Comprehensive Review and Critical Evaluation of the Half-Life of Tritium

Tritium contents in drinking and surface seawaters before the nuclear power plant planned in Sinop (Türkiye) and their radiological risks on human population

This study aims to determine the background levels of tritium radioisotope in drinking and seawater samples of Sinop province before the nuclear power plant was established in Sinop. In this context, a total of 174 water samples were collected, these are as follows: nine drinking water samples from the Sinop center and districts and 165 seawater samples from the seacoast from Samsun to Kastamonu. Tritium concentrations in the collected water samples were measured by the liquid scintillation counter. The minimum detectable activity for the method used was found to be 1.48 Bq/L. The tritium concentrations of the seawater and drinking water samples were found in the range of Collapse

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MESH Headings

• Adult
• Child
• Infant
• Humans
• Tritium
• Nuclear Power Plants
• Drinking Water
• Turkey

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Affiliation(s)

Serdar Dizman Department of Physics, Faculty of Arts and Sciences, Recep Tayyip Erdogan University, Rize 53100, Türkiye E-mail:
Feyza Zeynep Aşık Institute of Graduate Studies, Recep Tayyip Erdogan University, Rize 53100, Türkiye
Ali Erdem Özçelik Department of Landscape and Architecture (Geomatics Engineer), Faculty of Engineering and Architecture, Recep Tayyip Erdogan University, Rize 53100, Türkiye
Recep Keser Department of Basic Sciences, Faculty of Engineering, Samsun University, Samsun 55100, Türkiye
Filiz Korkmaz Görür Department of Physics, Faculty of Arts and Science, Bolu Abant İzzet Baysal University, Bolu 14100, Türkiye

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Congressional Symmetry: Years Remaining Mirror Years Served in the U.S. House and Senate

Our overarching goal in this paper was to both test and identify applications for a fundamental theorem of replacement-level populations known as the Stationary Population Identity (SPI), a mathematical model that equates the fraction of a population age x and the fraction with x years to live. Since true stationarity is virtually non-existent in human populations as well as in populations of non-human species, we used historical data on the memberships in both chambers of the U.S. Congress as population proxies. We conceived their fixed numbers (e.g., 100 Senators; 435 Representatives) as stationary populations, and their years served and years remaining as the equivalent of life lived and life remaining. Our main result was the affirmation of the mathematical prediction-i.e., the robust symmetry of years served and years remaining in Congress over the approximately 230 years of its existence (1789-2022). A number of applications emerged from this regularity and the distributional patterns therein including (1) new metrics such as Congressional half-life and other quantiles (e.g., 95% turnover); (2) predictability of the distribution of member's years remaining; (3) the extraordinary information content of a single number-the mean number of years served [i.e., derive birth (b) and death (d) rates; use of d as exponential rate parameter for model life tables]; (4) the concept of and metrics associated with period-specific populations (Congress); (5) Congressional life cycle concept with Formation, Growth, Senescence and Extinction Phases; and (6) longitudinal party transition rates for 100% Life Cycle turnover (Democrat/Republican) i.e., each seat from predecessor party-to-incumbent party and from incumbent party-to-successor party. Although our focus is on the use of historical data for Congressional members, we believe that most of the results are general and thus both relevant and applicable to most types of stationary or quasi-stationary populations including to the future world of zero population growth (ZPG).

High-Temperature Intrinsic Defect Chemistry of Li8PbO6 Ceramic Breeding Material

Understanding the intrinsic defect chemistry of tritium breeder materials proposed for use in future fusion reactors is imperative, as certain defects may act as traps leading to retention of tritium in the ceramic matrix. In this paper, we use combined density functional theory simulations with simple thermodynamics to explore the intrinsic defect chemistry of octalithium plumbate (Li8PbO6) as a function of both temperature and oxygen partial pressure. Importantly, we consider vibrational contributions to the energies of the reference states used in the calculations of the defect formation energies. Our results indicate that including these temperature effects can modify the predicted defect chemistry for materials at a high temperature. For Li8PbO6, the defect chemistry is predicted to be dominated by the VLi-1 defect, which will likely act as a trap for tritium. The charge compensating mechanism is predicted to change as a function of the conditions, with the Lii+1 interstitial defect providing compensation at low temperatures and the VO2+ vacancy defect occurring close to the Li2O saturation limit.

Identification of nitrogen pollution sources and transport transformation processes in groundwater of different landforms using C, H, N, and O isotope techniques: an example from the lower Weihe River

Nitrogen pollution in groundwater is an environmental issue of global concern. Identifying nitrogen pollution sources and determining migration and transformation processes are the major ways to prevent and control nitrogen pollution in the groundwater on a regional scale. In this study, groundwater in the lower Wei River was investigated by combining multi-isotope tracing techniques with the SIAR hybrid model (source resolution) to trace the nitrate sources and their contribution rate to nitrogen pollution in groundwater of different geomorphological units, considering types of geomorphology as the units. The multi-isotope tracing technique allows dynamic analysis of nitrate sources, and the combination of this technology can improve the accuracy of nitrogen source traceability. The results indicated that the pH of the water bodies in the study area ranged from 6.83 to 8.01, which is neutral and weakly alkaline. The nitrogen pollution was mainly due to nitrates. The significant factors affecting nitrogen migration in groundwater are the geomorphological type, the chemical characteristics of the groundwater, and the age of the groundwater. Nitrogen migration and transformation processes in the study area were dominated by nitrification, and sources of nitrate pollution were mainly animal manure and domestic sewage (32.6%), followed by atmospheric deposition (26.8%), soil nitrogen (20.9%), and chemical fertilizer (19.7%). The main sources of nitrate in groundwater from river flats, alluvial plains, and loess tableland were animal manure and domestic sewage (43.7%), animal manure and domestic sewage (59.1%), and atmospheric deposition (55.5%), respectively. The result is mainly related to the different structural characteristics of various geomorphic units and the intensity of human activities. This study can provide a theoretical basis for the relevant agencies to develop plans to combat groundwater pollution.

