Use Of Noble Gases Research Articles

Neon encapsulation by a hydroquinone organic crystalline clathrate under ambient conditions

The recent use of noble gases in laser devices and semiconductor lithography has greatly increased. However, there is no commercial technology for the storage of noble gases in solid materials owing to their chemical inertness and relative lightness. Here we report the simple synthesis and characteristics of a hydroquinone clathrate that stably captures neon at atmospheric pressure and room temperature. The highly flexible structure enables neon encapsulation in the one-dimensional channels of the clathrate framework despite their inter-cage migration through the hexagonal entrance of the cages. The neon uptake of as-synthesized hydroquinone clathrates is 37.3 g L−1 at 1 bar and 298 K. Increasing the temperature accelerates the release of neon from the flexible hydroquinone clathrate hydrogen-bonded organic framework, leading to guest-free clathrate formation at 1 bar and 400 K. This method represents a technological development for better storage and the controlled release of noble gases in solid structured materials.

Monitoring of magmatic–hydrothermal system by noble gas and carbon isotopic compositions of fumarolic gases

We repeatedly measured isotopic compositions of noble gases and CO2 in volcanic gases sampled at six fumaroles around the Kusatsu-Shirane volcano (Japan) between 2014 and 2021 to detect variations reflecting recent volcanic activity. The synchronous increases in 3He/4He at some fumaroles suggest an increase in magmatic gas supply since 2018. The increase in magmatic gas supply is also supported by the temporal variations in 3He/CO2 ratios and carbon isotopic ratios of CO2. The 3He/40Ar* ratios (40Ar*: magmatic 40Ar) show significant increases in the period of high 3He/4He ratios. The temporal variation in 3He/40Ar* ratios may reflect changes in magma vesicularity. Therefore, the 3He/40Ar* ratio of fumarolic gases is a useful parameter to monitor the current state of degassing magma, which is essential for understanding the deep process of volcanic unrest and may contribute to identifying precursors of a future eruption. These results provide additional validation for the use of noble gas and carbon isotopic compositions of fumarolic gases for monitoring magmatic–hydrothermal systems.

The Use of Noble Gases to Constrain Subsurface Fluid Dynamics in the Hydrocarbon Systems

Geochemical techniques have been widely applied to study the generation and migration of hydrocarbons in sedimentary basins over the last several decades. Diagnostic biomarkers and stable carbon and hydrogen isotopes (such as δ13C and D) are generally used to identify the sources and thermal maturity of hydrocarbons and to reveal the accumulation process and mechanism of oil and gas reservoirs. However, some questions, such as secondary migration processes and pathways of oil and gas, and the relationship between groundwater flow and hydrocarbon transport, remain unclear and challenging. The low abundance and chemical inertness properties allow noble gases to serve as robust tools for tracing subsurface fluid flow. Additionally, they can be used for identifying and quantifying the role of the concomitant groundwater related to the generation and migration of hydrocarbons. This paper reviews the previous modeling work on using noble gases to study the fluid flow, flow paths, and gas/oil-water interactions in hydrocarbon systems. Noble gases from various sources can be readily identified due to their distinct isotopic and elemental signatures. Atmosphere-derived noble gases can be used to evaluate the amount of involved aquifer water associated with the hydrocarbon system and determine the groundwater migration paths and flow rates. Radiogenic noble gases accumulate over time, providing information about the subsurface fluid residence time. Questions concerning the specific trapping sites and mechanisms that affect heavy noble gas adsorption into organic sediments are still unresolved. Investigating the hydrocarbon generation, migration, and subsurface crustal fluid interactions in the hydrocarbon reservoirs can improve our understanding of noble gases as useful tracers in the subsurface environment and provide valuable geological evidence for the exploration and production of petroleum sources.

