Academic literature on the topic 'Volcanogenic fluoride'

One deposit and 217 occurrences of fluorite, grouped in the fluorite, the rare-metal-fluorite, and the polymetal-fluorite mineral formations, are known in RussiaТs North-East. Occurrences of fluorite formations are most widespread, while the stratiform occurrences in the Urultun-Taskan zone at the Omulevskoye uplift are especially rich in resources. Fluorite occurrences themselves are widespread within the Okhotsk-Chukotka volcanogenic belt. Fluorite-bearing belts, areas, and zones are distinguished. Fluorite minerogenic resources of RussiaТs North-East are estimated.

AbstractIn the Ordovician Snowdon Volcanic Group caldera quartz-magnetite-hematite-pyrite assemblages occur in a breccia vein in rhyolitic tuff and vein swarms in basalt. The veins developed pre-cleavage. Elevated levels of tin and tungsten in the veins, and of fluorine in the wall rocks, suggest a magmatic contribution to the mineralising fluids. The chemistry of the veins differs from that of the base-metal sulphide veins found elsewhere in the caldera.

Abstract. Improving the constraints on the atmospheric fate and depletion rates of acidic compounds persistently emitted by non-erupting (quiescent) volcanoes is important for quantitatively predicting the environmental impact of volcanic gas plumes. Here, we present new experimental data coupled with modelling studies to investigate the chemical processing of acidic volcanogenic species during tropospheric dispersion. Diffusive tube samplers were deployed at Mount Etna, a very active open-conduit basaltic volcano in eastern Sicily, and Vulcano Island, a closed-conduit quiescent volcano in the Aeolian Islands (northern Sicily). Sulphur dioxide (SO2), hydrogen sulphide (H2S), hydrogen chloride (HCl) and hydrogen fluoride (HF) concentrations in the volcanic plumes (typically several minutes to a few hours old) were repeatedly determined at distances from the summit vents ranging from 0.1 to ~10 km, and under different environmental conditions. At both volcanoes, acidic gas concentrations were found to decrease exponentially with distance from the summit vents (e.g., SO2 decreases from ~10 000 μg/m3 at 0.1 km from Etna's vents down to ~7 μg/m3 at ~10 km distance), reflecting the atmospheric dilution of the plume within the acid gas-free background troposphere. Conversely, SO2/HCl, SO2/HF, and SO2/H2S ratios in the plume showed no systematic changes with plume aging, and fit source compositions within analytical error. Assuming that SO2 losses by reaction are small during short-range atmospheric transport within quiescent (ash-free) volcanic plumes, our observations suggest that, for these short transport distances, atmospheric reactions for H2S and halogens are also negligible. The one-dimensional model MISTRA was used to simulate quantitatively the evolution of halogen and sulphur compounds in the plume of Mt. Etna. Model predictions support the hypothesis of minor HCl chemical processing during plume transport, at least in cloud-free conditions. Larger variations in the modelled SO2/HCl ratios were predicted under cloudy conditions, due to heterogeneous chlorine cycling in the aerosol phase. The modelled evolution of the SO2/H2S ratios is found to be substantially dependent on whether or not the interactions of H2S with halogens are included in the model. In the former case, H2S is assumed to be oxidized in the atmosphere mainly by OH, which results in minor chemical loss for H2S during plume aging and produces a fair match between modelled and measured SO2/H2S ratios. In the latter case, fast oxidation of H2S by Cl leads to H2S chemical lifetimes in the early plume of a few seconds, and thus SO2 to H2S ratios that increase sharply during plume transport. This disagreement between modelled and observed plume compositions suggests that more in-detail kinetic investigations are required for a proper evaluation of H2S chemical processing in volcanic plumes.

