Search results for "GAS"
showing 10 items of 12601 documents
Combined ground and aerial measurements resolve vent-specific gas fluxes from a multi-vent volcano
2020
Volcanoes with multiple summit vents present a methodological challenge for determining vent-specific gas emissions. Here, using a novel approach combining multiple ultraviolet cameras with synchronous aerial measurements, we calculate vent-specific gas compositions and fluxes for Stromboli volcano. Emissions from vent areas are spatially heterogeneous in composition and emission rate, with the central vent area dominating passive emissions, despite exhibiting the least explosive behaviour. Vents exhibiting Strombolian explosions emit low to negligible passive fluxes and are CO2-dominated, even during passive degassing. We propose a model for the conduit system based on contrasting rheologi…
Phlogopite-pargasite coexistence in an oxygen reduced spinel-peridotite ambient
2021
AbstractThe occurrence of phlogopite and amphibole in mantle ultramafic rocks is widely accepted as the modal effect of metasomatism in the upper mantle. However, their simultaneous formation during metasomatic events and the related sub-solidus equilibrium with the peridotite has not been extensively studied. In this work, we discuss the geochemical conditions at which the pargasite-phlogopite assemblage becomes stable, through the investigation of two mantle xenoliths from Mount Leura (Victoria State, Australia) that bear phlogopite and the phlogopite + amphibole (pargasite) pair disseminated in a harzburgite matrix. Combining a mineralogical study and thermodynamic modelling, we predict …
Evidence of active fluid seepage (AFS) in the southern region of the central Mediterranean Sea
2018
Abstract Active fluid seepage (AFS) at the seafloor is a global phenomenon associated with seafloor morphologies in different geodynamic contexts. Advanced geophysical techniques have allowed geoscientists to characterise pockmarks, mounds and flares associated with AFS. We present a range of new marine geological data acquired in the southern region of the central Mediterranean Sea (northern Sicily continental margin, northwestern Sicily Channel and offshore of the Maltese Islands), which allow us to identify AFSs. AFSs are spatially distributed as clusters, aligned or isolated at different depths, ranging from few decametres offshore of the Maltese Islands; up to 400 m offshore of norther…
Methanotrophy in geothermal soils, an overlooked process: The example of Nisyros island (Greece)
2020
Abstract A multidisciplinary field campaign was carried out at Nisyros Island (Greece). Hydrothermal gases were sampled and analysed, and CH4 and CO2 fluxes from the soils were measured with the accumulation chamber method. The sampling area (Lakki plain) covers an area of about 0.08 km2, and includes the main fumarolic areas of Kaminakia, Stefanos, Ramos, Lofos and Phlegeton. Flux values measured at 130 sites range from −3.4 to 1420 mg m−2 d−1 for CH4 and from 0.1 to 383 g m−2 d−1 for CO2. The fumarolic areas show very different CH4 degassing patterns, Kaminakia showing the highest CH4 output values (about 0.8 t a−1 from an area of about 30,000 m2) and Phlegeton the lowest (about 0.01 t a−…
Coping with the impacts of Urban Heat Islands A literature based study on understanding urban heat vulnerability and the need for resilience in citie…
2018
The urban heat island (UHI) is a phenomenon whereby temperature levels in urban areas are higher than in surrounding rural settings. Urban heat islands are a matter of increasing concern, since they can affect communities by exacerbating air pollution and greenhouse gas emissions (due to the greater use of air conditioning) and the occurrence of heat-related illness, and may lead to higher levels of mortality. This paper provides a description of the phenomena of (UHI) and an analysis of how cities are vulnerable to it. It highlights the need for resilience and the variety of means by which the UHI can be tackled. It describes a set of trends in two regions in Germany and Australia, which i…
Characterisation of the magmatic signature in gas emissions from Turrialba Volcano, Costa Rica
2014
The equilibrium composition of volcanic gases with their magma is often overprinted by interaction with a shallow hydrothermal system. Identifying the magmatic signature of volcanic gases is critical to relate their composition to properties of the magma (temperature, fO2, gas-melt segregation depth). We report measurements of the chemical composition and flux of the major gas species emitted from Turrialba Volcano during March 2013. Measurements were made of two vents in the summit region, one of which opened in 2010 and the other in 2012. We determined an average SO2 flux of 5.2 ± 1.9 kg s-1 using scanning ultraviolet spectroscopy, and molar proportions of H2O, CO2, SO2, HCl, CO and H2 ga…
First study of the heat and gas budget for Sirung volcano, Indonesia
2017
International audience; With at least four eruptions over the last 20 years, Sirung is currently one of the more active volcanoes in Indonesia. However, due to its remoteness, very little is known about the volcano and its hyperacid crater lake. We report here on the first measurements of gas and heat emissions from the volcano. Notable is the substantial heat loss from the crater lake surface, amounting to 220 MW. In addition, 17 Gg of SO2, representing 0.8% of Indonesian volcanic SO2 contribution into the atmosphere, 11 Gg of H2S, 17 Gg of CO2, and 550 Gg of H2O are discharged into the atmosphere from the volcano annually. The volatiles degassed from Sirung magmas are subjected to hydroth…
Chlorine Partitioning Between a Basaltic Melt and H2O-CO2 Fluids at Mount Etna
2009
Partitioning experiments between a basaltic melt from Mt. Etna and a low-density hydrous fluid or vapor containing H(2)O or H(2)O-CO(2) were performed at 1200-1260 degrees C, at pressures between 1 and 200 MPa, either near the nickel-nickel oxide (NNO) buffer or at two log units above it (NNO + 2), and with different chloride concentrations. Most of the experiments were done at chloride-brine-undersaturated conditions, although at the highest Cl concentrations explored brine saturation might have been reached. The average partition coefficients (D(Cl)(fluid/melt)) over the range of Cl concentrations were derived on a weight basis by plotting the calculated concentrations of Cl in the fluid …
Simulation of nitrous oxide emissions from wheat-cropped soils using CERES
2005
Estimation of nitrous oxide (N2O) emissions from arable soils, in relation to crop fertilization, is essential to devise strategies to mitigate the impact of agriculture on global warming. This paper presents the development and test of a N2O model resulting from the linkage of a dynamic soil-crop simulation model (CERES) with two sub-models of N2O production and reduction in soils. These sub-models (NOE and NGAS) account for both the nitrification and denitrification pathways. The resulting models (CERES–NOE and CERES–NGAS) were tested against experimental data collected on three contrasting wheat-cropped soils representative of the Beauce agricultural region in France. Although the input …
Natural gas hydrate investigations by synchrotron radiation X-ray cryo-tomographic microscopy (SRXCTM)
2008
[1] We report the 3D microstructure analyses of natural gas hydrates sampled from Gulf of Mexico. The samples were characterized by synchrotron radiation X-ray cryo-tomographic microscopy (SRXCTM) using the ‘TOMCAT’ beam line at the Swiss Light Source (SLS). The SRXCTM demonstrates its applicability to unlock some microscopic features of the marine hydrates, in particular of crystallite size and grain boundary network. The gas hydrate domains are surrounded by a network of pores of typically a few micrometers, which are largely due to decomposition. Out of the SRXCTM data, the porosity, total volume of the voids, the void surface area and number of the total gas-filled voids have been calcu…