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ePaper created 2012-09-28, 09:46:25 | version 1.24.0
Research in Jülich 2|201210 the air is. To do so, it measures the life- time of OH radicals. This new device is known as AirTauOH. It sucks in an even flow of external air and illuminates it with a laser. This causes the immediate forma- tion of OH radicals. The more reaction partners – or different types of molecules – can be found in the air, the shorter the lifetime of the OH radicals. FAST AND RELIABLE The decrease in concentration over time is registered exactly by another measuring cell. This allows conclusions to be drawn on how polluted the air is, but it does not help to determine whether the pollutants are natural or man-made. Other instruments on board record aero- sols or molecules present in the air, such as formaldehyde. According to Hof- zumahaus, “Space limitations mean that we can’t measure the entire range of all atmospheric molecules during the Zeppe- lin mission. But thanks to AirTauOH, we can determine how many reactive compo- nents are in the air at a particular point in time.” A group of molecules has been identi- fied as being particularly important for climate, namely volatile substances re- leased by plants. After oxidation, these can form aerosols in the atmosphere, which later contribute to the formation of clouds. Clouds reflect solar radiation and can therefore be considered to counter- act global warming. For this reason, an- other priority of the PEGASOS campaign is to verify and characterize the existence of aerosols above different regions. Conifers, for example, predominantly release terpenes into the air which create the fragrant aroma in a forest. Deciduous trees, on the other hand, tend to emit a substance known as isoprene. The two substances react at different speeds with the OH radicals, which impacts on the formation of aerosols in the atmosphere, as Jülich researchers recently discovered. In their study, they demonstrated that aerosol formation is impaired when the isoprene concentration is high in relation to the terpene concentration, as is fre- quently the case in summer. Under these conditions, the isoprene molecules basi- cally steal the terpenes’ reaction part- ners. This has considerable conse- quences. The volatile terpenes are no longer oxidized by the OH radicals and therefore no longer act as precursors for cloud nuclei. It is hoped that measure- ments above the extensive forest areas in Finland will provide data still lacking on the rivalry between the two plant sub- stances. “The Zeppelin follows flights routes set in advance to take into account exist- ing ground measuring stations,” empha- sizes Dr. Astrid Kiendler-Scharr. The re- searchers want to find out exactly what happens with the components of air on their way from the earth’s surface to an altitude of 2,000 metres. Design of the AirTauOH instrument, which measures air pollution. Intensive preliminary work at the Zeppelin hangar paid off: all measuring instruments as well as cooperation between engineers and technicians, pilots, and scientists work smoothly.