Amounts Of He Research Articles

Primitive noble gases sampled from ocean island basalts cannot be from the Earth’s core

Noble gas isotopes in plumes require a source of primitive volatiles largely isolated in the Earth for 4.5 Gyrs. Among the proposed reservoirs, the core is gaining interest in the absence of robust geochemical and geophysical evidence for a mantle source. This is supported by partitioning data showing that sufficient He and Ne could have been incorporated into the core to source plumes today. Here we perform ab initio calculations on the partitioning of He, Ne, Ar, Kr and Xe between liquid iron and silicate melt under core forming conditions. For He our results are consistent with previous studies allowing for substantial amounts of He in the core. In contrast, the partition coefficient for Ne is three orders of magnitude lower than He. This very low partition coefficient would result in a 3He/22Ne ratio of ~103 in the core, far higher than observed in ocean island basalts (OIBs). We conclude that the core is not the source of noble gases in OIBs.

Characterisation and Antibacterial Properties of Novel Biodegradable Films Based on Alginate and Roselle (Hibiscus sabdariffa L.) Extract.

Composite films were prepared with alginate and roselle extract (HE) at different concentrations (1%, 3%, and 5% w/v) via solvent casting technique and analyzed in terms of physical, mechanical, and antibacterial properties. The incorporation of HE into alginate films resulted in rough and heterogeneous surface characteristics with increasing concentrations of HE. The thickness and water vapor permeability of alginate–HE composite films were significantly higher (p < 0.05) compared to pure alginate films. Moreover, water content, solubility, swelling, tensile strength, and elongation at break value of the composite films decreased (p < 0.05) with increasing concentrations of the extract. FTIR spectra revealed shifts and intensity variations in the composite films and the formation of new peaks suggesting a possible interaction between alginate and HE. Alginate–HE films exhibited good antibacterial activity against Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Escherichia coli and Klebsiella pneumoniae) bacteria. The antibacterial effect of the films, more pronounced against Gram-positive bacteria, increased with higher amounts of HE. The resulting films may be utilised as new biodegradable, antibacterial films in the food packaging industry to prolong shelf life and preserve food safety.Graphical Supplementary InformationThe online version of this article (10.1007/s12649-022-01710-3) contains supplementary material, which is available to authorized users.

Carnegie Supernova Project-II: Near-infrared Spectroscopy of Stripped-envelope Core-collapse Supernovae*

Abstract We present 75 near-infrared (NIR; 0.8−2.5 μm) spectra of 34 stripped-envelope core-collapse supernovae (SESNe) obtained by the Carnegie Supernova Project-II (CSP-II), encompassing optical spectroscopic Types IIb, Ib, Ic, and Ic-BL. The spectra range in phase from pre-maximum to 80 days past maximum. This unique data set constitutes the largest NIR spectroscopic sample of SESNe to date. NIR spectroscopy provides observables with additional information that is not available in the optical. Specifically, the NIR contains the strong lines of He i and allows a more detailed look at whether Type Ic supernovae are completely stripped of their outer He layer. The NIR spectra of SESNe have broad similarities, but closer examination through statistical means reveals a strong dichotomy between NIR “He-rich” and “He-poor” SNe. These NIR subgroups correspond almost perfectly to the optical IIb/Ib and Ic/Ic-BL types, respectively. The largest difference between the two groups is observed in the 2 μm region, near the He i λ2.0581 μm line. The division between the two groups is not an arbitrary one along a continuous sequence. Early spectra of He-rich SESNe show much stronger He i λ2.0581 μm absorption compared to the He-poor group, but with a wide range of profile shapes. The same line also provides evidence for trace amounts of He in half of our SNe in the He-poor group.

Water-susceptible primordial noble gas components in less-altered CR chondrites: A possible link to cometary materials

