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Hot thermal fluids flow through the Earth's crust and carry valuable information about the deep subsurface. The monitoring of natural tracers transported in geothermal fluids, such as gases or ions, are relevant to better understand the geological processes in the Earth's subsurface and their relation to deep fluid dynamics. Recently developed technologies (e.g., portable gas-equilibrium membrane-inlet mass spectrometry) allow for the continuous monitoring of gas species at a much higher temporal resolution than the sampling procedures commonly used, based on a few individual samples. However, the monitoring of gas species from hot thermal fluids still poses experimental challenges tied to unwanted water vapor condensation in the headspace of the separation module, which irremediably leads to clogging (e.g., of the connecting capillaries) and failure of the detection device. In this contribution, we present two new experimental methods that provide suitable technical conditions to measure gases, even in high temperature geothermal fluids, using a portable gas analyzer. Two sites with different thermal water temperatures (first one ranging from 50 °C to 65 °C and second one close to boiling temperature) were selected. The first method was deployed on the thermal waters of Lavey-les-Bains (Vaud, Switzerland), for which we report results from October 2021. The second method was used in Beppu (Oita Prefecture, Japan), for which we report results from April 2018. Our results show that at both sites, our methods allow for continuous measurements of gas species (N2, Ar, O2, Kr, He, CH4, CO2 and H2) in thermal waters. Furthermore, they show that the variability of gas emanation from the two sites can only be adequately described by measurements with high temporal resolution, which both methods allow., Frontiers in Water, 4, ISSN:2624-9375

The present research is focused on the gravity-driven flashing of metastable water, a phenomenon which may be encountered in any system being heated from below, where an uprising hot fluid experiences a significant decrease in hydrostatic pressure. For sufficiently large vertical systems, be they a deep pool or some long duct such as a geyser, the temperature of the flowing fluid may exceed its saturation value and reach a so-called superheated, metastable state. From that situation, the metastable liquid may spontaneously vaporize through the form of bubbles as a way to tend toward thermal saturation, a process referred to as flashing. Specifically in this research, the emphasis is put on the case of a water pool heated from below, motivated by the absence in the scientific literature of any known report of the phenomenon in this precise configuration. By means of an experimental device called Aquarius, specifically designed and constructed during this research, the phenomenon is first evidenced in a heated pool. Then, its main characteristics are highlighted: instead of observing a cyclic flashing as for geysers, the emergence of bubbles from the superheated liquid appears typically steady in the presented tests. In addition, those created bubbles do emerge within the liquid bulk itself, into the most superheated area of the pool: underneath the liquid free surface. The dependence of the bubble production process on the heating power, operating pressure, initial pool level and amount of dissolved gases in the pool is then investigated. At last, an experimental data reduction by means of a set of mathematical correlations is achieved and a simple thermodynamic modeling of the studied system is proposed. (FSA - Sciences de l'ingénieur) -- UCL, 2023

This report details the quality control (QC) procedures applied to oxygen data collected from the Southern Ocean Time Series (SOTS) moorings between 2009 and 2021. These measurements help to quantify net community production (and thus carbon export). The quality controlled datasets are publicly available via the AODN Data Portal. This report should be consulted when using the data Published Refereed Current 14.a Oxygen Mature Organisational Multi-organisational National N/A N/A N/A N/A Method

International audience; Dissolved gases are particularly relevant tools for the investigation of environmental processes. Indeed, their solubility being a function of the variables of physical state of the medium (temperature, pressure, salinity), the dissolved noble gases are for instance good indicators of equilibrium conditions with the atmosphere and mixing of water bodies. Dissolved gases can also inform the biogeochemical functioning of natural systems by providing information on major processes such as photosynthesis, respiration or denitrification. Classical methods relying on the sampling, the storage and the ex situ analysis of water samples for the measurement of dissolved gases suffer from the difficulty of taking sufficiently frequent and representative samples as well as the analyte preservation. High-frequency in situ measurement of dissolved gases is therefore the most relevant for the study of environmental processes. The use of Membrane Inlet Mass Spectrometer (MIMS) technology provides access to high frequency measurements of a large set of dissolved gases in the field (He, Ne, Ar, Kr, Xe, N2, O2, CO2, CH4, N2O, H2) which offers a real opportunity for environmental studies.

