Tritium Concentrations In Groundwater Research Articles

Localizing and quantifying groundwater‐surface water interactions at different scales: A tracer approach at the River Moselle, Germany

AbstractGroundwater‐surface water interactions (GSI) connect rivers and streams with riparian areas and the adjacent aquifer. Although these interactions exert a substantial control of quantity and quality of both groundwater and surface water, knowledge on GSI along rivers at the regional scale, particularly for inland waterways, is still limited. We investigated GSI along the river Moselle, an important federal inland waterway in Germany, by using radon and tritium to identify gaining (water flux from the aquifer to the surface water) and losing (water flux from the surface water to the aquifer) stream conditions, respectively. Gaining stream conditions were identified by continuously measuring radon along the river during boat surveys with a high spatial resolution (every 2 km) during intermediate (October 2020) and near low flow conditions (August/September 2021). The tritium concentrations in surface water and groundwater and the resulting tritium inventories were used to characterize losing stream conditions Monthly tritium inventories from 2017 to 2022 revealed a mean loss for the whole period of 20.3 % and a mean gain of 21.8%. Both were probably triggered by a combination of losing stream conditions and flood‐induced mass transfer of water from the aquifer back into the river as well as discharge fluctuations. At the investigated site Lehmen there were direct indications of an influence of surface water due to elevated tritium concentrations in the groundwater (up to 13.3 Bq L−1). Using radon mass balance modelling, good agreements of simulated versus measured radon data with respect to two groundwater end‐member scenarios were obtained during intermediate flow (Spearman's ρ: 0.97 and 0.99; MAE: 10.1 and 3.4 Bq L−1) and near low flow (Spearman's ρ: 0.97 and 0.99; MAE: 11 and 6.5 Bq L−1). Considerable groundwater inflow was limited to the meander of Detzem, where cumulated groundwater inflow of about 19 m3 s−1 (9.5% of total discharge) and 4.2 m3 s−1 (3.8% of total discharge) was simulated during intermediate and near low flow, respectively. However, the groundwater inflow was relatively low compared to alpine streams, for example. The study will help to better identify and quantify GSI at the regional scale and provide methodological guidance for future studies focusing on inland waterways.

An Advanced Optimization Method to Minimize the Detection Limit of Liquid Scintillation Counter to Measure Low-Level Tritium Activity in Groundwater

In arid regions, the tritium concentration in groundwater is typically very low and often falls below the minimum detectable activity (MDA) of the conventional liquid scintillation counter (LSC). Therefore, to measure the tritium activity concentration, it is necessary to lower the detection limit so that the scintillation counter can detect it. In the present study, several methods are discussed which are effective at lowering the detectable activity of tritium. One of these methods is to enrich the tritium activity concentration by ten- to fortyfold of the initial concentration of the tritium. Twelve spiked samples with known amounts of tritium, five with high concentrations and seven with low concentrations, were enriched by the electrolysis process. The results indicated that enriching the tritium levels in groundwater lowers the MDA value. Other methods are minimizing background radiation using low-background materials for sample containers, increasing the measurement efficiency of the scintillation counter and counting time, and shielding the sample from environmental radiation using the shutter option in LSC. Moreover, reducing the number of interfering contaminants in the sample can lower the uncertainty in measuring the tritium concentration in the water sample, which is beneficial for detecting low-level tritium in water to ensure public health and safety.

Spatial variations of tritium concentrations in groundwater collected in the southern coastal region of Fukushima, Japan, after the nuclear accident

Spatial variations in tritium concentrations in groundwater were identified in the southern part of the coastal region in Fukushima Prefecture, Japan. Higher tritium concentrations were measured at wells near the Fukushima Daiichi Nuclear Power Station (F1NPS). Mean tritium concentrations in precipitation in the 5 weeks after the F1NPS accident were estimated to be 433 and 139 TU at a distance of 25 and 50 km, respectively, from the F1NPS. The elevations of tritium concentrations in groundwater were calculated using a simple mixing model of the precipitation and groundwater. By assuming that these precipitation was mixed into groundwater with a background tritium concentration in a hypothetical well, concentrations of 13 and 7 TU at distances of 25 and 50 km from the F1NPS, respectively, were obtained. The calculated concentrations are consistent with those measured at the studied wells. Therefore, the spatial variation in tritium concentrations in groundwater was probably caused by precipitation with high tritium concentrations as a result of the F1NPS accident. However, the highest estimated tritium concentrations in precipitation for the study site were much lower than the WHO limits for drinking water, and the concentrations decreased to almost background level at the wells by mixing with groundwater.

