regional lockdowns placed new demands never previously imposed on higher education. The University of Science Arts and Technology [USAT], located on the volcanic island of Montserrat, British West Indies began to prepare for such an eventuality since 2007 due to new volcanic eruptions. Despite 24/7 monitoring from the nearby state-of-the-art Montserrat volcano observatory, with little warning, the Soufriere Hills Volcano, located a distant 5 miles Southeast of the Campus spontaneously roared back to life in January 2007, venting clouds of volcanic ash and gas 8 kilometers (5 miles) into the sky with overflow lava and debris reaching the sea to the East and West; the volcano's lava dome continued to grow as it had since 2006, and local volcano experts worried that the rapidly growing lava dome, the mounting pressure building inside the dome could cause a catastrophic explosive eruption, and the renewed volcanic activity indicates that the volcano is now predicted to remain active well into the future. The volcanic activity caused the partial evacuation of the Island, including areas bordering the campus, resulting in the establishment of the USAT Campus satellite transmitter system [CST] in 2007. The CST enabled USAT the establishment of the first secure network on Island for the Secure Small Platform Online Course delivery network [SSPOC] and which enabled USAT to continue lecture operations uninterrupted with faculty that are highly experienced in the delivery of high quality Medical and Graduate education from both on-Island and remote locations in an efficient, timely, cost effective and highly productive and timely manner, while enabling students an on-island campus experience during periods of volcanicactivity including options for lectures, public health, epidemiology and environmental research, and selected experiences in areas of family and tropical medicine. During the current COVID pandemic and travel restriction imposed we further enhanced our on-line teaching system and secure SSPOC model, expanded International options, and as professors and students could not travel to the campus but all lectures were delivered online with absolutely no disruption or compromise in delivery of exceptional quality lectures and teaching experiences continued as if they occurred on campus.

Fracture propagation simulation and construction parameter optimization of eruptive phase volcanic rock

A large number of volcanic gas reservoirs are developed in the Sichuan Basin. Up to now, 92 wells have been drilled into Permian volcanic rock, which have good prospects for exploration. Among them, large areas of volcanic facies are distributed in the Sichuan Basin. The uneven distribution of pores in volcanic rocks of eruptive facies and the large difference in rock mechanics combination between different lithofacies make it difficult to develop volcanic gas reservoirs of eruptive facies effectively. Therefore, studying the characteristics of eruptive facies volcanic rocks and reservoir reconstruction schemes is very important for the later development of volcanic rocks Significantly, this paper builds a finite element model of a volcanic rock reservoir of the effusion facies based on the geological characteristics of the volcanic rock of the effusion facies, and optimizes the construction parameters in terms of construction displacement, fracturing fluid volume, and proppant. The research results show that, the injection pressure of the spouting phase under different stress difference conditions exhibits oscillating characteristics. The stress difference between the barrier and the reservoir is positively related to the injection point pressure and fracture fracturing. The recommended construction displacement is 4.5-5.5m3/min and the fracturing fluid dosage is 400-500m3, and the amount of proppant is between 30-40m3. The research content of this article is of great significance for the effective development of volcanic gas reservoirs in eruptive facies.

Research on Classification Management Method of Xushen Gas Field

Xushen gas field not only exploits volcanic gas reservoir, but also develops glutenite reservoir. In the production process, there are great differences in gas well productivity, formation pressure and single good reserves. By establishing the fine management mode of four types of wells, the “one type, one method, one well, one policy” has been realized. It mainly forms the multi-factor comprehensive production allocation technology with “two optimizations and three control” as the means, improves the winter peak regulation mechanism of withdrawal, supplement and shortterm emergency peak shaving, determines the drainage gas production technology to meet the current development needs, explores the treatment method of easy freezing plugging well with “three-step” as the main method, and effectively governs Low-yield and low-efficiency wells.

