BG2.4 | Oxygen, hydrogen and radiogenic isotope analyses of aquatic and terrestrial compounds: Advances in methods, models, and interpretation for environmental and anthropogenic processes.
EDI
Oxygen, hydrogen and radiogenic isotope analyses of aquatic and terrestrial compounds: Advances in methods, models, and interpretation for environmental and anthropogenic processes.
Convener: Marco Lehmann | Co-conveners: Marc-Andre CormierECSECS, Meisha Holloway-Phillips, Nemiah LaddECSECS, Francesco Izzo, Valeria Di Renzo
Orals
| Thu, 18 Apr, 16:15–18:00 (CEST)
 
Room 2.95
Posters on site
| Attendance Thu, 18 Apr, 10:45–12:30 (CEST) | Display Thu, 18 Apr, 08:30–12:30
 
Hall X1
Orals |
Thu, 16:15
Posters on site
Thu, 10:45
This session aims to bring together scientists from different fields applying oxygen, hydrogen, and radiogenic isotope measurements of environmentally derived compounds to unravel environmental processes and the complex interconnections existing between anthropogenic activities and the lithosphere, atmosphere, biosphere, and hydrosphere. We invite researchers working on different compounds (e.g., lipids, (hemi-) cellulose, lignin, non-structural carbohydrates, human and animal tissues, biominerals) from aquatic and terrestrial sources across all spatiotemporal scales and archives (e.g., herbarium, peat, sediments, loess, and tree rings). We also encourage researchers working with diverse techniques to present advances in methods, as well as researchers focusing on improving oxygen and hydrogen isotope-based models to discuss their approaches. In summary, the session will offer an overview of applications of oxygen and hydrogen isotopes across different ecosystems, as well as center on novel mineralogical and geochemical studies using radiogenic isotopes for improving our understanding of environmental issues related to human activities.

Session assets

Session materials

Orals: Thu, 18 Apr | Room 2.95

Chairpersons: Marco Lehmann, Marc-Andre Cormier, Valeria Di Renzo
16:15–16:20
5-minute convener introduction
Terrestrial ecoystems
16:20–16:40
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EGU24-18459
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solicited
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On-site presentation
Long-term ecophysiological signals from isotopomers: Principles and applications.  
Jürgen Schleucher, Lenny Haddad, Pieter Zuidema, Benjamin Smith, Mats Öquist, and John Marschall

Understanding plant responses to increasing CO2 is essential for predictions of plant productivity and of future climate (Walker et al. 2020). Isotope ratios (13C/12C and 2H/1H) have long been used in plant ecophysiology and for reconstruction of environmental variables. But it has also been known since decades that heavy isotopes are distributed unevenly WITHIN biological metabolites, i.e. that the abundances of 2H and 13C isotopomers vary. Because isotopomer variation is caused by enzyme isotope fractionation, it carries signals on the regulation of biochemical pathways. If such signals can be recovered from archives of plant material, they can report on plant-climate interactions on time scales from decades to millennia.

We use NMR (nuclear magnetic resonance) to analyze isotopomers of the glucose units of plant archives, and I will describe the principles and practicalities of isotopomer measurements. First, in manipulation experiments we calibrate isotopomer responses to environmental drivers, in particular CO2 and T. Second, we analyse isotopomers in plant archives such as tree-ring series over previous decades of rising CO2, and use the calibrations from the manipulation experiments to deduce shifts in photosynthetic metabolism over decades. We will present results on 2H and 13C isotopomer variation and associated ecophysiological signals.

We present data on 13C isotopomers in tree-ring cellulose and annual plants (Wieloch et al 2018). The results have implications for interpretation of the d13C of respired CO2. Furthermore, we show how 13C isotopomers give new insight into the pathways of C metabolism (Wieloch et al 2023).

Photorespiration is a side reaction of photosynthesis that reduces C assimilation in most vegetation. Photorespiration is reduced by increasing CO2 yet exacerbated by rising T, so its evolution under climate change and implications for global C fluxes are highly uncertain. We present data showing how 2H isotopomers can be used to track photorespiration in response to CO2 and T. The opposing effects of CO2 and T on photorespiration will determine if forests will in the future be a sink or source of CO2 (Van der Sleen et al. 2015; Sperry et al. 2019). For select tree species, we compare results from FACE experiments and from decades-long tree ring series, to detect possible acclimation of gas exchange of broad-leaved trees over

In summary, the presentation will describe how isotopomers can improve mechanistic understanding of plant function on long time scales, to be incorporated into Dynamic global vegetation models to improve predictions of C fluxes under climate change scenarios.

References

Walker et al., 2020 https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.16866.

Van der Sleen et al., 2015. https://doi.org/10.1038/ngeo2313.

Sperry et al., 2019. https://doi.org/10.1073/pnas.1913072116.

Wieloch et al., 2018 https://www.nature.com/articles/s41598-018-23422-2

Wieloch et al., 2023 https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.18965

 

How to cite: Schleucher, J., Haddad, L., Zuidema, P., Smith, B., Öquist, M., and Marschall, J.: Long-term ecophysiological signals from isotopomers: Principles and applications. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18459, https://doi.org/10.5194/egusphere-egu24-18459, 2024.

16:40–16:50
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EGU24-12841
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On-site presentation
Photosynthesis results in 2H-depleted carbohydrates, but why? 
Roland A. Werner and Meisha Holloway-Phillips

When you grow plants in the light, the hydrogen isotopic composition (δ2H) of plant compounds such as cellulose show lower δ2H values (are 2H-depleted) relative to plants grown heterotrophically in the dark. Therefore, it is logical to assume that photosynthetic reactions introduce 2H-depleted hydrogen atoms into carbohydrates. But where in the C reductive pathway (Calvin-Benson-Bassham cycle, CBB) does this occur? Or more interestingly, can we interpret the degree of 2H-depletion of plant compounds with respect to this key reaction(s)? With the recent resurgence of studies offering hydrogen isotopes as a new proxy for plant central carbon and energy metabolism, such a fundamental question seems pertinent to answer.

We 1) examine the stereospecific mechanism of hydride transfer via NADP(H) catalyzed by oxidoreductases (ferredoxin-NADP+ reductase, glyceraldehyde 3-phosphate dehydrogenase) as a key reason why photoproduced NADPH is not directly the source of 2H-depletion of autotrophically produced carbohydrates, 2) reconcile the site-specific deuterium abundance pattern differences between C3 and C4 (NADP-ME) species of hydrogen bound to position C-4 in glucose, and 3) urge greater investment in position-specific and complimentary metabolomic analyses to progress the development of hydrogen isotopes as a metabolic proxy.

How to cite: Werner, R. A. and Holloway-Phillips, M.: Photosynthesis results in 2H-depleted carbohydrates, but why?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12841, https://doi.org/10.5194/egusphere-egu24-12841, 2024.

