"The proposed Marie Curie Action CORN seeks to aid to the technical adaptation of online Proton Transfer Reaction Mass Spectrometry (PTR-MS) to measure ambient concentrations and fluxes of ammonia (NH3) and selected biogenic reduced volatile organic nitrogenous compounds (amines). The technological development is based on operating the PTR-MS instrument in a new mode, allowing for analysis with significantly improved sensitivity. The capability of an instrument to measure both ammonia and amines at high sensitivity and time resolution would be unique. Taking advantage of the derived high time resolution, the setup will be used for characterizing the exchange pattern of reduced nitrogen compounds over agricultural grassland ecosystems applying a micrometeorological flux approach (Eddy Covariance). Despite the prominent role of reduced nitrogen species in the environment and respective ecological problems related to the N-cycle, large uncertainties remain both in its exchange processes and related atmospheric chemistry and physics. A large fraction of reduced nitrogen occurs in the particulate phase, after forming salts upon reaction with acidic gases (ammonium nitrate and ammonium sulphate). Information on the occurrence of amines in the atmosphere is scarce, but there is increasing evidence of the role of organic reduced nitrogen compounds in the formation and secondary growth of aerosols. In general agriculture is understood to be a strong source both for ammonia and organic reduced nitrogen. Grassland ecosystems may be alternately important sinks and sources for reduced nitrogen. CORN will be integrated into a broad research initiative on the role of nitrogen fluxes from managed agricultural ecosystems. The training activities of the applicant will build on the expertise and activities of the host institute (ART, Zurich), both in the operation of the PTR-MS and in the application of micrometeorological flux measurement techniques on reactive trace gases."