Laboratory Experiments on Tsunamigenic Discrete Subaqueous Volcanic Eruptions. Part 1: Free Surface Disturbances

AbstractA submarine volcanic eruption has the potential to generate a dangerous local tsunami. To better understand the free surface disturbance generated by an underwater volcanic eruption, which will form the initial condition for any subsequent wave generation, we conducted a series of laboratory experiments. In these experiments, compressed air was injected into a tank filled with water to simulate an underwater eruption. The experiments were repeated over a range of different pressures and water depths. Each eruption can be divided into three phases: A momentum‐driven jet, a buoyancy‐driven plume, and a fountain‐generation regime. Our experiments exhibit two fountain regimes (a dome regime and a finger regime), with a transition between them. These fountain regimes have been observed in several real submarine volcanic eruptions. This paper proposes a Froude number criterion to combine the water depths and source conditions together with the aspect ratios of fountains to quantify different fountain regimes. This quantitative relationship holds for two real subaqueous volcanic eruption cases (Myojin‐Sho eruption in 1952 and 1996 eruption in Karymskoye Lake). The fountain of the Myojin‐Sho shallow submarine eruption on September 23,1952 appears to have been in the dome regime, which means it was a relatively weak eruption. Unlike other eruptions from this volcano, which did generate tsunamis, no tsunami waves were detected on September 23 . This study contributes to an enhanced understanding of the usually unseen mechanism of free surface disturbances by volcanic gas injection during submarine eruptions.

EMPA, XRD, and Raman Characterization of Ag-Bearing Djurleite from the Lubin Mine, Lower Silesia, Poland

The chalcocite group minerals are widely distributed among different hydrothermally affected rocks, the oxidized zone of copper sulfide deposits, or may be even crystalline from supersaturated volcanic gases. Some of the chalcocite group minerals form the main Cu orebodies. Djurleite (Cu31S16) is a rare member of the chalcocite group, with a very complex structure. The physical and chemical similarities between all members of the group make them almost unidentifiable by macroscopic and microscopic methods. In this study, Ag-bearing djurleite from the Kupferschiefer deposits, Lower Silesia, Poland, is characterized by EMPA (Electron Microprobe Analyses), XRD (X-Ray Diffraction), and Raman spectroscopy. Djurleite from the investigated site has the following general, average chemical formula: Cu30.86Ag0.1Fe0.04S16. The Ag content is up to 0.55 wt.%, while Fe is up to 0.19 wt.%. The presence of djurleite confirms a low-temperature (~90 °C), hydrothermal origin of the Cu-Ag deposit in Kupferschiefer, which is consistent with previously studies. Moreover, the authors believe that Ag-rich djurleite may often be mistaken for Ag-rich chalcocite, which used to be one of the main Ag-bearing minerals in the orebody from the Cu-Ag deposit in the Fore-Sudetic Monocline. However, the confirmation of such a statement requires more samples, which should be studied in detail.

Gas–water two-phase productivity model for fractured horizontal wells in volcanic gas reservoirs with natural fractures

ABSTRACT Volcanic gas reservoirs, as new exploration and development fields, are rich in resources and have broad exploration and development prospects. However, compared with the conventional sandstone gas reservoirs, volcanic gas reservoirs have more complex storage and permeability mode, with multiple media including pores, caves and fractures, which determines the strong heterogeneity, complicated seepage mechanisms, and difficult development of volcanic gas reservoirs. To further improve the prediction accuracy of fractured horizontal well productivity in volcanic gas reservoirs, Xushen low-permeability volcanic gas reservoirs are presented as examples herein using the equation of motion based on the principle of equal flow. Considering the stress-sensitive effect, starting pressure gradient, high-speed turbulence effect, and dual porous medium structure, as well as combining the nature of gas and real gas state equations, a gas–water two-phase productivity model is established for a matrix-natural fracture-artificial fracture-wellbore volcanic gas reservoir fractured horizontal well. In addition, factors affecting production are studied. Results indicate that stress-sensitivity coefficient of different media has different effects on the production. The natural-fracture stress-sensitive coefficient has the greatest influence on production. With the increase of the natural-fracture stress-sensitive coefficient, the gas production decreases and the reduction amplitude changes little, which is almost uniform. When natural-fracture stress-sensitive coefficient is 0.08, gas well production decreases by 14.24%. The second is the artificial main fracture stress-sensitivity coefficient. With the increase of the artificial main fracture stress-sensitivity coefficient, the decrease of gas production becomes larger. When artificial main fracture stress-sensitivity coefficient is 0.1, gas well production decreases by 6.6%. The matrix stress-sensitivity coefficient on production is the least, almost zero. The high-speed nonlinear coefficient significantly affected the production. With the increase of the high-speed nonlinear coefficient, the gas well production decreases, and the decrease rate is faster and faster. When the high-speed nonlinear coefficient increases to 10000 m−1, gas well production decreases by 45.65%. However, the starting pressure gradient had little effect on production. Finally, the model is verified by the actual production data of Xushen1-H2 well. The average errors of the gas production, water production, and pressure calculations are 9.65%, 9.63%, and 9.8%, respectively. This study contributes positively to the productivity prediction of fractured horizontal wells in low-permeability volcanic gas reservoirs.

