Aerial strategies advance volcanic gas measurements at inaccessible, strongly degassing volcanoes.
ABSTRACT: Volcanic emissions are a critical pathway in Earth's carbon cycle. Here, we show that aerial measurements of volcanic gases using unoccupied aerial systems (UAS) transform our ability to measure and monitor plumes remotely and to constrain global volatile fluxes from volcanoes. Combining multi-scale measurements from ground-based remote sensing, long-range aerial sampling, and satellites, we present comprehensive gas fluxes-3760 ± [600, 310] tons day-1 CO2 and 5150 ± [730, 340] tons day-1 SO2-for a strong yet previously uncharacterized volcanic emitter: Manam, Papua New Guinea. The CO2/ST ratio of 1.07 ± 0.06 suggests a modest slab sediment contribution to the sub-arc mantle. We find that aerial strategies reduce uncertainties associated with ground-based remote sensing of SO2 flux and enable near-real-time measurements of plume chemistry and carbon isotope composition. Our data emphasize the need to account for time averaging of temporal variability in volcanic gas emissions in global flux estimates.
Project description:The global flux of sulfur dioxide (SO2) emitted by passive volcanic degassing is a key parameter that constrains the fluxes of other volcanic gases (including carbon dioxide, CO2) and toxic trace metals (e.g., mercury). It is also a required input for atmospheric chemistry and climate models, since it impacts the tropospheric burden of sulfate aerosol, a major climate-forcing species. Despite its significance, an inventory of passive volcanic degassing is very difficult to produce, due largely to the patchy spatial and temporal coverage of ground-based SO2 measurements. We report here the first volcanic SO2 emissions inventory derived from global, coincident satellite measurements, made by the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite in 2005-2015. The OMI measurements permit estimation of SO2 emissions from over 90 volcanoes, including new constraints on fluxes from Indonesia, Papua New Guinea, the Aleutian Islands, the Kuril Islands and Kamchatka. On average over the past decade, the volcanic SO2 sources consistently detected from space have discharged a total of ~63?kt/day SO2 during passive degassing, or ~23?±?2?Tg/yr. We find that ~30% of the sources show significant decadal trends in SO2 emissions, with positive trends observed at multiple volcanoes in some regions including Vanuatu, southern Japan, Peru and Chile.
Project description:The global carbon dioxide (CO2) flux from subaerial volcanoes remains poorly quantified, limiting our understanding of the deep carbon cycle during geologic time and in modern Earth. Past attempts to extrapolate the global volcanic CO2 flux have been biased by observations being available for a relatively small number of accessible volcanoes. Here, we propose that the strong, but yet unmeasured, CO2 emissions from several remote degassing volcanoes worldwide can be predicted using regional/global relationships between the CO2/ST ratio of volcanic gases and whole-rock trace element compositions (e.g., Ba/La). From these globally linked gas/rock compositions, we predict the CO2/ST gas ratio of 34 top-degassing remote volcanoes with no available gas measurements. By scaling to volcanic SO2 fluxes from a global catalogue, we estimate a cumulative "unmeasured" CO2 output of 11.4 ± 1.1 Mt/yr (or 0.26 ± 0.02·1012 mol/yr). In combination with the measured CO2 output of 27.4 ± 3.6 Mt/yr (or 0.62 ± 0.08·1012 mol/yr), our results constrain the time-averaged (2005-2015) cumulative CO2 flux from the Earth's 91 most actively degassing subaerial volcanoes at 38.7 ± 2.9 Mt/yr (or 0.88 ± 0.06·1012 mol/yr).
Project description:Volcanic CO2 emissions play a key role in the geological carbon cycle, and monitoring of volcanic CO2 fluxes helps to forecast eruptions. The quantification of CO2 fluxes is challenging due to rapid dilution of magmatic CO2 in CO2-rich ambient air and the diffuse nature of many emissions, leading to large uncertainties in the global magmatic CO2 flux inventory. Here, we report measurements using a new DIAL laser remote sensing system for volcanic CO2 (CO2DIAL). Two sites in the volcanic zone of Campi Flegrei (Italy) were scanned, yielding CO2 path-amount profiles used to compute fluxes. Our results reveal a relatively high CO2 flux from Campi Flegrei, consistent with an increasing trend. Unlike previous methods, the CO2DIAL is able to measure integrated CO2 path-amounts at distances up to 2000?m using virtually any solid surface as a reflector, whilst also being highly portable. This opens a new frontier in quantification of geological and anthropogenic CO2 fluxes.
