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This paper describes the natural radioactivity due to (222)Rn and (220)Rn in mineral waters occurring at São Paulo and Minas Gerais states, Brazil, that are extensively used for drinking in public places, bottling and bathing purposes, among other. The measurements of these alpha-emitting radionuclides were also accompanied by the monitoring of temperature and some dissolved gases (O2, CO2 and H2S) in 75 water sources located in 14 municipalities of those states. Eight water sources yielded (220)Rn activity concentration values below the detection limit of 4 mBq/L. On other hand, (222)Rn activity concentration values exceeding the WHO guidance level of 100 Bq/L in drinking-water for public water supplies were found in two springs, named Villela and Dona Beja, whose discharge occurs in areas characterized by the presence of enhanced levels of natural radioelements in rocks. The obtained results were compared with the guidelines of the Brazilian Code of Mineral Waters (BCMW) that was established in 1945 and is still in force in the country. The (222)Rn and (220)Rn activity concentration data allowed perform dose radiation calculations based on the potential alpha energy concentration (PAEC), whose implications for health risk have been also considered in this paper., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Atmospheric gases that dissolve in groundwater at the time of recharge are valuable tracers of groundwater residence time, but corrections are sometimes required. Low‐solubility gases like SF6 are particularly susceptible to the effects of excess air, which is generally assumed to occur at the time of recharge. If after excess air correction SF6 is still elevated above the expected concentration for water in equilibrium with the atmosphere, this is often attributed to a terrigenic source. We propose that compressed air used during and after well installation is a potential source of excess air, which can sometimes explain elevated SF6 concentrations from wells drilled in the last few decades. This concept is demonstrated by correcting elevated SF6 and CFC‐12 measurements from 55 wells at field sites in the Pilbara region of Western Australia with up to 10 mL(STP)/kg of atmospheric air from the time of drilling (2006–2016). The resulting SF6 and CFC‐12 concentrations are consistent with recharge between 1950 and 1970 for most wells. Excess air in recharge from that period could not have contained enough SF6 to explain the measured concentrations. This decoupling of excess air from recharge is potentially also significant for other gaseous age tracers with limited solubility including SF5CF3, Halon 1301, 39Ar, 85Kr, and 81Kr. Key Points: Compressed air can be a source of excess dissolved gases in groundwaterExcess air from drilling might explain elevated SF6 in samples from wellsCorrections are sometimes possible using SF6‐CFC plots [ABSTRACT FROM AUTHOR]

[Display omitted] • Pt n (n = 1–3) cluster as the metal doping greatly improves the gas sensing of MoS 2 monolayer to three characteristic dissolved gases. • The adsorption and sensing property of Pt n (n = 1–3)-MoS 2 monolayer to CO 2 , CO, and H 2 are systematically analyzed and displayed. • Pt n (n = 1–3)-MoS 2 monolayer shows the outstanding and excellent gas sensing and selectivity to three dissolved gases. The adsorption performances and sensing properties of Pt n (n = 1–3) MoS 2 to three characteristic dissolved gases (CO 2 , CO, H 2) generated of partial discharges in converter transformer oil was analyzed using DFT. The adsorption structure, band structure, charge transfer, adsorption energy, density of states, sensitivity and recovery time were utilized to explore the gas adsorption and sensing mechanism. The results demonstrate Pt n (n = 1–3) cluster greatly enhance weak adsorption ability and sensing property of pure MoS 2 for CO 2 , CO, and H 2. This paper provides the theoretical possibility to investigate a novel MoS 2 -based gas sensor. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bromothymol blue's spectral properties were recorded in the presence of heavy water and of some selected electrolytes. • The removal of dissolved gases from the dye solution modifies its UV–vis absorption spectrum. • Re-admitted gases induce specific effects on the spectral features of the dye. The color of the pH indicator Bromothymol blue (BTB) changes from yellow to blue with increasing pH. The effect of some electrolytes (LiCl, NaCl, KCl, CsCl, KSCN and KClO 3) and of D 2 O on the spectral properties of dilute solutions of BTB is explored. The results are interpreted in terms of dimerization of the dye molecules and of the different hydration that D 2 O induces. The effects of dissolved gases on the spectral properties of BTB is studied. Complete removal of dissolved gas is achieved. Surprising effects on the UV–vis spectra emerged. After degassing solutions, gases were re-admitted via bubbling. The gases He, Ar, N 2 , CO 2 and CH 4.were studied. The effects can be explained by presence or absence of nano- and microbubbles of gas in the solution. These allow formation of dimers and multiple association via adsorption and so affect the spectral properties of the dye molecules. [ABSTRACT FROM AUTHOR]