Shadow effect of the pH distribution of surface waters around the Kakkonda geothermal field, Japan

Field surveys were carried out at the Kakkonda geothermal field, where the location of the neutral hydrothermal reservoir has been identified, to investigate the shadow effect of the pH distribution in the actual geothermal development field. Methods using the electrical conductivity (EC)–pH relation and catchment area were employed, and the validity of the data was evaluated to select the most appropriate data for verifying the shadow effect. Results consistent with the concept of a shadow effect were obtained because acidic surface waters strongly affected by volcanic gases were not distributed above the neutral hydrothermal reservoir.

Testing for ocean acidification during the Early Toarcian using δ44/40Ca and δ88/86Sr

During the Early Toarcian, volcanic gases released by the Karoo-Ferrar large igneous province are widely believed to have caused severe environmental disturbances, including ocean acidification. Here we show records of δ44/40Ca and δ88/86Sr through the Early Toarcian, as recorded in three groups of biogenic calcite: Megateuthididae belemnites, Passaloteuthididae belemnites, and brachiopods of the species Soaresirhynchia bouchardi. We evaluate the data to eliminate the influence on isotopic composition of varying temperature, calcification rate, and salinity, through the section that may mask the environmental signals.Neither δ44/40Ca nor δ88/86Sr show negative isotope excursions across the suggested acidification interval as would be expected had acidification occurred. A profile of δ11B, re-interpreted from a published study, shows no variation through the interval. Taken together, these data provide little support for ocean acidification at this time. In our belemnites, values of δ88/86Sr are independent of temperature or Sr/Ca. For brachiopods, too few data are available to determine whether such dependences exist. Values of δ44/40Ca show a weak temperature control of magnitude +0.020 ± 0.004 ‰/°C (2 s.d.). In belemnites, δ44/40Ca also correlates positively with Mg/Ca and Sr/Ca.

Brittle fragmentation by rapid gas separation in a Hawaiian fountain

Brittle fragmentation, generating small pyroclasts from magma, is a key process determining eruptive style. How low-viscosity magma fragments within a rising fountain in a brittle manner, however, is not well understood. Here we describe a fragmentation process in Hawaiian fountains on the basis of observations from the 2018 lower East Rift Zone eruption of Kīlauea Volcano, Hawai’i. The dominant fragmentation mechanism is inertia driven and produces a population of large fluidal pyroclasts. However, when sufficient volcanic gas is released in the fountain, a subpopulation of smaller and more vesicular pyroclasts is generated and entrained into the gas-dominant convective plume. The size distribution of these pyroclasts is similar to that of brittlely fragmented solid materials. The erupted high-vesicularity pyroclasts sometimes preserve a deformed shape. These observations suggest that late-stage rapid expansion lowers the gas temperature adiabatically and cools the outer surface of liquid pyroclasts below the glass transition temperature. The rigid crust fragments as the hot interior attempts to expand due to further volatile diffusion from the melt into bubbles. Adiabatic expansion of volcanic gas occurs in all eruptions. Brittle fragmentation induced by rapid adiabatic cooling may be a widespread process, although of varying importance, in explosive eruptions. In a Hawaiian fountain eruption, rapid gas expansion cools the melt below the glass transition temperature and causes brittle magma fragmentation, producing small, vesicular pyroclasts, according to observations of the 2018 eruption of Kīlauea.

