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  • 1
    In: Vadose Zone Journal, Wiley, Vol. 18, No. 1 ( 2019-01), p. 1-14
    Abstract: This new technology is suitable for field‐scale quantification of CO 2 in soil. The measurement scale ranges from decimeters up to decameters. The concentrations from the soil water and air phases are averaged. Transient CO 2 production and transport reflect plant growth. Biological activity in soil causes fluxes of O 2 into and CO 2 out of the soil with significant global relevance. Hence, the dynamics of CO 2 concentrations in soil can be used as an indicator for biological activity. However, there is an enormous spatial and temporal variability in soil respiration, which has led to the notion of hotspots and hot moments. This variability is attributed to the spatiotemporal heterogeneity of both plant–soil–microbiome interactions and the local conditions governing gas transport. For the characterization of a given soil, the local heterogeneities should be replaced by some meaningful average. To this end, we introduce a line sensor based on tubular gas‐selective membranes that is applicable at the field scale for a wide range in water content. It provides the average CO 2 concentration of the ambient soil along its length. The new technique corrects for fluctuating external conditions (i.e., temperature and air pressure) and the impact of water vapor without any further calibration. The new line sensor was tested in a laboratory mesocosm experiment where CO 2 concentrations were monitored at two depths during the growth of barley ( Hordeum vulgare L.). The results could be consistently related to plant development, plant density, and changing conditions for gas diffusion toward the soil surface. The comparison with an independent CO 2 sensor confirmed that the new sensor is actually capable of determining meaningful average CO 2 concentrations in a natural soil for long time periods.
    Type of Medium: Online Resource
    ISSN: 1539-1663 , 1539-1663
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2088189-7
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  • 2
    Online Resource
    Online Resource
    Copernicus GmbH ; 2020
    In:  Journal of Sensors and Sensor Systems Vol. 9, No. 2 ( 2020-10-05), p. 309-317
    In: Journal of Sensors and Sensor Systems, Copernicus GmbH, Vol. 9, No. 2 ( 2020-10-05), p. 309-317
    Abstract: Abstract. A miniaturized field-applicable sensor system was developed for the measurement of hydrogen (H2) in air in the concentration range 0.2–200 ppmv. The sensor system is based on the application of an yttria-stabilized zirconia (YSZ) solid electrolyte cell (SEC) as a coulometric detector with gas chromatographic (GC) pre-separation. The main system components for injection, chromatographic separation, and the oxygen pumping cell were significantly miniaturized and tested separately to characterize important measurement properties like selectivity, lower limit of detection, repeatability, and signal-to-noise ratio. Measurements were conducted under varying GC parameters and detector operating conditions. While changing the detector temperature influences the hydrogen peak significantly due to diffusion processes at the electrode–electrolyte interface; different oxygen-partial pressures at the measuring electrode have no visible effect. The combination of two packed columns with 1 m length, one filled with a molecular sieve (13X) and the other one with silica gel, enabled highly reproducible and selective H2 measurements with more than 90 % analyte turnover compared to Faraday's law. The resulting insights were used to define appropriate system parameters, construction guidelines, and material properties for the final test prototype.
    Type of Medium: Online Resource
    ISSN: 2194-878X
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2733700-5
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  • 3
    Online Resource
    Online Resource
    MDPI AG ; 2016
    In:  Sensors Vol. 16, No. 11 ( 2016-11-17), p. 1930-
    In: Sensors, MDPI AG, Vol. 16, No. 11 ( 2016-11-17), p. 1930-
    Type of Medium: Online Resource
    ISSN: 1424-8220
    Language: English
    Publisher: MDPI AG
    Publication Date: 2016
    detail.hit.zdb_id: 2052857-7
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