16:50–17:00
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EGU24-12594
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ECS
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On-site presentation
In situ estimation of hydrogen isotope fractionation associated with sucrose and cellulose synthesis from leaves to roots 
Jochem Baan, Meisha Holloway-Phillips, Daniel B. Nelson, and Ansgar Kahmen

Plant cellulose hydrogen (H) stable isotope compositions (δ2H) integrate hydrological and biochemical information, and therefore measurements from archives such as tree rings can be valuable for understanding past climate and plant metabolic responses to environmental change. Although the hydrological component that is integrated into cellulose δ2H values is relatively well understood, the biochemical reactions that can alter δ2H values of metabolites used for cellulose biosynthesis remain cryptic. Attempts at establishing models to simplify the interpretation of cellulose δ2H values have been made, like the widely used cellulose δ2H model by Roden et al. (2000) using the terms quantified by Yakir & DeNiro (1990). However, independent quantification of the parameters in this model, and assessment of their variability with respect to plant C metabolism, has been limited.

The cellulose δ2H model uses the δ2H compositions of leaf water and source water, autotrophic and heterotrophic 2H-fractionation (εA and εH, respectively), and the proportion of carbon (C) bound H that exchanges with xylem water during cellulose biosynthesis (ƒ) to explain variation in cellulose δ2H values. By growing plants along a gradient of source water δ2H values under autotrophic and heterotrophic conditions, the original, εA, εH, and ƒ were determined for the aquatic plant Lemna gibba L.. One drawback of this approach is that it assumes these terms are the same when plants are grown in the light vs the dark. We recently reassessed the model for terrestrial plants by measuring δ2H values of leaf sucrose and found species variation in εA (Holloway-Phillips et al., 2022), but were unable to resolve variation associated with ƒ and εH.

In the present experiment we assessed a new experimental approach to quantify all model parameters for autotrophically grown plants using regression analysis. This required growing plants with variation in the isotopic offset between xylem water and leaf water (∆LW) and measuring sucrose and cellulose δ2H values from leaves and roots. In a previous study we determined that mutation-induced inhibition of starch synthesis in leaves resulted in higher cellulose δ2H values compared with the wildtype, which was hypothesized to occur preceding sucrose synthesis in the leaves (Baan et al., 2023). Using this new approach, we tested whether this effect was indeed mostly established in source cells during de novo sucrose synthesis (εA), or was a result of 2H-fractionating processes in sink cells prior to cellulose synthesis (εH and ƒ). Preliminary analyses show an increase in leaf sucrose δ2H values in the mutant relative to the wild type, implying that εA is also dependent on plant C metabolism within a given species.

How to cite: Baan, J., Holloway-Phillips, M., Nelson, D. B., and Kahmen, A.: In situ estimation of hydrogen isotope fractionation associated with sucrose and cellulose synthesis from leaves to roots, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12594, https://doi.org/10.5194/egusphere-egu24-12594, 2024.

Aquatic ecoystems
17:00–17:10
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EGU24-19894
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ECS
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On-site presentation
Hydrogen isotope fractionation is controlled by CO2 in coccolithophore lipids 
Hongrui Zhang, Ismael Torres-Romero, Reto Wijker, Alexander Clakr, Madalina Jaggi, and Heather Stoll

Hydrogen isotope ratios (d2H) represent an important natural tracer of metabolic processes, but quantitative models of processes controlling H-fractionation in aquatic photosynthetic organisms are lacking. Here we elucidate the underlying physiological controls of 2H/1H fractionation in algal lipids by systematically manipulating temperature, light and, for the first time, CO2(aq) in continuous cultures of the haptophyte Gephyrocapsa oceanica. We analyze the hydrogen isotope fractionation in alkenones (aalkenone), a class of acyl lipids specific to this species and other haptophyte algae. We find a strong decrease in the aalkenone with increasingCO2(aq), and confirm aalkenone correlates with temperature and light. Based on the known biosynthesis pathways, we develop a new cellular model of the d2H of algal acyl lipids to evaluate processes contributing to these controls on fractionation. Simulations show that longer residence times of NADPH in the chloroplast favor greater exchange of NADPH with 2H-richer intracellular water, increasing aalkenone. Higher chloroplast CO2(aq) and temperature shorten NADPH residence time by enhancing the carbon fixation and lipid synthesis rates. The inverse correlation of aalkenone toCO2(aq) in our cultures suggests that carbon concentrating mechanisms (CCM) do not achieve a constant saturation of CO2 at the Rubisco site, but rather that chloroplast CO2 varies with external CO2(aq). The pervasive inverse correlation of aalkenone with CO2(aq) in the modern and preindustrial ocean also suggests that natural populations may not attain a constant saturation of Rubisco with the CCM. Rather than reconstructing growth water, aalkenone may be a powerful tool to elucidate carbon limitation of photosynthesis.

How to cite: Zhang, H., Torres-Romero, I., Wijker, R., Clakr, A., Jaggi, M., and Stoll, H.: Hydrogen isotope fractionation is controlled by CO2 in coccolithophore lipids, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19894, https://doi.org/10.5194/egusphere-egu24-19894, 2024.

17:10–17:20
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EGU24-9025
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ECS
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On-site presentation
A new lipid-based proxy for the reconstruction of past phytoplankton ecological dynamics 
Antonia Klatt, Cindy De Jonge, Daniel B. Nelson, Marta Reyes, Ricardo N. Santos, Fatemeh Ajallooeian, Carsten J. Schubert, Nathalie Dubois, and S. Nemiah Ladd

The composition of lacustrine phytoplankton communities plays a key role for biogeochemical cycling of carbon, nitrogen, and phosphorus. Through the linkage between lakes and terrestrial ecosystems, especially via carbon cycling and freshwater supply, changes in algal ecology can affect even non-aquatic habitats. To investigate past phytoplankton dynamics, paleolimnologists often rely on microscopic algal remains preserved in the sediment, e.g., diatom frustules. However, only few taxa produce fossil remains, and might not be fully representative for the phytoplankton community. Other studies have reconstructed phytoplankton dynamics based on source-specific algal lipids, but many lipids are not as source-specific as initially thought. Rather than focusing on specific lipid biomarkers, a more holistic analysis of algal lipid distributions and their isotopic composition might highlight shifts in the past phytoplankton community with a greater robustness.