Plants as indicators of tritium concentration in ground water at the Semipalatinsk test site

• The groundwater areas contaminated with 3 H are one of Semipalatinsk test site issues.

The influence of groundwater inputs and age on nutrient dynamics in a coral reef lagoon

Tritium dating of groundwater and a radon mass balance was used to assess the contribution of submarine groundwater discharge (SGD) to a nutrient budget in a tropical reef lagoon (Rarotonga, Cook Islands). Open ocean exchange accounted for the largest percentage of potential lagoon exports (nitrogen (N)=61%, phosphorous (P)=22%) with N export mostly in the form of dissolved organic nitrogen (DON) (93% of total N). SGD accounted for 29% and 11% of exported N and P respectively. Overall we could account for 92% of dissolved N but only 36% of dissolved P leaving the lagoon. However, if DON is assumed to be recalcitrant, SGD would be the major driver of lagoon N and would account for 81% of dissolved inorganic N (DIN) inputs and 47% of DIN exported form the lagoon. A small scale (~50m), high definition survey indicated areas of higher NH4+ towards the middle of the lagoon. This is indicative of SGD input away from the seepage face and may mean that SGD measurements made at the beach face underestimate the broader contribution of SGD to nutrient fluxes. Time series observations during a 100mm rain event indicated that these episodes can deliver high nutrient loads to the lagoon and may contribute to closing the phosphorous budget. Analysis of tritium concentrations in groundwater, surface waters and springs showed that old, deep groundwater (10–93years old) was the main source of SGD derived nutrients to the lagoon. This study demonstrates that there may be a long time lag between nutrient infiltration into aquifers and the discharge of nutrient loaded groundwater into the lagoon. As such, potential mitigation measures which decrease terrestrial nutrient loads may not result in decreased SGD nutrient fluxes for decades to come.

Hydrochemical characteristics and recharge sources of Lake Nuoertu in the Badain Jaran Desert

We present a case study of physical and chemical indicators and isotope characteristics of Lake Nuoertu, one of the largest and deepest lakes of the Badain Jaran Desert. We analyze the concentrations of eight ions, total dissolved solids, and stable isotope composition of the lake and groundwater, as well as radioactive isotope tritium concentration in groundwater. The results show that annual and seasonal variations of the physical and chemical characteristics of Lake Nuoertu water are significantly greater than those of groundwater. The lake is uniformly mixed in the horizontal and vertical directions, and the hydrochemical types of the lake at different depths are consistent for Na–Cl–CO3–(SO4). Stable isotope composition of the lake and groundwater at Nuoertu is distributed along the local evaporation line (EL) slope, which is less than the slope of the global meteoric water line. The comparatively small slope shows the characteristic strong evaporation in the study area. Lake water isotopes are mostly in the upper right corner of the EL, whereas groundwater is mostly in the lower left corner. The main recharge source of Nuoertu lake water is groundwater, in combination with lake water and groundwater level change. The age of tufa springs around Nuoertu is about 75–80 a, which shows that the initial recharge source of the lake is a mix between modern and 1952 or older; however, further research is required.