Clay mineral characteristics in volcanic tuffs of Dokdo, South Korea: implication on their genesis and evolution

Secondary alteration minerals like clays accompanied by volcanic activity can provide an important information on eruption cycle. Representative volcanic tuffs and seabed sediments were collected from the Dokdo volcanic island in East Sea, South Korea, to interpret eruption cycle based on clay mineral characteristics and other geochemical proxies (sulfur isotope composition, Si/Al, K/Al, among others). Tuffs are mainly composed of volcanic glass and hydrothermally altered phenocrysts. Secondary minerals such as clay mineral species in volcanic tuffs mostly were identified as smectite comprising dioctahedral sheets, based on expanding to 15.8 A after treatment with 1 M MgCl2 solution, and 060 reflections near at 1.48 A. Moreover, the results of infrared bands, based on (Al, Al)–OH (904–912 cm−1), (Al, Fe)–OH (865–877 cm−1), (Fe, Mg)–OH (778–798 cm−1) indicate the presence of dioctahedral sheets in clay mineral structure. Partially, occurrence of kaolinite and relatively low pH values and K/Al ratios at the Eolgulbawi tuff support chemical flexibility of clay mineral species. The δ34S value of Dongdo tuff (H2O–S: 15.3‰) is close to water leached sulfate, whereas Seodo tuff II including pyrite and native sulfur (− 5.5‰) shows a value of H2S-bearing volcanic gases. The similarity of chemical compositions between clay fractions and surrounding volcaniclastic rocks suggests that the smectite formed in low-temperature hydrothermal environments, where alkali elements were supplied under reducing conditions. Clay fractions separated from seabed sediments include diatom frustule with higher SiO2/Al2O3 ratios, and clay minerals contain mineral nitrogen originated from organic-rich seafloor sediments. Moreover, the δ34S values of seabed sediments (1.8‰, 8.4‰) indicate that the different origin of clay mineral species between tuffs and seabed sediments. It can be concluded that the alteration types and clay mineral characteristics are similar to the Surtseyan volcano, generally known as shallow-marine phreatomagmatic eruption and deposits. It further suggests that clay minerals sensitive to environmental change will be useful to interpret the volcanic environment characterized by explosive hydrovolcanic activities that occurred at the time of magma in contact with water before erupting into the atmosphere.

Synoptic analysis of a decade of daily measurements of SO<sub>2</sub> emission in the troposphere from volcanoes of the global ground-based Network for Observation of Volcanic and Atmospheric Change

Abstract. Volcanic plumes are common and far-reaching manifestations of volcanic activity during and between eruptions. Observations of the rate of emission and composition of volcanic plumes are essential to recognize and, in some cases, predict the state of volcanic activity. Measurements of the size and location of the plumes are important to assess the impact of the emission from sporadic or localized events to persistent or widespread processes of climatic and environmental importance. These observations provide information on volatile budgets on Earth, chemical evolution of magmas, and atmospheric circulation and dynamics. Space-based observations during the last decades have given us a global view of Earth's volcanic emission, particularly of sulfur dioxide (SO2). Although none of the satellite missions were intended to be used for measurement of volcanic gas emission, specially adapted algorithms have produced time-averaged global emission budgets. These have confirmed that tropospheric plumes, produced from persistent degassing of weak sources, dominate the total emission of volcanic SO2. Although space-based observations have provided this global insight into some aspects of Earth's volcanism, it still has important limitations. The magnitude and short-term variability of lower-atmosphere emissions, historically less accessible from space, remain largely uncertain. Operational monitoring of volcanic plumes, at scales relevant for adequate surveillance, has been facilitated through the use of ground-based scanning differential optical absorption spectrometer (ScanDOAS) instruments since the beginning of this century, largely due to the coordinated effort of the Network for Observation of Volcanic and Atmospheric Change (NOVAC). In this study, we present a compilation of results of homogenized post-analysis of measurements of SO2 flux and plume parameters obtained during the period March 2005 to January 2017 of 32 volcanoes in NOVAC. This inventory opens a window into the short-term emission patterns of a diverse set of volcanoes in terms of magma composition, geographical location, magnitude of emission, and style of eruptive activity. We find that passive volcanic degassing is by no means a stationary process in time and that large sub-daily variability is observed in the flux of volcanic gases, which has implications for emission budgets produced using short-term, sporadic observations. The use of a standard evaluation method allows for intercomparison between different volcanoes and between ground- and space-based measurements of the same volcanoes. The emission of several weakly degassing volcanoes, undetected by satellites, is presented for the first time. We also compare our results with those reported in the literature, providing ranges of variability in emission not accessible in the past. The open-access data repository introduced in this article will enable further exploitation of this unique dataset, with a focus on volcanological research, risk assessment, satellite-sensor validation, and improved quantification of the prevalent tropospheric component of global volcanic emission. Datasets for each volcano are made available at https://novac.chalmers.se (last access: 1 October 2020) under the CC-BY 4 license or through the DOI (digital object identifier) links provided in Table 1.