In this study, we introduce a new lipid-based proxy to reconstruct past phytoplankton community changes based on the abundance and hydrogen isotope ratios (δ2H) of short-chain fatty acids, phytosterols and phytol. Previous culturing and mesocosm experiments have shown that the relative offset between δ2H values of different algal lipids (εlipid1-lipid2) strongly differs among phytoplankton groups. For instance, εpalmitic acid-phytol values for green algae and cyanobacteria were ~150 ‰ higher than for other taxa. To validate these results in a natural system, we collected algal biomass samples from the water column of Lake Rot, a small eutrophic lake in central Switzerland, every second week from 2019 to 2020. Phytoplankton and microplankton cell counts were conducted for every sampling date. εlipid1-lipid2 values and algal lipid distributions were measured and related to biovolume changes of different algal groups. We used algal δ2Hlipid values from previous culturing studies weighted by phytoplankton biovolume in Lake Rot to model algal εlipid1-lipid2 values. To assess the potential heterotrophic impact on εlipid1-lipid2 values, we created a second model to simulate εlipid1-lipid2 values incorporating δ2Hlipid values from algae and microplankton. For this, we included hydrogen isotope fractionation between algal and plankton lipids as well as microplankton biovolume in Lake Rot. Modeled εlipid1-lipid2 values showed generally a good agreement with measured εlipid1-lipid2 values, validating εlipid1-lipid2 values as a potential proxy for phytoplankton dynamics. Moreover, measured εlipid1-lipid2 values were clearly represented by modeled algal εlipid1-lipid2 values suggesting that δ2Hlipid values in eutrophic lakes primarily reflect phytoplankton community composition with a negligible impact from microplankton. Our analysis of algal lipid distributions in the water column of Lake Rot revealed a significant positive correlation between the ratios of phytol and phytosterols (phytol:sterol ratio) as well as the sum of C18 fatty acids and C16:0 (C18:C16 ratio) and cyanobacterial biovolume.

We further apply our new lipid-based approach to a ~14 m long sediment core from Lake Rot, enabling a paleoecological reconstruction of phytoplankton community dynamics during the past ~13 kyr. Sedimentary phytol:sterol ratios, C18:C16 ratios, and εpalmitic acid-phytol indicate rising cyanobacterial biovolume during the last ~4000 years. Moreover, we compare the magnitude of change in the algal community in response to 20th century eutrophication with the natural variability throughout the Holocene.

How to cite: Klatt, A., De Jonge, C., Nelson, D. B., Reyes, M., Santos, R. N., Ajallooeian, F., Schubert, C. J., Dubois, N., and Ladd, S. N.: A new lipid-based proxy for the reconstruction of past phytoplankton ecological dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9025, https://doi.org/10.5194/egusphere-egu24-9025, 2024.

17:20–17:30
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EGU24-5205
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ECS
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On-site presentation
Late Holocene hydroclimate dynamics in the northern Alps based on compound-specific δ2H from Schliersee, Germany 
Maximilian Prochnow, Katharina Dulias, Paul Strobel, Marcel Bliedtner, Gerhard Daut, Sönke Szidat, Gary Salazar, Sudip Acharya, Rodrigo Martinez-Abarca, Anja Schwarz, Antje Schwalb, and Roland Zech

A comprehensive understanding of Holocene hydroclimate variability in the European Alps remains challenging because of the great spatial and temporal disparities between the northern and southern Alps, mainly caused by changes in atmospheric circulation patterns and different climate settings. Most of the hydroclimate studies are based on lake level and high-resolution flood reconstructions that can be potentially biased by catchment-specific effects and anthropogenic impacts. Moreover, floods are only single events and just one important aspect of paleohydrology. Phases of enhanced evaporation, transpiration and droughts are equally important ecologically and can occur between flooding events. Stable isotopes (δ18O) in speleothems and lake carbonates were applied to track past changes in atmospheric circulation and hydrology, but in the northern Alps, such studies mainly focus on the Late Glacial and Early Holocene.

We present the first compound-specific δ2H record based on terrestrial (n-C31) and aquatic (n-C25) n-alkanes from a sediment core collected from Schliersee, a pre-alpine lake located in Bavaria (Germany), and covering the Late Holocene (past ~4.3 ka). Based on previous calibration studies and new data, we use the δ2H record of n-C31 as a proxy for the isotopic composition of precipitation. We find that δ2Hn-C31 from Schliersee shows depleted values between ~1200 and ~500 cal. yr BP and enriched values before (2500 – 1200 cal. yr BP) and thereafter (500 cal. yr BP until today). This pattern is in good agreement with speleothem δ18O from Spannagel cave, Austria, and compound-specific δ2H from Lake Ghirla, southern Alps and was previously interpreted to reflect changes in moisture source. Therefore, our results support the concept that northern hemispheric cooling and changes in the North Atlantic Oscillation cause changes in moisture source related to shifts in the position of the Westerlies. Based on our results we conclude that this mechanism seem to have affected the isotopic composition of precipitation in both northern and southern Alps.

Moreover, aquatic δ2Hn-C25 is enriched by several tens of permille compared to terrestrial δ2Hn-C31, because of evaporative enrichment of lake water (Grafenstein & Labuhn, 2021 in: Ramstein et al., Springer Cham). Thus, we use their isotopic difference, expressed by Δaq–terr, as a proxy for evaporative enrichment. Our Δaq–terr shows a striking coincidence with tree-ring based drought reconstructions for Europe since the Medieval. This highlights that a “warm and dry” hydroclimate occurred during the Medieval (~1000 cal. yr BP), whereas “cool and wet” conditions prevailed during the Little Ice Age (~600 cal. yr BP). Furthermore, minima in Δaq–terr during the Little Ice Age seem to correspond to minima in solar forcing. High evaporative enrichment coincides with the observed anthropogenic warming during the last 250 years.

Our δ2H-record from Schliersee is consistent with other regional reconstructions and provides additional insights into the paleohydrology of the northern Alps. This highlights the potential of compound-specific δ2H analyses as a powerful tool for paleohydrological reconstructions and helps to better understand the hydroclimate dynamics across the Alps.

How to cite: Prochnow, M., Dulias, K., Strobel, P., Bliedtner, M., Daut, G., Szidat, S., Salazar, G., Acharya, S., Martinez-Abarca, R., Schwarz, A., Schwalb, A., and Zech, R.: Late Holocene hydroclimate dynamics in the northern Alps based on compound-specific δ2H from Schliersee, Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5205, https://doi.org/10.5194/egusphere-egu24-5205, 2024.

Novel stable isotope approaches
17:30–17:40
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EGU24-7306
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ECS
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On-site presentation
Stable Middle Miocene seawater isotopes in the eastern North Atlantic Ocean 
Katrin Haettig, Stefan Schouten, and Marcel T.J. van der Meer

The Middle Miocene is a phase of gradual climate cooling, CO2 decline and major episodes of seaward Antarctic ice expansion across the Middle Miocene Climate Transition. The global benthic foraminifera oxygen isotopes (δ18Obenthic) show a long-term increase by approximately 1‰, reflecting bottom water cooling and increase in global ice volume, although the latter is subject of debate. Here, we used a relatively new proxy based on hydrogen isotopes of long-chain alkenones (δ2HC37), produced by Haptophyte algae, to reconstruct surface seawater isotopes (e.g., Schouten et al., 2006; Weiss et al., 2019; Gould et al., 2019). This proxy is, in contrast to δ18Obenthic, not temperature dependent. Enabling us to reconstruct the isotopic evolution of the surface seawater from marine sedimentary records up to 40 Million years ago.

