Intercomparison of soil pore water extraction methods for stable isotope analysis

Funded by NSERC Discovery Grant U.S. Forest Service U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy, Bioenergy Technologies OfficePeer reviewedPostprin

Construction and specification of a cryogenic vacuum extraction device for application in stable water isotope analysis

Against the background of increasing use of stable water isotopes in hydrogeochemical research sciences, the Institute of Landscape Ecology and Resources Management (ILR) constructed a cryogenic vacuum extraction device. With the principle of cryogenic vacuum extraction, it is possible to determine the isotopic signature of environmental water, more precisely, of soil and plant water serving as pools of local water cycles by extracting their water under vacuum. In the extraction process, the sample is heated under a defined vacuum, which leads to a water evaporation from the soil, i. e. plant sample. Afterwards, the evolved vapour is frozen in a liquid nitrogen (cryogenic) cold trap (Ingraham and Shadel, 1992). After defrosting the obtained sample water, its isotopic signature is analysed via diode laser absorption spectroscopy (Los Gatos Research DLT-100- Liquid Water Isotope Analyser, Los Gatos Research Inc., 67 East Evelyn Avenue, Suite 3, Mountain View, CA, 94041-1529, US). Among the existing water extraction methods for soil and plant samples, cryogenic vacuum extraction is one of the most widely used methods (Peters and Yakir, 2008). Hence, the aim of this thesis was to create a vacuum-tight, reliable, and user-friendly cryogenic vacuum extraction device with an extendable modularity and several independently working extraction units for application in stable water isotope research science and, furthermore, to specify this apparatus through validation experiments. The constructed vacuum extraction device of the ILR is mainly based on the principle used by West et al. (2006) and by the Paul Scherrer Institute (PSI, Villigen, CH). Implying that an apparatus with independently working extraction units - basically consisting of stainless steel Swagelok® fittings for realising the vacuum-tightness and glassware for a visual observation of the extraction process - was build. Beyond the execution of the existing devices, the extraction apparatus is additionally equipped with a mechanism for high-purity nitrogen aeration. This execution prevents the loss of water vapour during defrosting after extraction by purging every sample with high-purity nitrogen gas after the water extraction procedure. Moreover, the aeration of the vacuum system with high-purity nitrogen gas instead of aeration with atmospheric air, overcomes the risk of a mixture of atmospheric water vapour with the extracted sample water. Nitrogen gas, as an inert gas, does not react with the extracted water, but serves as a protective layer over the extracted defrosting sample water, minimising the error of isotope fractionation. The new vacuum extraction device was tested in order to specify it. The concern of the validation experiments was to examine whether the water isotopic signature is changed through the extraction process, whether the high-purity nitrogen aeration affects the water isotopic composition, and whether cross-contamination among the six extraction units occurs. All validation tests were conducted with water – three different types of water with known isotopic composition - instead of soil or plant material for an easier implementation of the experiments and better comparability of the results. The validation experiments revealed that the constructed cryogenic vacuum extraction device is vacuum-tight and, consequently, there was no change in the isotopic signature of the extracted water due to a complete water extraction process. As expected, the high-purity nitrogen aeration after the water extraction did not change the isotopic signature of the extracted sample water, but could contribute to a better distribution of the values for the water isotopic signatures and, therefore, to a higher accuracy. Finally, while extracting two different types of water during one extraction process, no exchange among these waters could be observed, concluding that no cross-contamination among the six independent extraction units occurred. Summarising, the constructed cryogenic vacuum water extraction device guarantees stable extraction conditions. Thus, this apparatus is a proper tool to be applied in water isotope research sciences.Vor dem Hintergrund der zunehmenden