The formation of liquid inclusions is frequently observed to be disrupting in crystallization processes. But such crystals containing liquid inclusions might offer the possibility to be used as container systems by encapsulating other substances inside the inclusions. Experimental parameters to generate such microcontainer systems, i.e., crystals including liquid inclusions, of salicylic acid by means of antisolvent crystallization were investigated. It was shown that concentration, addition rate of the antisolvent, and gas content of the liquids related to the temperature have a distinct influence on the size of the formed inclusions. [ABSTRACT FROM AUTHOR]

This work presents the temporal evolution (April 2016 to June 2020) of the chemical and isotopic content of dissolved gas species (CO 2 , He, O 2 , N 2 and CH 4) present in groundwater at the Fuente del Valle (FV) and San Fernando (SF) galleries (Tenerife, Spain), and their relationship with the seismic activity observed on the island. CO 2 is the major dissolved gas species in the groundwater at both galleries, and the δ13C-CO 2 data show a clear endogenous origin as a result of interaction with deep fluids. A bubbling gas sample from Fuente del Valle revealed CO 2 rich gas with a considerable He component. The isotopic data of both components (δ13C-CO 2 and 3He/4He) in the bubbling gas support the sources inferred from the dissolved gas compositions, with the endogenous component affected by changes in volcanic-hydrothermal system activity. On October 2, 2016, a seismic swarm occurred, followed by an increase in seismic activity throughout Tenerife. After the event, geochemical variations were registered in the dissolved gas species, e.g., an increase in dissolved CO 2 and He content and CO 2 /O 2 , He/CO 2 , He/N 2 and CH 4 /CO 2 ratios. These changes suggest an injection of fluids into the Tenerife hydrothermal system during October 2016, confirming a connection between groundwater and the hydrothermal system. This investigation highlights the relevance of dissolved gases in groundwater as a tool for volcanic surveillance. • First extensive study of dissolved gases in groundwaters from Tenerife • Dissolved gas concentrations show changes coupled with a seismic swarm on Tenerife • Groundwaters have considerable dissolved He and CO 2 • Isotopic data provide important information about the endogenous origin of dissolved gases [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the natural radioactivity due to 222Rn and 220Rn in mineral waters occurring at São Paulo and Minas Gerais states, Brazil, that are extensively used for drinking in public places, bottling and bathing purposes, among other. The measurements of these alpha-emitting radionuclides were also accompanied by the monitoring of temperature and some dissolved gases (O2, CO2 and H2S) in 75 water sources located in 14 municipalities of those states. Eight water sources yielded 220Rn activity concentration values below the detection limit of 4 mBq/L. On other hand, 222Rn activity concentration values exceeding the WHO guidance level of 100 Bq/L in drinking-water for public water supplies were found in two springs, named Villela and Dona Beja, whose discharge occurs in areas characterized by the presence of enhanced levels of natural radioelements in rocks. The obtained results were compared with the guidelines of the Brazilian Code of Mineral Waters (BCMW) that was established in 1945 and is still in force in the country. The 222Rn and 220Rn activity concentration data allowed perform dose radiation calculations based on the potential alpha energy concentration (PAEC), whose implications for health risk have been also considered in this paper. [Copyright &y& Elsevier]

