Schlüsselwörter
(Englisch)
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nitrogen flux; atmosphere-biosphere; quantum cascade laser; infrared spectroscopy.
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Forschungsprogramme
(Englisch)
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COST-Action 729 - Assessing and managing nitrogen fluxes in the atmosphere-biosphere system in Europe
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Kurzbeschreibung
(Englisch)
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In Europe, atmospheric deposition of reactive nitrogen species is one of the major threats to ecosystems. Thus, quantification of the different fluxes and their interactions is essential to provide the basis for assessment tools to combat nitrogen accumulation in the environment. This project combines a range of established concepts to determine N-flux with a high-performance technique in infrared laser spectroscopy, which is based on novel quantum cascade lasers (QCL). The spectrometer will be set-up to allow the precise and rapid detection of NH3, N2O, CO2, H2O and possibly HNO3. Through the combination of two semiconductor lasers, a careful choice of appropriate wavelengths, and adapted sampling techniques, it will be possible to quantify all but HNO3 simultaneously with a time resolution suitable for eddy correlation (EC) flux measurements. The system will be operated at the Swiss CarboEurope and NitroEurope Grassland site near Oensingen on the Swiss plateau allowing for integrated measurements at the field scale, which is otherwise not accessible. A sophisticated instrument control will be developed to allow automatic switching between various flux measurement setups. These include Eddy correlation, dynamic and static chambers, soil membrane tube measurements and concentration gradient measurements. This approach is a valuable complement to the studies that are planned within the EU FP6 NitroEurope project.
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Weitere Hinweise und Angaben
(Englisch)
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Full name of research-institution/enterprise: Eidg. Materialsprüfungs- und Forschungsanstalt EMPA Air Pollution, Environmental Technology
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Partner und Internationale Organisationen
(Englisch)
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BE, CH, CZ, DE, DK, FI, FR, GR, HU, IT, LU, NL, NO, PL, PT, SE, UK
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Abstract
(Englisch)
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In Europe, atmospheric deposition of reactive nitrogen species is one of the major threats to ecosystems. Thus, quantification of the different fluxes and their interactions is essential to provide the basis for assessment tools to combat nitrogen accumulation in the environment. This project combines a range of established concepts to determine N-flux with a highperformance technique in infrared laser spectroscopy, which is based on novel quantum cascade lasers (QCL). The spectrometer is the first world-wide field application of continuous wave QCLs without cryogenic cooling, i.e. suited for long-term applications. It is based on two lasers at 1273 cm-1 (for CH4, N2O, H2O) and 1600 cm-1 (for NO2). The system was optimized and validated in the laboratory from August 2007 to November 2007 and has then been operational at the Swiss CarboEurope and NitroEurope Grassland site near Oensingen on the Swiss plateau until Mai 2009, allowing for integrated measurements at the field scale, which are otherwise not accessible. Our analysis of eddy covariance measurements in conjunction with semi-continuous chamber flux data and continuous N2O soil profiles suggests that gross production and gross consumption of N2O are of the same order, and as consequence only a minor fraction of N2O molecules produced in the soil reaches the atmosphere (Neftel et al., Tellus, 2007). Furthermore, the detailed analysis of laboratory and field data revealed that flux measurements of trace gases which rely on spectroscopic methods may be subject to significant bias due to a small but relevant cross sensitivity to water vapour (Neftel et al., Agricultural and Forest Meteorology, 2009). This insight has been published for N2O but has since been recognized as a general effect in laser based trace gas measurements. Furthermore, a comparison of analyzers for flux measurements of CH4 has been performed using a new field setup to simulate fluxes of trace compounds that would otherwise be below the detection limit and thus difficult to validate.
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Datenbankreferenzen
(Englisch)
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Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. +41 31 322 74 82 Swiss Project-Number: C06.0017
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