Source identification of methane in groundwater in shale gas development areas: A critical review of the state of the art, prospects, and future challenges

Shale gas exploration and development carry the risk of causing groundwater contamination and enhancing the greenhouse effect through methane leakage. Identifying the source of abnormal methane in groundwater of shale gas development areas is becoming a research hotspot in the fields of groundwater and climate change. This paper reviews the traditional methodology in identifying sources of methane and its deficiency in groundwater application. Then potential and advantages of using noble gases were discussed on how to overcome these limitations of the traditional method. Finally, based on noble gas, the current application status and future challenges of methane source identification in groundwater were analyzed. It can be summarized as: (1) due to chemical and/or microbial processes in the aquifer system, the traditional methodology for methane source identification, which utilizes molecular and isotopic compositions of hydrocarbon gas, has multiple interpretationsand large uncertainties; (2) the non-reactive nature and well-characterized isotopic compositions of noble gases in the atmosphere, hydrosphere, and crust, make noble gases ideal indicators of the sources of methane in groundwater. Moreover, the mechanism of formation and release of crustal noble gas prevent shale gas signatures from being interfered with by natural gas; (3) the key scientific tasks surrounding the use of noble gases for methane source identification include quantitatively separating the components of atmosphere-derived, mantle-derived, and crust-derived noble gases from the bulk noble gases in groundwater. It quantifies the solubility fractionation of noble gases induced by water-gas interaction during methane migration to the aquifer. The application of noble gases can bring a new perspective to tracing the source of methane in groundwater and is of great significance to the protection of groundwater quality in shale gas development areas and mitigation of climate change.

Effects of Argon-Based and Nitrogen-Based Modified Atmosphere Packaging Technology on the Quality of Pomegranate (Punica granatum L. cv. Wonderful) Arils.

Ready-to-eat pomegranate arils are considered a “functional food” for their health benefits and have desirable sensory characteristics, which have caused an increasing interest by the consumers for this product. The preparation process of ready-to-eat fruit products can cause severe injuries and worsen their quality and shelf life significantly. Modified atmosphere packaging (MAP) has been used broadly in the last years to maintain the quality of processed fruits and showed optimal results, in spite of the possible problems caused by the depletion of O2 and corresponding accumulation of CO2 in the package. This study was conducted to evaluate the effects of different MAP treatments, based on nitrogen or alternatively on a noble gas, argon, in combination with refrigerated storage (0, 4, 8, 12, and 16 days at 4 ± 1 °C and 90 ± 5% RH) on the qualitative parameters of pomegranate arils with the aim to prolong their post-harvest life maintaining the original quality. The argon-based MAP treatment (MAPAr) was the one that provided the best results, assuring a limited loss of weight and juice content. The use of noble gas allowed to maintain a high sugar/acid ratio until 16 days from packaging. Sensory analysis on all MAP treated arils and, on the juice, obtained from them were carried out, and judges showed a preference for MAPAr treated arils and juice until day 12 from packaging.

Application of natural and artificial tracers to constrain CO2 leakage and degassing in the K-COSEM site, South Korea

Although Carbon Capture and Storage (CCS) has been demonstrated successfully on many occasions, the potential leakage of deep sequestrated CO2 into shallow groundwater remains a concern. To address this, an artificial injection experiment was performed at the K-COSEM test site in Eumseong, South Korea, that involved the release of CO2–infused water (16.9 kg of CO2 in 5 m3) containing He and Kr tracers into a shallow, heterogeneous, weathered-granite aquifer. The initial CO2–fluid was slightly oversaturated at the subsurface injection point, and thus the plume was expected to initially degas CO2 before equilibrating at in-situ conditions. Monitoring of carbonate system parameters in nearby observation wells helped define the evolution of the injected fluids, while the noble gas tracers were used to clearly define the physical behavior of the CO2 plume (including an estimate of degassed CO2 equal to 0.9–3.1%). This study demonstrates the potential use of noble gases for monitoring CO2 leakage in shallow aquifers, constraining mass balance and phase changes of leaking fluids, and better understanding local flow pathways. Furthermore, breakthrough of noble gases in this study was different from some previous experiments, suggesting that monitoring efficiency of these tracers may depend on leakage and site conditions.

