Ash plume analysis reveals surprising results
When the eruption of Iceland's now infamous volcano Eyjafjallajökull brought an uncharacteristically peaceful silence to European flight paths in April 2010, the science world turned its attention to volcanic gas and its effects, and new European research reveals some surprising facts about the ash plume. The research, conducted by a team from the Max Planck Institute for Chemistry in Mainz, Germany, found that the ash plume contained not only the common volcanic gas sulfur dioxide, but also free chlorine radicals. Chlorine radicals are extremely reactive and even tiny amounts that can have a profound impact on local atmospheric chemistry. The findings, published in the journal Geophysical Research Letters, present the evidence of volcanic plume chlorine radical chemistry, which allowed the team to make calculations of chlorine radical concentrations. Although it has long been known that when volcanoes erupt they emit chlorine-containing gases, until now there was no evidence that highly reactive chlorine radicals were also present. The team found this conclusive evidence after analysing air collected from the ash cloud surrounding Eyjafjallajökull. In spring 2010 they conducted three flights into the ash cloud to collect air samples using a CARIBIC atmospheric measurement container. 'Each volcano has its own character,' comments Angela Baker, one of the study's authors. 'We found that hydrocarbon concentrations were up to 70% lower inside the Eyjafjallajökull ash cloud than outside. Reaction with chlorine radicals was the only realistic explanation for the hydrocarbon losses. And further investigation confirmed that free chlorine radicals were the cause.' The scientists found that there were concentrations of up to 66,000 chlorine atoms per cubic centimetre of air. Although this figure was modest compared to concentrations of other gases, it is remarkable due to the fact that chlorine radicals are normally absent and it only takes a small amount of them to make a big impact on atmospheric chemistry. Hydrocarbons like propane and butane can be found even in the cleanest and most remote parts of the lower atmosphere. Normally they are removed when they react with hydroxyl radicals, but they react much faster with chlorine radicals. These chlorine reactions leave a mark on the mixture of hydrocarbons in the air. By leaving this trace scientists can calculate how many chlorine radicals are present. Using the volcanic ash cloud chlorine radical concentrations found in Eyjafjallajökull's plume, the German researchers anticipate that similar results will be found in plumes from other volcanoes, such as those of another currently erupting Icelandic volcano Grimsvötn, which to the dismay of frequent flyers brought European flight paths to a (brief) standstill once again in May 2011.For more information, please visit:Max Planck Institute for Chemistry:http://www.mpic.de/Home.107.0.html?&L=2
Countries
Germany, Iceland