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Characterization of Organic Reduced Nitrogen species

Final Report Summary - CORN (Characterization of Organic Reduced Nitrogen species)

Major milestone of the Marie Curie fellowship was to contribute to an improved assessment of the fluxes of both ammonia (NH3) and selected reduced volatile organic nitrogen compounds (biogenic volatile amines) from agricultural ecosystems. Accomplished objectives comprised (1) optimization and detailed technical characterization of a customized online mass spectrometric analytical technology (PTRMS) for the analysis of atmospheric reduced nitrogen species (high time-resolution, sensitivity, precision) established in an innovative O2+-mode, (2) successful application of the PTRMS technology for concentration and micrometeorological flux measurements of reduced N-compounds, (3) implementation of an independent analytical technique for amine analysis to cross-check the PTRMS qualification/quantification for reduced N-compounds, (4) detailed characterization of agricultural sources for volatile reduced N-compounds other than NH3 (biogenic amines), both within field measurements and in laboratory experiments under controlled environmental conditions, (5) modelling of the exchange of reduced nitrogen species based on own experimental data, as to (6) gain deeper insight into the ecological understanding of agricultural land ecosystems.

A comprehensive manure field application experiment was implemented to test the customized PTRMS Eddy Correlation technology against established methods within a joint flux intercomparison exercise over an agricultural crop field and a grassland site in Oensingen Switzerland. Good agreement between all measurement techniques was achieved for NH3 fluxes. The newly established high time resolution flux method considerably advances the knowledge on the highly dynamic NH3 emissions processes. The socio-economic impact and the wider implications of the project will be to ultimately being able to (re)assess the sink-/-source balance of reduced nitrogen compounds within agricultural land ecosystems, to allow sustainable land management (and evaluate mitigation strategies), taking into account present climate change issues.

Volatile biogenic amines are nitrogen-bearing organic compounds which are assumed to be a significant component of the atmospheric N-cycle, but are not accounted for in recent assessments of the global N-cycle, due to the scarceness of available data. Beside NH3, amines represent the major residual of alkaloid components in the earth's atmosphere. There is increasing evidence for an important role of amines in the formation of new particulate matter, as well as for aerosol secondary growth. Hitherto, the information on the occurrence of reduced nitrogenous compounds other than ammonia in the atmosphere is marginal. Agriculture is the most important source of ammonia, and has been assumed to similarly contribute to the budget of volatile organic amines, presuming that the amine sources (and source distribution) are the same as for NH3. While livestock indoor air concentration measurements during the Fellowship confirm earlier literature results, in contrast, first flux measurements by means of the Aerodynamic Gradient method (AGM) after the application of manure in the field showed that concentrations and fluxes of biogenic volatile amines do scale with the fluxes of NH3, but were about 4 orders of magnitude lower than for NH3, i.e. much lower than expected from current literature assumptions. First experiments on cattle breath air by means of PTRMS fast NH3 and TMA measurements give evidence that exhalation (not volatilization from animal excrements) is the primary pathway for amine emission. Laboratory experiments attest that high concentrations of amines (and respective high ratio relative to NH3) build up during ruminant digestion. Our observations indicate that the high amine/ammonia ratios described earlier for livestock building indoor air can mainly be attributed to the animal's exhalation, especially in the case of ruminants.