Here, we compare foraminifera based oxygen isotope and alkenone based hydrogen isotope reconstructions of seawater from a shallow sediment record covering the Middle Miocene (IODP Site U1318, 409 m water depth, eastern North Atlantic Ocean, Sangiorgi et al., 2021). The local δ18Obenthic record shows a strong long-term increase across the Middle Miocene Climate Transition in agreement with global benthic stacks. However, our reconstructed surface seawater δ2H shows no long-term increasing trend and when correcting the local δ18Obenthic record for subsurface temperature with TEXH86, the bottom seawater δ18O record also shows no long-term trend. Our findings are in line with recently published records using clumped isotope temperatures which suggest a long-term decrease in temperature during the Middle Miocene large enough to explain the trend in oxygen isotopic composition of the benthic foraminifera without the need for a change in ice volume.

How to cite: Haettig, K., Schouten, S., and van der Meer, M. T. J.: Stable Middle Miocene seawater isotopes in the eastern North Atlantic Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7306, https://doi.org/10.5194/egusphere-egu24-7306, 2024.

17:40–17:50
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EGU24-8785
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On-site presentation
A novel method for analyzing δ18O by laser ablation IRMS 
Elina Sahlstedt, Neil Loader, and Katja Rinne-Garmston

Fine-scale variations in the oxygen isotope composition (δ18O) of organic matrices, such as tree rings, provide an important proxy for past environmental conditions. In practice, however, sampling at high resolution is resource intensive and time consuming, requiring the precise cutting, processing, and weighing of sequential samples prior to mass spectrometry. These factors have limited the production of high-resolution δ18O data for research purposes. We have developed a novel method for analyzing δ18O in organic matrices using laser ablation mass spectrometry. This “online” method directly couples a UV laser ablation unit with an isotope ratio mass spectrometer (IRMS). Measurements are conducted on carbon monoxide (CO) gas produced during the laser ablation process. Thus, we sidestep the requirement for separate sample cutting and weighing steps and can take advantage of the high resolution and accurate positioning capabilities of the laser with significantly increased sample throughput and effectively non-destructive sampling. Preliminary results, conducted by analyzing woody materials, indicate a typical measurement precision of ≤0.5 ‰ at spatial resolution of 100µm (spot size). Running a single analysis with the new method takes approximately 15 minutes, which is comparable to a δ18O analysis run by conventional, thermal conversion IRMS. In the future, the new method is expected to provide a valuable tool for investigating fine-scale variation in δ18O in organic matrices.

How to cite: Sahlstedt, E., Loader, N., and Rinne-Garmston, K.: A novel method for analyzing δ18O by laser ablation IRMS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8785, https://doi.org/10.5194/egusphere-egu24-8785, 2024.

Novel radiogenic approaches
17:50–18:00
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EGU24-15515
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On-site presentation
Comparing the strontium isotope signatures of human urinary stones, drinking waters and environmental matrices: A first case study from Italy 
Izzo Francesco, Langella Alessio, Di Renzo Valeria, D'Antonio Massimo, Tranfa Piergiorgio, Widory David, Salzano Luigi, Germinario Chiara, Grifa Celestino, Varricchio Ettore, and Mercurio Mariano

Urolithiasis is a rather common pathology among the adult population and the biominerals it produces, i.e., urinary stones, may represent a potential proxy to characterize the environmental matrices that surrounded patients before being diagnosed. The objective of the present investigation (recently published in Izzo et al., 2024) was to use 87Sr/86Sr, a peculiar geochemical tracer routinely used for interpreting geological processes, to correlate the characteristics of patients’ urolith and their lifestyle habits, trying to identify correlations with direct or indirect contacts with their geological and environmental surroundings (water, soil, rock, etc.). Analyzed samples consisted of 21 kidney and bladder stones that were collected at the Department of Urology of the San Pio Hospital (Benevento, Italy) from patients living in Campania Region admitted between 2018 and 2020. Investigation was also extended to a vital food for humans such as water. Local tap waters and bottle waters (38 samples) from totally different Italian areas were here analyzed in order to highlight if and how different geological and hydrogeological settings could influence their Sr isotope ratio characterizing the connections existing between humans and their surrounding environment.

The 87Sr/86Sr ratios of uroliths ranged from 0.70761 for an uricite sample to 0.70997 for a weddellite one and seem to be partly discriminated based on the mineralogy. The comparison with the isotope characteristics of Italian drinking waters shows a general overlap in 87Sr/86Sr with the biominerals. However, on a smaller geographic area (Campania Region), we observe small 87Sr/86Sr differences between the biominerals and local waters. This may be explained by external Sr inputs for example from agriculture practices, inhaled aerosols (i.e., particulate matter), animal manure and sewage, non-regional foods. Nevertheless, biominerals of patients that stated to drink and eat local water/wines and foods every day exhibited a narrower 87Sr/86Sr range roughly matching the typical isotope ratios of local geological materials and waters, as well as those of archaeological biominerals from the same area. This preliminary study evidences how the strontium isotope ratio of urinary stones records that of the patient's surrounding environmental matrices, although further investigations will be necessary to confirm this hypothesis.

 

Izzo F., Di Renzo V., Langella A., D’Antonio M., Tranfa P., Widory D., Salzano L., Germinario C., Grifa C., Varricchio E., Mercurio M. (2024) Investigating strontium isotope linkage between biominerals (uroliths), drinking water and environmental matrices. Environmental Pollution, https://doi.org/10.1016/j.envpol.2024.123316  

How to cite: Francesco, I., Alessio, L., Valeria, D. R., Massimo, D., Piergiorgio, T., David, W., Luigi, S., Chiara, G., Celestino, G., Ettore, V., and Mariano, M.: Comparing the strontium isotope signatures of human urinary stones, drinking waters and environmental matrices: A first case study from Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15515, https://doi.org/10.5194/egusphere-egu24-15515, 2024.

Posters on site: Thu, 18 Apr, 10:45–12:30 | Hall X1

Display time: Thu, 18 Apr, 08:30–Thu, 18 Apr, 12:30
Chairpersons: Nemiah Ladd, Meisha Holloway-Phillips, Francesco Izzo
Terrestrial ecoystems
X1.17
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EGU24-10626
The hydrogen isotope composition of nocturnal sucrose does not reflect the 2H-depletion of remobilized leaf starch 
Meisha Holloway-Philips, Anina Wacker, Daniel B. Nelson, Guillaume Tcherkez, Marco Lehmann, and Ansgar Kahmen

The hydrogen isotope composition (δ2H) of cellulose is inherently linked to that of sucrose synthesised in leaves. During the daytime, sucrose is synthesised from photosynthetic products, and at night, from remobilised starch. From theory, the δ2H of starch should be 2H-depleted relative to triose-phosphates generated during photosynthesis. Consequently, sucrose δ2H values should diurnally vary so that on a flux-weighted basis, cellulose δ2H values could provide a sensitive proxy for the partitioning of photoassimilates between sucrose and starch. However, this hypothesis is yet to be tested.

