爱尔兰火山爆发波及欧洲空气质量

A modern recurrence¹ of an extraordinary type of volcanic² eruption³ in Iceland could inject large quantities of hazardous⁴（有危险的） gases into North Atlantic and European flight corridors, potentially for months at a time, a new study suggests. Using computer simulations, researchers are investigating the likely atmospheric⁵ effects if a "flood lava⁶" eruption took place in Iceland today. Flood lava eruptions⁷, which stand out for the sheer amounts of lava and sulfurous gases they release and the way their lava sprays from cracks like fiery⁹ fountains, have occurred in Iceland four times in roughly the past thousand years, records indicate, the most recent being the deadly and remarkable¹⁰ eruption of Iceland's volcano Laki in 1783-84. When Laki sprang to life on June 8, 1783, it generated a sulfuric acid haze¹¹ that dispersed¹² over Iceland, France, England, the Netherlands, Sweden, Italy, and other countries. It killed a fifth of Iceland's population and three-quarters of the island's livestock¹³. It also destroyed crops, withered¹⁴ vegetation, and sowed human disease and death in several Northern European nations. During the eight months that Laki erupted, the volcano blasted 122 million tons of sulfur⁸ dioxide into the atmosphere -- seven times more than did the 1991 Mt. Pinatubo eruption in the Philippines and approximately 50 to 100 times more per day than Iceland's Eyjafjallajökull volcano released in 2010.

Researchers have found evidence in previous studies that a modern Laki-like eruption could disrupt European air traffic. Now, using two computer models that simulate physical and chemical behaviors of volcanic emissions¹⁵, atmospheric scientist Anja Schmidt of the University of Leeds in the U.K. and her colleagues are refining scientific understanding of the likely concentrations and distributions of hazardous sulfur dioxide gas and sulfuric acid from such an event.

If a Laki-like eruption were to begin in late spring or summer, as it did in 1783, the daily average concentrations of sulfur dioxide during that first month would exceed 40 parts per billion by volume (ppbv) in up to a third of the North Atlantic and European airspace, the new simulations show. That concentration falls just under the level of 47 ppbv at which the World Health Organization (WHO) deems chronic¹⁶ exposure to the gas a health hazard, although short-term exposures are considered hazardous only at much higher concentrations. In up to 10 percent of the air space, concentrations would exceed five times the WHO chronic exposure guideline, the researchers found.

The emissions wouldn't come from Laki itself, which volcanologists say has spent its fury, but could explode from several other Icelandic volcanic systems.

Most sulfur dioxide gas emitted by volcanoes rapidly undergoes chemical reactions to form an aerosol¹⁷ -- minuscule¹⁸ particles suspended in the atmosphere -- of sulfuric acid droplets¹⁹. In the new simulations -- focusing again on the first month of the eruption -- average daily concentrations of the droplets, in up to 10 percent of the air space, would exceed 10 times London's average daily concentration of the corrosive²⁰ pollutant²¹, the researchers found.

"It's known that flying through a volcanic ash cloud can damage aircraft. In the case of a Laki-type eruption, high sulfur dioxide and sulfuric acid concentrations will have to be considered as an additional hazard," Schmidt said. An acceptable level of exposure for aircraft and their passengers is something for government aviation officials and industry to address, she added.

Schmidt presented the preliminary results from the study today in Selfoss, Iceland at the Chapman Conference on Volcanism and the Atmosphere, a meeting sponsored by the American Geophysical Union (AGU). Her collaborators include Kenneth Carslaw, also of Leeds, Claire Witham and Matthew Hort of the UK Met Office, in Exeter, and Thor Thordarson of the University of Edinburgh, also in the U.K. Previous work by Thordarson and others had suggested that a new Laki-like eruption could disrupt air traffic.