Singlet oxygen generated by a new nonthermal atmospheric pressure air plasma device exerts a bactericidal effect on oral pathogens.

Oral diseases generally have certain bacteria associated with them. Non-thermal atmospheric pressure plasma (NTAP), generated at atmospheric pressure and room temperature, incorporates several molecules, including reactive oxygen species, that can inactivate various bacteria including oral pathogens. For this reason, several NTAP devices have been developed to treat oral diseases. Use of noble gases can enhance the bactericidal efficacy of NTAP, but this requires additional gas supply equipment. Therefore, a new NTAP device that employs ambient air as the working gas was developed. The device generates non-thermal atmospheric pressure air plasma. Here, the singlet oxygen (1O2) levels generated, their bactericidal effects on oral pathogens (Streptococcus mutans, Porphyromonas gingivalis, and Enterococcus faecalis), and the bacterial oxidative stress they imposed were measured. 1O2 generation in phosphatebuffered saline was assessed qualitatively using electron spin resonance (ESR) spectroscopy, and bactericidal efficacy was evaluated by counting of colony-forming units/mL. Bacterial oxidative stress was determined by measurement of hydrogen peroxide (H2O2) and superoxide dismutase (SOD) activity. ESR indicated that the level of 1O2 increased significantly and time-dependently, and was inversely correlated with distance, but the bactericidal effects were correlated only with treatment time (not distance) as H2O2 increased and SOD levels decreased, suggesting that the new device has potential applicability for treatment of oral disease.

Anesthetic Molecule Interaction of Noble Gases with Proteins and Lipids and their Effect: A Review.

Surgical operations are impossible without administering proper analgesia. Advancement in the field of anesthesia has invariably resulted in the accomplishment of all surgical processes without any inconvenience. Admittedly, the use of noble gas is on the decline. The noble gases may not interact chemically with any other substance under normal temperature and pressure but they may interact with proteins and lipids. Different anesthetic molecules may stimulate either proteins or lipids in membrane. There is a connection between the anesthetic molecules and the hydrophobic region of the membrane. In the present review, we attempt to highlight the interaction between the anesthetic molecule with proteins and lipids and their effects. We sketched few noble gases and some other existing molecules such as halothane and alcohol which interacted with proteins and lipids.

Release of radiogenic noble gases as a new signal of rock deformation

AbstractIn this study we investigate the release of radiogenic noble gas isotopes during mechanical deformation. We developed an analytical system for dynamic mass spectrometry of noble gas composition and helium release rate of gas produced during mechanical deformation of rocks. Our results indicate that rocks release accumulated radiogenic helium and argon from mineral grains as they undergo deformation. We found that the release of accumulated 4He and 40Ar from rocks follows a reproducible pattern and can provide insight into the deformation process. Increased gas release can be observed before dilation, and macroscopic failure is observed during high‐pressure triaxial rock deformation experiments. Accumulated radiogenic noble gases can be released due to fracturing of mineral grains during small‐scale strain in Earth materials. Helium and argon are highly mobile, conservative species and could be used to provide information on changes in the state of stress and strain in Earth materials, and as an early warning signal of macroscopic failure. These results pave the way for the use of noble gases to trace and monitor rock deformation for earthquake prediction and a variety of other subsurface engineering projects.

Morphology and characteristics of laser-induced aluminum plasma in argon and in air: A comparative study

