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Forschungszentrum Jülich - Research in Jülich 2_2012

8 O n its travels for research lasting several months, the flying re- search platform sets course for the Netherlands, Italy and Finland. The Zeppelin NT flies through very different air masses: it cruises above heavily pop- ulated industrial areas and large cities, flies over the Adriatic, and floats above vast forests. However, it does so without the feeling of being on holiday. The many measuring instruments on board contin- uously analyse the chemical composition of the air during the long flying time and record the data for research purposes. Prof. Spyros Pandis, coordinator of the Pan-European Gas-Aerosol-Climate Interaction Study (PEGASOS) outlines the scientific context: “This mission is one of the most extensive campaigns measuring air quality in Europe, if not worldwide. Our aim is to create datasets that can then be used as a reference for international air-quality research.” Within PEGASOS, the Zeppelin NT collects data for a total of 20 weeks co- ordinated by researchers from Jülich. Twenty-six partners from 14 European countries are working together with Is- rael in an effort to investigate the rela- tionships between atmospheric chemis- try and climate change. The findings will be used as a basis for climate protection measures throughout the EU. In order to collect these data, the Zeppelin transports highly specialized measuring instruments with a combined weight of around 1,000 kilograms. Of this, 390 kilograms are installed on a platform on top of the Zeppelin. The rea- son is that the most important chemical processes in air are induced by light. Un- derneath the Zeppelin – in the shadow of the mighty airship – these photochemi- cal reactions do not occur. TRACKING THE INTANGIBLE Understanding these photochemical reactions is one of the main priorities of the measurement campaign. At altitudes of 100 to 2,000 metres, scientists are investigating the self-cleaning ability of the atmosphere. The key molecule in this process is the hydroxyl radical (OH radical). It triggers the degradation of most pollutants and determines how long they survive in the atmosphere. The OH concentration is therefore a measure of the cleaning efficiency of the atmo- sphere. The hydroxyl radical is formed in the atmosphere from ozone and water molecules under UV radiation. In a natu- ral cycle, it is initially consumed when pollutants are degraded, but in many cases it is then subsequently recycled (see “The Cycle of Radicals”, p. 11). How- ever, in the last few years, Jülich re- searchers have come across discrepan- cies in the prevailing theory with respect to recycling. It is hoped that the Zeppelin flights will now clarify the matter. Hydroxyl radicals are highly reactive – and they are elusive. The radicals only exist for a fraction of a second. In 10,000,000,000,000 (ten trillion) air par- ticles, there is only ever a single particle of this atmospheric detergent. New measuring methods developed by Jülich scientists will now make it possible to reliably determine the concentration and lifetime of hydroxyl radicals in the at- mosphere. LIGHT, COMPACT, AND STABLE Dr. Andreas Hofzumahaus from the Jülich Institute of Energy and Climate Re- search (IEK-8) says, “We have developed two main methods of measuring the OH Research in Jülich 2|2012 At the launch in early May, Federal Research Minister Prof. Annette Schavan familiar- ized herself with the scientists’ goals. Sitting opposite her is Robert-Jan Smits, Direc- tor-General for Research and Innovation of the European Commission. FRANCEROUTES OF THE ZEPPELIN NT IN 2012 West mission South mission (flown: east route) South mission (alternative: west route) Airport Overnight/ refuelling stop

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