The live version of this SOP is on the Ocean Gliders community in GITHUB. The home repository of this publication is in the Ocean Best Practices Repository. This standard operating procedure (SOP) document for dissolved oxygen (DO) aims to guide the user through the steps necessary to collect good quality dissolved oxygen data using ocean gliders for both real time and post deployment data streams.

The technique of physical modeling of macro processes of solidification of castings on transparent models and liquids has been developed. The model liquids may be water with different salt contents. Glass bottles can be used for transparent models. Thermal insulation of the top of the model is required. The developed technique allows to investigate the effect of dissolved gases on the microstructure of castings. It has been shown that gases dissolved in liquids have a direct effect on the solidification process and its kinetics. It has been shown that hot water containing less dissolved air than cold water solidifies in the freezer faster than cold water.

Ushbu maqolada suyuqlik qaynash jarayonining fizik xususiyatlari ilmiy hamda tahliliy bayon qilinadi., This article describes the physical properties of the liquid boiling process scientifically and analytically.

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, N2, CFC, SF6, O2 and CO2). 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.

ilustraciones, gráficas, tablas El área periférica de la isla de Stromboli cuenta con distintos ambientes naturales idóneos para la evaluación y monitoreo del sistema volcánico activo; en este caso el agua del acuífero termal se caracteriza por presentar temperaturas hasta de 50°C y altas concentraciones de CO2 disuelto como resultado de desgasificación del magma. Estos aspectos permitieron modelar el sistema hidrotermal, evaluar la composición química y la temperatura del sistema geotérmico que alimenta los fluidos superficiales a partir de pozos termales localizados sobre el acuifero. El sistema hidrotermal en general es una mezcla de agua de mar y agua geotérmica en diferentes porcentajes. El estudio de la composición química e isotópica de las aguas de los pozos ha permitido estimar los diferentes porcentajes de mezcla, la temperatura del sistema geotérmico en profundidad y evaluar la interaccion del agua del acuífero con las rocas del reservorio. La temperatura del sistema geotérmico es alrededor de 180°C ±10°C y la composición química de los iones mayores es gobernada por agua de mar modificada con porcentajes de Cl- de 150 meq/l aproximadamente y con altos contenidos de K+ y de HCO3- entre (8 y 13 meq/l respectivamente), debido a procesos de interacción agua/roca y disolución de CO2 en el agua termal. (Texto tomado de la fuente). Geochemical modeling of the fluids of the peripheral system of the Stromboli Volcano and its relationship with recent volcanic activity The peripheral area of the island of Stromboli has different natural environments suitable for the evaluation and monitoring of the active volcanic system, in this case the thermal aquifer is characterized by presenting wells that capture water with temperatures up to 50°C and high concentrations of CO2 dissolved as a result of magma degassing. These aspects allowed modeling the hydrothermal system and evaluating the chemical composition and temperature of the geothermal system that feeds the surface fluids. The hydrothermal system in general is a mixture of seawater and geothermal water in different percentages. The study of the chemical and isotopic composition of the water from the wells has made it possible to estimate the different percentages and the temperature of the deep geothermal system, characterizing and evaluating the seawater modified by interaction with the rocks of the reservoir. The temperature of the deep geothermal system is around 180°C ±10°C and the chemical composition of the major ions is governed by modified seawater with Cl- percentages of approximately 150 meq/l and with high K+ and HCO3- contents, (between 8 and 13 meq/l respectively), due to water/rock interaction processes and dissolution of CO2 in the thermal water. El Istituto Nazionale di Geofisica e Vulcanologia (INGV) ,es una de las mayores instituciones europeas de investigación en el campo de las ciencias de la Tierra. Es responsable del estudio de los fenómenos geofísicos y vulcanológicos y de la gestión de las respectivas redes nacionales de monitoreo de fenómenos sísmicos y volcánicos . Maestría Magíster en Ciencias - Geología