We made diel measurements of sucrose and starch δ2H in three species – Vicia faba (bean), Raphanus sativus (radish), and Helianthus annuus (sunflower) differing in their sucrose/starch dynamics. Plants were grown under controlled environment conditions to minimise variation in leaf water δ2H and physiology, so that changes in sucrose δ2H could be attributed to day/night shifts in photoassmiliates vs transitory starch used for sucrose synthesis. We confirmed that transitory starch in leaves was 2H-depleted compared with sucrose, on average by around 100 ‰. However, whilst there were species-specific trends in daytime sucrose δ2H, surprisingly, there was no significant day-night difference in the three species. Several explanations are discussed for the lack of day/night variation in the δ2H of sucrose, including the signal being subsequently overwritten in the cytosolic processing of sugars or masked by 2H-enrichment at other positions to counteract the 2H-depleted starch signature. We qualify the latter possibility with a simplified steady-state isotopic model.

How to cite: Holloway-Philips, M., Wacker, A., Nelson, D. B., Tcherkez, G., Lehmann, M., and Kahmen, A.: The hydrogen isotope composition of nocturnal sucrose does not reflect the 2H-depletion of remobilized leaf starch, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10626, https://doi.org/10.5194/egusphere-egu24-10626, 2024.

X1.18
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EGU24-18348
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ECS
Robustness of the relationship between needle n-alkane δ²H and leaf water evaporative enrichment, amidst seasonally variable relationships between non-structural carbohydrate δ²H and respiration rate, in a boreal forest 
Charlotte Angove, Guido Wiesenberg, Marco Lehmann, Matthias Saurer, Yu Tang, Elina Sahlstedt, Tatjana Speckert, Pauliina Schiestl-Aalto, and Katja Rinne-Garmston

Stable isotopes of n-alkanes are important and rapidly developing tools for understanding paleoecology and past climatic conditions. However, there are knowledge gaps surrounding the physiological and environmental δ2H signals of n-alkanes. In this study, we investigated whether biosynthetic processes interfere with the consistency of the environmental signal in needle n-alkane δ²H. Therefore, we sampled two needle generations (one year-old needles, current-year needles) from five Pinus sylvestris trees at the boreal forest in Hyytiälä, Finland, during the 2019 growing season and analyzed δ2H of leaf non-structural carbohydrates (NSCs), starch, n-alkanes, and combined data with published leaf water isotope and shoot gas exchange measurements. We explored (1) time-integrated relationships between environmental variables and measured organic compound δ2H, and (2) evaluated whether the δ²H data of this study align with model predictions for NSC and leaf n-alkane δ²H values based on a process-based model for NSC δ2H hybridized with different leaf water heavy isotope enrichment and n-alkane models. Our findings suggest that NSC δ²H has temporally variable relationships to environmental variables which are related to needle generation and season, because current-year needle NSC δ²H was more closely correlated to respiration rate than a needle water isotope signal while one year-old needle NSC δ²H was more closely related to a leaf water evaporative enrichment signal. Interestingly, n-alkane δ²H did not exhibit the same seasonally variable relationship to respiration rate and were instead more closely related to a leaf water evaporative enrichment signal. Overall, results suggest that water compartmentalization in leaves can have a prominent enough role during n-alkane synthesis, that its effects can be observed at seasonal scale, which shows promise to the role of leaf n-alkane δ²H as a leaf evaporative enrichment signal without substantial interference by source water δ²H. However, we also highlight the role of signal dampening, by time integration and new needle growth.

 

How to cite: Angove, C., Wiesenberg, G., Lehmann, M., Saurer, M., Tang, Y., Sahlstedt, E., Speckert, T., Schiestl-Aalto, P., and Rinne-Garmston, K.: Robustness of the relationship between needle n-alkane δ²H and leaf water evaporative enrichment, amidst seasonally variable relationships between non-structural carbohydrate δ²H and respiration rate, in a boreal forest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18348, https://doi.org/10.5194/egusphere-egu24-18348, 2024.

X1.19
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EGU24-11920
Hydrogen and oxygen isotopes in tree-ring cellulose as indicators of source water variations 
Marco Lehmann, Haoyu Diao, Meisha Holloway-Phillips, Fabian Bernhard, Katrin Meusburger, Georg von Arx, Arthur Gessler, and Matthias Saurer

Although the hydrogen (δ2H) and oxygen (δ18O) isotopic signature of tree rings is dependent on the environmental water, such as precipitation and soil water that trees have taken up (i.e. “source water”), estimating the spatio-temporal origin of water sources through analysis of water stable isotopes in tree rings is not a straightforward approach. This is because 1) our knowledge on the contribution and the variability of individual isotopic fractionation steps between source water and tree rings is limited, and 2) in situ measurements that consider the seasonality of the isotopic composition of source water and cellulose synthesis are rare.

Within the framework of the EU Cost Action WATSON (#CA19120 - WATer isotopeS in the critical zONe), we analyzed (1) δ2H and δ18O in tree-ring cellulose and stem sugar, (2) δ2H and δ18O in soil water at shallower (15 cm) and deeper (80 cm) depths in up to bi-weekly resolution and (3) modelled isotopic variations in precipitation, soil water, stem xylem water, and leaf water using mechanistic and process-based models for three long-term forest monitoring sites in Switzerland over 20 years. We used this data to explain intra-annual (2021-2022) and inter-annual (2003-2022) δ2H and δ18O variations in tree-ring cellulose of beech (Fagus sylvatica) and spruce (Picea abies).

At the intra-annual scale, preliminary findings indicate a pronounced isotopic enrichment in the second half of the growing season and marked seasonal variations in the isotopic composition of soil water at shallower depths compared to deeper layers. However, such fluctuations were strongly dampenend in the intra-annual δ2H and δ18O variations observed in the tree-ring cellulose and stem sugars of both tree species, which may indicate the use of deeper soil water sources or scrambling of the source water isotope signal because of isotope fractionation before cellulose synthesis. In further analyses at the inter-annual scale, we will investigate how well δ2H and δ18O in tree rings can function as indicators of source water through time-window correlation analysis between water and tree-ring stable isotopes and comparisons between measured and modelled data.

Our study aims to enhance models of hydrogen and oxygen isotope fractionation. This will improve the use of both elements in tree rings as innovative ecohydrological proxies for retrospectively reconstructing environmental water sources.

How to cite: Lehmann, M., Diao, H., Holloway-Phillips, M., Bernhard, F., Meusburger, K., von Arx, G., Gessler, A., and Saurer, M.: Hydrogen and oxygen isotopes in tree-ring cellulose as indicators of source water variations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11920, https://doi.org/10.5194/egusphere-egu24-11920, 2024.

