Volcanic
Degassing
Objectives:
·
To
develop novel remote sensing techniques for surveillance of volcanic gases and
aerosols
·
To
develop comprehensive models for volcanic degassing
·
To
understand the atmospheric chemistry and transport of volcanic plumes
·
To
understand the impacts of volcanic gases and aerosols on human health and
terrestrial ecosystems
Fourier transform infrared spectroscopy (FTS) & geochemical modelling of volcanic degassing
Volcanoes
emit gases both during and between eruptions. Surveillance of gas composition
and flux is essential for interpretation of volcanic activity, since degassing
exerts a fundamental control on magma dynamics and eruption style. It also supports assessment of the role of
volcanic gases in atmospheric chemistry and dynamics. We have played a key role
in the development of the application of Fourier transform infrared
spectroscopy to field measurement of volcanic gases. The technique is now used by several observatory and university-based
scientists worldwide, including application to routine monitoring of Mount Etna
by a former research associate now at the Italian National Geophysical and
Volcanological Institute. We designed
and conducted the first volcanological experiments using solar occultation FTS,
and have played a significant role in the geochemical surveillance of Soufričre
Hills Volcano, Montserrat, since 1996.
Work there has led to a detailed interpretation of volatile sources and
fluxes, contributing to overall understanding of the eruption.
Contact: Clive Oppenheimer, Hayley Duffell, for final reports on NERC
projects click here.
Horrocks,
L.A., Oppenheimer, C., Burton, M.R., Duffell, H.R., Davies, N.M., Martin, N.A.,
and Bell, W., 2001, Open-path Fourier transform infrared spectroscopy of
SO2: an empirical error budget analysis, with implications for
volcano monitoring, Journal of Geophysical Research-Atmospheres,
106, 27647-27659.
Oppenheimer C, Francis P, Burton M, Maciejewski A, Boardman L, 1998, Remote measurement of volcanic gases by Fourier transform infrared spectroscopy, Applied Physics B, 67, 505-515.
Differential Optical Absorption Spectroscopy (DOAS)
In collaboration with Bo Galle (Chalmers University
of Technology, Gothenburg), we have recently established the potential of a new
miniature ultraviolet spectrometer for measuring the sulfur dioxide flux from
volcanoes. Tests with the compact and
easy-to-operate device at Masaya volcano (Nicaragua) and Soufričre Hills
Volcano (Montserrat) have proved extremely encouraging and the “mini-DOAS” is
sure to be rapidly adopted by volcano observatories and university-based groups
for measurements of this key volcanic gas.
Contact: Andrew
McGonigle
McGonigle, A., & Oppenheimer,
C., Optical sensing of volcanic gas and aerosol emissions, in Volcanic degassing, Geological Society
Special Publication, accepted.
Galle, B., Oppenheimer, C., Geyer, A., McGonigle, A., Edmonds, M., and Horrocks, L.A., 2002, A miniaturised ultraviolet spectrometer for remote sensing of SO2 fluxes: a new tool for volcano surveillance, Journal of Volcanology and Geothermal Research, in press.
Laser spectroscopy
Volcanic volatiles observed at the surface can be derived, in varying proportions, from mantle, slab or groundwater sources. One approach to probing these sources is the measurement of isotopic signatures. We are working in collaboration with Frank Tittel (Rice University, Houston) and Paolo de Natale (LENS, Firenze) in the development and application of novel laser spectrometers for volcanic gas detection and measurement. Preliminary tests of two Difference Frequency Generation lasers were carried out at Masaya volcano in 2000.
Contact: Clive Oppenheimer
Richter, D., Erdelyi, M., Curl, R.F., Tittel, F.K., Oppenheimer, C., Duffell, H.J., and Burton, M., 2002, Field measurement of volcanic gases using tunable diode laser based mid-infrared and Fourier transform infrared spectrometers, Optics and Lasers in Engineering, 37, 171-186.
Sun photometry
Portable Sun photometers provide an attractive means to measure volcanic aerosol remotely. Preliminary investigations into the technique were carried out at Mount Etna using the Cimel Sun photometer on loan from the NERC Equipment Pool for Spectroscopy. Measurements obtained under, and outside the plume permit subtraction of background atmospheric aerosol and modelling of the resulting spectra yields particle concentration and size distributions.
Contact: Matt Watson, Clive Oppenheimer
Sponsors: NERC
Watson, I.M., and Oppenheimer, C., 2001, Particle-size distributions of ash-rich volcanic plumes determined by sun photometry, Atmospheric Environment, 35, 3561-3572..
Watson, I.M., and Oppenheimer, C., 2000, Particle size distributions of Mt. Etna’s aerosol plume constrained by sun-photometry, Journal of Geophysical Research-Atmospheres, 105, 9823-9830.
Measurements and modelling of the atmospheric chemistry and transport of volcanic plumes and their environmental and health impacts
We have
been applying FTS, Sun-photometry, and direct sampling methods to investigate
gas and aerosol composition, aerosol size distribution, and chemistry of
tropospheric volcanic plumes. Our
recent observations have highlighted meteorological controls on particle size
distributions, and on removal of gaseous HCl, HF and SO2. Measurements carried out at Masaya volcano
in 2001 revealed for the first time the importance of very low pH,
submicron-sized sulfate particles as a primary emission (or possibly combustion
product) of magmatic degassing. This
work has important implications for the environmental and health impacts of
volcanic emissions, and their long range transport.
A key
long-term aim of this work is to build a set of linked physical, chemical and
statistical models to investigate the chemistry and transport of (primarily
tropospheric) volcanic clouds and, to quantify their atmospheric, environmental
and health impacts, especially with regard to the threat of major pollution
events arising from Icelandic volcanism. This will lead to a detailed
understanding of Britain’s and continental Europe’s vulnerability to a range of
potential Icelandic eruptions, and to development of new methods for risk
mitigation, and will have wide application in modelling other types of
pollution, and their implications for respiratory morbidity and cardiovascular
mortality. Such models will also permit
new studies of global scale volcano-climate interaction.
Contact: Tamsin Mather Clive
Oppenheimer, Claire Witham
Sponsors: NERC
Burton, M.R., Oppenheimer, C., Horrocks, L.A., Francis,
P.W., 2001, Diurnal changes in volcanic plume chemistry observed by
lunar and solar occultation spectroscopy, Geophysical
Research Letters, 28, 843-846.
Oppenheimer C, Francis P and Stix J, 1998, Depletion rates
of SO2 in tropospheric volcanic plumes, Geophsyical Research Letters, 25, 2671-2674.