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Cambridge, United Kingdom

Roberts T.J.,Lensfield Road | Roberts T.J.,TJ Roberts Research | Braban C.F.,Lensfield Road | Braban C.F.,UK Center for Ecology and Hydrology | And 10 more authors.
Chemical Geology | Year: 2012

We report here the development and application of a compact "geochemical nose" incorporating electrochemical sensors for gas measurements in volcanic plumes. A novel element of the instrument design is the arrangement of the sensors in a parallel array that enables near-simultaneous exposure and fast response. Data analysis methods were developed that utilise the multi-sensor output currents to extract gas mixing ratio abundances and eliminate cross-sensitivities. Use of filter methods is demonstrated to remove baseline drift or instrument noise. We introduce a new approach for analysis of measurements from sensors that have a slower response time (e.g. HCl), and apply this model to estimate HCl/SO 2 ratios. We deployed the sensor system at Aso volcano, Japan, detecting emissions from its fumarole field hot crater lake, and a mixed plume. We measured SO 2, H 2S, CO and HCl, ranging in abundance from ~10 2-10 4ppbv. Neither NO 2 nor Cl 2 were detected. For the fumarolic gases, molar ratios were measured as follows: H 2S/SO 2 is ~0.15, H 2/SO 2 ~0.25, CO/SO 2 ~0.02, HCl/SO 2 ~0.1. The crater lake plume's H 2S/SO 2 is ~0.03. The compositions are discussed in terms of degassing equilibria and plume chemistry. Our instrument design represents a cost-effective, low-power and highly portable system that can be readily adapted for operational surveillance of volcanic gases. © 2012 Elsevier B.V. Source

O'Shea S.J.,University of Manchester | Allen G.,University of Manchester | Gallagher M.W.,University of Manchester | Bower K.,University of Manchester | And 27 more authors.
Atmospheric Chemistry and Physics | Year: 2014

Airborne and ground-based measurements of methane (CH4), carbon dioxide (CO2) and boundary layer thermodynamics were recorded over the Fennoscandian landscape (67-69.5° N, 20-28° E) in July 2012 as part of the MAMM (Methane and other greenhouse gases in the Arctic: Measurements, process studies and Modelling) field campaign. Employing these airborne measurements and a simple boundary layer box model, net regional-scale (∼ 100 km) fluxes were calculated to be 1.2 ± 0.5 mgCH4 h-1 m-2 and -350 ± 143 mgCO2 h-1 m-2 . These airborne fluxes were found to be relatively consistent with seasonally averaged surface chamber (1.3 ± 1.0 mgCH4 h-1 m-2) and eddy covariance (1.3 ± 0.3 mgCH4 h-1 m-2 and -309 ± 306 mgCO2 h-1 m-2) flux measurements in the local area. The internal consistency of the aircraft-derived fluxes across a wide swath of Fennoscandia coupled with an excellent statistical comparison with local seasonally averaged ground-based measurements demonstrates the potential scalability of such localised measurements to regional-scale representativeness. Comparisons were also made to longerterm regional CH4 climatologies from the JULES (Joint UK Land Environment Simulator) and HYBRID8 land surface models within the area of the MAMM campaign. The average hourly emission flux output for the summer period (July-August) for the year 2012 was 0.084 mgCH4 h-1 m-2 (minimum 0.0 and maximum 0.21 mgCH4 h-1 m-2) for the JULES model and 0.088 mgCH4 h-1 m-2 (minimum 0.0008 and maximum 1.53 mgCH4 h-1 m-2) for HYBRID8. Based on these observations both models were found to significantly underestimate the CH4 emission flux in this region, which was linked to the under-prediction of the wetland extents generated by the models. © Author(s) 2014. Source

Reis-Filho J.A.,Federal University of Bahia | Reis-Filho J.A.,Institute Educacao | Freitas R.H.A.,Federal University of Santa Catarina | Loiola M.,Federal University of Bahia | And 6 more authors.
Endangered Species Research | Year: 2016

Overfishing is considered one of the main threats to the health of global marine fish populations. Elasmobranchs that are characterized by low reproductive outputs may be particularly sensitive to intense fishing pressures. The sawfishes stand out as a highly threatened group, due in part to their life history in shallow coastal waters and their ease of capture. In Brazil, sawfish populations are now virtually extinct and these declines have gone undocumented, leaving their precise causes and timing poorly understood. Here, based on ecological and fisheries know - ledge of local fishers, we document the disappearance of largetooth sawfish Pristis pristis from 5 estuaries on the central Brazilian coast. Fisher knowledge, combined with an estuarine morphology perspective, revealed important insights on this species, along with a timeline of its decline. Furthermore, fishers' accounts of the protracted decline revealed clear inter-estuary differences in the timing of population declines, potentially influenced by local geomorphological features. The onset of sawfish population decline appears to have been earlier in estuaries with a direct connection to the sea than in estuaries connected to an inner bay, occurring in the former case from the 1930s onward. A second wave of intensifying decline began in the 1970s in more structurally complex estuaries. Pressures from artisanal and modern fishery practices appear to have led to an earlier population decline in structurally less complex estuaries, while in larger and more complex ones this decline occurred decades later. The replacement of traditional by more modern fishing practices may have triggered the initial phase of local sawfish extinctions. © The authors 2016. Source

Goitom B.,University of Bristol | Goitom B.,Eritrea Institute of Technology | Oppenheimer C.,Downing Place | Hammond J.O.S.,Imperial College London | And 16 more authors.
Bulletin of Volcanology | Year: 2015

We present a synthesis of diverse observations of the first recorded eruption of Nabro volcano, Eritrea, which began on 12 June 2011. While no monitoring of the volcano was in effect at the time, it has been possible to reconstruct the nature and evolution of the eruption through analysis of regional seismological and infrasound data and satellite remote sensing data, supplemented by petrological analysis of erupted products and brief field surveys. The event is notable for the comparative rarity of recorded historical eruptions in the region and of caldera systems in general, for the prodigious quantity of SO2emitted into the atmosphere and the significant human impacts that ensued notwithstanding the low population density of the Afar region. It is also relevant in understanding the broader magmatic and tectonic significance of the volcanic massif of which Nabro forms a part and which strikes obliquely to the principal rifting directions in the Red Sea and northern Afar. The whole-rock compositions of the erupted lavas and tephra range from trachybasaltic to trachybasaltic andesite, and crystal-hosted melt inclusions contain up to 3,000 ppm of sulphur by weight. The eruption was preceded by significant seismicity, detected by regional networks of sensors and accompanied by sustained tremor. Substantial infrasound was recorded at distances of hundreds to thousands of kilometres from the vent, beginning at the onset of the eruption and continuing for weeks. Analysis of ground deformation suggests the eruption was fed by a shallow, NW–SE-trending dike, which is consistent with field and satellite observations of vent distributions. Despite lack of prior planning and preparedness for volcanic events in the country, rapid coordination of the emergency response mitigated the human costs of the eruption. © 2015, The Author(s). Source

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