Veranstaltungsprogramm

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Sitzungsübersicht
Datum: Mittwoch, 29.09.2021
9:00 - 9:30Posterfrühstück
Virtueller Veranstaltungsort: Posterausstellung - Meeting Link
 
9:30 - 10:30Block 6: Physiologie, Metabolismus, Medizin, Doping, Forensik, Lebensmittel
Virtueller Veranstaltungsort: Block 6 - Meeting Link
Chair der Sitzung: Frank Keppler, Universität Heidelberg
 
 
9:30 - 9:45

Stable isotopes for planetary health: Synthetic methionine

Cajetan Neubauer

University of Colorado Boulder, USA

Methionine is an amino acid that humans and farm animals must derive from food. This metabolite, a tightly regulated resource in ecosystems, has become a mass commodity in the global economy, with well over 1 million tons being produced annually from petroleum to fortify livestock feed. Methionine synthesis is an excellent exemplar of a planetary scale anthropogenic activity that manifests at the molecular scale of cellular metabolism, with potential systemic effects on human health and environments. Taking a planetary health perspective, I will explore in this talk the scale and historical trajectory of the methionine industry and provide a preliminary model for tracing this amino acid through the food supply into the human body.[1] We now want to test this model empirically using isotope analytics to quantify the synthetic proportion of methionine in foods and humans. The proposed approach is to use a mass spectrometry method developed in the last five years that is based on ESI-Orbitrap. It can reveal intramolecular stable isotope compositions of organic molecules at the natural abundance level.[2] I will also briefly discuss alternative isotope approaches for this project, as well as highlight topics where the new stable isotope technology might contribute insights in a biomedical context.

Related publications:

1. Neubauer C, Landecker H (2021) A planetary health perspective on synthetic methionine: Implications of opening the tap on a historically limiting nutrient. Lancet Planet Health

2. Neubauer C, Sweredoski MJ, Moradian A, Newman DK, Robins RJ, Eiler JM (2018). Scanning the isotopic structure of molecules by tandem mass spectrometry. Int J Mass Spec



9:45 - 10:00

Carbon isotope ratios of endogenous steroids found in human serum – method development, validation, and reference population-derived thresholds

Thomas Piper, Hans Geyer, Mario Thevis

Deutsche Sporthochschule Köln, Deutschland

In order to detect the misuse of testosterone (T) and testosterone prohormones, urinary steroids and steroid ratios are quantified and monitored in a longitudinal manner to enable the identification of atypical samples. These suspicious samples are then forwarded to isotope ratio mass spectrometry (IRMS)-based methods for confirmation. Especially concentration ratios like T over epitestosterone (E) or 5α-androstanediol (5αAdiol) over E proved to be valuable markers. Unfortunately, depending on the UGT2B17 genotype and/or the gender of the athlete, these markers may fail to provide evidence for T administrations when focusing exclusively urine samples.

In recent years, the potential of plasma steroids has been carefully investigated, which were found to be suitable to detect T administrations especially in female volunteers.[1-5] A current drawback of this approach is the missing possibility to confirm that elevated steroid concentrations found in plasma are solely derived from an administration of T or T-prohormones and cannot be attributed to possible confounding factors. Therefore, and in parallel to the procedure applied to urine samples, an IRMS method for plasma steroids has been developed and validated taking into account the limited sample volume for serum samples (usually not more than 1 mL). As endogenous reference compounds, unconjugated cholesterol and dehydroepiandrosterone-sulfate were found suitable while androsterone and epiandrosterone (both sulfoconjugated) were chosen as target analytes.

The method was based on multi-dimensional gas chromatography coupled to IRMS in order to increase recovery compared to liquid chromatography-based sample clean-up.[6] The method was validated employing linear mixing models, and finally a reference population encompassing n = 65 males and females was investigated to enable the calculation of population-based thresholds. As proof-of-concept, several serum samples from volunteers participating in T-replacement therapies were analyzed and found to be significantly depleted in their serum steroid target analytes.

1) Ponzetto F, Mehl F, Boccard J, et al. Anal Bioanal Chem 2016; 408: 705-719

2) Handelsman DJ, Bermon S. Drug Test Anal 2019; 11: 1566-1571

3) Elmongy H, Masquelier M, Ericsson M. J Chrom A 2020; 1613: 460686

4) Salamin O, Ponzetto F, Cauderay M, et al. Bioanalysis, 2020, DOI: 10.4155/bio-2020-0046

5) Knutsson JE, Andersson A, Baekken LV, et al. J Clin Endocrin & Metab 2020, DOI: 10.1210/clinem/dgaa904

6) Putz M, Piper T, Casilli A, et al. Analytica Chimica Acta 2018; 1030: 105-114.