We report detailed characterizations of the petrology, mineralogy, and noble gas signatures of Renazzo-type (CR) chondrites EET 92048, MIL 090657, NWA 801, and hydrothermally treated MIL 090657 samples to investigate primordial noble gases hosted by water-susceptible materials in aqueously less-altered CR chondrites. The noble gases were extracted by a stepwise heating method. The hydrothermal treatment on MIL 090657 resulted in the alteration of amorphous silicates in the matrix and the removal of large amounts of He and Ne that were released at low temperature from the untreated sample. The 36Ar/132Xe ratios in EET 92048 and MIL 090657 are ~5 times higher than that of the Q noble gas component, although both meteorites do not show any evidence for solar wind noble gases. The analyses revealed that aqueously less-altered CR chondrites contain two distinct primordial noble gas components hosted by water-susceptible materials: an isotopically Q-like Ne-rich component and an Ar-rich component. The characteristics of the Q-like Ne-rich component are consistent with those of Q-like Ne in cometary materials. We propose that the CR chondrites formed at a greater heliocentric distance and share similar materials hosting the Q-like Ne-rich component with comets. The presence of the Ar-rich component in the CR chondrites, as well as in ordinary chondrites and other anhydrous carbonaceous chondrites, provides evidence of the global distribution of the Ar-rich carriers in the ordinary and carbonaceous chondrite forming regions.

Infant and Toddler Consumption of a Lipid Nutrient Supplement After a 2-Week Home Repeated Exposure

Abstract Objectives Repeated exposure (RE) paradigms produce improvements in food acceptance during infancy, however, less is known about RE effectiveness in toddlers. Here we examine the effects of RE on acceptance of sweetened and unsweetened versions of a lipid nutrient supplement (LNS). Methods Mothers and children (n = 56, 86% NonHispanic White), aged 7–11.30 mo (n = 12; infants) and 12–24 mo (n = 44; toddlers), participated in a randomized, 2-week home exposure study and 2 lab visits (Baseline [V1] &amp; Post-exposure [V2]). Children were randomized to RE of 1) sweetened or 2) unsweetened versions of the LNS mixed into oatmeal. At V1, mothers offered version 1 of LNS (sweetened or unsweetened) until the child took 2 bites or refused 3 times. Then mothers fed the alternate version ([HE]; the LNS to which children were randomized for home exposure) until the child refused to eat more. Intake (g) of HE was measured. Mothers were given 10 servings of the HE version and told to offer their child the 10 servings over the following 2-week period. At V2, mothers again fed unlimited amounts of HE until the child refused to eat more and intake in grams was again measured. A linear mixed model for repeated measures tested change in intake of HE across V1 and V2 by age group (toddlers v. infants) and by LNS version (sweetened v. unsweetened). Significance of the statistical interaction (visit by age group and visit by version) was defined at P &amp;lt; 0.1. Results Fifty-five dyads (98%) completed V1 and V2. Caregivers offered their children, on average, 9 of 10 possible home exposure servings. Observed intake of the HE differed by age group (infants, V1 = 32.3 g ± 15.8, V2 = 28.8 ± 20.9 vs. toddlers, V1 = 15.5 g ± 16.3 V2 = 23.9 ± 19.5; P = .006). The linear mixed model confirmed (F = 3.41, P = .07) that intake of HE significantly increased from V1 to V2 in the toddler group, whereas intake in the infant group remained consistent between V1 and V2. The unsweetened version was preferentially consumed compared to the sweetened version (P = .07). Conclusions Children consumed the unsweetened version as well, if not better, than the sweetened version of the supplement. Over time, infants were consistent in their willingness to consume the supplement whereas toddlers showed an increase in intake, suggesting that toddlers may learn to eat the supplement through RE. Funding Sources Global Alliance for Improved Nutrition.

Formation of Al + (C 6 H 6 ) 13 : The Origin of Magic Number in Metal–Benzene Clusters Determined by the Nature of the Core

The identification of highly abundant, “magic” species in the mass spectra of clusters have proven to be valuable in nanoscience, leading to the discovery of new stable species such as fullerenes a...