C2H6 and C2H4 gases are two typical decompositions produced by partial discharge of transformer oil. To fully evaluate the feasibility of MoS2-based materials for the detection of C2H6 and C2H4 gases, the adsorption of C2H6 and C2H4 molecules on intrinsic and Au-doped MoS2 monolayer have been studied in this paper by the First-principle of Density Functional Theory (DFT). The adsorption mechanism of MoS2-based monolayer were investigated carefully in terms of adsorption energy, adsorption distance, bandgap structure, charge transfer and density of states (DOS). The calculated results show that the adsorption structures of the C2H6 and C2H4 molecules on Au-doped MoS2 monolayer with larger adsorption energies were stable, and have shorter adsorption distance, higher charge transfer, and stronger orbital hybridization compared with the corresponding MoS2 monolayer adsorption structures. It is concluded that the doped-Au atom affects the electronic structure of MoS2 monolayer to enhance the adsorption capacity. From this aspect, the present research offers a theoretical guidance to the application of Au-doped MoS2 materials as the sensing material for C2H6 and C2H4 gases.

Highlights • Surprisingly, recent papers claim higher sonochemical production of H2 under pure CO2. • Modeling considerations of the sonolytic formation of H2 under different saturation gases are highlighted. • Dissolved gases affect the sonochemical production of H2 through physical and chemical pathways. • For CO2-saturated water, degassing bubbles are formed instead of transient cavitation. • CO2 effects on sonolytic production of H2 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 (H2) from water, namely the radical attack of H2O and H2O2 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., N2, O2, 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 CO2-saturated water where degassing bubbles are formed instead of transient cavitation.

In this work, a high sensitivity micro-thermal conductivity detector (&mu, TCD) with four thermal conductivity cells was proposed. Compared with conventional TCD sensors, the thermal conductivity cell in this work was designed as a streamlined structure, the thermistors were supported by a strong cantilever beam and suspended in the center of the thermal conductivity cell, which was able to greatly reduce the dead volume of the thermal conductivity cell and the heat loss of the substrate, improving the detection sensitivity. The experimental results demonstrated that the &mu, TCD shows good stability and high sensitivity, which could rapidly detect light gases with a detection limit of 10 ppm and a quantitative repeatability of less than 1.1%.

Sicily hosts many natural manifestations that include thermal waters, gas discharges and mud volcanoes. Due to the significant geodynamic and geological differences, the fluid discharges along a NE-WS–oriented transect that run from the Peloritani Mts. to the Sciacca Plain shows a large variability in water and gas chemical and isotopic compositions. The studied waters are characterized by Ca-HCO3, Ca(Mg)-SO4, Ca-Cl and Na-Cl compositions produced by distinct geochemical processes such as water-rock-gas interactions, mixing between deep and shallow aquifers and seawater and direct and reverse ion exchanges. The gas chemistry is dominated by CO2 to the east and CO2-N2 to the west of the study area, whereas the central part shows mud volcanoes discharging CH4-rich gases. Water isotopes suggest that the thermal waters are fed by a meteoric recharge, although isotopic exchange processes between thermal fluids and host rocks at temperature >150°C are recognized. Accordingly, liquid geothermometry suggests equilibrium temperatures up to 220°C. The carbon in CO2 and helium isotopes of the emissions from the westernmost sector of Sicily indicate that these two gases consists of up to 40 % of a mantle component, the latter decreasing to the east down to 10% where CO2 of thermometamorphic origin dominates. Accordingly, conceptual models of the fluid circulation for the western, central and eastern sectors are proposed. The regional geothermal reservoir, hosted in carbonates in the western sector and locally outcropping, is of low to medium temperature. Higher temperature conditions (up to 200-220°C) are suggested by geothermometry and probably related to deeper levels of the system. Sicily can be regarded as a potentially suitable area for future investigations to evaluate specific activities aimed at exploiting the geothermal resource.