Radiocarbon Dating and Stable Isotopes Content in the Assessment of Groundwater Recharge at Santiago Island, Republic of Cape Verde

The over-exploitation of coastal aquifers has led to seawater intrusion issues in many parts of the globe; this problem, which is associated with water recharge deficit and anthropogenic pollution, represents the main source of groundwater degradation in Santiago Island in the Republic of Cape Verde’s archipelago. Brackish groundwater for agriculture and human consumption is being provided to several areas on Santiago Island as the only type of available water. Chemical and isotopic data obtained in three main groundwater systems were used in the characterization of the groundwater resources and in the identification of the main source responsible for their degradation. The obtained results indicate water–rock interaction as the major process responsible for the groundwater quality reflecting its lithological composition. Carbonatite dissolution can be partially responsible for the calcium increase along the groundwater flow path. Isotopic data (δ2H, δ18O; 3H and 14C) combined with the water chemistry provided a wide characterization of the groundwater recharge and identification of salinization processes (like seawater intrusion and marine aerosols dissolution in different sectors of the island). In the eastern part of Santiago Island, a different isotopic pattern (2H-18O) was observed in the groundwater samples, which was likely ascribed to different climate conditions. Carbon-14 determinations indicate apparent groundwater ages between 3.5 and 5.1 ka BP.

SLONIP—A Slovenian Web-Based Interactive Research Platform on Water Isotopes in Precipitation

Knowledge of how the isotopic composition (i.e., δ2H, δ18O and 3H) of precipitation changes within an individual catchment allows the origins of surface and groundwater to be differentiated and the dynamic characteristics of water within individual water bodies to be traced. This paper presents the Slovenian Network of Isotopes in Precipitation (SLONIP), a research platform that has been operating since April 2020. The SLONIP platform currently contains 2572 isotope data points of monthly composite precipitation from eight locations obtained from various investigations performed since 1981. It also provides information about a sample’s location, analysis, and links to the relevant scientific papers. It also presents the data in numerical and graphical form, including monthly, seasonal, and annual means and local meteoric water lines, all calculated using a Python code made freely available on GitHub. The platform provides essential information for geographically, climatologically, and geologically diverse regions like Slovenia and can help improve our understanding of the water cycle on a local and regional scale.

Thermodynamics and phase stability of Li8XO6octalithium ceramic breeder materials (X= Pb, Ce, Ge, Zr, Sn)

Octalithium ceramics with their high stoichiometric concentration of lithium offer exceptionally high tritium breeding ratios in comparison with other candidate breeder materials for tokamak fusion reactors, this is especially true with incorporation of a neutron multiplier into the crystal structures. Although, there are concerns surrounding the stability of these materials at operational temperatures. Therefore in this paper, we explore the thermodynamic properties of a selection of candidate octalithium ceramics in low and high temperature regimes (0-1200 K) using density functional perturbation theory. Enthalpies as well as Gibbs formation energies were used to distinguish candidates which may or may not be susceptible to degradation.

Deuterium Tracer for Accurate Online Lube-Oil-Consumption Measurement: Stability, Compatibility and Tribological Characteristics

Because of the impact of lubrication on the efficiency and the lifecycle cost and emissions, the lubricating-oil consumption (LOC) is one of the key indicators in the research and development of internal combustion engines. State-of-the-art methods for LOC measurement are based on the use of a certain tracer to track the oil consumption. However, all of the currently available tracers have their downsides (e.g., the use of a radioactive tracer, corrosive emissions, etc.). Therefore, in the course of this research project, a new tracer substance that is based on a stable nonradioactive isotope of hydrogen—deuterium—was developed and tested thoroughly. The LOC is monitored by a hydrogen/deuterium isotopic ration in the exhaust gas by using an isotopic water analyzer. Tribologically important properties, such as the viscosity, stability, and compatibility of the tracer were investigated by laboratory experiments by using several tools, such as infrared spectroscopy, gas chromatography, thermogravimetry, etc. The properties relevant to the applicability of the method, such as the accuracy and the reproducibility, were investigated by engine test-bench experiments. Finally, long-term stability tests of the tracer were conducted with a field test.

Quality control of image sensors using gaseous tritium light sources

We propose a practical method for radiometrically calibrating cameras using widely available gaseous tritium light sources (betalights). Along with the gain (conversion factor) and read noise level, the predictable photon flux of the source allows us to gauge the quantum efficiency. The design is easily reproducible with a 3D printer (three-dimensional printer) and three inexpensive parts. Suitable for common image sensors, we believe that the method has the potential to be a useful tool in microscopy facilities and optical laboratories alike. This article is part of the theme issue 'Super-resolution structured illumination microscopy (part 2)'.