X1.20
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EGU24-10248
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ECS
The hydrogen isotope footprint of source water in tree lignin methoxy groups 
Anna Wieland, Marco M. Lehmann, Claudia Guidi, Valentina Vitali, Paul Handrack, and Frank Keppler

The stable hydrogen isotope values of tree lignin methoxy groups (δ2Hmeth) show a robust relationship with source water hydrogen isotopes (δ2HSW), enabling the reconstruction of the source water origin using an average hydrogen isotopic fractionation (ε) of around -200 mUr between δ2Hmeth and δ2HSW values (Greule et al., 2021; Keppler et al., 2007). Reconstructed δ2HSW is currently mainly used for climatic reconstruction of temperature but could also be used to better understand ecohydrological processes such as root water uptake. As the use of lignin methoxy groups as a source water proxy is relatively new, there are still uncertainties regarding additional influences on δ2Hmeth interfering the reconstruction of δ2HSW. Factors such as temporal changes in the isotopic composition of source water, soil moisture, and changes in root system and biomass may influence lignin methoxy fractionation, and a better understanding of these factors is important to improve the application of this proxy.

Here, we analyzed wood samples collected from a dry pine forest in Switzerland, where an extensive irrigation experiment was conducted. The site was divided into eight plots and since 2003 four of these plots received irrigation during the growing season from a nearby channel fed by the Rhone River, doubling the annual precipitation amount in the irrigated (1200mm) compared to the control stands (600 mm). Irrigation water is about 46 ± 9 mUr more depleted in 2H than the soil water, resulting in average δ2H values of -76 vs -68 mUr in irrigated and control soil water (0-10 cm) (Guidi et al., 2023).

We present results of δ2Hmeth measurements from four irrigated and four control trees analyzed annually from 1990 to 2023. We observed a significant 2H depletion in the irrigated trees compared to the control trees, supporting the use of this proxy to reconstruct source water changes. By further comparing δ2Hmeth values of irrigated and control trees, including root and leaf samples, we gain additional insight into hydrogen isotope fractionation processes in trees, improving our understanding of the influences of biological processes on δ2Hmeth. With our study, we hope to contribute to the further development of a new ecohydrological proxy that potentially allows the reconstruction of past variations in root water uptake of plants.

References:

Greule, M., Wieland, A., Keppler, F., 2021. Measurements and applications of δ2H values of wood lignin methoxy groups for paleoclimatic studies. Quat. Sci. Rev. 268, 107107. https://doi.org/10.1016/j.quascirev.2021.107107

Guidi, C., Lehmann, M.M., Meusburger, K., Saurer, M., Vitali, V., Peter, M., Brunner, I., Hagedorn, F., 2023. Tracing sources and turnover of soil organic matter in a long-term irrigated dry forest using a novel hydrogen isotope approach. Soil Biol. Biochem. 184, 109113. https://doi.org/10.1016/j.soilbio.2023.109113

Keppler, F., Harper, D.B., Kalin, R.M., Meier-Augenstein, W., Farmer, N., Davis, S., Schmidt, H.L., Brown, D.M., Hamilton, J.T.G., 2007. Stable hydrogen isotope ratios of lignin methoxyl groups as a paleoclimate proxy and constraint of the geographical origin of wood. New Phytol. 176, 600–609. https://doi.org/10.1111/j.1469-8137.2007.02213.x

How to cite: Wieland, A., Lehmann, M. M., Guidi, C., Vitali, V., Handrack, P., and Keppler, F.: The hydrogen isotope footprint of source water in tree lignin methoxy groups, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10248, https://doi.org/10.5194/egusphere-egu24-10248, 2024.

X1.21
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EGU24-20065
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ECS
Non-Exchangeable Hydrogen Stable Isotope Analysis In Mango (Mangifera indica L.) Pectin Methoxy Groups 
Aiman Abrahim, Markus Greule, Peter Rinke, Christina Vlachou, and Simon Kelly

Hydrogen stable isotope analysis of fruits can provide valuable information about their geographical origin, growing conditions, and the underlying environmental factors. The isotopic ratios of Hydrogen in fruits are related to the water they absorb and incorporate during photosynthesis. Nevertheless, measuring non-exchangeable hydrogen isotope ratios in plant-related organic compounds such as carbohydrates and polysaccharides face well-known analytical challenges (1). One strategy to overcome this challenge is by an established method which determines the hydrogen isotope ratios in non-exchangeable methoxy groups of organic compounds (e.g., lignin, pectin) (2). Pectin is a type of polysaccharide that is naturally occurring in the cell walls of fruits and vegetables and has the potential to be useful for food traceability. We have adapted the site-specific hydrogen stable isotope method, originally developed for wood lignin, to the extraction and δ2H measurement of pectin in mango fruits cultivated in different countries to assess the feasibility of applying the data to geographical origin assignment.

Reference.

(1) Sauer, P. E., Schimmelmann, A., Sessions, A. L., & Topalov, K. (2009). Simplified batch equilibration for D/H determination of non‐exchangeable hydrogen in solid organic material. Rapid Communications in Mass Spectrometry: An International Journal Devoted to the Rapid Dissemination of Up‐to‐the‐Minute Research in Mass Spectrometry, 23(7), 949-956.

(2) Keppler, F., Harper, D. B., Kalin, R. M., Meier‐Augenstein, W., Farmer, N., Davis, S., ... & Hamilton, J. T. (2007). Stable hydrogen isotope ratios of lignin methoxyl groups as a paleoclimate proxy and constraint of the geographical origin of wood. New Phytologist, 176(3), 600-609.

How to cite: Abrahim, A., Greule, M., Rinke, P., Vlachou, C., and Kelly, S.: Non-Exchangeable Hydrogen Stable Isotope Analysis In Mango (Mangifera indica L.) Pectin Methoxy Groups, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20065, https://doi.org/10.5194/egusphere-egu24-20065, 2024.

Aquatic ecoystems
X1.22
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EGU24-17441
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ECS
Toward using δ2H values for investigating marine mixotrophy 
Marc-Andre Cormier, Jean-Baptiste Berard, Daniel Nelson, Kevin Flynn, Richard Lampitt, and Gael Bougaran

Hydrogen isotope ratios (δ2H) measured on lipids extracted from aquatic and terrestrial organisms are widely applied for studying past hydro-climatic conditions. A growing body of evidence suggests that δ2H values of lipids integrate not only climatic, but also metabolic information. Metabolic effects hinder the reconstruction of climatic conditions based on δ2H values from archives and urges for a better understanding of the key drivers of δ2H values in organic compounds. Once disentangled, such non-climatic information in δ2H values may become key for investigating misunderstood eco-physiological behaviours. One such behaviour is marine mixotrophy.