Abstract. Improving the constraints on the atmospheric fate and depletion rates of acidic compounds persistently emitted by non-erupting (quiescent) volcanoes is important for quantitatively predicting the environmental impact of volcanic gas plumes. Here, we present new experimental data coupled with modelling studies to investigate the chemical processing of acidic volcanogenic species during tropospheric dispersion. Diffusive tube samplers were deployed at Mount Etna, a very active open-conduit basaltic volcano in eastern Sicily, and Vulcano Island, a closed-conduit quiescent volcano in the Aeolian Islands (northern Sicily). Sulphur dioxide (SO2), hydrogen sulphide (H2S), hydrogen chloride (HCl) and hydrogen fluoride (HF) concentrations in the volcanic plumes (typically several minutes to a few hours old) were repeatedly determined at distances from the summit vents ranging from 0.1 to ~10 km, and under different environmental conditions. At both volcanoes, acidic gas concentrations were found to decrease exponentially with distance from the summit vents (e.g., SO2 decreases from ~10 000 μg/m3at 0.1 km from Etna's vents down to ~7 μg/m3 at ~10 km distance), reflecting the atmospheric dilution of the plume within the acid gas-free background troposphere. Conversely, SO2/HCl, SO2/HF, and SO2/H2S ratios in the plume showed no systematic changes with plume aging, and fit source compositions within analytical error. Assuming that SO2 losses by reaction are small during short-range atmospheric transport within quiescent (ash-free) volcanic plumes, our observations suggest that, for these short transport distances, atmospheric reactions for H2S and halogens are also negligible. The one-dimensional model MISTRA was used to simulate quantitatively the evolution of halogen and sulphur compounds in the plume of Mt. Etna. Model predictions support the hypothesis of minor HCl chemical processing during plume transport, at least in cloud-free conditions. Larger variations in the modelled SO2/HCl ratios were predicted under cloudy conditions, due to heterogeneous chlorine cycling in the aerosol phase. The modelled evolution of the SO2/H2S ratios is found to be substantially dependent on whether or not the interactions of H2S with halogens are included in the model. In the former case, H2S is assumed to be oxidized in the atmosphere mainly by OH, which results in minor chemical loss for H2S during plume aging and produces a fair match between modelled and measured SO2/H2S ratios. In the latter case, fast oxidation of H2S by Cl leads to H2S chemical lifetimes in the early plume of a few seconds, and thus SO2 to H2S ratios that increase sharply during plume transport. This disagreement between modelled and observed plume compositions suggests that more in-detail kinetic investigations are required for a proper evaluation of H2S chemical processing in volcanic plumes.

This thesis focuses on the environmental effects of volcanic eruptions such as Eyjafjallajökull (2010) from which volcanic gases and ash particles can impact upon ecosystems located thousands of kilometres from the source. Currently very little is known about the impact of volcanic pollutants such as SO4 and F on the carbon cycle. This study is a first step towards understanding the potential environmental impacts of volcanic eruptions on peatland and mineral soil C gas fluxes. Ombrotrophic peat mesocosms sampled from the Northern Peninne uplands, UK, were dosed over 20 weeks with concentrations of SO4-S (24.5 kg ha-1) and F (13.5 and 135 kg ha-1) simulating a distal Icelandic tephra deposit. Methane and CO2 gas fluxes were measured at regular intervals, but no significant differences were observed for any of the treatments when compared to the controls. This result contrasts with previous studies, which reported a suppression of CH4 emission with the addition of SO4. It can be explained if CH4 production has remained suppressed in the peat soils as a long-term consequence of heavy SO4 loadings in the Pennines area prior to the reduction of SO2 emissions from industrial sources in the 1970s. The mesocosm study results indicate that F deposition, at rates representative of tephra fallout does not interfere with C gas fluxes in peat soils, despite the well-established toxicity of F in the environment. However, F addition to a pristine peat soil in laboratory slurry experiments showed an increase in potential CH4 production rates thus further research is recommended. Addition of treatments containing high concentrations of F to peat mesocosms had a significant effect on soil solution chemistry. The addition of F increased the solubility of Al, Fe and acetate resulting in the accumulation of both species in solution near the peat surface. This build up of acetate, Al and Fe over the treatment period suggests that F breaks down organo-metallic compounds causing leaching of organic matter along with metal ions. This may have important implications for microbial communities within the peat that are associated with decomposition of organic matter and carbon cycling. After the 2010 eruption of Eyjafjallajökull, Iceland, a field experiment was carried out to assess the impact of tephra deposition on soil respiration from a grassland site. The results showed that the chemical effect of ash leaching resulted in a 30% reduction in ecosystem respiration. This study also highlighted the short-term physical effects of tephra deposition on the release of CO2 from soil as the tephra layer impeded CO2 release when wet. This work provides a useful contribution to the scientific understanding of the effects of volcanic SO4 and F on peatland ecosystems and the physical and chemical effects of ash deposition on soil respiration. Consideration of the impact of volcanic deposition on soil C fluxes in climate models is required in order to be able to fully appreciate how volcanism causes environmental changes.