Geochemical characteristics, origin, and mechanism of differential accumulation of natural gas in the carboniferous kelameili gas field in Junggar basin, China

Since the discovery of the Kelameili gas field, the exploration of volcanic gas reservoirs in the Junggar Basin has attracted considerable attention. However, owing to the limitations involved in studying the characteristics of the origin and distribution of the volcanic gas reservoirs in this area, the study of gas reservoirs in the South fault terrace area of the Kelameili gas field as a typical peripheral area is greatly restricted, and the exploration process is relatively slow. Therefore, it is necessary to analyse and compare the differences in the geochemical characteristics of the natural gas between the Kelameili gas field and the fault terrace area of the south belt by analysing the natural gas geochemistry, hydrocarbon generation evolution, and structural evolution. In addition, geochemical experiments involving the natural gas components, carbon isotopes, light hydrocarbons, hydrocarbon generation, and evolutionary history of the source rocks and the interpretation of seismic profiles reflecting the structural evolution, help clarifying the genetic type of the volcanic gas reservoirs and the source of the natural gas in this area. The results indicate the following. (1) The natural gas in the study area has undergone thermal genesis and is generated by kerogen cracking. It is a typical humic gas with high maturity. (2) The origin of the natural gas is the Carboniferous source rock in the depression, which is significantly different from the natural gas from the typical Permian and Jurassic. (3) The primary reason for the difference in natural gas accumulation is that the Carboniferous source rock entered the high-maturity stage in the Early Jurassic. The formation time of the trap is earlier than that of the high-maturity stage of the source rock evolution, which can capture multi-stage source rock products. (4) Based on the hydrocarbon source conditions that the hydrocarbon supply horizon of the Kelameili gas field has a high maturity of organic matter, and insufficient hydrocarbon supply, it is considered that traps capturing the multi-stage source rock products represent a larger scale of natural gas accumulation. The results of this study can deepen the understanding of volcanic gas reservoirs in the Junggar Basin and guidethe exploration and development of global volcanic gas reservoirs and the surrounding large-scale gas fields.

Correction to: Volcanic activity and gas emissions along the South Sandwich Arc

A Correction to this paper has been published: https://doi.org/10.1007/s00445-021-01436-5

Volcanic carbon cycling in East Lake, Newberry Volcano, Oregon, USA

Abstract The carbon cycle in East Lake (Newberry Volcano, Oregon, USA) is fueled by volcanic CO2 inputs with traces of Hg and H2S. The CO2 dissolves in deep lake waters and is removed in shallow waters through largely diffusive surface degassing and photosynthesis. Escaping gas and photosynthate have low δ13C values, leading to δ13C(DIC) (DIC—dissolved inorganic carbon) as high as +5.7‰ in surface waters, well above the common global lake range. A steep δ13C depth gradient is further established by respiration and absorption of light volcanic CO2 in bottom waters. The seasonal CO2 degassing starts at >100 t CO2/day after ice melting in the spring and declines to ∼40 t/day in late summer, degassing ∼11,700 t CO2/yr. Thus, volcano monitoring through gas fluxes from crater lakes should consider lacustrine processes that modulate the volcanic gas output over time. The flux contribution of a bubbling CO2 “hotspot” increased from 20% to >90% of the lake-wide CO2 flux from 2015 to 2019 CE, followed by a “toxic gas alert” in July 2020. East Lake is an active volcanic lake with a “geogenic” ecosystem driven primarily by hydrothermal inputs.