Procedure for Radio Dating of Water Using Nuclear Hydrological Isotopes Techniques

The regular rates of decay for unstable radioactive elements were found to constitute a virtual clocks within a material they are found to be component. Some water molecules are found to be radioactive due to the increase of tritium in the atmosphere. Tritium concentration in groundwater reflect atmospheric tritium levels when the water was last in contact with the atmosphere, therefore, any measurable tritium concentrations in groundwater system provides clear evidence of recharge occurring into the system during the last four decades. Since 1970s, the atmospheric tritium concentration has decreased. Thus, the presence of excess tritium in groundwater indicates recharge on a time scale of approximately 60 years. Samples are collected along with geographical coordinate of the sampling point. The samples are collected from precipitation, surface water and groundwater which undergo three stages of tritium analysis viz: Screening, Tritium enrichment (Electrolysis) and Scintillation counting. Tritium activity AB in (Bq/Kg) and tritium concentration AT in (TU) are related as:

Numerical simulation of tritium migration in groundwater at Wolsong Plant 1 site

On-site groundwater has been reported to be contaminated by the unplanned release of liquid radioactive material at some nuclear power plants. Thus, it is of utmost importance to implement a timely and effective groundwater protection program at a site based on a good understanding of groundwater flow and a reasonable prediction for the potential impact of the unplanned release. In this study, the tritium migration has been simulated based on the modeling result of groundwater at Wolsong Plant 1 site to assess the potential impact of an unplanned release in the form of a leak. The results indicate that the groundwater eventually flowed into the sea, leaving marine activities as the only possible exposure pathway for receptors. Furthermore, the tritium concentrations in groundwater were simulated to be lowered very quickly with groundwater approaching the sea. Therefore, an additional radiation dose contribution due to the discharge of the contaminated groundwater was estimated to be negligible. Particularly, the draining effect of the dewatering sumps was shown to have a strong influence on the groundwater flow characteristics and the simulation of tritium migration, mainly decreasing the spread rate of the contaminated groundwater, which is advantageous to the protection of groundwater.

Environmental isotope study of groundwater discharge from the large karst springs in West Syria: a case study of Figeh and Al-sin springs

Environmental isotopes (δ18O, δD and 3H) in precipitation and groundwater were integrated for the description of groundwater discharge from the large karst springs of Figeh and Al-sin located in West Syria. The two springs are considered as the most important springs in this Middle East country due to their huge discharge. The δ18O values are −8.91 and −6.49‰ for Figeh and Al-sin, respectively. The regression line for both precipitation and groundwater is described by the equation: δD = 7.9δ18O + 19.7, which shows no evaporation during precipitation and suggests that the groundwater is mainly from direct infiltration of precipitation. The altitude gradients in the precipitation were estimated to be −0.23‰/100 m for δ18O. The main recharge areas are 2,100 and 750 m.a.s.l., for Figeh and Al-sin springs, respectively. The tritium concentrations in groundwater are low and very close to the rainfall values of 4.5 and 3.5 TU for Bloudan and Kadmous meteoric stations, respectively. Adopting a model with exponential time distribution, the main residence time of groundwater in Figeh and Al-sin springs was evaluated to be 50–60 years. A value of around 3.9 and 4.2 billion m3 was obtained for Figeh and Al-sin, respectively, as the maximum groundwater reservoir size.

伊洛河盆地の地下水のトリチウムと安定同位体比について

The author has carried out the analysis of tritium and stable isotopes of surface water and groundwater to evaluate the groundwater flow system in the Yiluo River basin, China.1) Tritium concentrations of the groundwater in the slope of the southern and northwestern mountain range were higher than 10 T.U. and suggested that the residence time of these groundwater was younger than 50 years. On the other hand, tritium concentrations of the deep groundwater along the Yiluo River and in the lower area of the basin were very low. Therefore, the residence time were estimated to be longer than 60 years.2) The stable isotopic ratios of hydrogen and oxygen of the groundwater showed relatively low value in the southern peripheral part of the basin and showed relatively high value in the central part. In the eastern part, down-stream part, and the southeastern part of the basin, groundwater with low δD and δ18O flows toward the lower area of the basin.