Anwendung stabiler Wasserisotope in hydrogeochemischen Untersuchungen wurde eine kryogene Vakuumextraktionsanlage am Institut für Landschaftsökologie und Ressourcenmanagement (ILR) errichtet. Mit der kryogenen Vakuumextraktion ist es möglich, die Isotopensignatur von Umweltwasser bestimmen zu können, genauer von Boden- und Pflanzenwasser als Pools lokaler Wasserkreisläufe, durch die Extraktion ihres Wassers unter Vakuum. Dabei wird die zu extrahierende Probe unter einem angelegten Druck erhitzt, wodurch das Wasser aus der Boden- bzw. Pflanzenprobe evaporiert. Anschließend wird es in einer Flüssigstickstoff-Kühlfalle (kryogen) ausgefroren (Ingraham und Shadel, 1992). Nach dem Auftauen des erhaltenen Probenwassers, kann seine Isotopen-signatur mittels Diodenlaser-Absorptionsspektroskopie (Los Gatos Research DLT-100- Li-quid Water Isotope Analyser, Los Gatos Research Inc., 67 East Evelyn Avenue, Suite 3, Mountain View, CA, 94041-1529, US) bestimmt werden. Unter den existierenden Wasserextraktionsverfahren für Boden- und Pflanzenproben ist die kryogene Vakuumextraktion eine der meist verwendeten Methoden (Peters und Yakir, 2008). Demzufolge war das Ziel dieser Arbeit, eine vakuumdichte, verlässliche und benutzerfreundliche kryogene Vakuumextraktionsanlage mit einer erweiterbaren Modularität und unabhängig voneinander arbeitenden Extraktionseinheiten für den Einsatz in der stabilen Wasserisotopenforschung zu errichten und darüber hinaus diese Anlage durch Validierungsversuche zu spezifizieren. Die konstruierte Wasserextraktionsanlage des ILR basiert hauptsächlich auf dem Prinzip, welches von West et al. (2006) und am Paul Scherrer Institut (PSI, Villigen, CH) praktiziert wird. Dieses Prinzip impliziert, dass die Vakuumextraktionsanlage mit sechs unabhängig voneinander arbeitenden Extraktionseinheiten ausgestattet ist, die hauptsächlich aus Swagelok®-Stahlverschraubungen für die Vakuumdichtigkeit besteht sowie aus Glas für eine einfachere visuelle Überwachung des Extraktionsprozesses. Über die bereits bestehenden Anlagenaufbauten hinaus, verfügt die Wasserextraktionsanlage des ILR über eine Einrichtung zur Belüftung des Vakuumsystems mit hochreinem Stickstoffgas. Diese Ausstattung verhindert den evaporativen Wasserverlust während des Auftauens des extrahierten Wassers durch die Begasung jeder gewonnenen Wasserprobe mit hochreinem Stickstoffgas nach der Wasserextraktion. Darüber hinaus überwindet eine Belüftung mit hochreinem Stickstoffgas, anstelle einer Belüftung des Vakuumsystems mit Atmosphärenluft, das Risiko der Vermischung von atmosphärischem Wasserdampf mit dem extrahierten Probenwasser. Stickstoff ist ein inertes Gas, welches nicht mit dem extrahierten Wasser reagiert, aber als schützende Schicht über dem auftauenden Extraktionswasser dienen kann und damit den Fehler der Isotopenfraktionierung minimieren kann. Nach dem eigentlichen Aufbau der Vakuumextraktionsanlage wurde diese anhand von Validierungstest spezifiziert. Dabei sollte herausgefunden werden, ob die Wasserisotopensignatur durch den Extraktionsprozess verändert wird, ob die Belüftung mit Stickstoffgas die Wasserisotopenzusammensetzung beeinflusst und ob Querkontaminationen zwischen den sechs Extraktionseinheiten auftreten. Für eine einfachere Realisierung und eine bessere Vergleichbarkeit der Ergebnisse wurden alle Testversuche mit drei verschiedenen Wasserarten bekannter Isotopensignatur anstelle von Boden- oder Pflanzenproben durchgeführt. Die Validierungsversuche ergaben, dass die errichtete kryogene Extraktionsanlage vakuumdicht ist und daher aufgrund eines vollständigen Extraktionsprozesses keine Veränderungen der Isotopensignaturen des extrahierten Wassers auftraten. Wie erwartet, fand auch durch die Belüftung mit Stickstoffgas, keine Beeinflussung der Wasserisotopensignaturen des gewonnenen Probenwassers statt. Sie kann jedoch zu einer besseren Verteilung der Wasserisotopenwerte beitragen und damit zu einer höheren Genauigkeit der Ergebnisse. Schließlich konnte durch die parallele Extraktion zweier Wasserarten während eines Extraktionsprozesses herausgefunden werden, dass es zu keiner Vermischung des Probenwassers und damit keinen Querkontaminationen zwischen den einzelnen Extraktionseinheiten kommt. Zusammenfassend garantiert die kryogene Vakuumextraktionsanlage des ILR stabile Extraktionsbedingungen. Durch die Validierungsversuche konnte die einwandfreie Funktionalität bestätigt werden. Damit ist die kryogene Vakuumextraktionsanlage ein geeignetes Wasserextraktionsgerät für den Einsatz in der stabilen Wasserisotopenforschung

