Das Projekt "COST-Action 729 - Assessing and managing nitrogen fluxes in the atmosphere-biosphere system in Europe - Assessment of nitrogen biosphere-atmosphere exchange based on novel quantum cascade laser technology" wird vom Umweltbundesamt gefördert und von Eidgenössische Materialprüfungs- und Forschungsanstalt EMPA, Air Pollution durchgeführt. 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.
Das Projekt "Entwicklung eines Quantenkaskadenlaser Spektrometers zur kontinuierlichen Bestimmung von Methan Isotopen" wird vom Umweltbundesamt gefördert und von Eidgenössische Materialprüfungs- und Forschungsanstalt, Abteilung Luftfremdstoffe,Umwelttechnik durchgeführt. influences the abundance of ozone and the concentration of hydroxyl radicals which impacts virtually all of atmospheric chemistry.4 in promoting global warming. Furthermore, CH2) is the second most important of the anthropogenically influenced greenhouse gases. On a per-molecule basis it is 25 times more effective than CO4Methane (CH The total global methane emissions are relatively well known but the strength of each source component and their trends are not. Since the major source categories and the OH sink have distinct isotopic signatures in d13 and 4C-CHd4D-CH, high-frequency and high-precision measurements of these parameters would help constraining emission sources and the global budget. However, isotope-ratio mass-spectrometry (IRMS), the standard analytical tool for stable isotope ratios in trace gases, is a laboratory-based technique which limits temporal and spatial resolution capabilities. Alternatively, a isotopic species because of their characteristic rotational-vibrational transitions. 4bsorption spectroscopy in the mid-infrared is a direct method to distinguish between all relevant CHD, and the respective isotope ratios 3 and CH4CH13, 4CH12Within this project we will thus develop an instrument to continuously monitor d13 and 4C-CHd4D-CH, using state of the art quantum cascade laser absorption spectrometry (QCLAS). The instrument will be based on recently developed 7.5 mym, continuous wave room temperature lasers (cw-RT-QCL) and a novel astigmatic multipath cell with an optical path length of 200 m. To obtain the necessary precision of 0.1Prozent (d13) and 14C-CHProzent (d4D-CH), the QCLAS will be coupled to an automated, liquid-nitrogen free preconcentration unit.
Das Projekt "Kontinuierliche Bestimmung von N2O Isotopomeren in Umgebungsluft mittels Quantenkaskadenlaser-Absorptionspektrometrie" wird vom Umweltbundesamt gefördert und von Eidgenössische Materialprüfungs- und Forschungsanstalt, Abteilung Luftfremdstoffe,Umwelttechnik durchgeführt. Nitrous oxide (N2O) is a stratospheric ozone depleting substance and one of the four most important greenhouse gases. Its major sink, stratospheric destruction, is well quantified, but the global budget is rather uncertain due to a limited understanding of the dominant N2O sources. The study of the three main stable isotopes (14N15N16O / 15N14N16O / 14N14N16O) is a powerful way to trace the biogeochemical cycle of N2O. Absorption spectroscopy in the mid-infrared is potentially the most powerful, direct method to distinguish between all relevant N2O isotopes because of their characteristic rotational-vibrational transitions. It allows the determination of both the N2O concentration and the isotope ratios (d15Na and d15Nb). However, up to now isotope measurements with the required precision of less than 1 per mille for d15N were only possible at N2O concentration levels that are too high for environmental or atmospheric applications. Based on our latest improvements in laser spectroscopy, we expect a precision for d15N of 0.1 percent at 90 ppm of N2O in a compact and field-deployable quantum cascade laser isotope spectrometer (QCL-IS). While this is adequate to study many biological and technical processes, we also intend to develop a liquid nitrogen-free, fully-automated preconcentration unit. This unit will then be coupled to the QCL-IS to allow continuous ambient air measurements (ca. 320 ppb N2O) with a time resolution of 15 minutes. Studies based on the concentration of individual N2O isotopes and their ratio could significantly enhance our understanding of the global N2O budget. The key to this is source characterization, allocation and quantification of important processes, e.g. soil nitrification/denitrification, waste water treatment and combustion, which will become more accessible because of the novel analytical tool. Furthermore, the preconcentration unit and its coupling to QCLAS is a technique with a wide potential, since it might be used for other trace gases or isotopes with concentrations that are too low for currently available spectroscopy.
Das Projekt "Beschaffung eines Spektrometers basierend auf kontinuierlichen raumtemperatur Quantenkaskadenlasern (CW-RT-QCL) zur Spurengasanalytik" wird vom Umweltbundesamt gefördert und von Eidgenössische Materialprüfungs- und Forschungsanstalt, Abteilung Luftfremdstoffe,Umwelttechnik durchgeführt. Infrared spectroscopy is a powerful technique for the continuous measurement of trace gases in ambient air. A new generation of laser based instruments became available with the development of pulsed, room temperature quantum cascade lasers (RT-QCL) over the last ten years. Their cryogenic free operation is highly important for unattended measurements. However, RT-QCL based systems are often restricted in sensitivity due to the rather broad instrumental linewidth. Furthermore, the limited output power often requires liquid nitrogen cooled detectors to reach the necessary signal to noise ratio. The newest generation of lasers can be operated as continuous wave devices above room temperature (CW-RT-QCL). This is the key to a better spectroscopic performance because of their smaller linewidth, and to Peltier cooled detectors thanks to a significant increase in laser power. Their full potential can, however, only be explored if the quantum cascade laser spectrometer (QCLAS) is fully optimized for these most recent laser devices. The progress of QCLAS is well illustrated by formaldehyde. While this substance was out of reach for cryogenic free laser instruments until now, we expect HCOH to be measurable in ambient air by a novel spectrometer for high-precision trace gas analysis based on continuous wave quantum cascade lasers. HCHO in the atmosphere is one of the key compounds for photochemical reactions leading to the production of radicals and secondary photooxidants. Considering its importance, the database about the distribution of formaldehyde is still limited, which is mainly due to analytical difficulties. Our work will be based on the newest generation of QCLAS based on CW-RT-QCL. Both laser and spectrometer are currently in their final stage of development and, combined, will provide a unique instrument for trace gas analysis. Their first application is planned for continuous measurements of formaldehyde, but other substances (i.e. HNO3, CO, NO2 HONO, HCOOH) may be measured with the same optical platform. This novel QCLAS is a key technology to keep our research groups at the front of current developments in ambient air monitoring, atmospheric chemistry, source identification and source quantification. It is also a powerful infrastructure that will be used in collaboration with many different national and international research groups.