Press release: Göttingen researchers investigate the chemical composition of the ash cloud

Nr. 90/2010 - 14.05.2010

(pug) After the eruption of the Icelandic volcano Eyjafjallajökull researchers from the University Göttingen have, for the first time, used an electron microprobe to analyze individual dust particles from the ash cloud and investigated their chemical composition. The researchers collected their samples from the surface of freshly washed cars after a light rain. Even though only a few milligrams (1 milligram = 0,001 grams) per square meter were deposited, Prof. Dr. Gerhard Wörner and Dr. Andreas Kronz from the Faculty for Geosciences and Geography, Geochemistry Division, were able to make the ash particles visible under an electron microscope. Their analyses offer important data for the assessment of the ash load of the atmosphere in general and resulting threat to air traffic. "In its composition the ash cloud was not denser than a summer sandstorm in the Sahara over North Africa but it was only located at a certain atmospheric height,“ said Prof. Wörner. "However, the composition is quite different. Now it is up to the engineers to find out how and in what concentrations the volcanic ash can damage aircraft engines.“

The ash particles under investigation consist largely of silicate glass: they developed in the volcanic vent when hot lava met cold glacier water and burst into small particles. The eruption leads to additional fragmentation of the lava and, because of the rapid cooling down, the particles solidify abruptly into glass. In addition to the typical elements of silicon, aluminium, magnesium, iron, and calcium, as well as crystals typical for Iceland, the researchers were able to detect increased concentrations of chlorine and sulfur on the surface of the particles using a microprobe. This suggests that volcanic gases from the eruption cloud were deposited on the ash particles. Additionally, the researchers discovered vermicular ash particles whose origins are still unclear. "These ash aggregates could be a consequence of the lightning caused by static electric charging in the eruption cloud. To find out more we will compare the Göttingen ash particles with deposits directly on the crater rim. We are already in contact with researchers in Iceland,“ Prof. Wörner stated.

On April 19th. a measurement flight of the German Aerospace Center in Oberpfaffenhofen resulted in first insights into the concentration and size of the ash particles at altitudes between four to 5,5 kilometers. With a grain size of less than 0,01 millimeters, one cubic meter of air contains about 60 micrograms of ashes. "When this extremely fine dust dropped down to earth from the ash cloud, about one to two kilograms of particulate matter were distributed over the area of about one square kilometer. That amount corresponds to a child's shovel worth of particulate matter distributed over the entire Göttingen city centre. Road traffic alone produces higher amounts of particulate matter," explains Prof. Wörner.

Note to editors:
Pictures on this subject can be found on the Internet at www.uni-goettingen.de/de/152416.html and are available for download.

Contact address:
Dr. Andreas Kronz
Prof. Dr. Gerhard Wörner
Georg-August-Universität Göttingen
Faculty for Geosciences and Geography
Geochemistry Division
Goldschmidtstraße 1, 37077 Göttingen
Tel. +49 (0551) 39-9336 (office) and 39-3975 (Laboratory)
E-Mail: akronz@gwdg.de and gwoerner@gwdg.de
Internet: www.uni-geochem.gwdg.de