Temporal and spatial assessment of groundwater contamination with nitrate using nitrate pollution index (NPI), groundwater pollution index (GPI), and GIS (case study: Essaouira basin, Morocco)

Groundwater aquifers in Morocco's coastal regions are under serious threat as a result of climate change. This study was conducted to evaluate and map the quality of water resources, by evaluating the level of pollution of the groundwater in the Meskala-Ouazzi sub-basin, a coastal area of Essaouira based on the physico-chemical analysis of 58 samples using a geographic information system (GIS) technique, analytical analysis, nitrate pollution index (NPI), and groundwater pollution index (GPI). The diagram piper of the study area is dominated by Cl-Ca-Mg, Cl-Na, HCO3-Ca-Mg, and SO4-Ca types. The concentrations of nitrate ranged from 2 to 175 mg/L. It was discovered that 22% of the groundwater samples had nitrate amounts greater than the World Health Organization's recommended maximum allowable level of 50 mg/L. The NPI ranged between - 0.9 and 7.8. According to the classification of NPI, 44.8% of the total groundwater samples represent clean water, indicating that the groundwater in the study area is suitable for irrigation. GPI values ranging from 0.6 to 3.7, with an average of 1.7, identifies 37.9% of all groundwater samples as low polluted. The inverse distance weighting (IDW) approach was used to generate a spatial distribution map, which indicates that appropriate groundwater is present in the sub-upstream basin's part. Overall, the forte concentration in groundwater samples detected in western and central areas showed that the nitrate originated from large amounts of nitrogen fertilizer used by humans in agricultural activities during periods of irrigation. The low tritium (δ3H) content shows that the aquifer recharge is stale water and excessive use of fertilizers leads to groundwater pollution faster over time.

Recent Developments for the Deuterium and Tritium Labeling of Organic Molecules

Organic compounds labeled with hydrogen isotopes play a crucial role in numerous areas, from materials science to medicinal chemistry. Indeed, while the replacement of hydrogen by deuterium gives rise to improved absorption, distribution, metabolism, and excretion (ADME) properties in drugs and enables the preparation of internal standards for analytical mass spectrometry, the use of tritium-labeled compounds is a key technique all along drug discovery and development in the pharmaceutical industry. For these reasons, the interest in new methodologies for the isotopic enrichment of organic molecules and the extent of their applications are equally rising. In this regard, this Review intends to comprehensively discuss the new developments in this area over the last years (2017-2021). Notably, besides the fundamental hydrogen isotope exchange (HIE) reactions and the use of isotopically labeled analogues of common organic reagents, a plethora of reductive and dehalogenative deuteration techniques and other transformations with isotope incorporation are emerging and are now part of the labeling toolkit.

Hydrogen adsorption process in nanocrystalline nuclear graphite

Kinetics and mechanism of hydrogen adsorption in as-obtained and ground nuclear graphite Wendelstein 7-X are examined. In the first time interval the adsorption process is determined by dissociation of the hydrogen molecule, occurring at the outer surface and in open micropores of nuclear graphite particles. However, in the second time interval, the slowest step in the hydrogen adsorption is inter-granular and inter-crystallite diffusion in nanopores of graphite. The X-ray analysis shows, that grinding of as-obtained nuclear graphite results in finer particles with finer nanocrystals and larger density of opened pores and carbon reactive sites. The capacity and rate of adsorption increase with comminution of nuclear graphite particles and adsorbed hydrogen does not substantially alter the microstructure of nuclear graphite.

Atmospheric washout of 35S during single rain events - Implications for 35S sampling schemes

Cosmogenic radiosulfur (³⁵S; half-life: 87.4 days) is transferred with the rain to the groundwater (as ³⁵SO₄^2-) and can be used as residence time tracer for the detection of sub-yearly groundwater residence times. Due to the distinct but non-regular annual ³⁵S pattern in precipitation, related data evaluation requires consideration of a³⁵S input function that is based on representative rain samples. While minor rain events can easily be sampled quantitatively and hence representatively, a long-lasting rain event may get documented by a sample that represents only a certain sequence of the event, thus potentially resulting in a³⁵S activity concentration that might not be representative. With the aim to examine the magnitude of temporal variations of the ³⁵S activity concentration in rain during long-lasting rain events, we present and discuss two related exemplary ³⁵S time series. Furthermore, we evaluate the applicability of the parameters total sulfate and electrical conductivity (EC), both detected in rainwater as easily attainable ³⁵S proxies. The results of the study show (i) that the ³⁵S activity concentration may vary substantially during long-lasting rain events due to atmospheric migration processes and aerosol washout and (ii) that neither sulfate nor EC are suitable as ³⁵S proxies due to the different origin of ³⁵S on the one hand and sulfate/EC on the other. Hence, for the determination of a³⁵S activity concentration that is representative for a long-lasting rain event ³⁵S analyses of an adequate number of sub-samples cannot be avoided.

Health effects triggered by tritium: how do we get public understanding based on scientifically supported evidence?

The Commission for 'Corresponding to Radiation Disaster of the Japanese Radiation Research Society' formulated a description of potential health effects triggered by tritium. This was in response to the issue of discharging water containing tritium filtered by the Advanced Liquid Processing System (ALPS), generated and stored in Fukushima Daiichi Nuclear Power Station after the accident. In this review article, the contents of the description, originally provided in Japanese, which gives clear and detailed explanation about potential health effects triggered by tritium based on reliable scientific evidence in an understandable way for the public, were summarized. Then, additional information about biochemical or environmental behavior of organically bound tritium (OBT) were summarized in order to help scientists who communicate with general public.

Comparative evaluation of 2H- versus 3H-based enrichment factor determination on the uncertainty and accuracy of low-level tritium analyses of environmental waters

Analysis of low-level tritium (³H) in environmental waters requires pre-concentration using electrolytic enrichment prior to decay counting. Accurate and precise electrolytic enrichment factors (EF) are required to determine the sample's environmental ³H concentration. Two methods are used to determine EFs: i) the Spike Proxy Method (SPM) and ii) the Deuterium Method (DM) with each having several modalities. We conducted a comparative assessment of four EF strategies using 250 mL and 500 mL electrolytic enrichment of three low-level ³H proficiency water standards (0.5-7 TU) to see which strategy gave the most accurate ³H results based on z- and Zeta-scores. Our comparative evaluation revealed the DM offers consistently superior ³H results, with more precise EF determinations compared to the three SPM strategies. The DM gave the best z-scores with an EF relative combined uncertainty of about 0.5‰ and a negligible contribution to the overall uncertainty budget due to the EF determination. Moreover, the DM can improve productivity by eliminating the spike and gravimetric procedures from routine analyses and can give rapid cell enrichment performance feedback prior to decay counting. We recommend low-level tritium laboratories consider adopting the DM into their ³H sample enrichment and analysis operations.

