Description: Das Projekt "Isotopic constraints on seasonal N2O dynamics in marine and lacustrine environments" wird vom Umweltbundesamt gefördert und von Universität Basel, Umweltgeowissenschaften durchgeführt. Nitrous oxide (N2O) is now the third largest contributor to radiative forcing of the long-lived greenhouse gases. Human inputs of nitrogen (N), mainly as fertilizers, have stimulated the microbial N cycle transformations that are the dominant source of N2O. The partitioning between the anthropogenic and natural N2O sources is relatively well constrained at 7 and 11 Tg N/yr, respectively. However, large uncertainties remain in the relative contributions of terrestrial versus aquatic environments and with regards to the underlying biogeochemical controls on microbial N2O production. Such uncertainties present challenges for those devising and implementing N2O emissions policies, and make it difficult to interpret prehistoric atmospheric N2O fluctuations and predict the response of N2O production rates to future climate change. Aquatic N2O fluxes are often highly variable through time and space. The variation is likely modulated by fluctuations in the biogeochemical conditions, which may affect microbial N2O production pathways differentially. N2O can be produced by several processes, such as microbial nitrification (ammonia oxidation), denitrification, and nitrifier-denitrification, and multiple groups of microorganisms are involved. Yet, the exact environmental controls on temporal/spatial variations in net N2O production and the balance between the different pathways are still poorly constrained. It is highly probable that changes in the microbial processes that generate N2O are closely linked to seasonal changes in water productivity, organic matter remineralization rates, and in turn water-column redox-conditions. In this study we propose using incubation-based stable N-isotope tracer methods and natural N isotope measurements in dissolved N2O to identify and quantify specific N2O production pathways in two aquatic environments with strong seasonal N cycle dynamics: eutrophic Lake Lugano in southern Switzerland and the highly productive Benguela Upwelling region along the coast of southwestern Africa. Our main goals will be to shed light on the dynamics and controls on N2O production in two comparable environments. Within the frame of one postdoctoral project we propose to address the following research questions: - Hw much do ammonia oxidation, nitrifier-denitrification, and denitrification, respectively, contribute to N2O formation in Lake Lugano and the Benguela Upwelling? - Which biogeochemical factors control nitrifier-denitrification rates, and are there systematic differences between the marine and freshwater environment? (...)
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Origin: /Bund/UBA/UFORDAT
Tags: Ammonium ? Denitrifikation ? Stickstoffgehalt ? Tierhaltungsanlage ? Ammoniak ? Ammoniumverbindung ? Chlorophyll ? Nitrat ? Seen ? Biogeochemie ? Auftrieb ? Düngemittel ? Nitrifikation ? Stickstoffdioxid ? Reaktiver Stickstoff ? Tracer ? Schweiz ? Namibia ? Stickstoffemission ? Stickstoffeintrag ? Lachgas ? Limnisches Ökosystem ? Marines Ökosystem ? Stickstoffbilanz ? Stickstoffverbindung ? Stoffwechselprodukt ? Organisches Material ? Gelöste Stoffe ? Meereschemie ? Sauerstoffgehalt ? Aquatisches Ökosystem ? Oxidation ? pH-Wert ? Reaktionsmechanismus ? Bilanz ? Stickstoffkreislauf ? Stoffbilanz ? Studie ? Mikroorganismen ? Hydrochemie ? Isotop ? Jahreszeit ? Küstenregion ? Wasser ? Kausalzusammenhang ? Messdaten ? Produktivität ? Schadstoffbildung ? Standortbedingung ? Globale Aspekte ? Treibhausgas ? Klimawandel ? Küste ? Wassermikroorganismen ? Lake Lugano ? Stickstoffbakterien ? ammonia oxidation ? nitrifier denitrification ? Benguela ? Tracerhydrologie ? Luganersee ? See [Binnengewässer] ? nitrogen isotopes ? Isotopenverhältnis ? upwelling zones ?
License: cc-by-nc-nd/4.0
Language: Englisch/English
Time ranges: 2013-04-01 - 2015-03-31
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