Project description:Volcanic gas emission measurements inform predictions of hazard and atmospheric impacts. For these measurements, Multi-Gas sensors provide low-cost in situ monitoring of gas composition but to date have lacked the ability to detect halogens. Here, two Multi-Gas instruments characterized passive outgassing emissions from Mt. Etna's (Italy) three summit craters, Voragine (VOR), North-east Crater (NEC) and Bocca Nuova (BN) on 2 October 2013. Signal processing (Sensor Response Model, SRM) approaches are used to analyse H2S/SO2 and HCl/SO2 ratios. A new ability to monitor volcanic HCl using miniature electrochemical sensors is here demonstrated. A "direct-exposure" Multi-Gas instrument contained SO2, H2S and HCl sensors, whose sensitivities, cross-sensitivities and response times were characterized by laboratory calibration. SRM analysis of the field data yields H2S/SO2 and HCl/SO2 molar ratios, finding H2S/SO2 = 0.02 (0.01-0.03), with distinct HCl/SO2 for the VOR, NEC and BN crater emissions of 0.41 (0.38-0.43), 0.58 (0.54-0.60) and 0.20 (0.17-0.33). A second Multi-Gas instrument provided CO2/SO2 and H2O/SO2 and enabled cross-comparison of SO2. The Multi-Gas-measured SO2-HCl-H2S-CO2-H2O compositions provide insights into volcanic outgassing. H2S/SO2 ratios indicate gas equilibration at slightly below magmatic temperatures, assuming that the magmatic redox state is preserved. Low SO2/HCl alongside low CO2/SO2 indicates a partially outgassed magma source. We highlight the potential for low-cost HCl sensing of H2S-poor HCl-rich volcanic emissions elsewhere. Further tests are needed for H2S-rich plumes and for long-term monitoring. Our study brings two new advances to volcano hazard monitoring: real-time in situ measurement of HCl and improved Multi-Gas SRM measurements of gas ratios.
Project description:Over the last four decades, space-based nadir observations of sulfur dioxide (SO2) proved to be a key data source for assessing the environmental impacts of volcanic emissions, for monitoring volcanic activity and early signs of eruptions, and ultimately mitigating related hazards on local populations and aviation. Despite its importance, a detailed picture of global SO2 daily degassing is difficult to produce, notably for lower-tropospheric plumes, due largely to the limited spatial resolution and coverage or lack of sensitivity and selectivity to SO2 of current (and previous) nadir sensors. We report here the first volcanic SO2 measurements from the hyperspectral TROPOspheric Monitoring Instrument (TROPOMI) launched in October 2017 onboard the ESA's Sentinel-5 Precursor platform. Using the operational processing algorithm, we explore the benefit of improved spatial resolution to the monitoring of global volcanic degassing. We find that TROPOMI surpasses any space nadir sensor in its ability to detect weak degassing signals and captures day-to-day changes in SO2 emissions. The detection limit of TROPOMI to SO2 emissions is a factor of 4 better than the heritage Aura/Ozone Monitoring Instrument (OMI). Here we show that TROPOMI SO2 daily observations carry a wealth of information on volcanic activity. Provided with adequate wind speed data, temporally resolved SO2 fluxes can be obtained at hourly time steps or shorter. We anticipate that TROPOMI SO2 data will help to monitor global volcanic daily degassing and better understand volcanic processes and impacts.
Project description:There is a pressing need to verify air pollutant and greenhouse gas emissions from anthropogenic fossil energy sources to enforce current and future regulations. We demonstrate the feasibility of using simultaneous remote sensing observations of column abundances of CO2, CO, and NO2 to inform and verify emission inventories. We report, to our knowledge, the first ever simultaneous column enhancements in CO2 (3-10 ppm) and NO2 (1-3 Dobson Units), and evidence of ?(13)CO2 depletion in an urban region with two large coal-fired power plants with distinct scrubbing technologies that have resulted in ?NOx/?CO2 emission ratios that differ by a factor of two. Ground-based total atmospheric column trace gas abundances change synchronously and correlate well with simultaneous in situ point measurements during plume interceptions. Emission ratios of ?NOx/?CO2 and ?SO2/?CO2 derived from in situ atmospheric observations agree with those reported by in-stack monitors. Forward simulations using in-stack emissions agree with remote column CO2 and NO2 plume observations after fine scale adjustments. Both observed and simulated column ?NO2/?CO2 ratios indicate that a large fraction (70-75%) of the region is polluted. We demonstrate that the column emission ratios of ?NO2/?CO2 can resolve changes from day-to-day variation in sources with distinct emission factors (clean and dirty power plants, urban, and fires). We apportion these sources by using NO2, SO2, and CO as signatures. Our high-frequency remote sensing observations of CO2 and coemitted pollutants offer promise for the verification of power plant emission factors and abatement technologies from ground and space.