In laser-induced breakdown spectroscopy (LIBS), ablation takes place in general in an ambient gas of the atmospheric pressure, often in air but also in noble gas such as argon or helium. The use of noble gas is known to significantly improve the performance of the technique. We investigate in this work the morphology and the characteristics of induced plasma in argon and in air. The purpose is to understand the mechanism of the analytical performance improvement by the use of argon ambient with respective to air ambient and the dependence on the other experimental parameters such as the laser fluence. The observation of plasma morphology in different ambient gases provides also information for better design of the detection system which optimizes the signal collection according to the used ambient gases. More specifically, the expansion of the plasma induced on an aluminum target with nanosecond infrared (1064nm) laser pulse in two ambient gases, argon and the atmospheric air, has been studied with spectroscopic imaging at short delays and with emission spectroscopy at longer delays. With relatively low ablation laser fluence (65J/cm2), similar morphologies have been observed in argon and in air over the early stage of plasma expansion, while diagnostics at longer delay shows stronger emission, higher electron density and temperature for plasma induced in argon. With higher ablation laser fluence (160J/cm2) however, different expansion behaviors have been observed, with a stagnating aluminum vapor near the target surface in air while a propagating plume away from the target in argon. The craters left on the target surface show as well corresponding difference: in air, the crater is very shallow with a target surface chaotically affected by the laser pulse, indicating an effective re-deposition of the ablated material back to the crater; while in Ar a deeper crater is observed, indicating an efficient mass removal by laser ablation. At longer delays, a brighter, denser and hotter plasma is always observed in argon than in air as with lower ablation laser fluences. The observed different influences of the ambient gas on the plasma expansion behavior for different laser fluences are related to the different modes of laser-supported absorption waves, namely laser-supported combustion (LSC) wave and laser-supported detonation (LSD) wave.

What can you do to protect the newborn brain?

Hypoxic-ischemic brain injury is a leading cause of mortality and morbidity in neonates. Treating such injury by interrupting the excitotoxic-oxidative cascade is of immense importance. This review will focus on novel techniques of neuroprotection and describe the latest advances in established therapeutic methods. Although the primacy of therapeutic hypothermia in treating hypoxic-ischemic encephalopathy is well established, recent research establishes that the arbitrarily chosen regimen of cooling to 33°C for 72 h may indeed be the most appropriate method. The optimal duration of antenatal magnesium therapy for neuroprotection remains unsettled, though it is reassuring that even 12 h or less of magnesium therapy results in comparable neurological outcomes. Combining adjuvant therapies such as melatonin or erythropoietin with therapeutic hypothermia results in favorable neurological outcomes compared with hypothermia alone. Finally, stem cell-based therapies show considerable potential in preclinical studies. Significant advances have occurred in the management of neonatal brain injury. With establishment of the optimal temperature and duration of hypothermia, combinatory therapies using adjuncts hold the greatest promise. Promising preclinical approaches such as stem cell-based therapy and use of noble gases need to be confirmed with clinical trials.

Enhanced UV light detection using wavelength-shifting properties of Silicon nanoparticles

Detection of UV photons is becoming increasingly necessary with the use of noble gases and liquids in elementary particle experiments. Cerenkov light in crystals and glasses, scintillation light in neutrino, dark matter, and rare decay experiments all require sensitivity to UV photons. New sensor materials are needed that can directly detect UV photons and/or absorb UV photons and re-emit light in the visible range measurable by existing photosensors. It has been shown that silicon nanoparticles are sensitive to UV light in a wavelength range around ∼ 200 nm. UV light is absorbed and re-emitted at wavelengths in the visible range depending on the size of the nanoparticles. Initial tests of the wavelength-shifting properties of silicon nanoparticles are presented here that indicate by placing a film of nanoparticles in front of a standard visible-wavelength detecting photosensor, the response of the sensor is significantly enhanced at wavelengths < 320 nm.