10:00 - 10:15

Making plant methane formation visible – the effect of light exposure and light intensity on plant methane formation by application of 13C-labelled dimethyl sulfoxide

Moritz Schroll1, Katharina Lenhart2,3, Steffen Greiner3, Frank Keppler1,4

1Heidelberg University, Heidelberg, Germany; 2Bingen University of Applied Sciences, Bingen, Germany; 3Center for Organismal Studies, Heidelberg, Germany; 4Heidelberg Center for the Environment, Heidelberg University, Germany

In recent years methane (CH4) formation by vegetation in the presence of oxygen has been studied intensively, but its underlying formation process(es) are still poorly understood. Currently, reported CH4 emission rates vary by orders of magnitude and thus make global estimates of CH4 emissions by vegetation difficult. In addition, the process(es) of plant CH4 formation are mostly unknown. In this presentation, we introduce a new approach for a making CH4 formation by plants visible. By application of 13C-labelled dimethyl sulfoxide (DMSO) onto the leaves of tobacco plants (Nicotiana tabacum) and Chinese silver grass (Miscanthus sinensis), DMSO was identified as a precursor of CH4 in plants and the effect of light on CH4 formation was examined by measuring δ13C-CH4 values during incubations via Cavity Ring-Down Spectroscopy.

Both plant species clearly showed an increase in δ13C-CH4 values, and therefore CH4 formation, during the incubations while exposed to light. Higher light intensities lead to higher CH4 formation rates in N. tabacum and to lower CH4 formation rates in M. sinensis. When examined in the dark no formation of CH4 could be detected for N. tabacum, whilst M. sinensis still produced around 50 % of CH4 in the dark when compared to light exposure. Our findings unambiguously confirm DMSO as a precursor of plant CH4 and suggest that CH4 formation in plants is highly dependent on light exposure, light intensity, and plant species. Furthermore, our work presents a new isotopic approach for investigating mechanisms of CH4 formation in plants which has the potential to identify the underlying physiological processes, that without the use of stable isotopes could not be solely determined by CH4 concentration measurements.



10:15 - 10:30

Geographical provenance determination of wood through combination of isotope ratios

Jana C. Köhne1, Bernd Degen1, Anette Goeske2

1Thünen-Institut für Forstgenetik, Deutschland; 2Thünen-Institut für Agrarklimaschutz, Deutschland

As illegal logging develops more and more into a global problem, analytical methods to proof timber origin are necessary. In two pilot studies wood samples were collected to examine the possibilities of provenance determination of wood with stable isotope analyses as an addition of the “Large Scale Project” to develop genetic reference data to identify timber origin. The project was led by the Thuenen-Institute of Forest Genetics. In the first pilot study, wood samples of the tree species Carapa guianensis and Hymenaea courbaril were collected on a country scale at five locations for both species and an additional location for Hymenaea courbaril in Brazil with multiple 100 km distances up to 3,000 km between the geographical groups (locations) (Large Scale). The second pilot study addressed the regional scale in three different countries (Small Scale). In a range of 100 km wood samples were gathered for Hymenaea courbaril and H. jutai in two forest concessions in Brazil and for Dipteryx ferrea in Peru and Lophira alata in Cameroon in three concessions each. Forest concession are areas where logging companies received the permission for timber harvest from the state.

In the Large Scale study most isotope ratios showed differences between the geographical groups with most differences being statistical significant. Furthermore, weak significant correlations with latitude and longitude for d18O were observed, for d13C and d2H only with longitude and d15N correlated weakly with latitude. In a statistical self-assignment, the success rate in total was 59% for Carapa guianensis and 54% for Hymenaea sp.. Nevertheless the locations in Brazil were not distinguishable from each other in a principal component analysis.

In the Small Scale study, the isotope ratios of C and N, measured so far, did not allow for a significant separation of forest concession nor did they show significant correlation with latitude or longitude.

In conclusion there seems to be a geographical signal in the isotope results of the different location for the four isotope ratios of C, N, O and H but it was not strong enough for a secure geographic assignment. As next steps we want to check the performance of a combined application of gene markers and stale isotopes for geographic assignment of timber. Sampling design and lab methods also offer space for optimisation.

 
10:30 - 10:50Poster Kurzvorträge - zu Themenblock 4; 1; 5
Virtueller Veranstaltungsort: Poster Kurzvorträge 4;1;5 - Meeting Link
Block 4: Ökosysteme
Block 1: Analytik, Methoden, Technik und Qualitätssicherung stabiler Isotope
Block 5: Klima und Atmosphäre
 
 
10:30 - 10:33

Using in-situ and destructive measurements of stable water isotopes to quantify ecohydrological feedback processes of different forest stands

Judith Mach, Laura Kinzinger, Stefan Seeger, Fabian Fritz, Paula Hilgert, Markus Weiler, Maren Dubbert, Christiane Werner, Natalie Orlowski

Albert-Ludwigs-Universität Freiburg, Professur für Hydrologie, Deutschland

Stable water isotopes are a promising tracer for studying water movement through ecosystems. Traditionally, destructive sampling techniques are applied to measure the isotopic signature in soils and plant xylem but these methods are limited in their temporal resolution and have proven to be fraught with uncertainty. Recent development of in-situ membrane-based probes for direct measurements of soil and tree xylem water isotopes (SWIP) allow continuous observations along soil profiles or within trees at different heights. Such new in-situ measurements provide an unprecedented combination of high temporal and spatial resolution data. Also, by using the same probes for the soil as well as the plant compartment, all measurements can be compared directly.