Environmental isotopic and hydrochemical study of water in the karst aquifer and submarine springs of the Syrian coast

The groundwater of major karst systems and submarine springs in the coastal limestone aquifer of Syria has been investigated using chemical and isotopic techniques. The δ18O values of groundwater range from −6.8 to −5.05‰, while those for submarine springs vary from −6.34 to +1.08‰ (eastern Mediterranean seawater samples have a mean of +1.7‰). Groundwater originates from the direct infiltration of atmospheric water. Stable isotopes show that the elevation of the recharge zones feeding the Banyas area (400–600 m a.s.l.) is higher than that feeding the Amrit area (100–300 m a.s.l.). The 18Oextracted (18O content of the seawater contribution) for the major submarine springs suggests a mean recharge area elevation of 600–700 m a.s.l., and lower than 400 m a.s.l. for the spring close to Amrit. Based on the measured velocity and the percentage of fresh water at the submarine springs outlet, the estimated discharge rate is 350 million m3/year. The tritium concentrations in groundwater (1.6–5.9 TU) are low and very close to the current rainfall values (2.9–5.6 TU). Adopting a model with exponential time distribution, the mean turnover time of groundwater in the Al-sen spring was evaluated to be 60 years. A value of about 3.7 billion m3 was obtained for the maximum groundwater reservoir size.

The mechanism of unsaturated flow through a volcanic ash layer under humid climatic conditions

AbstractIt is very interesting and meaningful to investigate the rainfall‐groundwater recharge process under the humid climatic condition of Japan, where mean annual precipitation is about 1600 mm. The present study has investigated soil water movement in the unsaturated zones of a volcanic ash layer, called the ‘Kanto Loam formation’, using environmental tritium as a tracer. The site selected is a flat ground surface on a terraced upland which has a deep unsaturated zone (about 20 m) with a relatively high water content (about 70 per cent) consisting of nearly uniform Kanto Loam formation.The tritium concentrations in groundwater, soil waters having different matric potentials, precipitation, and the seepage water moving through the formation into a man‐made cave were measured to characterize the rainfall‐groundwater recharge process and the effect of large pore spaces in the formation mentioned by previous studies.Because of the humid climate of Japan, there appears to be a unique soil water flow characteristic which may involve percolation through large pore spaces during heavy rainfall. However, in a fine grained and high water content soil like the Kanto Loam formation, the existence of this flow through large pore spaces does not have a significant effect upon the whole recharge process. The recharge model of displacement flow with dispersion is useful in estimating the tritium concentration profile of soil water. The calculated result shows a recharge rate of 2.5 mm/day. The value obtained reflects the hydrological characteristics of the uplands covered with volcanic ash.

Application of the tritium interface method for determining recharge rates to unconfined drift aquifers, I. Homogeneous case

The depth of penetration of bomb tritium into the saturated zone was used to calculate the rate of groundwater recharge to an unconfined homogeneous drift aquifer in Cape Cod, Massachusetts (U.S.A.). The aquifer is of glaciofluvial origin and is composed of well sorted sand and gravel. Tritium concentration in groundwater ranged from 0 to 85 T.U. Bomb tritium (> 5 T.U.) was found in 45 groundwater samples collected from 1.5 to 27.1 m below the water table; prebomb tritium concentrations (< 5 T.U.) were identified in 4 samples collected from 25.6 to 41.1 m below the water table. Assuming piston-type flow beneath groundwater divides, the rate of recharge to the aquifer was found to range from 33.7 to 40.6 cm yr −1. This range agrees favorably with recharge estimates previously determined from water budget analyses.

Tritium concentrations of groundwater in Naka Terrace, Ibaraki Prefecture, Japan

Levels of tritium in groundwater of the inland area of Naka Terrace were measured during 1981–1983 to establish a baseline for evaluation of any changes which may result from release of tritium from nuclear facilities in the coastal region of the terrace. Most of the samples yielded concentrations in the range 40–90 pCi litre −1, which were similar to those of two rivers bordering the area of concern, whereas tritium levels in monthly precipitation samples were in the range 30–50 pCi litre −1. These results imply that the rivers are fed from groundwater reservoirs, which are releasing the higher tritium levels recharged during the previous 20 years when bomb-produced tritium caused higher levels in precipitation. Only two groundwater samples yielded concentrations below detection limit, both from the deep Pleistocene gravel layer in a buried river channel underlying the terrace. Some ground-waters in the coastal area yielding more than 100 pCi litre −1 are considered to be already influenced by tritium released from nuclear facilities.