Free and dissolved gases in cold water samples from the Castrocaro spa, Northern Italy, were analyzed for their chemical composition. These gases were interpreted as the result of the binary mixing between a N2- and a CH4-rich component. CO2 is generally a minor constituent. N2/Ar ratios below the air typical value suggest that air saturated water (ASW) is the most likely source of atmospheric-derived components. This atmospheric end-member is predominant in low-salinity waters. Conversely, CH4-enriched gases are mainly associated with brackish to saline waters. The occurrence of minor amounts of light hydrocarbons (C2-C3) indicates a predominant biogenic origin of CH4. The He isotopic composition of the CH4-richest sample (3He/4He = 0.22 Ra) is in the range of values measured for cold seeps and mud volcanoes along the Northern Apennines foothills, and indicates a predominant crustal origin of this gas.

The utilization of groundwater heat pump systems is increasing in Norway, which are currently widely employed for heating and cooling applications in the town center of Melhus. The investigations of the Melhus installations are detecting gas exsolution as a possible trigger for precipitation reaction that causes incrustation of iron and manganese compounds in the systems. This paper discusses risks associated with gas exsolution and considers gas exsolution triggers in a typical Norwegian groundwater heat pump (GWHP) system configuration. The concept of the solubility grade line (SGL) is developed and suggested as a tool for optimizing the design. Based on SGL analysis and the intention of avoiding gas exsolution during heat production, an alternative system design in the same aquifer is presented and compared. The analyses show that the traditional system design is predisposed to gas clogging risks and prone to vacuum pressures in parts of the system. The alternative design mediates the risks by adjusting the well and piping configuration and by applying a backpressure technique. The results demonstrate how the groundwater heat pump system design can be customized according to local aquifer conditions to avoid gas exsolution during operation. It is recommended that the presented method of analysis should be utilized in dimensioning of systems and included in the monitoring scheme of the systems. © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

To realize a high response and high selectivity gas sensor for the detection dissolved gases in transformer oil, in this study, the adsorption of four kinds of gases (H2, CO, C2H2, and CH4) on Pd-graphyne was investigated, and the gas sensing properties were evaluated. The energetically-favorable structure of Pd-Doped &gamma, graphyne was first studied, including through a comparison of different adsorption sites and a discussion of the electronic properties. Then, the adsorption of these four molecules on Pd-graphyne was explored. The adsorption structure, adsorption energy, electron transfer, electron density distribution, band structure, and density of states were calculated and analyzed. The results show that Pd prefers to be adsorbed on the middle of three C&equiv, C bonds, and that the band gap of &gamma, graphyne becomes smaller after adsorption. The CO adsorption exhibits the largest adsorption energy and electron transfer, and effects an obvious change to the structure and electronic properties to Pd-graphyne. Because of the conductance decrease after adsorption of CO and the acceptable recovery time at high temperatures, Pd-graphyne is a promising gas sensing material with which to detect CO with high selectivity. This work offers theoretical support for the design of a nanomaterial-based gas sensor using a novel structure for industrial applications.