Here, we present preliminary results of our in-situ isotope measuring platform from different forest stands in the Black Forest (Germany). The measurement setup encompasses three experimental treatments: i) pure beech, ii) pure spruce and iii) mixed beech and spruce stands. By measuring soil water in different depths as well as xylem water at different heights, we will not only identify species-specific differences in their water uptake patterns but also the impact of interspecific competition for water. Additional destructive measurements of stable water isotopes from throughfall, stemflow, soil and tree xylem water will be used to gain further information but also to compare in-situ with destructive isotope measurement techniques.



10:33 - 10:36

Antibiotics increase methane production rates in freshwater sediments: Evidence from an anaerobic incubation

Eric Bollinger1,2, Jochen P Zubrod1,2, Sabine Filker3, Andreas Lorke1, Mirco Bundschuh1,2,4

1iES Landau, Institute for Environmental Sciences, University of Koblenz-Landau; 2Eusserthal Ecosystem Research Station, University of Koblenz-Landau; 3Department of Molecular Ecology, University of Technology Kaiserslautern; 4Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences

Methane (CH4) is after carbon dioxide (CO2) the second most important greenhouse gas and is inter alia produced in natural freshwater ecosystems. In the face of increasing CH4 emissions from natural sources, researchers have investigated environmental factors and climate change feedbacks to explain this increment. Despite being omnipresent in freshwaters, knowledge on the influence of chemical stressors of anthropogenic origin (e.g. antibiotics) on methanogenesis is not present to date. To address this knowledge gap, we incubated freshwater sediment for 42 days under anaerobic conditions in presence of a five-component antibiotic mixture at four levels (from 0 to 5000 µg/L). Weekly measurements of CH4 and CO2 in the headspace showed that the CH4 production rate can be increased by up to 94% at 5000 µg/L and up to 29% at field-relevant concentrations (i.e., 50 µg/L). The compound-specific δ13C values of CH4 and CO2 indicate that the processing dynamics are changed while the successional stages are not. Despite the complications of transferring experimental CH4 production rates to realistic field relevant CH4 emissions, the study suggests that chemical stressors contribute to the emissions of greenhouse gases by affecting the methanogenesis in freshwaters.



10:36 - 10:39

Exploring fundamentals of quantitative 13CO2/12CO2 tracer studies of CO2 exchange and biomass in plants: assessment of system performance and determination of isotopic end-members for mixing model

Jianjun Zhu, Juan C. Baca Cabrera, Regina T. Hirl, Hans Schnyder, Rudi Schäufele

Technical University of Munich, Deutschland

Labelling with carbon isotopes is the technique of choice to study carbon dynamics in plants, including CO2 exchange, biomass and carbohydrates. Labelling experiments consist of two phases: An establishment phase, where plants are grown in the presence of CO2 with constant isotopic composition, and a labeling phase, where the establishment CO2 is replaced by a CO2 with differing isotopic composition. However, labelling systems can be prone to technical artifacts like contamination with extraneous CO2, fluctuations of the isotopic composition of the establishment and labelling CO2 etc. Also, the accurate determination of carbon tracer kinetics requires an accurate determination of the two end-members for isotopic mixing models. So far, systematic testing of labelling systems has been rare and incomplete. Here, we present details of a chamber labelling system for plant mesocosms and the analysis of its performance with respect to possible technical artifacts. This also includes the analysis of different approaches for the end-member determination. We performed labelling experiments with perennial ryegrass (Lolium perenne L.) combined with 13CO2/12CO2 gas exchange and carbohydrate measurements, in growth chambers under three CO2 concentrations: 200, 400, and 800 mmol mol-1. Each treatment was run in two growth chambers, with identical growth conditions but with two different CO2 sources (13C-depleted: δ13C -43.5 ‰ or 13C-rich: δ13C -5.6 ‰). After the establishment phase, the CO2 supplied to each chamber was switched from depleted to enriched or vice versa for a 7 days-long labelling phase. When gas exchange rates were approximately steady on a day-by-day basis, CO2 concentrations and δ13C in the chambers were also virtually constant over time. The spread in δ13C of the CO2 sources during the establishment phase matched the spread in δ13C of the two CO2-sources at the chamber outlets at all CO2 concentrations, showing that chamber CO2 was not contaminated with extraneous CO2. This was also confirmed by the close correspondence of C-isotope discrimination (Δ) during gas exchange in the light at every CO2 concentration. However, due to inevitable opening of the chambers during maintenance and plant sampling operations, Δ determined on respiratory CO2, shoot and root biomass as well as shoot carbohydrates was slightly (1.1 ‰), but consistently (P < 0.01) smaller in the 13C-depleted relative to the 13C-rich CO2 chambers during the establishment phase. Thus, for precise analyses of tracer kinetics in respiratory CO2, biomass or carbohydrates, the determination of the end-members of the mixing model had to be based on sample type-specific Δ measurements.


