N - Isotopes of Ammonia and Ammonium in and over the Atlantic (NISAAA)

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N-transfer rates in the boundary layer between atmosphere and ocean play a critical role to understand global life processes and their development. The ratio of stable isotopes of N2 and nitrate were mainly used to understand transfer rates and transfer mechanisms of nitrogen compounds. We want to determine isotope ratios of atmospheric ammonia over the ocean for the first time and in conjunction N - isotope ratios in particulate ammonium, in order to evaluate sources, transports, transformations and sinks of atmospheric NH3. Isotope ratios of NH4+ and of physically dissolved NH3 x H2O in the surface water of the Atlantic will be determined to relate ocean and atmospheric NH3. On a meridional transection from 80° north to 70° south RV "Polarstern" will traverse representative maritime provinces and air-mass zones, so that a first impression can be gained on the distribution of N - isotopes in ammonia and ammonium. New constraining barriers can thus be set up with isotope ratios of N-NH3 and NH4+ for cycles and models of N - components in the earth system.