While science requires tools to measure the contributions of phototrophic and heterotrophic growth in plankton, my colleagues and I have already shown that lipid δ2H values are uniquely sensitive to the expression of heterotrophy relative to photosynthesis in plants. This presentation will discuss groundwork experiments performed with chlorophytes and dinoflagellates exploring whether δ2H values of diverse compounds produced by protists are similarly sensitive to their central metabolic pathway. New δ2H analyses performed on fatty acids, phytols and sterols from these experiments, using an isotope ratio mass spectrometer (IRMS) coupled to a gas chromatograph (GC), will be discussed. Our data suggest that lipids δ2H values are indeed sensitive to the level of heterotrophic growth in diverse protists.

If this relation can be confirmed and calibrated, compound specific H isotope analyses could provide a powerful means to study the role of mixotrophy on the global carbon cycle and the occurrences of HABs.

How to cite: Cormier, M.-A., Berard, J.-B., Nelson, D., Flynn, K., Lampitt, R., and Bougaran, G.: Toward using δ2H values for investigating marine mixotrophy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17441, https://doi.org/10.5194/egusphere-egu24-17441, 2024.

X1.23
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EGU24-12882
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ECS
Comparison of lipid biomarkers and their hydrogen isotopic values in submerged vascular macrophytes and charophytes 
Ricardo N. Santos, Bernhard Aichner, Daniel B. Nelson, Sabine Hilt, and Sarah N. Ladd

Submerged macrophytes incorporate lake water directly during lipid synthesis, making the δ2H values of their lipids a crucial tool for reconstructing past hydrology and lake states. Despite this significance, the lipid biomarkers of aquatic plants have received less attention compared to terrestrial plants. In particular, in the context of organic geochemical applications, submerged aquatic plants are typically considered as a single group, ignoring potential differences in lipid distributions and hydrogen isotope composition between vascular macrophytes and macroalgae such as charophytes. This gap limits the use of lipid biomarkers in lake sediments to understand past lake water isotopes and vegetation dynamics.

In this study, we analyzed the lipid contents and δ2H values of fatty acids, n-alkanes, and the chlorophyll side-chain phytol from paired vascular macrophytes and charophytes collected from 12 oligo-mesotrophic hardwater lakes in northeast Germany. We aim to assess differences between macrophyte groups and their relation to environmental factors and lake water properties, such as lake water δ2H values and pH levels.

Our preliminary results reveal a notable predominance of fatty acids over n-alkanes in both macrophyte groups. Vascular macrophytes tended to exhibit a higher, albeit variable, abundance of n-alkanes, fatty acids, and phytol concentrations compared to charophytes. The n-alkanes profiles were mainly comprised of mid to long-chain hydrocarbons (n-C23 to n-C27) and exhibited striking variability among macrophytes. Nonetheless, charophytes were notably characterized by a prominent dominance of n-C27. While the C16:0 fatty acid was the most abundant hydrocarbon in both macrophyte types, vascular macrophytes exhibit a greater abundance of long-chain (C24 toC30) fatty acids. However, our data revealed marked differences in the relative abundance of these long-chained compounds. The overall disparities in the lipid profiles point to distinct lipid biosynthesis pathways or environmental adaptations among the studied aquatic plants. Despite the differences in lipid distributions, no systematic differences were observed in the δ2H values for any studied compound class between the two macrophyte groups, Our results suggest that reconstructions of lake water isotopes based on δ2H values of aquatic plant lipids are unlikely to be influenced by changes in the relative contributions from vascular macrophytes and charophytes.

How to cite: N. Santos, R., Aichner, B., B. Nelson, D., Hilt, S., and N. Ladd, S.: Comparison of lipid biomarkers and their hydrogen isotopic values in submerged vascular macrophytes and charophytes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12882, https://doi.org/10.5194/egusphere-egu24-12882, 2024.

Novel stable isotope approaches
X1.24
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EGU24-12750
Varying amounts of isotopic exchange among dual water hydrogen isotope exchange methods indicate different pools of exchangeable hydrogen  
Daniel B. Nelson, Meisha Holloway-Phillips, and Ansgar Kahmen

The hydrogen isotopic composition of organic compounds carries information relating to the isotopic composition of biosynthetic source water, as well as source-organism biochemistry. This has led to diverse applications in areas such as paleoclimatology, ecology, and criminal forensics. Yet, measurement poses a unique isotopic challenge because hydrogen bound to oxygen or nitrogen can exchange with ambient water or vapor, unlike the hydrogen that is bound to carbon. This creates a need to account for this so-called exchangeable hydrogen. In some cases, this can be done by permanent replacement via chemical derivatization, but this is often not convenient or even possible. This has led to the development of dual water equilibration methods in which the exchangeable hydrogen in a sample is equilibrated with water with a known isotopic composition in a controlled manner as the last step in sample preparation prior to measurement. Dual water equilibration methods have facilitated applications in a range of subdisciplines, especially for applications focused on plant carbohydrate-rich materials such as cellulose and bulk wood, and on keratin in animal migration and ecology.

 

The term “exchangeable hydrogen” has generally been used inconsistently in environmental applications. In some cases, the term is used to describe only the hydrogen that can freely exchange with ambient vapor at room temperature conditions, while in other cases the term directly refers to all hydrogen that is not covalently bound to carbon and can therefore theoretically undergo isotopic exchange. These two definitions are inconsistent with one another because in many biomolecules, such as cellulose and keratin, a large portion of the hydrogen that is not carbon-bound is engaged in hydrogen bonding and is important for the macromolecular structure of the material. This bridging hydrogen, although not carbon-bound, is more difficult to isotopically exchange, and has the potential to be excluded by some types of dual water equilibration approaches. As a consequence, the fraction of hydrogen that is measured as exchangeable varies between sample types and methodologies, resulting in different hydrogen isotope values.

 

In this study we compared hydrogen isotope values after dual water equilibrations on plant carbohydrates and animal keratins using two different analytical approaches, one of which targeted only the freely exchangeable hydrogen pool, and the other of which targeted the theoretically exchangeable hydrogen pool. For all sample types, we observed large differences in the calculated fraction of exchangeable hydrogen, with the freely exchangeable approach yielding exchange rates 10-15 % smaller than those from the theoretically exchangeable approach. The data also showed a greater range of hydrogen isotope values for the approach that achieved higher degrees of hydrogen exchange, suggesting that the range in bridging hydrogen isotope values among samples was lower than that of carbon-bound hydrogen. We suggest modification of the term “exchangeable” in dual water equilibration studies to indicate whether the freely or the potentially exchangeable hydrogen is being targeted, and therefore the extent to which the bridging hydrogen has been isotopically exchanged.

How to cite: Nelson, D. B., Holloway-Phillips, M., and Kahmen, A.: Varying amounts of isotopic exchange among dual water hydrogen isotope exchange methods indicate different pools of exchangeable hydrogen , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12750, https://doi.org/10.5194/egusphere-egu24-12750, 2024.