Na nastanek kavitacije vpliva kvaliteta vode, ki jo določa količina neraztopljenih plinov v njej. V raziskovalnem delu smo z Van Slykovo napravo iz leta 1917, ki se je sprva uporabljala za določevanje plinov v krvi, želeli določiti, koliko raztopljenih in neraztopljenih plinov se izloči v vodah različne kvalitete. Z omenjeno napravo lahko določamo le skupno količino plinov, torej raztopljenih in neraztopljenih, ki so se po opravljenem eksperimentu izločili iz vode. Rezultate smo ustrezno preračunali in na njihovi podlagi določili količino raztopljenega in neraztopljenega kisika, ki se je izločil iz vode. Ker zgolj s to metodo ne moremo določiti vsebnosti raztopljenega in neraztopljenega kisika, smo rezultate teh meritev združili z meritvami, ki smo jih pridobili z optičnim merjenjem koncentracije raztopljenega kisika. Eksperiment smo izvajali z vzorci deionizirane in vodovodne vode. Na podlagi meritev smo ugotovili, da ima vodovodna voda večji delež neraztopljenega kisika. Neraztopljeni plini se nahajajo v mikromehurčkih oziroma so ujeti v kavitacijska jedra, zato lahko na podlagi rezultatov, pridobljenih iz eksperimentalnega dela, podamo ugotovitev, da se kavitacija pogosteje pojavlja v vodovodni vodi. The formation of cavitation is influenced by the quality of the water, which is determined by the amount of dissolved gases in it. In our research work we wanted to determine, how much dissolved and undissolved gases are excreted in waters of varying quality. We worked with the Van Slyke apparatus from 1917, which was initially used to determine blood gases. With this device we can only determine the total amount of gases, that is dissolved and undissolved, which have been eliminated from the water after the experiment. The results were also appropriately calculated, so we could determine the amount of dissolved and undissolved oxygen that was released from the water. Because dissolved and undissolved oxygen content can’t be determined only by this method, we combined the results of these measurements with those obtained by optical measurement of dissolved oxygen concentration. The experiment was carried out with samples of deionized and tap water. Based on measurements, we found out that tap water has a higher proportion of undissolved oxygen. The undissolved gases are located in the microbubbles or are trapped in the cavitation core, therefore, based on the results obtained from the experimental work, we can conclude that cavitation occurs more frequently in tap water.

A solution for forecasting the dissolved gases in oil-immersed transformers has been proposed based on the wavelet technique and least squares support vector machine. In order to optimize the hyper-parameters of the constructed wavelet LS-SVM regression, the imperialist competition algorithm was then applied. In this study, the assessment of prediction performance is based on the squared correlation coefficient and mean absolute percentage error methods. According to the proposed method, this novel procedure was applied to a simulated case and the experimental results show that the dissolved gas contents could be accurately predicted using this method. Besides, the proposed approach was compared to other prediction methods such as the back propagation neural network, the radial basis function neural network, and generalized regression neural network. By comparison, it was inferred that this method is more effective than previous forecasting methods.

Hydrogen is an important intermediate that is produced during carbohydrate fermentation to volatile fatty acid and utilized by methanogens to produce methane in the rumen. Ruminal volatile fatty acid and dissolved methane concentrations are more than 500 times greater than dissolved hydrogen concentration. Therefore, we hypothesized that dissolved hydrogen might have a higher sensitivity in response to dietary changes compared with volatile fatty acid and dissolved methane. Using goats, we investigated the effects of increasing dietary starch content (maize replaced with wheat bran) and supplementing with rhubarb rhizomes and roots on the relationships among dissolved hydrogen, dissolved methane and other fermentation end products. The study was conducted in a replicated 4×4 Latin square with a 2×2 factorial arrangement of four treatments: two starch levels (220 v. 320 g/kg dry matter (DM)), without and with rhubarb supplement (0% v. 2.8% of total mixed ration). Increased dietary starch and rhubarb supplementation did not alter volatile fatty acid concentrations or methane emissions in terms of g/day, g/g DM intake and g/g organic matter digested. However, goats fed the high-starch diet had greater dissolved hydrogen (P=0.005) and relative abundance of Selenomonas ruminantium (Plt;0.01), and lower (P=0.02) copy number of protozoa than those fed the low-starch diet. Rhubarb increased ruminal dissolved H2 (P=0.03) and total volatile fatty acid concentration (Plt;0.001), but decreased copies of bacteria (P=0.002). In conclusion, dissolved hydrogen appears to be more sensitive to dietary changes with starch content and rhubarb supplementation, when compared with volatile fatty acid concentrations and methane production.