Tritium concentrations and consequent doses in bottled natural and mineral waters sold in Turkey and Azerbaijan

In this study, tritium levels in commercially sold bottled natural and mineral waters in Turkey and Azerbaijan were determined. Tritium measurements were performed using Liquid Scintillation Counter (PerkinElmer TriCarb 2910 TR). 16 natural and 11 mineral samples from Turkey and 7 natural and 8 mineral samples from Azerbaijan, for a total of 42 commercially sold water samples were analyzed. The Minimum Detectable Activity (MDA) value for the method used was found as 1.69 Bq L^-1. In total, 7 of the natural water samples and 8 of the mineral water samples were found to be below the MDA value. The average activity concentrations in natural and mineral water samples were found as 2.23 ± 0.90 Bq L^-1 and 2.51 ± 0.90 Bq L^-1 for Turkey and 2.69 ± 0.91 Bq L^-1 and 2.43 ± 0.89 Bq L^-1 for Azerbaijan, respectively. In addition, annual effective dose rates and lifetime cancer risk values for the water samples were calculated. These radiological parameters were compared with the values recommended by international organizations. The results demonstrated that consumption by humans of the studied waters would not constitute any health risks in terms of tritium.

Complexity of groundwater age mixing near a seawater intrusion zone based on multiple tracers and Bayesian inference

Aquifer flow systems near seawater interfaces can be complicated by density-driven flows and the formation of stagnation zones, which inevitably introduces uncertainty into groundwater age-dating. While age-dating has proved effective to understand the seawater intrusion and aquifer salinization process in coastal aquifers, further efforts are needed to propagate model and data uncertainty to the uncertainty associated with the inferred age distributions. This study was performed in a coastal aquifer located close to the Yellow Sea, South Korea, where there is a decreasing trend of groundwater levels due to recent heavy exploitation, raising a warning of induced seawater intrusion. We inferred the groundwater age distributions in wells around the intrusion zone and estimated the uncertainty associated with the inference based on multiple age tracers including ³H, tritiogenic ³He, radiogenic ⁴He, CFC-11, CFC-12 and CFC-113 using Bayesian inference. We examined various models representing the age distributions including traditional parametric Lumped Parameter Models (LPMs) and two non-parametric "shape-free" models. The results showed that the mean ages at the study site ranged from 10.9 to 522.5 y. Complex, multimodal distributions of ages occurred near a seawater intrusion area and upland recharge zones, implying converging paths of a wide range of different ages in those regions. In particular, the age distributions estimated near the seawater intrusion interface were characterized by heavy-tailed mixing structures with elevated concentrations of ⁴He. This likely indicates density-driven upward flow at the seawater intrusion interface, forcing old groundwater rich in ⁴He into the shallow aquifer. The Bayesian inference estimated large uncertainties particularly for the old age distributions, which was attributed partly to the gradual accumulation of ⁴He in groundwater. The Bayesian inference improved understanding of flow dynamics at a complex seawater interface and identified opportunities to further reduce uncertainty of old water age estimates that characterize upwelling groundwater near the interface.

Coastal Aquifer Salinization in Semi-Arid Regions: The Case of Grombalia (Tunisia)

Groundwater resources are facing increasing pressure especially in semi-arid regions where they often represent the main freshwater resource to sustain human needs. Several aquifers in the Mediterranean basin suffer from salinization and quality degradation. This study provides an assessment of Grombalia coastal aquifer (Tunisia) based on multidisciplinary approach that combines chemical and isotopic (δ2H, δ18O, 3H, 14C and δ13C) methods to characterize the relation between groundwater quality variation and aquifer recharge. The results indicate that total dissolved solids exceed 1000 mg/L in the most of samples excepting the recharge area. In addition to water–rock interaction, evaporation and nitrate pollution contributing to groundwater mineralization, the reverse cation exchange process constitute an important mechanism controlling groundwater mineralization with enhancing risk of saltwater intrusion. Environmental isotope tracers reveal that groundwater is evolving within an open system to close system. A significant component of recent water that is recharging Grombalia aquifer system is confirmed by applying correction models based on the δ13C values and 14C activities and tritium contents. However, this recharge, which is mainly associated to the return flow of irrigation water, contributes to the groundwater salinization, especially for the shallow aquifer.

Origin and percolation times of Milandre Cave drip water determined by tritium time series and beryllium-7 data from Switzerland

Early observations of the tritium (³H) activity in precipitation from Switzerland started in 1967 in Bern and a monitoring program with improved analytical techniques was carried out between 1971 and 2009. Between 2012 and 2015, we performed tritium analyses on daily precipitation samples from north-western Switzerland to better constrain the tritium variability. We also collected waters dripping inside Milandre Cave (Jura Mountains) with a 4-6 months' resolution in order to estimate the age of the drip water, which is mandatory to interpret the high-resolution speleothem (cave carbonate deposits) records. Over the monitoring period, the mean tritium concentration in the daily precipitation samples was approximately 8.7 ± 4.7 TU with distinct seasonality showing higher values in spring and summer (from April-May to August-September). The similarity in trends with the other cosmogenic radionuclide beryllium-7 (⁷Be) suggests that, for the study site, tritium in precipitation essentially originates from stratospheric input in spring. In winter, precipitation dynamics with increasing moisture originating from the Atlantic and diluted during transport contribute to low values close to the Atlantic background. In cave drip water, the depleted activity level of tritium indicates a relatively long percolation time from the surface to the cave of several years. A residual superimposed short tritium variability provides evidence for the occurrence of fast flowing water paths. The contribution from both components were quantified based on a two-component lumped parameter-mixing model. Finally, we show that tritium concentrations in cave drip water are linked to the moisture origin and atmospheric transport pathways.

