A novel technique for studying volcanic gas chemistry and dispersion on short time scales

2020 ◽  
Author(s):  
Christopher Fuchs ◽  
Jonas Kuhn ◽  
Nicole Bobrowski ◽  
Ulrich Platt
Keyword(s):  
Time Scales ◽  
Correlation Spectroscopy ◽  
Limiting Factors ◽  
Trace Gas ◽  
Volcanic Plume ◽  
Ambient Atmosphere ◽  
Volcanic Gas ◽  
Gas Emissions ◽  
Novel Technique ◽  
Fabry Perot

<p>Volcanic gas emissions, in particular, of sulphur and halogen species, play an important role in atmospheric chemistry. Due to the complex reaction kinetics of halogen radicals inside the volcanic plume, many properties like e.g. chemistry limiting factors and timescales of reactions, are still not well understood. <br>Imaging techniques based on optical remote sensing can get valuable insights into the study of both volcanic degassing fluxes and chemical conversions within the plume that continuously mixes with the atmosphere. However, state-of-the-art techniques are either too slow to resolve plume chemistry processes on its intrinsic time scales (e.g. DOAS) or show many cross sensitivities and hence are limited to rather high trace gas concentrations (e.g. SO<sub>2</sub> cameras). </p><p>We introduce a novel technique for volcanic trace gas imaging, which, by employing a Fabry-Perot interferometer (FPI), uses detailed spectral information for the detection of the target trace gas. Cross sensitivities are thereby drastically reduced, allowing for the detection of much lower SO<sub>2 </sub>concentrations and imaging of other trace gas species like, e.g., BrO, OClO. Furthermore, the inherent calibration of the new techniques avoids the requirement of additional DOAS measurements or gas cells for calibration.</p><p>We present the first measurements of volcanic SO<sub>2</sub> with an imaging Fabry-Perot interferometer correlation spectroscopy (IFPICS) prototype. The sensitivity of ≈ 10<sup>19 </sup>cm<sup>2</sup> molec<sup>-1</sup> is comparable to filter based SO<sub>2</sub> cameras, whereas the selectivity is much higher (e.g. no ozone interference). This will largely increase the accuracy of SO<sub>2</sub> emission rates, which are routinely used to approximate fluxes of other volcanic gas emissions into the atmosphere.</p><p>Additionally, sensitivity studies for further trace gases combining laboratory measurements and radiation transfer modelling show promising prospected BrO detection limits of < 10<sup>14</sup> molec cm<sup>-</sup>², corresponding to mixing ratios of 10 to 100 ppt in volcanic plumes. The direct visualisation of BrO within the volcanic plume mixing with the ambient atmosphere will give important insights into the plume’s halogen chemistry and, thereby, its impact on the atmosphere.</p>

Technological advances to improve the quantification of volcanic emissions

2021 ◽  
Author(s):  
Christopher Fuchs ◽  
Jonas Kuhn ◽  
Nicole Bobrowski ◽  
Ulrich Platt
Keyword(s):  
Remote Sensing ◽  
Temporal Resolution ◽  
Volcanic Activity ◽  
Imaging Techniques ◽  
Correlation Spectroscopy ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Integration Time ◽  
Volcanic Plume ◽  
Flux Measurements

<p>Variations in volcanic trace gas composition and fluxes are a valuable indicator for changes in magmatic systems and therefore allow monitoring of the volcanic activity. An established method to measure trace gas emissions is to use remote sensing techniques like, for example, Differential Optical Absorption Spectroscopy (DOAS) and more recently SO<sub>2</sub>-cameras, that can quantify volcanic sulphur dioxide (SO<sub>2</sub>) emissions during quiescent degassing and eruptive phases, making it possible to correlate fluxes with volcanic activity. </p><p>We present flux measurements of volcanic SO<sub>2</sub> emissions based on the novel remote sensing technique of Imaging Fabry-Pérot Interferometer Correlation Spectroscopy (IFPICS) in the UV spectral range. The basic principle of IFPICS lies in the application of an Fabry-Pérot Interferometer (FPI) as wavelength selective element. The FPIs periodic transmission profile is matched to the periodic spectral absorption features of SO<sub>2</sub>, resulting in high spectral information for its detection. This technique yields a higher trace gas selectivity and sensitivity than imaging approaches based on interference filters, e.g. SO<sub>2</sub>-cameras and an increased spatio-temporal resolution over spectroscopic imaging techniques, e.g. imaging DOAS. Hence, IFPICS shows reduced cross sensitivities to broadband absorption (e.g. to ozone, aerosols), which allows the application to weaker volcanic SO<sub>2</sub> emitters and increases the range of possible atmospheric conditions. It further raises the possibility to apply IFPICS to other trace gas species like, for example, bromine monoxide, that still can be characterized with a high spatial and temporal resolution (< 1 HZ).</p><p>In October 2020, we acquired SO<sub>2</sub> column density distribution images of Mt Etna volcanic plume with a detection limit of 2x10<sup>17</sup> molec cm<sup>-2</sup>, 1 s integration time, 400x400 pixel spatial, and 0.3 Hz temporal resolution.  We compare the SO<sub>2</sub> fluxes retrieved by IFPICS with simultaneous flux measurements using the mutli-axis DOAS technique.</p>