Dissolved gas analysis (DGA) is widely used to detect the incipient fault of power transformers. However, the accuracy is greatly limited by selection of DGA features and performance of fault diagnostic model. This paper proposed a fault diagnostic method integrating feature selection and diagnostic model optimization. Firstly, this paper set up three feature sets with eight basic DGA gases, 28 DGA gas ratios and 36 hybrid DGA features, respectively. Then, to eliminate the interference of weak-relevant and irrelevant features, the genetic-algorithm-SVM-feature-screen (GA-SVM-FS) model was built to screen out the optimal hybrid DGA features subset (OHFS) from three feature sets. Next, using the OHFS as the input, the support vector machine (SVM) multi-classifier optimized by ISGOSVM (SVM classifier optimized by improved social group optimization) was built to diagnose fault types of transformers. Finally, the performance of OHFS and ISGOSVM diagnostic model was tested and compared with traditional DGA features and diagnostic models, respectively. The results show that the OHFS screened out is comprised of 14 features, including 12 gas ratios and two gases. The accuracy of OHFS is 3–30% higher than traditional DGA features, and the accuracy of ISGOSVM can increase by 3% to 14% compared with the SGOSVM (SVM classifier optimized by social group optimization), GASVM (SVM classifier optimized by genetic algorithm optimization), PSOSVM (SVM classifier optimized by particle swarm optimization), and SVM diagnostic models. The proposed approach integrating the OHFS with ISGOSVM achieves the highest accuracy of fault diagnose (92.86%).

Cloudy apple juice has been treated by thermosonication in batch mode as an alternative processing to thermal treatment. Thermosonication was found to be effective to inactivate polyphenol oxidase; however, pectinmethylesterase was found to be more resistant. An increase of the working ultrasound amplitude and the amount of energy supplied to the juice led to lower enzyme residual activities. Enzyme inactivation kinetics were determined at different temperatures (from 44 to 67 °C). Inactivation data were described by the first order kinetic model and the Weibull model, both models yielding good fitting. Thermosonication treatment caused a homogenization effect reflected in the shifting of the particle size distribution towards smaller diameters. The effect of the nature of dissolved gases in the juice on enzyme inactivation was studied by displacing the air dissolved in the juice by bubbling nitrogen or carbon dioxide, previous to the thermosonication experiments. Higher inactivation rates were obtained by displacing the air with nitrogen. Industrial relevance Consumers demand of natural and fresh-like products has driven the food industry to investigate alternative technologies to replace conventional food heat treatments that may affect food quality. Among these technologies, thermosonication treatment is an attractive technology that can inactivate microorganisms and enzymes. This work shows that some enzymes that cause deleterious effect on cloudy apple juice can be more effectively inactivated by thermosonication than by thermal treatment, in the same temperature range, reducing the damages caused by heating., Spanish Government (MINECO) and the European Regional Development Fund (ERDF) for financial support of project CTQ2015- 64396-R and AEI's contract. To MINECO for RM's pre-doctoral contract (BES-2013-063937). To University of Burgos for AGS's pre-doctoral contract. To Consejería de Educación, Junta de Castilla y León and ERDF for financial support of project BU055U16 and O. Benito Román´s Post-doctoral contract.