Proficiency testing of 78 international laboratories measuring tritium in environmental waters by decay counting and mass spectrometry for age dating and water resources assessment

RATIONALE

Tritium (³ H) is an important hydrological tracer that has been commonly used for over 60 years to evaluate water residence times and water dynamics in shallow/recent groundwaters, streams, lakes and the ocean. We tested the analytical performance of 78 international laboratories engaged in low-level ³ H assays for water age dating and monitoring of environmental waters.

METHODS

Seven test waters were distributed by the IAEA to 78 international tritium laboratories. Set 1 included a tritium-free groundwater plus three ultra-low ³ H samples (0.5-7 TU) for meeting groundwater dating specifications. Set 2 contained three higher ³ H-content samples (40-500 TU) suitable for testing of environmental monitoring laboratories.

RESULTS

Seventy of the laboratories used liquid scintillation counting with or without electrolytic enrichment, seven utilized ³ He accumulation and mass spectrometry, and one used gas-proportional counting. Only ~50% of laboratories demonstrated the ability to generate accurate ³ H data that was precise enough for water age dating purposes.

CONCLUSIONS

The proficiency test helped identify recurrent weaknesses and potential solutions. Strategies for performance improvements of ³ H laboratories include: (a) improved quantification of ³ H detection limits and analytical uncertainty, (b) stricter quality control practices in routine operations along with care and recalibration of ³ H standards traceable to primary NIST standards, (c) annual assessment of tritium enrichment factors and instrumental performance, and (d) for water age dating purposes the use of electrolytic enrichment systems having the highest possible ³ H enrichment factors (e.g. >50×).

Graphene Oxide Membranes for Isotopic Water Mixture Filtration: Preparation, Physicochemical Characterization, and Performance Assessment

There is an increasing demand for nuclear reactors, driven by the global need for low CO₂ producing energy sources. The use of light (H₂O) or heavy water (D₂O) in a nuclear reactor environment produces radioactive tritiated heavy (HTO, DTO) water as an inevitable contaminant. Considering the need for tritiated water removal and also the high commercial value of purified water isotopes, technologies that can efficiently separate isotopic mixtures of water in nuclear reactors are highly desirable. This study presents an experimental approach for producing graphene oxide (GO) membranes and assessing their performance in the filtration of isotopic water mixtures. Specifically, using D₂O/H₂O mixtures as model systems, we investigate the effect of physicochemical properties of GO, as well as membrane preparation conditions on membrane filtration efficiency. We find that membranes assembled using larger GO platelets of lower oxidation level generally exhibit higher deuterated water (HDO, D₂O) rejection and filtrate flux. Moreover, membrane preparation conditions have a strong impact on the interlayer space between stacked GO nanoplatelets in the membrane, hence as a direct effect on filtration performance. Our experimental results also show a strong, nonmonotonic dependence of separation performance on operating temperature, as well as the existence of local temperature optima. Our work provides guidelines for simple and scalable preparation of GO membranes with very good mechanical stability, capable of achieving efficient separation of isotopic water.

Regional Isotopic Signatures of Groundwater in Croatia

Tracer methods are useful for investigating groundwater travel times and recharge rates and analysing impacts on groundwater quality. The most frequently used tracers are stable isotopes and tritium. Stable isotopes of oxygen (δ18O) and hydrogen (δ2H) are mainly used as indicators of the recharge condition. Tritium (3H) is used to estimate an approximate mean groundwater age. This paper presents the results of an analysis of stable isotope data and tritium activity in Croatian groundwater samples that were collected between 1997 and 2014 at approximately 100 sites. The composition of the stable isotopes of groundwater in Croatia originates from recent precipitation and is described using two regional groundwater lines. One of them is applied to groundwater accumulated in the aquifers in the Pannonian part of Croatia and the other is for groundwater accumulated in the Dinaric karst of Croatia. The isotope content shows that the studied groundwater is mainly modern water. A mix of sub-modern and modern water is mostly accumulated in semi-confined porous aquifers in northern Croatia, deep carbonate aquifers, and (sub)thermal springs.

New electrolytic enrichment system for tritium determination in water research institute in Bratislava and IT'S first results of tritium activity in precipitation

The method of tritium activity measurements by electrolytic enrichment in combination with liquid scintillation counting is well known for many years. In the Water Research Institute in Bratislava was this system employed since the 60-ties of the 20th century. In 2018 the laboratory of radiochemistry of Water Research Institute obtained a new electrolytic enrichment system with higher enrichment factor (varying from 9 to 22, depending on the total ampere-hours used). The enrichment factor of the previous system was about 6. Complementary to the new system, also the new LCS counter Quantulus GCT 6220 was added. This spectrometer has active background suppression function (Guard Compensation Technology - GCT) and for the tritium measurement the background counts decreased from cca. 9 cpm (for Tricarb 2900 TR) to approximately 1 cpm. To demonstrate the capabilities of this system, we present results of the tritium concentration in precipitations during the period from May 2016 to May 2019. The seasonal variations of tritium activities in precipitation are observed, with maximum values in spring season and minimum in winter. Additionally, selected tritium activities from the extensive monitoring of river waters in Slovakia are presented.