scholarly journals Quantitative imaging of volcanic SO<sub>2</sub> plumes using Fabry–Pérot interferometer correlation spectroscopy

2021 ◽  
Vol 14 (1) ◽  
pp. 295-307
Author(s):  
Christopher Fuchs ◽  
Jonas Kuhn ◽  
Nicole Bobrowski ◽  
Ulrich Platt
Keyword(s):  
Temporal Resolution ◽  
Cross Sections ◽  
Imaging Techniques ◽  
Quantitative Imaging ◽  
Trace Gases ◽  
High Specificity ◽  
Correlation Spectroscopy ◽  
Volcanic Plume ◽  
Model Calculations ◽  
Fabry Perot

Abstract. We present first measurements with a novel imaging technique for atmospheric trace gases in the UV spectral range. Imaging Fabry–Pérot interferometer correlation spectroscopy (IFPICS) employs a Fabry–Pérot interferometer (FPI) as the wavelength-selective element. Matching the FPI's distinct, periodic transmission features to the characteristic differential absorption structures of the investigated trace gas allows us to measure differential atmospheric column density (CD) distributions of numerous trace gases with high spatial and temporal resolution. Here we demonstrate measurements of sulfur dioxide (SO2), while earlier model calculations show that bromine monoxide (BrO) and nitrogen dioxide (NO2) are also possible. The high specificity in the spectral detection of IFPICS minimises cross-interferences to other trace gases and aerosol extinction, allowing precise determination of gas fluxes. Furthermore, the instrument response can be modelled using absorption cross sections and a solar atlas spectrum from the literature, thereby avoiding additional calibration procedures, e.g. using gas cells. In a field campaign, we recorded the temporal CD evolution of SO2 in the volcanic plume of Mt. Etna, with an exposure time of 1 s and 400×400 pixel spatial resolution. The temporal resolution of the time series was limited by the available non-ideal prototype hardware to about 5.5 s. Nevertheless, a detection limit of 2.1×1017 molec cm−2 could be reached, which is comparable to traditional and much less selective volcanic SO2 imaging techniques.

scholarly journals Towards imaging of atmospheric trace gases using Fabry Perot Interferometer Correlation Spectroscopy in the UV and visible spectral range

2018 ◽  
Author(s):  
Jonas Kuhn ◽  
Ulrich Platt ◽  
Nicole Bobrowski ◽  
Thomas Wagner
Keyword(s):  
Temporal Resolution ◽  
State Of The Art ◽  
Trace Gases ◽  
Visible Spectral Range ◽  
Correlation Spectroscopy ◽  
Trace Gas ◽  
Atmospheric Trace Gases ◽  
Fabry Perot ◽  
Sensitivity And Selectivity ◽  
Spatio Temporal

Abstract. Many processes in the lower atmosphere including transport, turbulent mixing and chemical conversions happen on time scales of the order of seconds (e.g. at point sources). Remote sensing of atmospheric trace gases in the UV and visible spectral range (UV/Vis) commonly uses dispersive spectroscopy (e.g. Differential Optical Absorption Spectroscopy, DOAS). The recorded spectra allow for the direct identification, separation and quantification of narrow band absorption of trace gases. However, these techniques are typically limited to a single viewing direction and limited by the light throughput of the spectrometer setup. While two dimensional imaging is possible by spatial scanning, the temporal resolution remains poor (often several minutes per image). Therefore, processes on time scales of seconds cannot be directly resolved by state of the art dispersive methods. We investigate the application of Fabry-Perot Interferometers (FPIs) for the optical remote sensing of atmospheric trace gases in the UV/Vis. By choosing a FPI transmission spectrum, which is optimised to correlate with narrow band (ideally periodic) absorption structures of the target trace gas, column densities of the trace gas can be determined with a sensitivity and selectivity comparable to dispersive spectroscopy, using only a small number of spectral channels (FPI tuning settings). Different from dispersive optical elements, the FPI can be implemented in full frame imaging setups (cameras), which can reach high spatio-temporal resolution. In principle, FPI Correlation Spectroscopy can be applied for any trace gas with distinct absorption structures in the UV/Vis. We present calculations for the application of FPI Correlation Spectroscopy to SO2, BrO and NO2 for exemplary measurement scenarios. Besides high sensitivity and selectivity we find that the spatio temporal resolution of FPI Correlation Spectroscopy can be more than two orders of magnitude higher than state of the art DOAS measurements. As proof of concept we built a one-pixel prototype implementing the technique for SO2 in the UV. Good agreement with our calculations and conventional measurement techniques are demonstrated and no cross sensitivities to other trace gases are observed.