X1.25
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EGU24-12823
Nitrogen Isotopic Studies in an Urban Estuary: Not Just a story of Anthropogenic Influences 
Peter Swart, Amel Saied, Maribeth Gidley, Aliza Karim, Elzabeth Kelly, Rachel Silverstein, Chistopher Sinigalliano, Tiffany Troxler, and Sean Ahearn

Over a twelve-month period, between June 2021 and June 2022, a study was carried out that investigated possible causes of water quality decline in northern Biscayne Bay (South Florida, USA).  During this investigation a large number of different water quality parameters were monitored at 22 sites and waterways feeding into the Bay (Miami River, Little River, Biscayne Canal, and Snake Creek) in this area. Additional samples were also collected in the central region of Biscayne Bay around Virginia Key and Key Biscayne, Coconut Grove, and Matheson Hammock. At each site water and vegetation samples were collected.  Water samples were analyzed for standard nutrient parameters (TN, TP, NO3-, NH4, chlorophyll, turbidity, salinity, and dissolved oxygen content) and vegetation samples analyzed for their δ15N and δ13C values, and CN ratios. A smaller number of additional water samples were collected for the analysis of the δ18O and δ15N values of the NO3- and sediment samples were analyzed for their dδ15N values at each site. This presentation concentrates principally on the nitrogen isotopic portion of the study. The highest δ15N values were found in algae and plants collected from the Biscayne Canal, Little River, and Miami River sites, while lower values were measured at the central Biscayne Bay sites.  The Little River sites showed a strong seasonality with δ15N values ranging from +8 ‰ in the wet season to over +13‰ at the start of the dry season, while Miami River and Biscayne Canal sites remained at values of between +9 to +13‰ throughout the year.   While elevated δ15N  values are associated with the input of anthropogenic waste, leaking from septic tanks along the canals, elevation of the d15N values in excess of typical human δ15N values is driven by fractionation during nitrification and incorporation by assimilation. We propose that nitrogen derived from septic tanks ,with elevated δ15N  values, mixes with nitrogen derived from the natural environment as well as from artificial fertilizers (both with lower δ15N values) to produce a pool of nitrogen with intermediate δ15N values.  This reservoir is then further enriched in 15N during the process of assimilation and nitrification which fractionates the δ15N  value of the residual NO3-. 

How to cite: Swart, P., Saied, A., Gidley, M., Karim, A., Kelly, E., Silverstein, R., Sinigalliano, C., Troxler, T., and Ahearn, S.: Nitrogen Isotopic Studies in an Urban Estuary: Not Just a story of Anthropogenic Influences, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12823, https://doi.org/10.5194/egusphere-egu24-12823, 2024.

Novel radiogenic approaches
X1.26
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EGU24-9906
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ECS
Unveiling geological identities: use of 87Sr/86Sr in food and beverages traceability, focusing on wines from Solopaca (Campania, Italy) 
Piergiorgio Tranfa, Valeria Di Renzo, Francesco Izzo, Alessio Langella, Mariano Mercurio, Vincenzo Mercurio, Piergiulio Cappelletti, and Massimo D'Antonio

Research on food and beverages traceability, i.e., assessing their environmental origin, has advanced significantly in recent years thanks in large part to strontium isotope geochemistry. The unique Sr isotope signature (87Sr/86Sr) found in soils, plants, and waters makes the relation between food/beverages and environment achievable. This signature is derived from the local geological substratum and is influenced by age and initial concentration of rubidium in the rocks, and to geological processes. The release of strontium ions from the bedrock due to weathering processes, resulting from the interaction of circulating fluids with rocks, contributes to the accumulation of Sr in waters and soils. Part of this Sr is bioavailable and its 87Sr/86Sr ratio can be used as a valid tracer to identify the region of origin of wines. Considering an original 87Sr/86Sr ratio in rocks and soil of a given locality, it is demonstrated that strontium is first absorbed by plant roots, then by grapes, and finally by wine, without isotopic fractionation. As a result, the analysis of the wine' Sr isotope ratio establishes a precise connection between the product and its geological provenance, giving each wine a unique geofingerprint. This study aims to verify the strong relationship between the product (wine) and its region by building on these foundations. The final objective is to make the wine recognizable and distinguishable from comparable products so that it can be protected from fraud and adulteration. Using the 87Sr/86Sr systematics, coupled with traditional analyses such as thermal, XRD and FTIR analyses, 24 samples (8 soil samples, 8 grape samples and 8 microvinification samples) from Solopaca (Campania, Italy) were investigated. In order to provide a thorough Sr-isotopic characterization, soil samples were analyzed for both total and bioavailable Sr fractions. This method improves the investigation of environmental processes at every stage of the wine-making process.

How to cite: Tranfa, P., Di Renzo, V., Izzo, F., Langella, A., Mercurio, M., Mercurio, V., Cappelletti, P., and D'Antonio, M.: Unveiling geological identities: use of 87Sr/86Sr in food and beverages traceability, focusing on wines from Solopaca (Campania, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9906, https://doi.org/10.5194/egusphere-egu24-9906, 2024.

X1.27
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EGU24-8937
A promising approach in isotope geochemistry: 87Sr/86Sr in human teeth and hair to study dietary and environmental effects. 
Ilenia Arienzo, Valeria Di Renzo, Carlo Pelullo, and Massimo D'Antonio

In recent years Sr isotope geochemistry has provided a huge contribution to environmental and food traceability studies. This is possible because soils, plants and water are characterized by a specific Sr isotopic signature (expressed through the 87Sr/86Sr ratio), which derives from the local geological substratum which, in turn, depends on geological processes and on the age and initial rubidium (Rb) content of the rocks, given that 87Rb decays to 87Sr over time. Since the relative abundance of Sr isotopes does not change during the path through the food chain, the 87Sr/86Sr ratio in human tissues reflects that of the “environment” in which people live and feed. In particular, tooth enamel (which forms during the first years of life) does not exchange with external Sr after mineralization. For this reason, its isotopic composition mostly reflects the 87Sr/86Sr of the food intake that individuals used for energy, growth and maintaining the processes of life, during their childhood.

In this work, the Sr isotopic characterization of deciduous human teeth and hair, water, soil, plants and food was carried out. Donors are all born and currently residing in Campania (Southern Italy), of different age and sex. The 87Sr/86Sr of deciduous teeth provides a direct link to the mother’s milk, or to the artificial milk, which are the first foods for the newborn individuals, whereas the 87Sr/86Sr of hair is directly related to the diet in adulthood. Moreover, the mother’s milk is in part related to the local geological substratum and in part to the diet that has become no longer local, but global. Despite adult individuals have different diets, the isotopic fingerprint of enamel teeth is similar for all breastfeed children. Results from this study have scientific implications also for human mobility studies.

How to cite: Arienzo, I., Di Renzo, V., Pelullo, C., and D'Antonio, M.: A promising approach in isotope geochemistry: 87Sr/86Sr in human teeth and hair to study dietary and environmental effects., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8937, https://doi.org/10.5194/egusphere-egu24-8937, 2024.