Long-Term Isotope Records of Precipitation in Zagreb, Croatia

The isotope composition of precipitation has been monitored in monthly precipitation at Zagreb, Croatia, since 1976. Here, we present a statistical analysis of available long-term isotope data (3H activity concentration, δ2H, δ18O, and deuterium excess) and compare them to basic meteorological data. The aim was to see whether isotope composition reflected observed climate changes in Zagreb: a significant increase in the annual air temperature and larger variations in the precipitation amount. Annual mean δ18O and δ2H values showed an increase of 0.017‰ and 0.14‰ per year, respectively, with larger differences in monthly mean values in the first half of the year than in the second half. Mean annual d-excess remained constant over the whole long-term period, with a tendency for monthly mean d-excess values to decrease in the first half of the year and increase in the second half due to the influence of air masses originating from the eastern Mediterranean. Changes in the stable isotope composition of precipitation thus resembled changes in the temperature, the circulation pattern of air masses, and the precipitation regime. A local meteoric water line was obtained using different regression methods, which did not result in significant differences between nonweighted and precipitation-weighted slope and intercept values. Deviations from the Global Meteoric Water Line GMWL (lower slopes and intercepts) were observed in two recent periods and could be explained by changes in climate parameters. The temperature gradient of δ18O was 0.33‰/°C. The tritium activity concentrations in precipitation showed slight decreases during the last two decades, and the mean A in the most recent period, 2012–2018, was 7.6 ± 0.8 Tritium Units (TU).

Medical Treatment and Dose Estimation of a Person Exposed to Tritium

In this study, we aimed to investigate the damaging effects and clinical therapy of internal contamination with tritium to provide information and gain experience for medical treatments in case of an emergency due to a nuclear accident. Histories were taken by several doctors who observed and recorded the clinical symptoms of the patient described herein. The general health situation was evaluated by laboratory and equipment analyses. Tritium concentrations in the urine were estimated according to relevant standards during the monitoring period using a liquid scintillation counting method. Clinical observation revealed that the patient had symptoms of mild asthenia and sleep disorder with improvement after appropriate treatment. The last committed effective dose was determined through measurement of the urine tritium concentration and dose estimation and was estimated to be 0.123 mSv; the total effective dose was 14.536 mSv. The medical treatment and dose estimation in this patient with tritium contamination were successful and can provide a reference for similar cases in the future.

Noble gas composition and 3H/3He groundwater ages in the Gardermoen Aquifer, Norway: Improved understanding of flow dynamics as a tool for water management

This study presents a novel data set of noble gas compositions and ³H/³He measurements in groundwater samples from the Gardermoen Aquifer in Norway. The motivation was to test the applicability of noble gases as tracers in constraining the conceptual model and improve the understanding of deeper parts of the aquifer. Flow models have been used as tools for water resource management at the Oslo international airport, which is located within the aquifer recharge area, and bordering towards protected nature reserves. Current models are well calibrated for upper parts of the aquifer, and in line with new noble gas data. However, in some areas large inverse pressure gradients are observed. Interpretation of noble gas data proved useful in understanding these pressure deviations as a result of water retention in low permeability layers of clay and silt. Noble gas composition, isotopic ratios and tritium water ages define different water "types". Mixing along flow path or as a consequence of pumping were found to be indicators of geological heterogeneity, and were used to evaluate degree of flow separation as well as vertical versus horizontal flux. ³H/³He water ages varied between 0 and 50 years, increasing with depth below the groundwater table and along flow paths. These data indicate lower vertical permeability and longer residence times in deeper parts of the aquifer than suggested by previous models. This study is of high relevance in the continued water resource management scheme at Gardermoen, for improving existing models and in sound, long-term monitoring of groundwater, ensuring sustained influx towards sensitive biotopes.

Dual in-aquifer and near surface processes drive arsenic mobilization in Cambodian groundwaters

Millions of people globally, and particularly in South and Southeast Asia, face chronic exposure to arsenic from reducing groundwaters in which. Arsenic release to is widely attributed largely to reductive dissolution of arsenic-bearing iron minerals, driven by metal reducing bacteria using bioavailable organic matter as an electron donor. However, the nature of the organic matter implicated in arsenic mobilization, and the location within the subsurface where these processes occur, remains debated. In a high resolution study of a largely pristine, shallow aquifer in Kandal Province, Cambodia, we have used a complementary suite of geochemical tracers (including ¹⁴C, ³H, ³He, ⁴He, Ne, δ¹⁸O, δD, CFCs and SF₆) to study the evolution in arsenic-prone shallow reducing groundwaters along dominant flow paths. The observation of widespread apparent ³H-³He ages of <55years fundamentally challenges some previous models which concluded that groundwater residence times were on the order of hundreds of years. Surface-derived organic matter is transported to depths of >30m, and the relationships between age-related tracers and arsenic suggest that this surface-derived organic matter is likely to contribute to in-aquifer arsenic mobilization. A strong relationship between ³H-³He age and depth suggests the dominance of a vertical hydrological control with an overall vertical flow velocity of ~0.4±0.1m·yr^-1 across the field area. A calculated overall groundwater arsenic accumulation rate of ~0.08±0.03μM·yr^-1 is broadly comparable to previous estimates from other researchers for similar reducing aquifers in Bangladesh. Although apparent arsenic groundwater accumulation rates varied significantly with site (e.g. between sand versus clay dominated sequences), rates are generally highest near the surface, perhaps reflecting the proximity to the redox cline and/or depth-dependent characteristics of the OM pool, and confounded by localized processes such as continued in-aquifer mobilization, sorption/desorption, and methanogenesis.