Hypothesis In literature it is stated that the stability of oil-in-water emulsions could be enhanced by decreasing the so-called “hydrophobic interactions” between surfaces through removal of dissolved atmospheric gases. Since the effect of the dissolved gases depends on the hydrophobicity of the oil phase, as well as the system pressure, we vary this effect systematically and monitor droplet coalescence in a tailor-made microfluidic device. Experiments The coalescence of oil drops in standard and degassed conditions was studied by direct observation using a microfluidic setup. Two model oils (heptane and xylene) were used to represent different hydrophobicity of the dispersed phases, together with an oil with dynamic interfacial behaviour (diluted crude oil). In addition, the effect of the volume fraction, droplet size and degassing method was studied. Findings At ambient pressure, the degassing of the continuous phase reduced the extent of coalescence for the model oils, which is in agreement with other reports. No effect of the dissolved gases was found on the drop formation process. At elevated pressures, the dissolved gases influenced only the most hydrophobic oil (heptane), while causing no effect in the other systems. The coalescence frequencies decreased upon the reduction of the drop sizes, which was justified with the theory for two interacting spheres.

The growing awareness of global warming potential has internationally aroused interest and demand in reducing greenhouse gas emissions produced by human activity. Each year, the UK consumes a significant amount of energy for residential and industrial space heating and domestic hot water production. At present, gas boilers are mostly installed in the domestic water heating which contributes significantly to excessive CO2 emissions and consumption of primary energy resources. However, air-source heat pump system has higher performance efficiency comparing to the traditional gas boiler, which can reduce the carbon dioxide emission and the usage of primary energy resources. The coefficient of efficiency of the heat pump can be range from 2 to 4.5 in various situations. The market shares of heat pump have been predicted to increase in the coming years to meet the requirement of the European Union Commission. There were about 22,000 heat pumps set up in the UK with 18 percent growth comparing to 2016 as reported by BSRIA. A range from 0.6 to 5.7 million heat pumps are estimated by the National Grid to be set up by 2030 to increase the energy efficiency of the UK. Although the energy efficiency of the heat pump is extremely high, there is still a space for improvement in air-source heat pump water heating system. The performance of the heat pump water heating system can be further enhanced if the dissolved gases in its hot water circuit can be efficiently discharged. The undissolved bubbles can stack in a specific position of the radiator, which would cause the cold spot. This could immensely reduce the efficiency of the heat pump water heating system. To avoid this happening, the bubble behaviors in the heat pump water heating system need to be extensively investigated. The better understanding of the bubble behaviors in an air-source heat pump water heating system can contribute to the design of an air evacuation valve and heat pump piping systems. In this thesis, the effects of various heat pump hot water side parameters on gas microbubble diameters and bubble productions were measured and analyzed by varying different experimental conditions. Correspondingly, a summarized conclusion has been presented to predict the gas microbubble’s diameter distributions and volumetric void fraction distributions at different operating conditions. These parameters include various system pressures, water flow rates, and saturation ratios. In this thesis, the main results showed that larger average bubble diameter is at the higher water flow rates at heat pump exit. At 2.2 bar condition, when system water flow rate increased from 800 l/h to 1150 l/h, the average bubble diameter increased from 0.086 mm to 0.108 mm. Moreover, the average bubble diameters increase along with the decrease in system pressures. At 1000 l/h condition, when system pressure increased from 2.2 bar to 2.7 bar, the average bubble diameter decreased from 0.100 mm to 0.087 mm. At 850 l/h condition, when system pressure increased from 1.7 bar to 2.5 bar, the average bubble diameter decreased from 0.101 mm to 0.081 mm. In addition, the average bubble diameters slightly increase along with the increase in saturation ratio. Besides, a prediction equation for the bubble diameter distribution in the water pipe was proposed. At SR 1.15 and 2.5 bar condition, when water flow rate increased from 900 l/h to 1100 l/h, volumetric void fraction decreased from 2.25 E-05 to 4.83 E-06. However, at 1000 l/h and SR 1.15 condition, when system pressure increased from 2.2 bar to 2.7 bar, volumetric void fraction decreased from 2.16 E-05 to 3.78 E-06. It is found that the highest city main saturation ratio was achieved at 1.07 at the specific environmental condition.

