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The ongoing intensification of the hydrological cycle calls for the identification and assessment of factors controlling catchment resilience to climate change. Stable isotopes of O and H in streams and precipitation are cardinal tools in this respect – notably for investigating questions related to water source, flowpaths and transit times. However, the spatial and temporal variability of these tracers remain largely unknown – essentially due to the limited availability of long historical time series of O-H isotope signatures in stream water, as opposed to the multi-decadal records in precipitation of the IAEA’s GNIP database (https://www.iaea.org/services/networks/gnip). Based on their quality as natural archives of in-stream environmental conditions, freshwater mussels have been recently used for complementing stream water δ18O isotope records. With an average life span of ca. 10 years (up to 200 years for the freshwater pearl mussel), their potential is significant, considering the fact that nearly 1200 freshwater bivalve species inhabit a large variety of river systems and lakes around the globe (Pfister et al., 2018). Our proof-of-concept work has shown that δ18O values extracted from their shells closely mirror the variance of the measured stream water δ18O – both showing a strong damping of the precipitation signal. In our follow-up study, we leverage prior work by Schöne et al. (2020) on potential links between the NAO index, precipitation isotope signatures and subsequent interdecadal variabilities in reconstructed stream water δ18O signals for three catchments located in Sweden. Using freshwater bivalve shell δ18O as a proxy of stream water δ18O signatures, we hypothesize that interdecadal shifts in atmospheric circulation patterns translate into modifications of δ18O isotope signatures in precipitation and subsequent stream water δ18O signals – the latter potentially revealing changes in young stream water fractions related to fast flow paths. In parallel, we stipulate that the long-term δ18O signal in precipitation can be retrieved from historic records and reanalysis data of climate variables, as well as from synoptic atmospheric circulation classifications. Here we focus on findings gained from a unique dataset of 5 years-worth of sub-daily precipitation O-H isotope data from the Belvaux (L) meteorological station, comprising 1443 rainfall samples. We investigated the links between local climate variables, the rainfall amount, atmospheric circulation patterns, and the precipitation δ18O signal. Our results show (i) an anticipated strong temperature-induced seasonality of the δ18O signal, characteristic for semi-continental sites, (ii) a weak but significant amount effect, (iii) a circulation type-dependant influence of local climate variables on the δ18O signal, and (iv) a high variability at the event-scale – indicating the influence of complex frontal systems and moisture recycling. We leveraged these findings for building a multiple linear regression model, explaining up to 50 percent of the variability of the δ18O signal at sub-daily resolution and closely matching the isotopic signal when applying moving averages over periods within a monthly range.