Water, nitrate and atrazine transfer through the unsaturated zone of the Chalk aquifer in northern France

The water quality of the Chalk aquifer is degrading due to fertilizers and pesticides use which are classified as toxic to public health. The study aims to provide a better understanding of the transfer processes in the unsaturated zone of the Chalk aquifer using different environmental tracers (nitrate, atrazine and tritium). The study was conducted in an underground quarry in northern France (St. Martin le Noeud). The quarry provides direct access to the lower part of the unsaturated zone of the Chalk at a depth of 18-30 m. Fifteen sites throughout the quarry display percolation directly from the unsaturated zone. Since percolation intensity is heterogeneous at one site, a comparison was made between the variation of geochemical properties of ten samples from one site and the spatial variation of samples from 15 sites throughout the quarry. Using the Siegel-Tukey and Wilcoxon tests, we found that the variation between the sites is higher than the variation within one site. Therefore, one percolation sample can be used to represent one site. The transfer time of nitrate and atrazine is estimated based on its use in the cultivated fields. Pore water with no contamination indicates water infiltrated before the use of contaminants at the surface, and pore water with a high concentration of contaminants indicates water infiltrated during the use of contaminants at the surface. The transfer time of water molecules is estimated using the time series of tritium. Transfer velocities were computed for each environmental tracer (nitrate, atrazine and tritium) by dividing the estimated transfer time by the depth of each site. Two transfer velocity ranges are determined: (1) <0.32 ± 0.02 m/year and (2) between 0.72 ± 0.14 and 2.15 ± 0.43 m/year, showing most water transfer through the matrix but also a mixture of water with different velocities.

Monitoring of tritium concentration in Hanoi's precipitation from 2011 to 2016

Tritium is a radioisotope of hydrogen and a component of the water molecule. It is a marker for reservoirs such as the stratosphere, troposphere, and oceans involved in the hydrological cycle. Tritium monitoring is an essential research tool in hydro-climate, dating for water and recharge groundwater. The Isotope Hydrology Laboratory has collected monthly precipitation samples in Hanoi for tritium concentration analysis. This paper reports the tritium concentrations in precipitation in the city from 2011 to 2016. The results show that monthly tritium concentration reached a maximum of 7.07 Tritium Units (TU) in August 2011. The mean annual tritium concentration stabilized from 2.03 to 3.36 TU. It suggests that tritium in monitoring station precipitation is predominantly natural. The seasonal variation trend of ³H in precipitation at the Hanoi station is similar to those monitored at the Hong Kong station. The correlation of tritium and rainfall was also estimated.

Dispersion and removal characteristics of tritium originated from nuclear power plants in the atmosphere

The activities of tritium in water-vapor (n = 649) and precipitation (n = 2404) samples were measured from 1998 to 2015 around the Wolsong nuclear power plant (NPP) site where four pressurized heavy water reactors and two pressurized water reactors operated. The activity concentrations of tritium in the water-vapor and precipitation samples were in the ranges of 2.2-2200 Bq/L and 0.3-1090 Bq/L, respectively. The concentrations of tritium in the water-vapor in spring were approximately 7 times higher than those in fall and winter, mainly owing to the wind directions at the power plant location. The annual geometric mean activities of tritium in the water-vapor and precipitation samples varied within 56% and 83% from the average, respectively, depending primarily on the annual discharge amount of tritium to the atmosphere. The activities of tritium in the water-vapor and precipitation samples rapidly decreased away from the power plant. Approximately 0.5-30% of tritium discharged from the NPP site was removed by precipitation to the ground within an area with a radius of 30 km from the NPP site, which linearly depended on the precipitation amount. Our results suggest that the wind direction and precipitation, in addition to the amount of discharge, are important factors that control the tritium concentrations in air near the NPP site.

Distribution of environmental tritium in rivers, groundwater, mine water and precipitation in Goa, India

Tritium concentration in rivers, groundwater, precipitation and mine pits water, all over Goa state was characterized to find out spatial and temporal variability of tritium. Twenty four water samples were collected during pre-monsoon and post-monsoon and analyzed for their tritium concentration. The mean tritium concentration in surface and sub-surface hydrosphere is 2.5 (±0.6) TU. The mean concentration of tritium in rivers, groundwater, mines pits water and rain water are 2.9 (±0.5) TU, 1.95 (±0.5) TU, 2.5(±0.3) TU and 3.1(±0.1) TU respectively. The tritium distribution in all the samples shows modern precipitation (post-1950) component in surface and sub-surface hydrosphere of Goa. The HYSPLIT4.0 air mass trajectory model and atmospheric circulation pattern suggest that the moisture origin was from the Arabian Sea and this low tritium moisture is diluting the tritium concentration of surface hydrosphere near the coastal area. The tritium concentration in surface hydrosphere shows more and more enrichment as one move inland (i.e. away from the coast). Significant seasonal change is observed in the surface hydrosphere. The pre-monsoon samples showed higher tritium concentration than post-monsoon samples. This may be due to high rate of re-evaporation of water and a reduction in the supply of oceanic moisture during the summer (pre-monsoon).

Characterization of mechanisms and processes controlling groundwater salinization in coastal semi-arid area using hydrochemical and isotopic investigations (Essaouira basin, Morocco)

The aquifer system of Essaouira basin is recognized as one of the most important aquifers in Morocco. The purpose of this study is to highlight the origin and the mechanisms responsible for the salinization of this aquifer system, thus based on the two hydrogeochemical and isotopic approaches. The results indicate that the central and downstream parts are dominated by the facies Cl-Ca-Mg and SO₄-Ca-Mg with the dominance of the first facies, while the facies Cl-Ca-Mg, SO₄-Ca-Mg, and HCO₃-Ca-Mg dominate the upstream part with the dominance of the list facies. Hydrochemical approach shows that the groundwater mineralization in the study area is controlled by (i) the ion exchange phenomenon, under the marine intrusion and (ii) the dissolution of carbonate minerals (calcite, dolomite, and aragonite) and evaporate minerals (halite, gypsum, and anhydrite). High levels of NO₃ would come from domestic pollutants, including livestock waste during water withdrawal. The isotopic method shows (i) aquifers recharge in the study area is provided by Atlantic precipitation without significant evaporation, (ii) the presence of recent water (after nuclear tests) and other (before nuclear tests), and (iii) various recharge altitudes from 300 to 1150 m asl. However, this investigation provides a foundation for effective groundwater management and effective mitigation of aquifer impacts.