Diffusion of helium in radiation-damaged zircon

Diffusion of helium was characterized in natural zircon that had been implanted with Kr at a range of energies to simulate the effects of alpha recoil in natural radiation damage. Polished slabs of zircon, oriented either normal or parallel to c, were implanted with Kr+ ions at a series of energies to produce a damaged region ∼ 1μm in thickness, then implanted with 100keV 3He at a dose of 1×1015 3He/cm2, which placed the 3He within the region damaged by the Kr ion implantation. The implanted zircons were annealed isothermally in Pt capsules in 1-atm furnaces at temperatures ranging from 51 to 252°C and times ranging from 15min to 3 weeks. 3He distributions following experiments were measured with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. For diffusion in zircon normal to c, we obtain the following Arrhenius relation:D=1.7×10−8 exp(−71±2kJ mol−1/RT) m2sec−1.This activation energy for diffusion is about half of the value for He diffusion in zircon from the same sample locality but without Kr implantation, measured with an otherwise similar experimental and analytical approach (Cherniak et al., 2009). He diffusivities in the Kr-implanted material are also significantly faster. Further, He diffusivities normal and parallel to c in the Kr-implanted zircon are similar, in contrast to the marked diffusional anisotropy (with differences of two orders of magnitude for diffusion normal and parallel to c) observed for He diffusion in this zircon in samples not implanted with Kr.These data indicate that heavily damaged zircon will have very limited retentivity of helium. Only those zircons larger than a few hundred μm will have mean closure temperatures exceeding typical earth surface temperatures; mean closure temperatures for He in highly damaged zircon will be about ∼200°C lower than those for relatively undamaged zircon. At 200°C, equivalent amounts of He will be lost from severely damaged zircon at a rate about a million times faster than from relatively undamaged zircon. For retentivity of He comparable to that for low-damage zircon at 200°C, the severely damaged zircon would require residence temperatures of ∼ -10°C.

New project for precise neutron lifetime measurement at J-PARC

The decay lifetime of free neutrons (∼880 s) is an important parameter of the weak interaction and for Big Bang Nucleosynthesis. However, results of measurements currently show discrepancies depending on the method used. As most experiments nowadays employ ultra cold neutrons, we have developed a new cold-beam experiment which we perform at the Japan Proton Accelerator Research Complex. As a special feature, a polarized neutron beam is bunched by a spin flip chopper. A time projection chamber operated with He and CO2gas, including a well-controlled amount of3He, is used for detection of the beta-decays and simultaneous determination of the beam intensity. Using the data between 2014 and 2016, we evaluated our first, preliminary result of the neutron lifetime as 896 ± 10(stat.)−10+14(sys.) s. We plan several upgrades to achieve our precision goal of 1 s.

Characterisation of helium ion irradiated bulk tungsten: A comparison with the in-situ TEM technique

Transmission electron microscopy (TEM) of ex-situ He ion irradiated bulk W has been performed to quantitatively compare the damage microstructure to that observed in regions of comparable thicknesses during in-situ ion irradiation with TEM experiments. Samples were irradiated to achieve He-appm/DPA ratios of 2000 and 500 at temperatures of 500 and 800 °C to 1.5 and 3.0 DPA. For irradiations at 500 °C, bubble diameters (∼2 nm) were larger and areal bubble densities (∼1012 bubbles/cm2) were lower than those in the in-situ experiments. This is attributed to greater amounts of He being retained in the ex-situ bulk experiments whereas in the in-situ experiments some may escape due to the proximity of surfaces. Dislocation loops were observed in all samples and were characterised as b = ±½<111> type with no b = <100> type loops. Dislocation loop populations were dominated by interstitial type (∼60%) agreeing with in-situ experiments. However, dislocation loops in this work were larger, ranging in size from 7 to 100 nm and large concentrations of entangled dislocation lines were observed in the bulk of the grain as compared to in the in-situ experiments.

Oxygen and helium in stripped-envelope supernovae

We present an analysis of 507 spectra of 173 stripped-envelope (SE) supernovae (SNe) discovered by the untargeted Palomar Transient Factory (PTF) and intermediate PTF (iPTF) surveys. Our sample contains 55 Type IIb SNe (SNe IIb), 45 Type Ib SNe (SNe Ib), 56 Type Ic SNe (SNe Ic), and 17 Type Ib/c SNe (SNe Ib/c). We have compared the SE SN subtypes via measurements of the pseudo-equivalent widths (pEWs) and velocities of the He I λλ5876, 7065 and O I λ7774 absorption lines. Consistent with previous work, we find that SNe Ic show higher pEWs and velocities in O I λ7774 compared to SNe IIb and Ib. The pEWs of the He I λλ5876, 7065 lines are similar in SNe Ib and IIb after maximum light. The He I λλ5876, 7065 velocities at maximum light are higher in SNe Ib compared to SNe IIb. We identify an anticorrelation between the He I λ7065 pEW and O I λ7774 velocity among SNe IIb and Ib. This can be interpreted as a continuum in the amount of He present at the time of explosion. It has been suggested that SNe Ib and Ic have similar amounts of He, and that lower mixing could be responsible for hiding He in SNe Ic. However, our data contradict this mixing hypothesis. The observed difference in the expansion rate of the ejecta around maximum light of SNe Ic (Vm = √2Ek/Mej ≈ 15 000 km s−1) and SNe Ib (Vm ≈ 9000 km s−1) would imply an average He mass difference of ∼1.4 M⊙, if the other explosion parameters are assumed to be unchanged between the SE SN subtypes. We conclude that SNe Ic do not hide He but lose He due to envelope stripping.