Studienlandschaft Schwingbachtal: an out-door full-scale learning tool newly equipped with augmented reality

This paper addresses education and communication in hydrology and geosciences. Many approaches can be used, such as the well-known seminars, modelling exercises and practical field work but out-door learning in our discipline is a must, and this paper focuses on the recent development of a new out-door learning tool at the landscape scale. To facilitate improved teaching and hands-on experience, we designed the Studienlandschaft Schwingbachtal. Equipped with field instrumentation, education trails, and geocache, we now implemented an augmented reality App, adding virtual teaching objects on the real landscape. The App development is detailed, to serve as methodology for people wishing to implement such a tool. The resulting application, namely the Schwingbachtal App, is described as an example. We conclude that such an App is useful for communication and education purposes, making learning pleasant, and offering personalized options

Overcoming information asymmetry in the plastics value chain with digital product passports : how decentralised identifiers and verifiable credentials can enable a circular economy for plastics

This paper analyses the potential of digital information technology to enable the reliable provision of product information along the plastics supply chain. The authors investigate the possible contribution of a product passport equipped with decentralised identifiers and verifiable credentials to overcome information deficits and information asymmetry in the circular plastics economy. Through this, high-quality plastics recycling could be enabled on a larger scale than currently possible

Assessment of multiple stable isotopes for tracking regional and organic authenticity of plant products in Hesse, Germany

As demand for regional and organically produced foodstuff has increased in Europe, the need has arisen to verify the products’ origin and production method. For food authenticity tracking (production method and origin), we examined 286 samples of wheat (Triticum aestivum), potatoes (Solanum tuberosum), and apples (Malus domestica) from different regions in Germany for their stable isotope compositions of oxygen, hydrogen, carbon, nitrogen and sulphur. Single-variate authentication methods were used. Suitable isotope tracers to determine wheat's regional origin were δ 18O and δ 34S. δ 13C helped to distinguish between organic and conventional wheat samples. For the separation of the production regions of potatoes, several isotope tracers were suitable (e.g. δ 18O, δ 2H, δ 15N, δ 13C and δ 34S isotopes in potato protein), but only protein δ 15N was suitable to differentiate between organic and conventional potato samples. For the apple samples, 2H and 18O isotopes helped to identify production regions, but no significant statistical differences could be found between organically and conventionally farmed apples. For food authenticity tracking, our study showed the need to take the various isotopes into account. There is an urgent need for a broad reference database if isotope measurements are to become a main tool for determining product's origin

Daratumumab monotherapy in patients with treatment-refractory multiple myeloma (SIRIUS): an open-label, randomised, phase 2 trial

BACKGROUND: New treatment options are needed for patients with multiple myeloma that is refractory to proteasome inhibitors and immunomodulatory drugs. We assessed daratumumab, a novel CD38-targeted monoclonal antibody, in patients with refractory multiple myeloma. METHODS: In this open-label, multicentre, phase 2 trial done in Canada, Spain, and the USA, patients (age ≥18 years) with multiple myeloma who were previously treated with at least three lines of therapy (including proteasome inhibitors and immunomodulatory drugs), or were refractory to both proteasome inhibitors and immunomodulatory drugs, were randomly allocated in a 1:1 ratio to receive intravenous daratumumab 8 mg/kg or 16 mg/kg in part 1 stage 1 of the study, to decide the dose for further assessment in part 2. Patients received 8 mg/kg every 4 weeks, or 16 mg/kg per week for 8 weeks (cycles 1 and 2), then every 2 weeks for 16 weeks (cycles 3-6), and then every 4 weeks thereafter (cycle 7 and higher). The allocation schedule was computer-generated and randomisation, with permuted blocks, was done centrally with an interactive web response system. In part 1 stage 2 and part 2, patients received 16 mg/kg dosed as in part 1 stage 1. The primary endpoint was overall response rate (partial response [PR] + very good PR + complete response [CR] + stringent CR). All patients who received at least one dose of daratumumab were included in the analysis. The trial is registered with ClinicalTrials.gov, number NCT01985126. FINDINGS: The study is ongoing. In part 1 stage 1 of the study, 18 patients were randomly allocated to the 8 mg/kg group and 16 to the 16 mg/kg group. Findings are reported for the 106 patients who received daratumumab 16 mg/kg in parts 1 and 2. Patients received a median of five previous lines of therapy (range 2-14). 85 (80%) patients had previously received autologous stem cell transplantation, 101 (95%) were refractory to the most recent proteasome inhibitors and immunomodulatory drugs used, and 103 (97%) were refractory to the last line of therapy. Overall responses were noted in 31 patients (29.2%, 95% CI 20.8-38.9)-three (2.8%, 0.6-8.0) had a stringent CR, ten (9.4%, 4.6-16.7) had a very good PR, and 18 (17.0%, 10.4-25.5) had a PR. The median time to first response was 1.0 month (range 0.9-5.6). Median duration of response was 7.4 months (95% CI 5.5-not estimable) and progression-free survival was 3.7 months (95% CI 2.8-4.6). The 12-month overall survival was 64.8% (95% CI 51.2-75.5) and, at a subsequent cutoff, median overall survival was 17.5 months (95% CI 13.7-not estimable). Daratumumab was well tolerated; fatigue (42 [40%] patients) and anaemia (35 [33%]) of any grade were the most common adverse events. No drug-related adverse events led to treatment discontinuation. INTERPRETATION: Daratumumab monotherapy showed encouraging efficacy in heavily pretreated and refractory patients with multiple myeloma, with a favourable safety profile in this population of patients. FUNDING: Janssen Research & Development