Project description:Volcanoes are the main pathway to the surface for volatiles that are stored within the Earth. Carbon dioxide (CO2) is of particular interest because of its potential for climate forcing. Understanding the balance of CO2 that is transferred from the Earth's surface to the Earth's interior, hinges on accurate quantification of the long-term emissions of volcanic CO2 to the atmosphere. Here we present an updated evaluation of the world's volcanic CO2 emissions that takes advantage of recent improvements in satellite-based monitoring of sulfur dioxide, the establishment of ground-based networks for semi-continuous CO2-SO2 gas sensing and a new approach to estimate key volcanic gas parameters based on magma compositions. Our results reveal a global volcanic CO2 flux of 51.3?±?5.7 Tg CO2/y (11.7?×?1011?mol CO2/y) for non-eruptive degassing and 1.8?±?0.9 Tg/y for eruptive degassing during the period from 2005 to 2015. While lower than recent estimates, this global volcanic flux implies that a significant proportion of the surface-derived CO2 subducted into the Earth's mantle is either stored below the arc crust, is efficiently consumed by microbial activity before entering the deeper parts of the subduction system, or becomes recycled into the deep mantle to potentially form diamonds.
Project description:Accurate estimates of global carbon emissions are critical for understanding global warming. This paper estimates net carbon emissions from land use change in Bolivia during the periods 1990-2000 and 2000-2010 using a model that takes into account deforestation, forest degradation, forest regrowth, gradual carbon decomposition and accumulation, as well as heterogeneity in both above ground and below ground carbon contents at the 10 by 10 km grid level. The approach permits detailed maps of net emissions by region and type of land cover. We estimate that net CO2 emissions from land use change in Bolivia increased from about 65 million tons per year during 1990-2000 to about 93 million tons per year during 2000-2010, while CO2 emissions per capita and per unit of GDP have remained fairly stable over the sample period. If we allow for estimated biomass increases in mature forests, net CO2 emissions drop to close to zero. Finally, we find these results are robust to alternative methods of calculating emissions.
Project description: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 rheological properties between vent areas. Our methodology has advantages for resolving contrasting outgassing dynamics given that measured bulk plume compositions are often intermediate between those of the distinct vent areas. We therefore emphasise the need for a vent-specific approach at multi-vent volcanoes and suggest that our approach could provide a transformative advance in volcano monitoring applications.
Project description:Estimating the quantity of CO2 diffusively emitted from the Earth's surface has important implications for volcanic surveillance and global atmospheric CO2 budgets. However, the identification and quantification of non-hydrothermal contributions to CO2 release can be ambiguous. Here, we describe a multi-parametric approach employed at the Nisyros caldera, Aegean Arc, Greece, to assess the relative influence of deep and shallow gases released from the soil. In April 2019, we measured diffuse soil surface CO2 fluxes, together with their carbon isotope compositions, and at a depth of 80 cm, the CO2 concentration, soil temperature, and the activities of radon and thoron. The contributions of deep CO2 and biogenic CO2 fluxes were distinguished on the basis of their carbon isotope compositions. A Principal Component Analysis (PCA), performed on the measured parameters, effectively discriminates between a deep- and a shallow degassing component. The total CO2 output estimated from a relatively small testing area was two times higher with respect to that observed in a previous survey (October 2018). The difference is ascribed to variation in the soil biogenic CO2 production, that was high in April 2019 (a wet period) and low or absent in October 2018 (a dry period). Accounting for seasonal biogenic activity is therefore critical in monitoring and quantifying CO2 emissions in volcanic areas, because they can partially- or completely overwhelm the volcanic-hydrothermal signal.