A Self‐Powered Triboelectric Nanosensor for Mercury Ion Detection

Mercury is a highly toxic metal that can pose serious dangers to the environment and human health. Therefore, monitoring the mercury concentration is an extremely important issue to prevent such a toxic metal from endangering human life. Hg ions are by far the most stable inorganic form of mercury, which are non-biodegradable and bioaccumulable. Even at a very low concentrations, they can still be fatal to human brain, heart, and kidney. Multiple approaches, such as atomic absorption/emission spectrometry and inductively coupled plasma mass spectrometry (ICP-MS), have been applied to detect the Hg ions in environmental and biological samples. Among these approaches, ICP-MS is the method that has the highest sensitivity and the widest linear range. However, sample preparation before measurement is rather complicated and time-consuming, and requires expensive instrumentation and the use of noble gas. Another drawback of this method is the difficulty in performing infield analysis. In consideration of the above disadvantages, researchers have instead developed a number of optical methods (colorimetric or fluorometric assays, and systems based on surface plasmon resonance or surfaceenhanced Raman scattering) and electrochemical sensors for the detection of Hg ions. Optical approaches are advantageous in high sensitivity and selectivity, and practicable for in-field analysis, yet they are involved with sophisticated chemistry in incorporating organic probes, such as crown ethers, porphyrins, specific proteins, DNA, and polymers, which substantially limits their application range. To overcome the limitations of these methods, the concept of self-powered nanosensors has recently been proposed and tested for its potential toward toxic pollutant detection. The working principle of self-powered nanosensors is based on combining/integrating nanogenerators with sensors. The nanogenerators harvest energy from the environment to power the sensors. Owing to its convenient monitoring mechanism, the self-powered nanosensors could be the most desirable and promising prototype for environmental protection/detection in the near future because no battery is needed to power the device. For the time being, the major challenge is how to develop a fully integrated, stand-alone and selfpowered nanosensor. The triboelectric effect is an old but well-known phenomenon in daily life. Recently, it has been utilized as an effective way to harvest mechanical energy. Contact between two materials with different triboelectric polarity yields surface charge transfer. The periodic contact and separation of the oppositely charged surfaces can create a dipole layer and a potential drop, which drives the flow of electrons through an external load in responding to the mechanical agitation. As for triboelectric nanogenerator (TENG), maximizing the charge generation on opposite sides can be achieved by selecting the materials with the largest difference in the ability to attract electrons and changing the surface morphology. For the plate-structured TENG, it needs more time and stronger applied force to ensure the contact and separation of the two oppositely charged material surfaces upon pressing and releasing are complete, especially under the electrostatic attraction between them. Adding spacers between two plates or using arch-shaped substrates have been demonstrated to improve the output of TENG. Herein, we show that the principle of the TENG can be used as a sensor for the detection of Hg ions. The first step is to improve the performance of the TENG through the assembly of Au nanoparticles (NPs) onto the metal plate. These assembled AuNPs not only act as steady gaps between the two plates at the strain-free condition, but also enable the function of enlarging the contact area of the two plates, which will increase the electrical output of the TENG. Through further modification of 3-mercaptopropionic acid (3-MPA) molecules on the assembled AuNPs, the high-output nanogenerator can become a highly sensitive and selective nanosensor toward Hg ions detection because of the different triboelectric polarity of AuNPs and Hg ions. On the basis of this unique structure, the output voltage and current of the triboelectric nanosensor (TENG) reached 105 V and 63 mA with an effective dimension of 1 cm 1 cm. Under optimum conditions, this TENG is selective for the detection of Hg ions, with a detection limit of 30 nm and linear range from 100 nm to 5 mm. A commercial LED lamp was tested as the indicator to replace the expensive electrometer and showed the possibility to simplify the detection system. Our study demonstrates an innovative and unique approach toward selfpowered detection of Hg. [*] Dr. Z.-H. Lin, G. Zhu, Y. S. Zhou, Dr. Y. Yang, P. Bai, J. Chen, Prof. Z. L. Wang School of Material Science and Engineering Georgia Institute of Technology, Atlanta, GA 30332-0245 (USA) E-mail: zlwang@gatech.edu

Noble gas signatures of high recharge pulses and migrating jet stream in the late Pleistocene over Black Mesa, Arizona, United States