scholarly journals Towards imaging of atmospheric trace gases using Fabry–Pérot interferometer correlation spectroscopy in the UV and visible spectral range

2019 ◽  
Vol 12 (1) ◽  
pp. 735-747 ◽  
Author(s):  
Jonas Kuhn ◽  
Ulrich Platt ◽  
Nicole Bobrowski ◽  
Thomas Wagner
Keyword(s):  
Temporal Resolution ◽  
Spectral Range ◽  
Trace Gases ◽  
Visible Spectral Range ◽  
Correlation Spectroscopy ◽  
Trace Gas ◽  
Atmospheric Trace Gases ◽  
Fabry Perot ◽  
Sensitivity And Selectivity ◽  
Spatio Temporal

Abstract. Many processes in the lower atmosphere including transport, turbulent mixing and chemical conversions happen on timescales of the order of seconds (e.g. at point sources). Remote sensing of atmospheric trace gases in the UV and visible spectral range (UV–Vis) commonly uses dispersive spectroscopy (e.g. differential optical absorption spectroscopy, DOAS). The recorded spectra allow for the direct identification, separation and quantification of narrow-band absorption of trace gases. However, these techniques are typically limited to a single viewing direction and limited by the light throughput of the spectrometer set-up. While two-dimensional imaging is possible by spatial scanning, the temporal resolution remains poor (often several minutes per image). Therefore, processes on timescales of seconds cannot be directly resolved by state-of-the-art dispersive methods. We investigate the application of Fabry–Pérot interferometers (FPIs) for the optical remote sensing of atmospheric trace gases in the UV–Vis spectral range. By choosing a FPI transmission spectrum, which is optimised to correlate with narrow-band (ideally periodic) absorption structures of the target trace gas, column densities of the trace gas can be determined with a sensitivity and selectivity comparable to dispersive spectroscopy, using only a small number of spectral channels (FPI tuning settings). Different from dispersive optical elements, the FPI can be implemented in full-frame imaging set-ups (cameras), which can reach high spatio-temporal resolution. In principle, FPI correlation spectroscopy can be applied for any trace gas with distinct absorption structures in the UV–Vis range. We present calculations for the application of FPI correlation spectroscopy to SO2, BrO and NO2 for exemplary measurement scenarios. In addition to high sensitivity and selectivity we find that the spatio temporal resolution of FPI correlation spectroscopy can be more than 2 orders of magnitude higher than state-of-the-art DOAS measurements. As proof of concept we built a 1-pixel prototype implementing the technique for SO2 in the UV. Good agreement with our calculations and conventional measurement techniques is demonstrated and no cross sensitivities to other trace gases are observed.

scholarly journals Quantitative imaging of volcanic SO<sub>2</sub> plumes with Fabry Pérot Interferometer Correlation Spectroscopy

2020 ◽  
Author(s):  
Christopher Fuchs ◽  
Jonas Kuhn ◽  
Nicole Bobrowski ◽  
Ulrich Platt
Keyword(s):  
Cross Sections ◽  
Imaging Techniques ◽  
Quantitative Imaging ◽  
Trace Gases ◽  
High Specificity ◽  
Precise Determination ◽  
Correlation Spectroscopy ◽  
Integration Time ◽  
Volcanic Plume ◽  
Fabry Perot

Abstract. We present first measurements with a novel imaging technique for atmospheric trace gases in the UV spectral range. Imaging Fabry Pérot Interferometer Correlation Spectroscopy (IFPICS), employs a Fabry Pérot Interferometer (FPI) as wavelength selective element. Matching the FPIs distinct, periodic transmission features to the characteristic differential absorption structures of the investigated trace gas allows to measure differential atmospheric column density (CD) distributions of numerous trace gases, e.g. sulphur dioxide (SO2), bromine monoxide (BrO), or nitrogen dioxide (NO2), with high spatial and temporal resolution. The high specificity in the spectral detection of IFPICS minimises cross interferences to other trace gases and aerosol extinction allowing precise determination of gas fluxes. Furthermore, the instrument response can be modelled using absorption cross sections and a solar atlas spectrum from the literature, thereby avoiding additional calibration procedures, e.g. using gas cells. In a field campaign, we recorded the temporal CD evolution of SO2 in the volcanic plume of Mt. Etna with an integration time of 1 s and 400 × 400 pixels spatial resolution. The first IFPICS prototype can reach a detection limit of 2.1 × 1017 molec cm−2 s−1/2, which is comparable to traditional and much less selective volcanic SO2 imaging techniques.