Photochemical modelling of atmospheric oxygen levels confirms two stable states

Various proxies and numerical models have been used to constrain O2 levels over geological time, but considerable uncertainty remains. Previous investigations using 1-D photochemical models have predicted how O3 concentrations vary with assumed ground-level O2 concentrations, and indicate how the ozone layer might have developed over Earth history. These classic models have utilised the numerical simplification of fixed mixing ratio boundary conditions. Critically, this modelling assumption requires verification that predicted fluxes of biogenic and volcanic gases are realistic, but also that the resulting steady states are in fact stable equilibrium solutions against trivial changes in flux.Here, we use a 1-D photochemical model with fixed flux boundary conditions to simulate the effects on O3 and O2 concentrations as O2 (and CH4) fluxes are systematically varied. Our results suggest that stable equilibrium solutions exist for trace- and high-O2/O3 cases, separated by a region of instability. In particular, the model produces few stable solutions with ground O2 mixing ratios between 6×10−7 and 2×10−3 (3×10−6 and 1% of present atmospheric levels). A fully UV-shielding ozone layer only exists in the high-O2 states. Our atmospheric modelling supports prior work suggesting a rapid bimodal transition between reducing and oxidising conditions and proposes Proterozoic oxygen levels higher than some recent proxies suggest. We show that the boundary conditions of photochemical models matter, and should be chosen and explained with care.

Zirconium gallocyanin MS complex as a highly selective reagent for the spectophotometric determination of fluoride

A new photometric procedure for the determination of fluoride ion based on its destruction of zirconium-gallocyanin MS complex is described.The method exhibits great selectivity towards fluoride compared to alkaline-earth, non-ferrous and rare-earth metals, iron, sulfate, nitrate, and phosphate ions and allows to carry out the determination of fluoride in complex objects complex without a preliminary separation of matrix components. The linear range of the quantitative determination of F− was determined to be 0.03 to 2 mg/L with a detection limit of 0.02 mg/L and a correlation coefficient of 0.9989. This method has been successfully applied to the determination of fluorides in natural waters, metallurgic wastewaters, cryolite and condensates of volcanic gases and has good convergence with the results of potentiometric analysis.

High Organic Burial Efficiency Is Required to Explain Mass Balance in Earth's Early Carbon Cycle

AbstractEarth's carbon cycle maintains a stable climate and biosphere on geological timescales. Feedbacks regulate the size of the surface carbon reservoir, and on million‐year timescales the carbon cycle must be in steady state. A major question about the early Earth is whether carbon was cycled through the surface reservoir more quickly or slowly than it is today. The answer to this question holds important implications for Earth's climate state, the size of the biosphere through time, and the expression of atmospheric biosignatures on Earth‐like planets. Here, we examine total carbon inputs and outputs from the Earth's surface over time. We find stark disagreement between the canonical histories of carbon outgassing and carbon burial, with the former implying high rates of throughput on the early Earth and the latter suggesting sluggish carbon cycling. We consider solutions to this apparent paradox and conclude that the most likely resolution is that high organic burial efficiency in the Precambrian enabled substantial carbon burial despite limited biological productivity. We then consider this model in terms of Archean redox balance and find that in order to maintain atmospheric anoxia prior to the Great Oxidation Event, high burial efficiency likely needed to be accompanied by greater outgassing of reductants. Similar mechanisms likely govern carbon burial and redox balance on terrestrial exoplanets, suggesting that outgassing rates and the redox state of volcanic gases likely play a critical role in setting the tempo of planetary oxygenation.