Research Article| January 01, 2010 Noble gas signatures of high recharge pulses and migrating jet stream in the late Pleistocene over Black Mesa, Arizona, United States Chen Zhu; Chen Zhu * 1Department of Geological Sciences, Indiana University, Bloomington, Indiana 47405, USA *E-mail: chenzhu@indiana.edu. Search for other works by this author on: GSW Google Scholar Rolf Kipfer Rolf Kipfer 2Swiss Federal Institute of Aquatic Science and Technology (EAWAG), 8600 Duebendorf, Switzerland Search for other works by this author on: GSW Google Scholar Geology (2010) 38 (1): 83–86. https://doi.org/10.1130/G30369.1 Article history received: 07 May 2009 rev-recd: 06 Aug 2009 accepted: 11 Aug 2009 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Chen Zhu, Rolf Kipfer; Noble gas signatures of high recharge pulses and migrating jet stream in the late Pleistocene over Black Mesa, Arizona, United States. Geology 2010;; 38 (1): 83–86. doi: https://doi.org/10.1130/G30369.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Many semiarid and arid regions of the world are almost entirely dependent on groundwater for water supply, yet many of these aquifers were primarily recharged during the late Pleistocene. Here we show that new noble gas data record the high pulses of recharge to the Navajo Sandstone aquifer at Black Mesa, Arizona, between 14 and 17 ka, which was associated with the passing of the southern branch of the jet stream. Higher excess neon coincided with high water levels independently deduced from numerical modeling of groundwater flow and 14C data in previous studies. This development allows the use of noble gases not only as a tool to reconstruct paleotemperatures, but also as a new tool to reconstruct paleohydraulic conditions and to verify the conceptual and hydraulic assumptions of existing groundwater models. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Noble gases as tools for subsurface monitoring of CO2 leakage

Abstract We are developing the use of noble gases as tools to survey the integrity of CO 2 geological storages. The advantage of using noble gases stems from their chemical inactivity which does not delay them when they migrate in leaking pathways. Using the aquifers located above the CO 2 deep storages as leak integrators and monitoring them for noble gas contents could make it possible to forecast a future CO 2 arrival. To achieve this possibility, the CO 2 in place in the storages must contain noble gases. Noble gases can be present naturally in geological reservoirs as a mantle-derived signal, or could be injected with CO 2 as helium spikes or atmospheric argon. As an analogue of a CO 2 reservoir, we have studied the Montmiral CO 2 natural reservoir (about 2500 meters below the surface, near Valence, France) using a new analytical facility, Garodiox, linked to a quadrupole mass spectrometer. The reservoir gas phase (979˜9% pure CO 2 ) was first sampled at the outlet of a deep well and analyzed for its noble gas content. The helium has a high volume fraction ([ 4 He]=301±29ppm), and the helium/neon ratio is high ( 4 He/ 20 Ne=364±48). The origin of helium is described by a 3 He/ 4 He ratio of 0.75±0.12 Ra. Then, waters from shallow aquifers (at depths of about 100 meters below the surface) were sampled in mechanically sealed copper tubes. Each water sample was analyzed to determine (1) the dissolved noble gas content (He, Ne), (2) the dissolved inorganic carbon (DIC) concentration and (3) the δ 13 C of DIC. In the deeper water samples, the signature of the deep reservoir noble gas signal is recognized. We also find a relationship between the 4He/Ne ratios and the distance to the wells that reach the CO 2 reservoir. We show a trend which is interpreted as the consequence of the deep reservoir gas leaking into the shallow aquifers, via a poorly sealed well (abandoned since 1956). The study of the Montmiral CO 2 accumulation makes it possible to define a procedure based on the use of shallow aquifers as subsurface monitoring tools. This study highlights the interest of the use of conservative tracers, whose signatures are different from the natural compositions. Compared to CO 2 , conservative tracers are not involved in chemical reactions or in biological processes. Therefore, they are more easily detectable in subsurface environments.