Targeting the deployment of sustainable human and robotic exploration on the Moon by the end of this decade, there is a pressing need for better understanding the lunar water cycle and the availability of water for ISRU. The O-H isotope signatures in lunar water are key for determining the water origin in the Earth-Moon system and the mechanisms controlling water distribution and redistribution on the Moon. This has profound implications for understanding the Earth-Moon system’s history and the stability and renewability of water deposits.Lunar volatiles are involved in a largely unconstrained and complex system of input, transport, trapping, recycling, and loss. The water origin on the Earth-Moon system remains poorly understood. The δD signatures from Apollo samples and meteorites suggest various contributing reservoirs of different origins for lunar water, and/or secondary processes [1], [2]. The different origins include: i) Magmatic (primordial) [3]; ii) asteroidal/cometary impacts [4], [5]; iii) solar wind H+ [1]; iv) mixed origin (solar wind H+/inclusion within meteorite impact glasses or volcanic glasses [6]).The Roscosmos/ESA Luna 27 mission [7] is one of several international lunar polar missions for in-situ analyses of lunar surface, targeting pressing scientific and industrial knowledge gaps. To interpret the results derived from those polar missions it is critical to understand the extent and nature of any potential water ice loss and related isotope fractionation during the sampling chain.Experimental studies on isotope fractionation during ice sublimation in nonequilibrium conditions are scarce. These studies concluded on different trends: i) no relevant isotope fractionation up to 40% ice mass loss [8], ii) relevant Rayleigh-like fractionation trend [9]. There is no kinetic isotope fractionation model (theoretical or experimental) for ice sublimation in low pressure systems at cryogenic temperatures, which considers the expected physical processes. Thus, the calculation of water ice isotope signatures remains highly uncertain, hindering the assessment of potential lunar water resources and the interpretation of scientific planetary data.Here we present a theoretical isotope fractionation model derived from concepts developed by Criss (1999) [10] and adapted to the physical processes expected under lunar conditions, which will contribute to i) more robust interpretations of water ice behaviour in lunar environment and/or extra-terrestrial and/or extreme terrestrial environments; ii) mission operational planning, data processing, extraction/processing techniques; iii) exploration/exploitation roadmap, space mining business plan, natural resources management. [1] B. M. Jones et al., 2018. Geophys. Res. Lett., 45(20), 10,959-10,967; [2] F. M. McCubbin and J. J. Barnes, 2019. Earth Planet. Sci. Lett., 526; [3] A. E. Saal et al., 2013. Science, 340(6138), 1317–1320; [4] J. P. Greenwood et al., 2011. Nat. Geosci., 4(2), 79–82; [5] J. J. Barnes et al., 2016. Nat. Commun., 7(1), 11684; [6] C. I. Honniball et al., 2021. Nat. Astron., 5(2), 121–127; [7] D. J. Heather et al., 2021. Lunar Planet. Sci. Conf. LPI, Abstract #2111; [8] J. Mortimer et al., 2018. Planet. Space Sci., 158(Feb), 25–33; [9] R. H. Brown et al., 2012. Planet. Space Sci., 60(1), 166–180 [10] R. E. Criss, 1999. USA: Oxford University Press.

The isotopic composition of water (2H/1H and 18O/16O) has been widely used in hydrology, ecology, paleoclimatology and forensic science. However, sampling frequency limits many such studies and there is now a clear need for field-portable mass spectrometer and laser-based spectrometer devices to measure water isotopic composition in-situ and at high temporal resolution. Here we explore the use of Nafion membranes as a potential Membrane Introduction (MI) inlet system for high frequency isotope analysis. As yet, the fractionation behaviour of 2H/1H and 18O/16O isotopic ratios in water transported through Nafion membranes has not been investigated. We quantify this behaviour for water samples with different matrices (organic matter and pollutants) and salinity concentrations across a wide range of isotopic ratios and different membrane thicknesses. Nafion membranes showed no fractionation effects on reported isotope ratios for natural waters. Also no fractionation effects were detected with salinity. Membrane thickness affected slightly the precision and accuracy of the isotopic ratio analysis and our tests showed that thinner Nafion membranes provide better results. However, for samples contaminated with organic matter, the thicker membranes performed better for the 2H/1H isotopic ratio, while for samples contaminated with pollutants, the thicker membranes performed better for the 18O/16O isotopic ratio. Overall, Nafion membranes appear well suited to MI inlet use and our work suggests that the optimal Nafion membrane thickness is 50–150 µm.

The Weierbach experimental catchment (0.45 km²) is the most instrumented and studied sub‐catchment in the Alzette River basin in Luxembourg. Within the last decade, it has matured towards an interdisciplinary critical zone observatory focusing on a better understanding of hydrological and hydro‐geochemical processes. The Weierbach catchment is embedded in an elevated sub‐horizontal plateau, characterized by slate bedrock and representative of the Ardennes Massif. Its climate is semi‐marine, with precipitation being rather evenly distributed throughout the year. Base flow is lowest from July to September, essentially due to higher losses through evapotranspiration in summer. The regolith is composed of Devonian slates, overlaid by Pleistocene slope deposits and entirely covered by forest with 70% deciduous and 30% coniferous trees. Since 2009, the Weierbach has been extensively equipped for continuously monitoring water fluxes and physico‐chemical parameters within different compartments of the critical zone. Additionally, these compartments are sampled fortnightly at several locations to analyze δ¹⁸O and δ²H isotopic composition of water including rainfall, throughfall, soil water, groundwater and streamwater. This ongoing monitoring and sampling programme is used for answering pressing questions related to fundamental catchment functions of water infiltration, storage, mixing and release in forest ecosystems. A recently started research line aims at investigating interactions between forest eco‐hydrosystems with the atmosphere and understanding how catchments will respond to a non‐stationary climate.