10:39 - 10:42

Unravelling the diet of extinct cave bears in Romania using δ15N isotopic analysis of amino acids

Peter Tung1,2, Herve Bocherens1,2, Dorothee Drucker1,2, Yuichi Naito1,3

1Senckenberg Gesellschaft für Naturforschung, Deutschland; 2Universität Tübingen, Deutschland; 3Nagoya University Museum, Japan

Compound specific isotopic analysis of individual amino acids (CSIA-AA) was performed to unravel dietary information on Late Pleistocene cave bears (Ursus spelaeus). In contrast to other regions of Europe, U. spelaeus from Romaniashowed variable and exceptionally high δ15N values (5.2 to 9.8‰) that leads to speculation of meat consumption. The CSIA-AA approach used is unique in that it offsets the natural baseline δ15N variation (e.g. environmental, behavioural or physiological traits). It can thereby provide a more accurate estimate of trophic position (TP).

Amino acids from ancient bone collagen of U. spelaeus were derivatized, separated via gas chromatography, combusted/reduced, then measured for δ15N using stable isotope mass spectrometry (GC-C-IRMS). This method is based on the differential fractionation of two amino acid groups: trophic AAs (i.e., glutamic acid) that fractionate 15N greatly (~8.0‰) compared to source AAs (i.e., phenylalanine) that fractionate 15N very little (~0.4‰) per trophic step. The latter (δ15Nphe) thus reflects the nitrogen source baseline (i.e. the primary producers) of the ecosystem.

Results rule out (i) significant dietary aquatic resources; (ii) carnivory as the main feeding behaviour. Rather, TPs of 1.8–2.2 (N = 6) are indicative of a plant-dependent diet, including for those cave bears with high bulk δ15N values. Using CSIA-AA, TPs of 1.9-2.1 were determined for U. spelaeus confirming a pure herbivorous diet (see Figure 1). Bulk collagen δ15N values of can be explained by (i) a δ15N shift of the baseline in the local ecosystem, and/or (ii) the consumption of some specific plants with high δ15N values. Our findings have interesting implications regarding the evolution of herbivory among carnivorans. Furthermore, understanding feeding behaviour of U. spelaeus may provide key insights into their extinction.

We used an Agilent 7890B GC coupled to an Elementar GC5 Interface module in line with a reduction furnace, cryogenic trap (LN2) and an IsoPrime 100 IRMS.

Reference Paper:

Naito, Y.I., Meleg, I.N., Robu, M. et al. Heavy reliance on plants for Romanian cave bears evidenced by amino acid nitrogen isotope analysis. Sci Rep 10, 6612 (2020). https://doi.org/10.1038/s41598-020-62990-0



10:42 - 10:45

Development of an open-split-based dual-inlet system for mass spectrometers

Stephan Räss1,2, Markus Leuenberger1,2

1Universität Bern, Schweiz; 2Oeschger Centre for Climate Change Research

The inlet system integrated into the Elementar isoprime precisION is a changeover-valve-based dual-inlet system which is not ideally suitable for high-precision measurements of elemental and stable isotope ratios. In order to attain higher precisions an open-split-based dual-inlet system was designed and built by the Climate and Environmental Physics Division of the University of Bern featuring almost no metallic surfaces and altering the pressure of the measured gases in the ionization chamber as little as possible. By means of these two measures the occurrence of fractionation processes during the transfer of gases from the gas containers to the mass spectrometer as well as in the ionization chamber is noticeably reduced by the in-house built dual-inlet system when compared to the dual-inlet system built by Elementar.
Since 2020, an in-house built dual-inlet system, which was named „NIS-II“, is installed at the high altitude research station Jungfraujoch, Switzerland, for measuring various delta values of atmospheric gas samples such as δO2/N2 and δAr/N2 and δ17O, δ18O of O2 and δ15N2 of N2. Furthermore, an NIS-II was recently taken into operation in Bern in order to check whether it is possible to measure clumped isotopes of oxygen, nitrogen and carbon dioxide molecules on gaseous samples of different origins.



10:45 - 10:48

Tracing nitrogen transformations induced by 15N labelled cattle slurry applied with different techniques in winter wheat

Caroline Buchen-Tschiskale, Heinz Flessa, Reinhard Well

Thünen-Institut für Agrarklimaschutz, Deutschland

The effects of slurry application techniques on ammonia (NH3) volatilisation and nitrous oxide (N2O) fluxes are well documented. However, application techniques may also impact dinitrogen (N2) fluxes, as they can influence denitrification activity by changing slurry and soil aeration (e.g. by injection techniques), nitrate formation (e.g. by adding nitrification inhibitors) and the pH value (e.g. by slurry acidification). Up to now, measuring N2 fluxes and following pathways of slurry nitrogen (N) transformation under field conditions is still challenging.