On the use of noble gases and binary mixtures as reactor coolants and CBC working fluids

Abstract This paper investigates the attributes and limitations of noble gases and binary mixtures as potential working fluids for gas-cooled nuclear power plants with Closed Brayton Cycles (CBC). Compared are the heat transfer coefficient and pressure losses of helium and other noble gases and binary mixtures, at typical operating conditions in commercial power plants (7.0 MPa and 400–1200 K), for the same molecular flow rate and geometry. Also investigated is the impact of the working fluid choice on the performance of nuclear power plants with direct CBCs and single-shaft and multiple-shafts turbo-machines. The effects of the working fluid choice on the number of stages of the turbo-machines and the nuclear power plant’s thermal efficiency and electrical power output are calculated and compared. Although He has high heat transfer coefficient and significantly lower pumping requirement, the heat transfer coefficient of the He–Xe binary gas mixture with a molecular weight of 15 g/mol is ∼7% higher and the turbo-machines have 75% fewer stages than for helium. The pumping requirement for this binary mixture, however, is 3.5 times that of helium, decreasing the plant peak efficiency by ∼2 percentage points. Thus, using He–Xe, over He, as working fluid for gas-cooled reactor power plants would have to be based on considerations of reducing the size, mass, and cost of the turbo-machines.

The use of noble gases as a tracer in carbon dioxide sequestration

The use of noble gases as a tracer in carbon dioxide sequestration

Production, Release and Transport of Noble Gases in the Continental Crust

Noble gases within the crust originate from three main sources: the atmosphere, introduced into the crust dissolved in groundwater; the mantle, in regions of magmatic activity; and those produced in the crust by the result of radioactive decay processes. The continental crust contains approximately 40% of the terrestrial radioelements (Rudnick and Fountain 1995) that produce noble gases and, after the mantle and the atmosphere, forms the third major terrestrial noble gas reservoir (neglecting the core). In addition to these sources, contributions from interplanetary dust particles (IDP), cosmic ray interaction with the crustal surface and anthropogenic noble gases can in some cases be a significant source of noble gases in crustal materials. The use of noble gases to understand the role of fluids in different geological settings relies on their low natural abundance and chemical inertness. The low abundance of noble gases in crustal systems and their distinct isotopic character means that contributions from these different sources can often be resolved and quantified. With this, information is gained about the source of associated fluids, the environment from which they originated the physical manner in which they have been transported to the sampling site and the different phases that may have interacted within the crustal fluid system. This is only possible, however, with a detailed understanding of the processes that control the concentration and isotopic composition of the noble gases in different crustal environments. The first part of this chapter deals with the three different mechanisms of noble gas production within the crust—radiogenic, nucleogenic, fissiogenic (Fig. 1⇓). We show how production ratios are affected not only by the source region radioelement concentration, but in the case of nucleogenic reactions, also by the spatial distribution and concentration of the target elements. For completeness we consider cosmogenic noble gas production rates and Interplanetary …

Palaeotemperature reconstruction from noble gases in ground water taking into account equilibration with entrapped air

Noble-gas concentrations in ground water have been used as a proxy for past air temperatures, but the accuracy of this approach has been limited by the existence of a temperature-independent component of the noble gases in ground water, termed 'excess air' whose origin and composition is poorly understood. In particular, the evidence from noble gases in a Brazilian aquifer for a cooling of more than 5 C in tropical America during the Last Glacial Maximum has been called into question. Here we propose a model for dissolved gases in ground water, which describes the formation of excess air by equilibration of ground water with entrapped air in quasi-saturated soils. Our model predicts previously unexplained noble-gas data sets, including the concentration of atmospheric helium, and yields consistent results for the non-atmospheric helium isotopes that are used for dating ground water. Using this model of excess air, we re-evaluate the use of noble gases from ground water for reconstructing past temperatures. Our results corroborate the inferred cooling in Brazil during the Last Glacial Maximum, and indicate that even larger cooling took place at mid-latitudes.

Studies on Noble Gas Scintillators

The results from a study of the use of noble gases without wavelength shifters as scintillation detectors for nuclear particles are presented. The spectra and the time dependence of the fluorescence induced by ?-particles in helium, neon, argon, krypton and xenon, have been investigated by single photoelectron techniques and are reported. A study of the scintillation efficiency as a function of gas pressure and of dimensions of the scintillation chamber, shows the great importance of geometrical factors in light collection. In all cases, experimental results on pulse heights and decay times would be reproduced within ± 5 % and the operation of these gas scin tillators as particle detectors was found to be satisfactory.