Spectral measurement of atmospheric SO2 levels in volcanic plumes monitors volcanic activity
Volcanoes inspire both fear and fascination, and yet with most located in remote or sparsely populated areas, we don’t think of them as impacting our everyday lives. When the Icelandic volcano Eyjafjallajökull erupted in 2010, however, ash clouds caused air traffic to be halted, travelers were stranded across the world and the airline industry lost vast amounts of revenue. Eruption of lava from the Holuhraun lava field originating from the Bárdarbunga volcano, also in Iceland, raised fears of a repeat in early September 2014, and spectroscopy was ready to help sound the warning.
Holuhraun is on track to spew more lava than has been seen in any Icelandic eruption in the last two centuries. The daily concentration of potentially dangerous SO2 emitted has exceeded the estimated SO2 pollution from all industries across Europe combined, and is affecting local air quality. The impact of major eruptions are potentially far more severe with the change in air chemistry and reduced light levels adversely affecting weather patterns, crop growth and human health.
A Spectroscopic Forecast
Volcanic gas emissions – sulfur dioxide (SO2) in particular – are used to understand and forecast volcanic activity. Portable, compact spectrometers have become the instrument of choice for monitoring SO2 emission rates of volcanoes before and during eruptions, and are even used to track plume movement over time. A group of researchers from Chalmers University in Sweden have installed two miniaturized differential optical absorption spectroscopy (mini-DOAS) systems based on Ocean Optics Maya2000 Pro spectrometers at the site in Holuhraun, and are using them to understand the region’s current and anticipated volcanic activity.
DOAS allows spectroscopists in the field to harness the sun as a light source, using it together with a narrow field of view telescope and spectrometer to create a large-scale absorption spectroscopy system in the sky. As sunlight passes through the atmosphere, SO2 causes certain UV wavelengths to be absorbed. Estimates of plume geometry together with filtering and spectral fitting are used to complete the analysis and determine the concentration of SO2 in the plume.
An Eye on the Skies
Though the danger of a large eruption has subsided, the lava flow continues at Holuhraun. As it does so, it is reassuring to know that spectroscopy is keeping a watchful eye, providing the monitoring needed to understand this fiery force. Both the skyways above and the people in its path will be safer as a result.
Holuhraun has remained active since August 2014, with the threat of additional gas emissions if eruptions continue. Researchers in the Optical Remote Sensing Group at Chalmers continue to monitor the site and others around the world, developing new ground-based sensing methods and spectral modeling to derive improved estimates of gas emissions.
Optical System – Absorption
- Maya2000 Pro spectrometer (280-380 nm)
- Telescope attachment
- Custom optical patch cord fiber