scholarly journals Depositional setting and limiting factors of early Late Cretaceous glaucony formation: implications from Cenomanian glauconitic strata (Elbtal Group, Germany)

Facies ◽  
2021 ◽  
Vol 67 (3) ◽  
Author(s):  
Markus Wilmsen ◽  
Udita Bansal
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Time Scales ◽  
Late Cretaceous ◽  
Limiting Factors ◽  
High Accumulation ◽  
Spatio Temporal ◽  
Facies Types ◽  
Facies Succession ◽  
Early Late

AbstractCenomanian strata of the Elbtal Group (Saxony, eastern Germany) reflect a major global sea-level rise and contain, in certain intervals, a green authigenic clay mineral in abundance. Based on the integrated study of five new core sections, the environmental background and spatio-temporal patterns of these glauconitic strata are reconstructed and some general preconditions allegedly needed for glaucony formation are critically questioned. XRD analyses of green grains extracted from selected samples confirm their glauconitic mineralogy. Based on field observations as well as on the careful evaluation of litho- and microfacies, 12 glauconitc facies types (GFTs), broadly reflecting a proximal–distal gradient, have been identified, containing granular and matrix glaucony of exclusively intrasequential origin. When observed in stratigraphic succession, GFT-1 to GFT-12 commonly occur superimposed in transgressive cycles starting with the glauconitic basal conglomerates, followed up-section by glauconitic sandstones, sandy glauconitites, fine-grained, bioturbated, argillaceous and/or marly glauconitic sandstones; glauconitic argillaceous marls, glauconitic marlstones, and glauconitic calcareous nodules continue the retrogradational fining-upward trend. The vertical facies succession with upwards decreasing glaucony content demonstrates that the center of production and deposition of glaucony in the Cenomanian of Saxony was the nearshore zone. This time-transgressive glaucony depocenter tracks the regional onlap patterns of the Elbtal Group, shifting southeastwards during the Cenomanian 2nd-order sea-level rise. The substantial development of glaucony in the thick (60 m) uppermost Cenomanian Pennrich Formation, reflecting a tidal, shallow-marine, nearshore siliciclastic depositional system and temporally corresponding to only ~ 400 kyr, shows that glaucony formation occurred under wet, warm-temperate conditions, high accumulation rates and on rather short-term time scales. Our new integrated data thus indicate that environmental factors such as great water depth, cool temperatures, long time scales, and sediment starvation had no impact on early Late Cretaceous glaucony formation in Saxony, suggesting that the determining factors of ancient glaucony may be fundamentally different from recent conditions and revealing certain limitations of the uniformitarian approach.

scholarly journals From Femtoseconds to Hours–Measuring Dynamics over 18 Orders of Magnitude with Coherent X-rays

2021 ◽  
Vol 11 (13) ◽  
pp. 6179
Author(s):  
Felix Lehmkühler ◽  
Wojciech Roseker ◽  
Gerhard Grübel
Keyword(s):  
Time Scales ◽  
Free Electron Laser ◽  
Photon Correlation Spectroscopy ◽  
Signal To Noise Ratio ◽  
Coherent Scattering ◽  
Correlation Spectroscopy ◽  
X Rays ◽  
Photon Correlation ◽  
X Ray ◽  
Scattering Technique

X-ray photon correlation spectroscopy (XPCS) enables the study of sample dynamics between micrometer and atomic length scales. As a coherent scattering technique, it benefits from the increased brilliance of the next-generation synchrotron radiation and Free-Electron Laser (FEL) sources. In this article, we will introduce the XPCS concepts and review the latest developments of XPCS with special attention on the extension of accessible time scales to sub-μs and the application of XPCS at FELs. Furthermore, we will discuss future opportunities of XPCS and the related technique X-ray speckle visibility spectroscopy (XSVS) at new X-ray sources. Due to its particular signal-to-noise ratio, the time scales accessible by XPCS scale with the square of the coherent flux, allowing to dramatically extend its applications. This will soon enable studies over more than 18 orders of magnitude in time by XPCS and XSVS.

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