Volcanic ash cloud: X-rays reveal grounding jets was right choice

Volcanic ash Wednesday

When Eyjafjallajökull spewed volcanic ash into the atmosphere in 2010, airlines were thrown into chaos as the aviation authorities grounded all planes. But was the move justified, did it stop potentially catastrophic damage to aircraft? A new study that takes a close look at the behaviour of ash particles would suggest so.

On 14th April 2010, meltwaters from the Eyjafjallajökull glacier mixed with hot magma emerging from the volcanic site causing an explosive eruption that carried an uncommonly fine ash thousands of metres into the air and into the jet stream, which then quickly dispersed it across European airspace. Such particulates hitting aircraft had in previous events led to "sandblasted" windows and molten deposits in jet engines that led to failure. Given the scale of the Eyjafjallajökull ash cloud, the only sensible response was to ground all aircraft.

At the time, airline passengers from all walks of life were trapped in airport departure and arrivals lounges some for many days while others attempted to complete journeys by land and sea. Many wondered whether there really was any scientific basis of the adopting the precautionary principle in the face of Eyjafjallajökull. The media repeatedly hounded politicians and aviation authorities for answers as the frustration of their readers, listeners and viewers grew. Now, a paper published by a joint Icelandic and Danish team in the US journal, Proceedings of the National Academy of Sciences, provides evidence that caution was indeed the best option.

Ashes to ashes

Researchers from the Institute of Earth Sciences, at the University of Iceland, in Reykjavik, and the Nano-Science Center, at the University of Copenhagen, as well as Reykjavik Energy, had collected dry ash samples immediately after the explosive event and compared them with fresh ash from a more typical eruption a few days later. They used a raft of techniques including X-ray photoelectron spectroscopy and atomic force microscopy, to explore the physical and chemical characteristics of this dry ash in the hope of determining whether health and safety fears had a solid grounding in science.

"We used spectroscopy to assess toxicity risk and to determine the composition of the individual ash particles," Stipp told SpectroscopyNOW, "both XPS and EDXS on an electron microprobe, which we used to interpret hardness and melting temperature." The work has also led to the development of a new risk-assessment protocol that could be used to test the nature of ash from future events and allow the aviation authorities to make an informed decision.

"On single particles, we identified the composition of nanometre-scale salt coatings and measured the mass of adsorbed salts with picogram resolution," the team reports in PNAS. "The particles of explosive ash that reached Europe in the jet stream were especially sharp and abrasive over their entire size range, from submillimetre to tens of nanometres. Edges remained sharp even after a couple of weeks of abrasion in stirred water suspensions." These findings suggest that risk to aircraft and to passengers would have been relatively high if aircraft and in particular jet aircraft had been allowed to fly while the ash cloud was its densest.

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.