Helium load on W-O coatings grown by pulsed laser deposition

W-O deposits with complex morphologies and significant He contents will growth on the surface of plasma facing components exposed to He discharges. To mimic the re/co-deposition process, W-O coatings were loaded with He by implanting He+ ions on W films grown by pulsed laser deposition (PLD). The use of appropriate PLD experimental parameters such as pressurised Ar or He background atmospheres induces the deposition of porous or compact W structures enhancing afterwards the gathering of different amounts of O under exposure to atmospheric air. After multiple ion implantation stages using 150 keV, 100 keV and 50 keV incident He+ ion beams with a total fluence of 5 × 1017 ion/cm2, significant amounts of He were identified in porous coatings by Rutherford backscattering (RBS). Time-of-flight elastic recoil detection (ToF-ERDA) measurements showed that most of the implanted He was already released from the porous coatings five month after implantation, while for the case of compact layers the He content remains significant at deeper layers and smoothly decrease towards the surface, as result of a different morphology and nanostructure. The proposed method involving PLD and ion implantation seems adequate to produce W-O films load by He that may be used as reference samples for fusion investigations.

Plasma-wall interaction studies in the full-W ASDEX upgrade during helium plasma discharges

Plasma-wall interactions have been studied in the full-W ASDEX Upgrade during its dedicated helium campaign. Relatively clean plasmas with a He content of >80% could be obtained by applying ion cyclotron wall conditioning (ICWC) discharges upon changeover from D to He. However, co-deposited layers with significant amounts of He and D were measured on W samples exposed to ICWC plasmas at the low-field side (outer) midplane. This is a sign of local migration and accumulation of materials and residual fuel in regions shadowed from direct plasma exposure albeit globally D was removed from the vessel. When exposing W samples to ELMy H-mode helium plasmas in the outer strike-point region, no net erosion was observed but the surfaces had been covered with co-deposited layers mainly consisting of W, B, C, and D and being the thickest on rough and modified surfaces. This is different from the typical erosion-deposition patterns in D plasmas, where usually sharp net-erosion peaks surrounded by prominent net-deposition maxima for W are observed close to the strike point. Moreover, no clear signs of W nanostructure growth or destruction could be seen. The growth of deposited layers may impact the operation of future fusion reactors and is attributed to strong sources in the main chamber that under suitable conditions may switch the balance from net erosion into net deposition, even close to the strike points. In addition, the absence of noticeable chemical erosion in helium plasmas may have affected the thickness of the deposited layers. Retention of He, for its part, remained small and uniform throughout the strike-point region although our results indicate that samples with smooth surfaces can contain an order of magnitude less He than their rough counterparts.

Fabrication and characterization of He-charged ODS-FeCrNi films deposited by a radio-frequency plasma magnetron sputtering technique

He-charged oxide dispersion strengthened (ODS) FeCrNi films were prepared by a radio-frequency (RF) plasma magnetron sputtering method in a He and Ar mixed atmosphere at 150 °C. As a comparison, He-charged FeCrNi films were also fabricated at the same conditions through direct current (DC) plasma magnetron sputtering. The doping of He atoms and Y2O3 in the FeCrNi films was realized by the high backscattered rate of He ions and Y2O3/FeCrNi composite target sputtering method, respectively. Inductive coupled plasma (ICP) and x-ray photoelectron spectroscopy (XPS) analysis confirmed the existence of Y2O3 in FeCrNi films, and Y2O3 content hardly changed with sputtering He/Ar ratio. Cross-sectional scanning electron microscopy (SEM) shows that the FeCrNi films were composed of dense columnar nanocrystallines and the thickness of the films was obviously dependent on He/Ar ratio. Nanoindentation measurements revealed that the FeCrNi films fabricated through DC/RF plasma magnetron sputtering methods exhibited similar hardness values at each He/Ar ratio, while the dispersion of Y2O3 apparently increased the hardness of the films. Elastic recoil detection (ERD) showed that DC/RF magnetron sputtered FeCrNi films contained similar He amounts (∼17 at.%). Compared with the minimal change of He level with depth in DC-sputtered films, the He amount decreases gradually in depth in the RF-sputtered films. The Y2O3-doped FeCrNi films were shown to exhibit much smaller amounts of He owing to the lower backscattering possibility of Y2O3 and the inhibition effect of nano-sized Y2O3 particles on the He element.

