Volcano remote sensing with ground-based spectroscopy

The chemical compositions and emission rates of volcanic gases carry important information about underground magmatic and hydrothermal conditions, with application in eruption forecasting. Volcanic plumes are also studied because of their impacts upon the atmosphere, climate and human health. Remote sensing techniques are being increasingly used in this field because they provide real-time data and can be applied at safe distances from the target, even throughout violent eruptive episodes. However, notwithstanding the many scientific insights into volcanic behaviour already achieved with these approaches, technological limitations have placed firm restrictions upon the utility of the acquired data. For instance, volcanic SO2 emission rate measurements are typically inaccurate (errors can be greater than 100%) and have poor time resolution (ca once per week). Volcanic gas geochemistry is currently being revolutionized by the recent implementation of a new generation of remote sensing tools, which are overcoming the above limitations and are providing degassing data of unprecedented quality. In this article, I review this field at this exciting point of transition, covering the techniques used and the insights thereby obtained, and I speculate upon the breakthroughs that are now tantalizingly close

Elemental sulfur reduction in the deep‐sea vent thermophile, Thermovibrio ammonificans

The reduction of elemental sulfur is an important energy-conserving pathway in prokaryotes inhabiting geothermal environments, where sulfur respiration contributes to sulfur biogeochemical cycling. Despite this, the pathways through which elemental sulfur is reduced to hydrogen sulfide remain unclear in most microorganisms. We integrated growth experiments using Thermovibrio ammonificans, a deep-sea vent thermophile that conserves energy from the oxidation of hydrogen and reduction of both nitrate and elemental sulfur, with comparative transcriptomic and proteomic approaches, coupled with scanning electron microscopy. Our results revealed that two members of the FAD-dependent pyridine nucleotide disulfide reductase family, similar to sulfide-quinone reductase and to NADH-dependent sulfur reductase (NSR), respectively, are over-expressed during sulfur respiration. Scanning electron micrographs and sulfur sequestration experiments indicated that direct access of T. ammonificans to sulfur particles strongly promoted growth. The sulfur metabolism of T. ammonificans appears to require abiotic transition rom bulk elemental sulfur to polysulfide to nanoparticulate sulfur at an acidic pH, coupled to biological hydrogen oxidation. A coupled biotic-abiotic mechanism for sulfur respiration is put forward, mediated by an NSR-like protein as the terminal reductase