Field deployable and portable automatic water samplers are common tools in hydrology. They allow the unattended collection of water samples at predetermined times or triggered by external sensors, reducing personnel labour and costs. Several automated water samplers have been described in the literature. However, the vast majority of these samplers are not commercialised and their use is very limited or restricted to research applications. We can broadly classify these samplers in three groups: in situ samplers, sequential precipitation samplers and siphon automatic samplers. The latest are commonly used by hydrologists, environmental monitoring agencies and in wastewater treatment plants. They were first patented and commercialized in the 1980s by Teledyne-ISCO (Lincoln, NE, USA). They use a peristaltic pump to transfer water into several containers. However, the siphon automatic samplers are large, heavy and typically collect a maximum of 24 samples of 0.5 or 1 L. Here, we present a new automatic water sampler that has a larger and variable storage capacity (from 64 to 400) of smaller containers (from 2 to 40 mL). We argue that for many applications large sample volumes are no longer required due to the improvement of chemical analytic techniques. Standard laboratory storage boxes are filled with standard laboratory containers and directly placed inside the sampler, reducing the processing time once the samplers are back in the laboratory. Containers remain always closed with a septum cap to prevent evaporation. The sampler allows tub rinsing between sample collection to prevent contamination and memory effects. It is portable, has a low-power consumption and is robust for its use under field conditions. We tested the prototype in the laboratory and in the field. We will present the sampler mechanical functioning, the results of the tests (e.g. sample preservation and memory effects) and the user-friendly interface to define sampling schemes.

Diatoms are unicellular eukaryotic algae that are widely distributed in aquatic environments. In particular, their presence is abundant in stream flows, whereas the instance and transport of cells through subsurface flow is controversial. In this work, we study the transport of diatoms through soils by designing laboratory percolation experiments on undisturbed loamy and sandy soil cores. To label diatom tracers and enhance their detectability, we develop protocols to functionalize frustules of purified diatomite and Conticribra weissflogii cultures with rhodamine 123 and 2-(4-pyridyl)-5[4-dimethylaminoethyl-aminocarbamoyl)-methoxy]phenyloxazole, respectively. Labelled diatoms demonstrate good detectability and resilience under weathering agents. We execute percolation experiments for maximum time domains of approximately 600 min where volumes of water up to 3600 ml are deployed on the soil core surface. Under such experimental conditions, fluorescent diatoms are not recovered in samples of percolated material as per microscopy and spectrofluorometry. While further field studies are needed to fully investigate diatom transport, our findings shed new light on the potential of using biotic tracers for surface hydrological processes. Copyright © 2015 John Wiley & Sons, Ltd.

Le principal objectif de ce travail etait d'evaluer la concentration et la dynamique de certains xenobiotiques (hormones, antibiotiques, analgesiques) dans les eaux de surface au Luxembourg. A cet effet, plusieurs points d'echantillonnage ont ete realises dans une station d'epuration, le long de l'Alzette (profil longitudinal) et de facon plus ponctuelle sur un petit bassin d'affluent lors d'episodes de crue. Un deuxieme objectif etait d'extraire tous ces composes en une seule etape sur phase solide (SPE) pour les quantifier en spectrometrie de masse en tandem. Les resultats obtenus montrent essentiellement une forte teneur en ibuprofene et des taux non negligeables en hormones et sulfonamides.