Estimation of the long term helium production in high burn-up spent fuel due to alpha decay and consequences for the canister

ABSTRACTIn the KBS-3 repository concept and safety analysis, the copper container with a cast iron insert plays a central role in assuring isolation of the waste from the surrounding during long periods of time. All processes that affect its stability are thoroughly analysed, including potential detrimental processes inside the canister. For this reason, an estimation of the helium produced during the long term decay of alpha emitters in the spent fuel is necessary to evaluate if the pressures generated inside can have consequences for the canister.The spent nuclear fuel to be disposed of in Sweden is mainly LWR fuel. The maximum burn-up expected is 60 MWd/kg U for BWR and PWR. A small quantity of BWR MOX is expected to be stored with a maximum burn-up of 50 MWd/kg U.This work has focused on carrying out calculations of the amounts of He generated during more than 1 million years in Swedish spent nuclear fuels with a benchmarking exercise by using both codes AMBER and Origen-ARP. The performance and agreement of the codes in the He generation from α-decay have been checked and validated against data reported in literature [1].In the calculation of the maximal pressure inside the canister, the quantity of helium used to pre-pressurise the fuel rods has been accounted for. The pressure inside the canister due to He generation is at all times much lower than the hydrostatic pressure and/or the bentonite swelling pressure outside the canister.

Competition Between the Superfluid Overlayer and the Mobile Solid Layer of 3He-4He Mixture Films on Porous Gold

In the previous quartz crystal microbalance measurements for 4He films adsorbed on porous gold, we have observed a competition between superfluidity and slippage: In low areal densities, the resonance frequency increases gradually below T S due to the slippage of solid layer, while at high areal densities the slippage disappears and the superfluid onset of liquid overlayer is observed at T C . In the crossover region, the slippage below T S is suddenly suppressed at T D , which is much lower than T C . In the present work, we introduced a small amount of 3He onto 4He films, and studied the competition as a function of 3He areal density ρ 3. As ρ 3 is increased, T C is monotonically lowered. In contrast, T D increases up to a certain value of ρ 3, and then turns over to decrease in parallel to T C .

Direct Harvesting of Helium-3 (3He) From Heavy Water Nuclear Reactors

The thermal neutron activation of deuterium inside a heavy-water-moderated or -cooled nuclear reactor produces a build-up of tritium in the heavy water. The in situ decay of tritium can, for certain reactor types and operating conditions, produce potentially useable amounts of 3He, which can be directly extracted via the heavy-water cover gas without first separating, collecting and storing tritium outside the reactor. It is estimated that the amount of 3He available for recovery from the moderator cover gas of a 700 MWe class Pressurized Heavy Water Reactor (PHWR) ranges from 0.1 to 0.7 m3 (STP) per annum, varying with the tritium activity buildup in the moderator. The harvesting of 3He would generate approximately 12.7 m3 (STP) of 3He, worth more than $30M at current market rates, over a typical 25-year operating cycle of the PHWR. This paper discusses the production of 3He in the moderator of a PHWR and its extraction from the 4He moderator cover gas system using conventional methods.

On the optimisation of the use of 3He in radiation portal monitors

Radiation Portal Monitors (RPMs) are used to detect illicit trafficking of nuclear or other radioactive material concealed in vehicles, cargo containers or people at strategic check points, such as borders, seaports and airports. Most of them include neutron detectors for the interception of potential plutonium smuggling.The most common technology used for neutron detection in RPMs is based on 3He proportional counters. The recent severe shortage of this rare and expensive gas has created a problem of capacity for manufacturers to provide enough detectors to satisfy the market demand.In this paper we analyse the design of typical commercial RPMs and try to optimise the detector parameters in order either to maximise the efficiency using the same amount of 3He or minimise the amount of gas needed to reach the same detection performance: by reducing the volume or gas pressure in an optimised design.