Thus, we applied a combined 15N labelling approach including slurry NH4+-N and soil NO3--N in undisturbed soil cores, set up as lysimeters and with growing winter wheat for a study period of 60 days. Slurry treatments include the following application techniques: trailing hose with and without acidification (H2SO4), slot injection with and without nitrification inhibitor (DMPP). Soil cores without slurry application were used as control. In a first step, soil nitrate was 15N labelled by homogeneous injection of a K15NO3- solution at a low N application rate (4 kg N ha-1), while one week later, 68 kg N ha-115N-labelled cattle slurry was applied. The 15N labelled cattle slurry consisted of fresh dairy cattle faeces (natural abundance), water and 15N labelled synthetic urine. N2O and N2 emission were measured using the modified 15N gas flux method with N2-depleted atmosphere. To close the N balance and follow the different N transformation pathways, 15N losses by leaching, 15N uptake by plant and residual 15N in belowground biomass, microbial biomass and soil were analysed by IRMS.

The major gaseous loss pathway was NH3 with up to 8 kg N ha-1 in the trailing hose treatment, while slot injection significantly reduced NH3-N losses. Regardless the application technique, N2O fluxes were very low (up to 0.1 kg N2O-N ha-1), while N2 reached up to 3 kg N ha-1. The N2O/(N2O+N2) ratio of dentification was always <0.1. The main pathways of the total N budget were gaseous N losses (NH3, N2O, N2) with 11-44%, soil N pool with 32-48% and plant uptake with 18-26% of 15N applied. N leaching and changes in the residual mineral nitrogen pool played only a minor role in the total N balance. Although there were no differences in the application techniques, it should be highlighted that the 15N recovery was almost complete, indicating that the experiment was able to capture the relevant 15N fates with the comprehensive setup that was applied.



10:48 - 10:50

Applying the 15N gas flux method in a lab incubation as an alternative to laborious field studies

Björn Kemmann1, Reinhard Well1, Stefan Burkart1, Thorsten Ruf2, Christoph Emmerling2

1Thünen Institut für Agrarklimaschutz, Deutschland; 2Universität Trier, Raum- und Umweltwissenschaften, Bodenkunde, Deutschland

Applying the 15N gas flux method (15NGF) in the field can be very challenging. The establishment of a reliable setup is time consuming, expensive, and requires a decent infrastructure at the field sites. Additionally, the atmospheric N2 background reduces measurement precision for detecting low tracer-derived N2 emissions. We incubated undisturbed soil cores (14.4 cm diameter and 35 cm height) from two remote field sites: an annual cropping system (Zea mays) and a perennial cropping system (Silphium perfoliatum). The incubation took place in a fully-automated facility, which provided us with an N2-reduced atmosphere, options to control temperature, irrigation and drainage, and allowed better control over the homogeneity of 15N-nitrate pool labelling, as compared to what is possible in the field. Using the 15NGF method with undisturbed soil cores allowed us to quantify differences in source-specific N2 and N2O emissions while including the effect of soil structure under dynamic waterlogged conditions. Additional information about nitrogen transformation processes between the cropping systems were obtained in bulk soil by analysing soil mineral 15N (NO3- and NH4+) via membrane-inlet mass spectrometry. The incubation experiment consisted of three different phases with increasing soil water content: (1) entire core just below field capacity; (2) lower 10 cm waterlogged; and (3) lower 25 cm waterlogged. The soil from the S. perfoliatum field had a significantly lower product ratio of denitrification (N2O/N2+N2O) with increasing waterlogging than the Z. mays soil. However, pool-derived N2O emissions from the S. perfoliatum soil were not significantly lower than from Z. mays soil. Hence, we could show that the soil structure from the perennial cropping field resulted in higher N2 emissions rather than lower N2O emissions. Although perennial systems are generally expected to provide a greenhouse gas mitigation potential, we were able to replicate conditions that could not have been easily addressed in the field, and show that, in comparing soil from these fields, that was not the case.

 
10:50 - 11:00Pause
 
11:00 - 12:30Block 7: Deutsches Isotopennetz GIN
Virtueller Veranstaltungsort: Block 7 - Meeting Link
Chair der Sitzung: Robert van Geldern, Universität Erlangen-Nürnberg
Chair der Sitzung: Nils Michelsen, TU Darmstadt
 
 
11:00 - 11:15

Die Tritiumverteilung in Niederschlag und Oberflächenwasser in Deutschland – ein Beitrag zum deutschen Isotopennetzwerk