The Resource Curse and Rentier States in the Caspian Region : A Need for Context Analysis

Although much attention is paid to the Caspian region with regard to energy issues, the domestic consequences of the region’s resource production have so far constituted a neglected field of research. A systematic survey of the latest research trends in the economic and political causalities of the resource curse and of rentier states reveals that there is a need for context analysis. In reference to this, the paper traces any shortcomings and promising approaches in the existent body of literature on the Caspian region. Following on from this, the paper then proposes a new approach; specifically, one in which any differences and similarities in the context conditions are captured. This enables a more precise exploration of the exact ways in which they form contemporary post-Soviet Caspian rentier states.Obwohl der Region am Kaspischen Meer im Zuge von Energiediskursen große Aufmerksamkeit zuteil wird, stellen die innerstaatlichen Folgen der Ressourcenproduktion in der Region ein bislang vernachlässigtes Forschungsfeld dar. Ein systematischer Überblick über die jüngsten Forschungstrends zu wirtschaftlichen und politischen Kausalzusammenhängen des Ressourcenfluchs und zu Rentierstaaten offenbart die Notwendigkeit von Kontextanalysen. Hierauf Bezug nehmend, analysiert der Aufsatz sowohl die Mängel als auch viel versprechende Ansätze in der betreffenden Literatur zur Region am Kaspischen Meer. Der Aufsatz stellt letztendlich einen neuen Ansatz vor, der Unterschiede und Gemeinsamkeiten in den Kontextbedingungen erfasst, um zu erforschen, wie diese die gegenwärtigen post-sowjetischen Rentierstaaten in der Region am Kaspischen Meer tatsächlich prägen

Sampling soil water along the pF curve for δ2H and δ18O analysis

Soil water stable isotopes are widely used across disciplines (e.g., hydrology, ecology, soil science, and biogeochemistry). However, the full potential of stables isotopes as a tool for characterizing the origin, flow path, transport processes and residence times of water in different eco-, hydro-, and geological compartments has not yet been exploited. This is mainly due to the large variety of different methods for pore water extraction. While recent work has shown that matric potential affects the equilibrium fractionation, little work has examined how different water retention characteristics might affect the sampled water isotopic composition. Here, we present a simple laboratory experiment with two well-studied standard soils differing in their physico-chemical properties (e.g., clayey loam and silty sand). Samples were sieved, oven-dried and spiked with water of known isotopic composition to full saturation. For investigating the effect of water retention characteristics on the extracted water isotopic composition, we used pressure extractors to sample isotopically labelled soil water along the pF curve. After pressure extraction, we further extracted the soil samples via cryogenic vacuum extraction. The null hypothesis guiding our work was that water held at different tensions shows the same isotopic composition. Our results showed that the sampled soil water differed isotopically from the introduced isotopic label over time and sequentially along the pF curve. Our and previous studies suggest caution in interpreting isotope results of extracted soil water and a need to better characterize processes that govern isotope fractionation with respect to soil water retention characteristics. In the future, knowledge about soil water retention characteristics with respect to soil water isotopic composition could be applied to predict soil water fractionation effects under natural and non-stationary conditions. In this regard, isotope retention characteristics as an analog to water retention characteristics have been proposed as a way forward since matric potential affects the equilibrium fractionation between the bound water and the water vapour

Linking Spatial Patterns of Groundwater Table Dynamics and Streamflow Generation Processes in a Small Developed Catchment

Knowledge about water flow paths is essential for understanding biogeochemical fluxes in developed agricultural landscapes, i.e., the input of nutrients into surface waters, soil erosion, or pesticide fate. Several methods are available to study rainfall-runoff processes and flux partitioning: hydrometric based approaches, chemical tracers, modeling, and stable isotope applications. In this study a multi-method approach was conducted to gain insights into the hydrological fluxes and process understanding within the complex anthropogenic-influenced catchment of the Vollnkirchener Bach, Germany. Our results indicate that the catchment responds differently to precipitation input signals and dominant runoff-generation processes change throughout the year. Rainfall-induced runoff events during dry periods are characterized by a temporarily active combined sewer overflow. During stormflow, a large contribution of fast event water is observed. At low flow conditions losing and gaining conditions occur in parallel. However, when catchment’s moisture conditions are high, an ephemeral source from clay shale-graywacke dominated forested sites becomes active. The study reveals that the collection of detailed distributed hydrometric data combined with isotopic tracers, provides fundamental information on the complex catchment behavior, which can finally be utilized for conceptualizing water fluxes at a small catchment scale