A novel refrigerator attaining temperature below λ point

The present study proposes a novel refrigerator in theory, which uses 4He as working fluid to directly reach 2.3 K and uses a small amount of 3He to attain the temperature below 1.7 K. The compact and highly efficient new refrigerator works with the Vuilleumier cycle. The novel refrigerator is driven by a thermal compressor which creatively uses mix-refrigerants J-T refrigerator alternative to liquid nitrogen as the power source. Furthermore, the Vuilleumier cycle can be used to achieve temperature below liquid helium with the improvement of the ultra-low temperature regenerator material. A new method of reaching the temperature below 1.7 K is proposed on the regenerative refrigerator, which could be an important breakthrough for the cryogenic science and technology.

Single grain noble gas analysis of Antarctic micrometeorites by stepwise heating method with a newly constructed miniature furnace

Ten micrometeorites weighing 0.14–18.5 μg, each retrieved from surface snow near the Dome Fuji Station, Antarctica (snow-AMMs), were studied to elucidate their noble gases, mineralogy, morphology, and chemical compositions. Low densities in the range of 0.2–1.4 g/cm3 estimated for seven samples suggested a porous inner structure. Noble gases were extracted from each particle using stepwise heating with a laboratory manufactured miniature furnace. Isotopic ratios of He and Ne indicate that the light noble gases with high 4He concentrations ranging from 10−2 to 10−4 cm3 STP/g are mostly of solar origin. The higher concentrations of 4He observed for several samples are comparable with those of IDPs enriched in solar He, but exceed those reported for ice-AMMs. In contrast to He and Ne, heavy noble gases Ar, Kr, and Xe are primordial ones resembling Q-gas trapped in chondrites, although a small contribution of solar Ar is indicated for some samples with higher 36 Ar/132Xe ratios than that for the Q-gas. Three particles released appreciable amounts of He at temperatures lower than 800°C, suggesting heating temperatures lower than 700°C at the time of atmospheric entry. Other particles released at most 10% of total He at the temperatures up to 800°C. Based on their sizes, weights, and release profiles of 4He, initial speeds of less than 14 km/s at atmospheric entry were indicated for the particles. The slow entry speeds imply that all the snow-AMMs studied in this work were likely derived from asteroids. The present work demonstrates that the miniature furnace can be applicable to noble gas analysis of tiny grains from the Itokawa asteroidal regolith materials returned by the Hayabusa mission.

Gas and water geochemistry of geothermal systems in Dominica, Lesser Antilles island arc

Four of the nine potentially active volcanoes on the island of Dominica in the Lesser Antilles volcanic island arc have associated active volcanic-hydrothermal systems. Between 2000 and 2006 the gas and thermal waters from these systems were investigated to geochemically characterise the fluids, gain insight into the temperature and equilibrium state of the underlying reservoirs, and evaluate the feasibility of monitoring geothermal features as a volcano surveillance tool in Dominica. The geothermal gases are typical of those found in arc-type settings, with N 2 excess and low amounts of He and Ar. The dry gas is dominated by CO 2 (ranging from 492 to 993 mmol/mol), and has a hydrothermal signature with hydrogen sulphide as the main sulphurous gas. The waters are predominantly acid-sulphate (SO 4 = 100–4200 mg/L, pH ≤ 4), and likely formed as a result of dilution of acidic gases in near surface oxygenated groundwater. Enrichment in both δ 18O and δD with respect to the global meteoric water line (GMWL) confirms that the waters are of primarily meteoric origin, but have been affected by evaporation processes. Quartz geothermometers gave equilibrium temperatures of 83 °C–203 °C. These temperatures contrast with the higher equilibrium temperature ranges (170 °C–350 °C) obtained for the gases using the H 2/Ar*–CH 4/CO 2 gas ratios plot, suggesting that the quartz geothermometers are affected by non-attainment of equilibrium. This may be a result of precipitation of the dissolved silica and/or dilution by relatively cold shallow aquifers of the thermal fluids. Generally, no significant variations in fluid gas chemistry of the hydrothermal systems were observed during the study period, and we propose that there were no changes in the state of volcanic activity in this period. One exception to this occurred in a feature known as the Boiling Lake, which underwent a month-long period of significant compositional, temperature and water level fluctuations ascribed to a drastic decrease of hydrothermal input related to a perturbation in the lake (probably seismically induced). This geochemical study is part of an ongoing monitoring programme of Dominica geothermal systems, aimed at establishing long-term geochemical observations for the purpose of volcano monitoring.