Axel Schmidt, Michael Engel, Rike Völpel, Lars Duester

Bundesanstalt für Gewässerkunde, Deutschland

An der Bundesanstalt für Gewässerkunde (BfG) werden seit den 1970iger Jahren Oberflächenwasser- und Niederschlagsproben auf Tritium untersucht. Hierzu betreibt die BfG - mit Unterstützung der Wasserstraßen- und Schifffahrtsverwaltung (WSV), des Deutschen Wetterdienstes (DWD) und einiger Landesämter - ein bundesweites Netz aus insgesamt 69 Probenahmestationen mit dem Ziel, die Umweltradioaktivität großräumig zu überwachen. Dazu werden die Wasserproben aller Stationen als Monatsmischproben in den Laboren der BfG elektrolytisch angereichert und radiochemisch analysiert. Mittlerweile liegen alleine für Tritium mehr als 8000 Einzeldatensätze für Niederschlag und 23000 Einzeldatensätze für Oberflächenwasser frei zugänglich vor und können z.B. im Rahmen der Initiative „German Isotope Network - GIN“ verwendet werden.

Tritium (H-3) wird natürlicherweise durch Spallationsreaktionen in der Atmosphäre gebildet, anschließend zu überschwerem Wasser oxidiert und durch Niederschlag in die Oberflächengewässer eingetragen, wodurch es Bestandteil des hydrologischen Kreislaufes ist.

Die Tritiumkonzentrationen im Niederschlag sind im langjährigen Mittel (Untersuchungszeitraum 2010-2020) an der Station Cuxhaven (Nordsee) mit 10 TU am höchsten; landeinwärts verringern sich die Gehalte generell und liegen beispielsweise bei 8,9 TU an der Station Garmisch (Alpen). Das „Spring Leak“ – Phänomen führt im Frühsommer, im Vergleich zum restlichen Jahr, zu erhöhten Werten. Ebenso lagen die Tritiumkonzentrationen aufgrund geringer Niederschläge im Jahr 2018 an allen Stationen zwischen 15 % und 25 % über dem langjährigen Mittel.

Die Tritiumgehalte der Oberflächenwasserproben sind ebenfalls an der Nordseeküste mit etwa 33 TU (Station Helgoland) am höchsten; im Bereich der Ostsee liegen sie bei 7 TU (Station Travemünde) und sind damit mit den Konzentrationen im Landesinneren vergleichbar (z.B. 6,3 TU - Station Ulm). Überlagert werden diese natürlichen Werte durch z.T. stark erhöhte Tritiumkonzentrationen im Bereich von Kernkraftwerken, da diese im Rahmen ihres Routinebetriebes Tritium-haltiges Wasser diskontinuierlich über die Vorfluter in die Flüsse abgeben. So wird beispielsweise durch das französische Kernkraftwerk Cattenom regelmäßig Tritium in die Mosel eingeleitet, welches dann mit dem Fluss transportiert und durch Dispersionsprozesse verdünnt wird. So werden beispielsweise bis zu 500 TU im Oberflächenwasser an der Station Wincheringen (Fluss-km 222) und bis zu 200 TU an der Station Koblenz (Fluss-km 1,2) gemessen.

Diese Tritiumvariationen im Oberflächen- und Niederschlagswasser lassen sich für eine Vielzahl von wissenschaftlichen Fragestellungen verwenden. Im Rahmen dieser Präsentation sollen einige Anwendungen vorgestellt und anhand dessen die Möglichkeiten der Nutzung von Tritium als aquatischer Tracer auch heutzutage skizziert werden.



11:15 - 11:30

Tritium in der südlichen Nordsee: ein Tracer für lokal gebildeten Wasserdampf

Jürgen Sültenfuß

Universität Bremen, Deutschland

Weltweit wurden ab Beginn der Wasserstoffbombentests Tritium-Konzentrationen im Niederschlag aufgezeichnet.

Das Global Network of Isotopes in Precipitation (GNIP) wurde 1958 von der IAEA und der WMO gegründet und ging 1961 in Betrieb. Seit dieser Zeit nahm die Anzahl der durchgeführten Analysen kontinuierlich ab. In der südlichen Hemisphäre und auch in tropischen und subtropischen Regionen der Nordhemisphäre verringerten sich Tritiumkonzentrationen bis heute auf Werte, die der Grenze der technisch möglichen Auslösung mit Szintillationszählern entsprechen. Die Bedeutung der Messwerte aus diesen Regionen nahm daher stark ab und Messprogramme wurden eingestellt.

Das Bundesamt für Gewässerkunde (BfG) misst Tritium im Niederschlag als Monatsmittel aus fast zwei Dutzend Orten in Deutschland. Diese Datenreihen und deren Besonderheiten werden mit Tritium im Niederschlag in der deutschen Küstenregion der Nordsee vergleichen.

Merkmale, Besonderheiten:

  1. Unterschiede zwischen Maximum Konzentration im Sommer und Minimum Konzentrationen im Winter geben Hinweise auf Zumischung von Wasserdampf mit geringen Tritiumkonzentrationen aus dem Ozean während eines Jahres.
  2. Identifizierung der Variation der natürlichen atmosphärischen Tritium Produktionsrate aufgrund der Änderung des solaren Partikelstroms.
  3. Beitrag von lokalen Wasserdampfquellen am Niederschlagswasser.
  4. Abnahme des anthropogenen Tritiumbeitrags: sind historische Messungen des natürlichen Tritiums plausibel?
  5. Wie verlässlich sind gemessene Tritiumkonzentrationen im Niederschlag für die Rekonstruktion des zurückliegenden Tritiumeintrags in das Grundwasser?