An improved method based on equilibrium partitioning between water samples and an inert host gas, introduced after sampling, is proposed for determining multiple species of dissolved gases in brackish water. The method itself, and the most convenient equations for describing gas solubilities in brackish waters, is described in detail. The method allows the rapid characterization of several sites and represents a useful tool for geochemical surveys. A comparison between replicate samples analyzed using different procedures demonstrates the efficiency of the method and indicates that the abundances of the main dissolved gases can be obtained, which can then be used to determine underlying geochemical processes. A Microsoft Excel worksheet is provided to easily calculate the concentration of dissolved gas species. [ABSTRACT FROM AUTHOR]

With reference to developed microfluidic systems, an experimental investigation is performed to define the effect of dissolved gases on the explosive evaporation of liquid in a confined microchamber. A stroboscopic imaging technique was used to visualize the stages of explosive evaporation. It was found that for liquids containing dissolved gases, a large, long-living gas bubble forms under the impulsively heated surface. During vapor cavity growth and collapse, the gas bubble is deformed and destroyed. Complicated bubble structures are formed. A gas bubble strongly damps the growth of the vapor cavity, which should be considered for design purposes. [ABSTRACT FROM AUTHOR]

• We sampled air and water at different depths until 120 m along a thick vadose zone. • We investigated transfers of gas and groundwater through a thick vadose zone. • We investigated Excess Air formation in a karstic system with a thick vadose zone. • The air of the vadose zone is in equilibrium with the atmosphere until 120 m. • The main part of Excess Air is formed due to water table variations. This study analyses the impact of a thick vadose zone on gaseous transfers and Excess Air (EA) formation using dissolved noble and anthropogenic gas tracers (Ne, Ar, N 2 , CFC, SF 6 , O 2 and CO 2). Understanding gas transfers integrates the issues of equilibrium and water/air exchanges along the vadose zone. In this study, the noble and anthropogenic gases were analysed in air and water over vadose zone depths of 120 m and over two contrasted hydrodynamic periods therefore enabling a rare insight into the spatial and seasonal variations of equilibrium and water/air exchanges in a heterogeneous karst environment. The results highlight that both noble and anthropogenic gases of the caves are in equilibrium with the atmosphere up to at least depths of 120 m. In water, the Noble Gas Temperature (NGT) remains stable at 8 °C whilst some EA is formed (up to 1.3 cm3 STP/kg at 120 m) during transfers in the vadose zone. The high EA concentrations measured at the spring outlet, until 10.7 cm3 STP/kg, cannot be explained by an increase during transfers via the vadose zone. This high EA concentration is due to rapid and high water level variations during recharge. The implications of these results are important to advance our understanding in the use of noble and anthropogenic gases in characterising recharge and quantifying groundwater residence times. In particular, these results help to identify the parts of the aquifer actively involved in dissolved gas transfers, highlight the futility of using a time-lag factor for groundwater residence times in karstic systems, and improve our understanding of the EA formation processes. [ABSTRACT FROM AUTHOR]

Abstract: We present high-precision measurements by a new isotope dilution technique of a suite of inert gases in the North Pacific. Remarkably smooth gradients in Ar, Kr and Xe from near equilibrium in intermediate waters to several percent undersaturated in deep waters were observed. The general pattern in the deepest waters was that Ar, Kr and Xe were undersaturated (Ar least and Xe most), while N2 was close to equilibrium, and Ne was supersaturated. We propose that this pattern was produced by the interaction between the different physical properties of the gases (solubility and the temperature dependence of solubility) with the rapid cooling and high wind speeds that characterize deep-water formation regions. In a simple model of deep-water formation by convection, the saturations of the more temperature-sensitive gases were quickly driven down by rapid cooling and could not reequilibrate with the atmosphere before the end of the winter. In contrast, the gas exchange rate of the more bubble-sensitive gases (Ne and N2) was able to meet or exceed the drawdown by cooling. Our simple convection model demonstrates that the heavier noble gases (Ar, Kr and Xe) are sensitive on seasonal timescales to the competing effects of cooling and air–sea gas exchange that are also important to setting the concentration of CO2 in newly formed waters. [Copyright &y& Elsevier]

