 |
| Titel |
Developing and testing a low cost method for high resolution measurements of volcanic water vapour emissions at Vulcano and Mt. Etna |
| VerfasserIn |
Tom D. Pering, Andrew J. S. McGonigle, Giancarlo Tamburello, Alessandro Aiuppa, Marcello Bitetto, Cosimo Rubino |
| Konferenz |
EGU General Assembly 2015
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250108178
|
| Publikation (Nr.) |
 EGU/EGU2015-7920.pdf |
|
|
|
|
|
| Zusammenfassung |
| The most voluminous of emissions from volcanoes are from water vapour (H2O) (Carroll and Holloway, 1994), however, measurements of this species receive little focus due to the difficulty of independent measurement, largely a result of high atmospheric background concentrations which often undergo rapid fluctuations. A feasible method of measuring H2O emissions at high temporal and spatial resolutions would therefore be highly valuable. We describe a new and low-cost method combining modified web cameras (i.e. with infrared filters removed) with measurements of temperature and relative humidity to produce high resolution measurements (≈ 0.25 Hz) of H2O emissions. The cameras are affixed with near-infrared filters at points where water vapour absorbs (940 nm) and doesn’t absorb (850 nm) incident light. Absorption of H2O is then determined by using Lambert-Beer’s law on a pixel by pixel basis, producing a high spatial resolution image. The system is then calibrated by placing a Multi-GAS unit within the gas source and camera field-of-view, which measures; SO2, CO2, H2S and relative humidity. By combining the point measurements of the Multi-GAS unit with pixel values for absorption, first correcting for the width of the gas source (generally a Gaussian distribution), a calibration curve is produced which allows the conversion of absorption values to mass of water within a pixel. In combination with relative humidity measurements made outside of the plume it is then possible to subtract the non-volcanic background H2O concentration to produce a high resolution calibrated volcanic H2O flux. This technique is demonstrated in detail at the active fumarolic system on Vulcano (Aeolian Islands, Italy). Data processing and image acquisition was completed in Matlab® using a purpose built code. The technique is also demonstrated for the plume of the North-East Crater of Mt. Etna (Sicily, Italy). Here, contemporaneously acquired measurements of SO2 using a UV camera, combined with gas ratios in the plume, allow for the first comparison between CO2, SO2 and H2O emissions at high resolution, however, calibration and conversion to real H2O values in this instance is more complex and problematic. Although, non-calibrated measurements still prove useful by providing a basis for comparing periodicity with other gas species. Indeed, in tandem with recent observations of CO2 and SO2 flux at Mt. Etna (e.g. Tamburello et al. 2013; Pering et al. 2014), H2O emissions also demonstrate periodicity over similar periods to those previously observed. |
|
|
|
|
|
|