Es werden Tritiumkonzentrationen im Niederschlag der Stationen des BfG mit Tritiumkonzentrationen im Grundwasser nahe der Deutschen Bucht verglichen.

Messungen von Tritium im Oberflächenwasser der Nordsee zeigen einen starken Anstieg der Werte seit Mitte der 1990iger Jahre. Zu dieser Zeit stiegen die Tritiumemissionen der Wiederaufbereitungsanlage in LaHague massiv.

Die Regensammler Station in Cuxhaven zeigt bis 1990 Tritiumwerte unterhalb anderer Stationen in Deutschland. Nach 2000 liegen die Werte aus Cuxhaven aber immer oberhalb der Werte anderer Stationen. Auch Grundwasserproben von den Ostfriesischen Inseln und nahe der Nordseeküste in Schleswig-Holsteins datiert auf Neubildungszeiten nach 2000 weisen deutlich höhere Tritiumkonzentrationen als der deutschlandweite Mittelwert der Niederschläge auf.

In der Nordsee zeigt sich die Ausbreitung von Tritium aus LaHague im östlich strömenden Küstenrandstrom und beschränkt damit räumlich die Region in der tritiumreicher Wasserdampf gebildet werden kann.



11:30 - 11:45

Distribution of young groundwater in the North German Basin

Annika Desens, Georg Houben

BGR, Deutschland

The Federal Institute for Geosciences and Natural Resources (BGR) is currently collecting all available groundwater age data on the territory of the Federal Republic of Germany. The background to this is that the German Site Selection Act for radioactive waste disposal sites defines groundwater age as an exclusion criterion. If young groundwater is detected in the vicinity of potential host formations, these sites must be excluded as a repository for high-level radioactive waste. In the by-laws, detectable concentrations of tritium (3H) and carbon-14 (14C) are specifically mentioned as indicators for young groundwater.

Groundwater ages also can be used for many other scientific questions, e.g. for studies on the transport of pollutants, such as nitrate and pesticides, for groundwater recharge estimations and for the calibration of regional groundwater models.

In addition to the collection of data, which will be archived in a publicly accessible database, the project will investigate the influence of various parameters on the determination of groundwater age, e.g. the screen length and the recharge rate and the distribution of young groundwater in the various hydrogeological units.

In the presentation, a short introduction to the database will be given and the first results on the spatial distribution will be shown. In addition, the first statistical evaluations on the depth-specific distribution of young groundwater in the North German Basin will be presented.



11:45 - 12:00

Stable isotope patterns of German rivers with aspects of scales and continuity

Paul Königer1, Christine Stumpp2,3, Axel Schmidt4

1Groundwater Resources Quality and Dynamics, Federal Institute for Geosciences and Natural Resources (BGR), Hannover, Germany; 2Institute for Soil Physics and Rural Water Management, University of Natural Resources and Life Sciences (BOKU), Vienna, Austria; 3Institute of Groundwater Ecology, Helmholtz Zentrum München, Neuherberg (HMGU), Germany; 4Environmental Radioactivity and Monitoring, Federal Institute of Hydrology (BfG), Koblenz, Germany

The stable isotope composition of river water (2H, 18O) in large basins mainly reflect precipitation, snow-melt or ice-melt inputs and modifications due to surface storage, mixing and contributions of time delayed groundwater components. Continuous observations of river water stable isotope patterns in high-resolution of time and space serve as characteristic fingerprints for specific locations or whole river basins. In Germany, river monitoring for radioactive isotopes started in the mid 1970s organized by the Federal Institute of Hydrology (BfG). Today a monitoring network for stable isotopes at 50 stations in monthly resolution is available [1, 2, 3] as part of the monitoring program of the BfG. The time series for stable isotopes are longer than three years and for some stations of up to 30 years. Additionally, daily river water samples were collected during the extraordinary dry autumn in October 2018 until January 2019 at six selected stations in the Rhine and five stations in the Elbe basin.

Most dominating stable isotope effects in river water are those of seasonality and altitudes, but also a continental effect is visible from δ18O vs. δ2H plots. Snow and ice-melt contribution in the Rhine and Danube during the summer months and a consecutive dilution of these signals by tributary rivers is visible. Close to the coasts in northern Germany, stable isotope patterns reflect influence of seawater and tides. Daily patterns during the dry season 2018/2019 do surprisingly not exhibit extreme changes but rather trends on enhanced groundwater contribution. Comparing German river basins of different sizes and mean catchment altitude reveal influences of scales. Long time series allows a discussion of the challenge to collect continuous data, but also uncertainties of measurements and the need for laboratory inter-comparisons.