Dissolution testing is a critical method for the determination of pharmaceutical product quality and bioequivalence. For some products, dissolved gases in the dissolution medium affect dissolution results thus requiring degassing of the medium prior to use. In this study, we use a total dissolved gas and oxygen meter to measure both oxygen and total gases in dissolution media before and after application of a variety of deaeration methods. Dissolution testing results using a 10 mg Prednisone tablet (NCDA #2) are compared with the percent saturation of oxygen and total gases found in the medium. Reaeration of the medium during different stirring rates was also measured. This study confirms that measurement of total gases and not just oxygen in the medium is necessary to assess adequacy for dissolution testing. For those deaeration techniques that are performed at room temperature, the percent saturation of the total dissolved gases must be well below 100% to prevent outgassing once medium is brought to dissolution test method temperature, typically 37°C. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95: 1606–1613, 2006 [ABSTRACT FROM AUTHOR]

Nutrient ecology and trace gas processing are intimately coupled in the surface ocean and participate in key linkages through the Earth biogeochemical system. We have added water column photochemistry for volatile sulfur and organic compounds to large scale nutrient cycle modules, in order to create a one dimensional, open ocean ecochemistry simulator. Phyto- and zooplankton, recyclers and biological waste products are represented through N and Fe densities. Dimethyl sulfide, carbonyl sulfide and the methyl halides are tracked individually along with certain precursors and nonmethane hydrocarbons. The model is applied along the 180 degree meridian in the Northern Hemisphere. Ecodynamics are validated against satellite ocean color maps. Biological/photochemical production terms are then iterated upon to match measured distributions for the trace gases. Data are most complete for dimethyl sulfide. Major patterns in its climatology are captured within individual ecological provinces. However, at the basin scale reduced sulfur release must be varied over almost an order of magnitude because the mechanism developed contains only one plant taxon. Based on sparser data, first order rate constants are estimated for phytoplanktonic exudation of the methyl halides. Parameters are also established for photolytic injection of carbonyl sulfide and propylene from the dissolved organics. Ocean general circulation models and interactive ocean-atmosphere transport simulations are discussed as frameworks for future application. [ABSTRACT FROM AUTHOR]

• Surprisingly, recent papers claim higher sonochemical production of H 2 under pure CO 2. • Modeling considerations of the sonolytic formation of H 2 under different saturation gases are highlighted. • Dissolved gases affect the sonochemical production of H 2 through physical and chemical pathways. • For CO 2 -saturated water, degassing bubbles are formed instead of transient cavitation. • CO 2 effects on sonolytic production of H 2 in recent papers are mostly due to wrong procedures. Although most of researchers agree on the elementary reactions behind the sonolytic formation of molecular hydrogen (H 2) from water, namely the radical attack of H 2 O and H 2 O 2 and the free radicals recombination, several recent papers ignore the intervention of the dissolved gas molecules in the kinetic pathways of free radicals, and hence may wrongly assess the effect of dissolved gases on the sonochemical production of hydrogen. One may fairly ask to which extent is it acceptable to ignore the role of the dissolved gas and its eventual decomposition inside the acoustic cavitation bubble? The present opinion paper discusses numerically the ways in which the nature of dissolved gas, i.e., N 2 , O 2 , Ar and air, may influence the kinetics of sonochemical hydrogen formation. The model evaluates the extent of direct physical effects, i.e., dynamics of bubble oscillation and collapse events if any, against indirect chemical effects, i.e., the chemical reactions of free radicals formation and consequently hydrogen emergence, it demonstrates the improvement in the sonochemical hydrogen production under argon and sheds light on several misinterpretations reported in earlier works, due to wrong assumptions mainly related to initial conditions. The paper also highlights the role of dissolved gases in the nature of created cavitation and hence the eventual bubble population phenomena that may prevent the achievement of the sonochemical activity. This is particularly demonstrated experimentally using a 20 kHz Sinaptec transducer and a Photron SA 5 high speed camera, in the case of CO 2 -saturated water where degassing bubbles are formed instead of transient cavitation. [ABSTRACT FROM AUTHOR]