Assessing Decadal Trends of a Nitrate-Contaminated Shallow Aquifer in Western Nebraska Using Groundwater Isotopes, Age-Dating, and Monitoring

Shallow aquifers are prone to nitrate contamination worldwide. In western Nebraska, high groundwater nitrate concentrations ([NO3−]) have resulted in the exploration of new groundwater and nitrogen management regulations in the North Platte Natural Resources District (NPNRD). A small region of NPNRD (“Dutch Flats”) was the focus of intensive groundwater sampling by the United States Geological Survey from 1995 to 1999. Nearly two decades later, notable shifts have occurred in variables related to groundwater recharge and [NO3−], including irrigation methods. The objective of this study was to evaluate how changes in these variables, in part due to regulatory changes, have impacted nitrate-contaminated groundwater in the Dutch Flats area. Groundwater samples were collected to assess changes in: (1) recharge rates; (2) biogeochemical processes; and (3) [NO3−]. Groundwater age increased in 63% of wells and estimated recharge rates were lower for 88% of wells sampled (n = 8). However, mean age and recharge rate estimated in 2016 (19.3 years; R = 0.35 m/year) did not differ significantly from mean values determined in 1998 (15.6 years; R = 0.50 m/year). δ15N-NO3− (n = 14) and dissolved oxygen data indicate no major changes in biogeochemical processes. Available long-term data suggest a downward trend in normalized [NO3−] from 1998 to 2016, and lower [NO3−] was observed in 60% of wells sampled in both years (n = 87), but median values were not significantly different. Collectively, results suggest the groundwater system is responding to environmental variables to a degree that is detectable (e.g., trends in [NO3−]), although more time and/or substantial changes may be required before it is possible to detect significantly different mean recharge.

The distribution of tritium in aquatic environments, Lithuania

The aim of this study is to investigate mobile radionuclide tritium (³H or T) activity dynamics in aquatic environments related to Ignalina NPP (INPP) site and water bodies located in remote areas unaffected by the INPP. The ³H excess in the INPP environment was analyzed and compared to the variable ³H background level over the period of operation of the INPP (end of 1983 - end of 2009) and during the initial stage of decommissioning (2010-2017). ³H in the INPP vicinity has been studied in the water of artificial channels related to operation of the INPP and site drainage, in natural surface water bodies and, at a smaller scale, in unconfined groundwater. This study presents an extensive ³H data set extending back to 1980, i.e. before INPP operation started. To assess the contribution of global sources to ³H dynamics, monthly precipitation was also studied, along with water from the Baltic Sea, Curonian Lagoon and Nemunas River were studied as well, all three of these located in the Lithuanian maritime zone. The ³H activity concentration in water was measured using liquid scintillation counting (LSC) techniques (direct counting and counting after enrichment). During the period of INPP operation, ³H from liquid effluent could be clearly observed in discharge channels, occurring in rather low diluted conditions, as well as in Lake Druksiai, the cooling basin, at an even more diluted level. The highest ³H activity concentration in Lake Druksiai was observed in 2003 and reached 201.3 ± 1.3 TU at a time when ³H activity concentrations in background water bodies was 9.2 ± 3.5 TU. After the closure of the INPP, the ³H liquid effluent rate reduced by approximately two orders of magnitude (from 10¹² Bq in 1991 to 10¹⁰ Bq in 2016) and when decommissioning activity commenced then the ³H activity concentration fell to that approaching the background level (19-27 TU) that can still be observed in industrial discharge and rainwater drainage channels. ³H as a result of leakage from the INPP can be observed in groundwater only in direct proximity to the INPP site near the radioactive waste storage zone.

Palladium(II)-Mediated C-H Tritiation of Complex Pharmaceuticals

Tritium-labeled molecules are critical tools for elucidating the binding and metabolic properties of bioactive compounds, particularly during pharmaceutical discovery. Direct tritiation of inert C-H bonds with T₂ gas is an ideal approach for tritium labeling, but significant gaps remain for direct tritiation of structurally complex molecules with diverse functional groups. Here we report the first application of palladium(II) C-H activation chemistry for tritiation with T₂ gas. This practical transformation exhibits novel substrate scope and greater functional group tolerance compared to previous state of the art tritiation methods, and has been applied to directly tritiate 9 complex pharmaceuticals and an unprotected dipeptide. The isolated tritium-labeled products exhibit >15 Ci mmol^-1 specific activity, exceeding the typical requirements for application in studies of molecular interaction and metabolism.

Radiobiological effects of tritiated water short-term exposure on V79 clonogenic cell survival

PURPOSE

We set out to improve the accuracy of absorbed dose calculations for in vitro measurements of the relative biological effectiveness (RBE) of tritiated water (HTO) for the clonogenic cell survival assay, also considering the influence of the end-of-track linear energy transfer (LET) of low-energy electrons.

MATERIALS AND METHODS

The COmputation Of Local Electron Release (COOLER) program was adopted to investigate the cell geometry and the tritium full beta-decay spectrum impact on the S-values and subsequently on the RBE of HTO for clonogenic cell survival at similar high dose rates (HDR).

RESULTS

S-values for cells growing in suspension are usually comparable to those for adherent cells. RBEs calculated at the 10% survival fraction through the use of the average energy are almost similar to those obtained with the beta-spectrum. For adherent cells, an RBE of 1.6 was found when HTO cell survival curves were compared to acute γ-ray exposures. Irrespective of the geometrical configuration, the RBE was 2.0 when the comparison was made with similar dose rates.

CONCLUSIONS

These results underline the importance of irradiating at equal dose rates and cell culture conditions when measuring in vitro RBE-values.