References:

[1] Reckerth A., Stichler W., Schmidt A., Stumpp C. (2017): Long-term data set analysis of stable isotopic composition in German rivers. J Hydrol. 552: 718-731.

[2] Stumpp C., Klaus J., Stichler W. (2014): Analysis of long-term stable isotopic composition in German precipitation. J Hydrol. 517: 351-361.

[3] Koeniger P., Leibundgut Ch., Stichler W. (2009): Spatial and temporal characterization of stable isotopes in river water as indicators of groundwater contribution and confirmation of modelling results; a study of the Weser River, Germany. IEHS 45 (4): 289-302.



12:00 - 12:15

Very high resolution Automated Rain Water Sampler for stable water isotope monitoring

Christoff Andermann, Torsten Queißer, Markus Reich, Oliver Rach, Niels Hovius, Dirk Sachse

GFZ Potsdam, Deutschland

With changing climate, increasing world population, the linked shortage of resources and pollution of the environment necessitates adequate tools and technics to monitor the Earth’s system. Measuring isotope ratios and trace elements dissolved in rainwater are useful utensils to understand the system and trace sources and pathways as well as to examine the timescales of transport of rainwater. Yet, it is very difficult to track, trace and measure rainwater pathways over landscapes and oceans. In particular, sampling and sample preservation is notoriously difficult and, in many cases, very laborious in manpower and technical demanding. Comprehensive and automated monitoring of precipitation waters in space and time can improve our process understanding to better predict the nature and magnitude of future hydrometeorological changes. Today, no commercial, and only a few research level, automated sampling devices for rainwater exist. However, no existing sampling technology fulfills the quality criteria for sophisticated hydro-chemical rainwater analysis in particular in remote areas over long time periods.

Facing this lack of high-quality technical solutions, we present a newly developed automatic and autonomous precipitation water sampler for stable water isotope analysis of rainwater. Our autosampler can take 165 discrete rainwater samples with a minimum time resolution of 5min or volume wise 2mm of rainfall. The device is designed to be highly autonomous and robust for long-term deployment in harsh and remote areas and fulfills the high demands on sampling and storage for isotope analysis (i.e. sealing of samples from atmospheric influences, no contamination and preservation of the sample material). The sampling device is portable, has low power consumption, is remotely accessible and thus has a real-time adaptable sampling protocol strategy, and can be maintained at distance without any need to visit the location.

The device was tested in several evaluation and benchmarking cycles. First lab tests with dyed waters and waters with strongly differing isotopic signature demonstrate that the device can obtain, store and conserve samples without cross contamination over long periods of time. The device has been tested so far under several conditions, e.g. heavy summer thunderstorms with more than 50mm/24h of rainfall, sustained winter rainfall and in cold conditions involving melting of snow. Furthermore, we run a benchmark test with several devices in parallel. Finally, in October 2020, we had installed six devices, in collaboration with Germany's National Meteorological Service (Deutscher Wetterdienst DWD), in a South-West to North-East transect across the Harz mountains in Germany.

This automated rainwater sampler provides a sophisticated technological solution for monitoring moisture pathways and water transfer processes with the analytical quality of laboratory standard measurements on a new level of temporal and spatial resolution.



12:15 - 12:30

GIN and beyond: Cumulative rain collectors for isotope studies in challenging climates

Nils Michelsen1, Zeneb Najmi1, Paul Königer1,2, Christoph Schüth1

1Institute of Applied Geosciences, Technical University of Darmstadt, Germany; 2BGR Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover, Germany

Data on the isotopic composition of precipitation often represent a key component in isotope studies of the water cycle. For gathering the corresponding samples, various types of cumulative precipitation collectors are available. Among these samplers, the tube-dip-in-water collector with pressure equilibration tube (Gröning et al., 2012) is particularly popular, largely due to its simplicity and rather effective evaporation reduction (Michelsen et al., 2018).

In cool climates however, the use of this sampler can be challenging, because water may freeze inside the collection bottle and block the inlet tube (Gröning et al., 2012). Extended exposure to warm conditions can be problematic as well, particularly if the collected water volume is small compared to the size of the collection vessel (Michelsen et al., 2018).

Here, we outline a few simple designs, which can help to overcome the above-mentioned difficulties and may hence be useful in the German Isotope Network (GIN) and beyond.

References

Gröning, M., Lutz, H.O., Roller-Lutz, Z., Kralik, M., Gourcy, L., Pöltenstein, L., 2012. A simple rain collector preventing water re-evaporation dedicated for δ18O and δ2H analysis of cumulative precipitation samples, Journal of Hydrology 448–449, 195–200.

Michelsen, N., van Geldern, R., Roßmann, Y., Bauer, I., Schulz, S., Barth, J. A. C., Schüth, C., 2018. Comparison of cumulative precipitation collectors used in isotope hydrology, Chemical Geology, 488, 171–179.

 
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