The dissolved oxygen (DO) content in seawater is controlled by several unrelated processes including exchange with air, metabolism of plants and animals, microbial and chemical decomposition of organic matter, hydrodynamic features such as mixing, advection, convection, and up- or down-welling. The DO content is always the result of multifactorial influences and the reasons for changes may be difficult to assess. In stratified Baltic waters, DO depletion occurs regularly below the halocline. When only physical processes are involved, the DO concentration in water is governed by the laws of solubility, i.e., it is a function of atmospheric pressure, water temperature, and salinity. The corresponding equilibrium concentration is generally called solubility. It is an essential reference for the interpretation of DO data. Precise solubility data, tables, and mathematical functions have been established (Carpenter, 1966; Murray and Riley, 1969; Weiss, 1970) and adopted by the international community (UNESCO, 1973). However, Weiss (1981) drew attention to an error in the international tables in which the values are low by 0.10 % since they are based on ideal gas molar volume instead of actual dioxygen molar volume. Later, the Joint Panel on Oceanographic Tables and Standards (JPOTS) recommended that the oxygen solubility equation of Benson and Krause (1984), which incorporated improved solubility measurements, be adopted and the tables updated (UNESCO, 1986). However, the UNESCO paper only referred to the equation that gives concentrations in the unit μmol kg-1. 1.2 Purpose and aims Monitoring of dissolved oxygen and hydrogen sulphide can provide information of an indirect effect of eutrophication, but hydrogen sulphide and oxygen depletion is also a naturally occurring condition in some areas. The purpose of the monitoring is to map the spatial distribution of concentrations of dissolved oxygen and hydrogen sulphide, with the aim to be able to assess the status of the seafloor and the waters above and to ensure that the data is comparable for the HELCOM pre-core indicator ‘Shallow water oxygen’ and core indicator ‘Oxygen debt’. The indicator descriptions, including their monitoring requirements, are given in the HELCOM core indicator web site: http://www.helcom.fi/baltic-sea-trends/indicators/oxygen- Published Refereed Current 14.a Oxygen Mature Multi-organisational International Method Specification of criteria

For more than a century, global change has led to a profound modification of our societies, our lifestyles and, of course, our environment. This trajectory followed willy-nilly by all mankind has consequences for natural systems and already seems to lead the future generations ahead of serious challenges. In order not to compromise our ability to meet these future ordeals, and because of the urgent need for action, part of the scientific community has chosen to concentrate on the near-surface environment that supports terrestrial life: the Critical Zone. The emergence of this concept underlines the need to develop multidisciplinary scientific approaches integrating a wide variety of temporal and spatial scales. As the link between the different compartments of the Critical Zone (Atmosphere, Biosphere, Hydrosphere, Lithosphere and Pedosphere), water is an essential molecule controlling the exchanges of energy and matter whose dynamics require special attention. In view of the diversity and spatiotemporal variability of water and matter transfers arising in aquatic environments, new methods of investigation are needed. The general objective of this thesis is to describe the interest and the potential lying in the use of dissolved gases, especially when they are measured at high frequency in the field, in order to characterise the hydrobiogeochemical dynamics of the natural waters of the Critical Zone at different spatial and temporal scales. To perfect this ambition, this work focused first on the development of an innovative instrumentation, then, on the implementation of novel tracers integrated into original experimental setups and finally, on the acquisition, processing and analysis of different dissolved gas datasets focusing on groundwater., Depuis plus d’un siècle, les changements globaux sont à l’origine de profondes modifications de nos sociétés, nos modes de vie et il en va bien sûr de même pour notre environnement. Cette trajectoire empruntée, bon gré mal gré, par l’ensemble de l’humanité n’est pas sans conséquences pour les systèmes naturels et semble déjà mener les générations futures au-devant de grands défis. Afin de ne pas compromettre notre capacité à relever ces épreuves futures et, devant l’urgence du besoin d’action, une partie de la communauté scientifique a choisi de concentrer ses efforts sur la couche superficielle de notre planète qui soutient la vie terrestre : la Zone Critique. L’émergence de ce concept souligne la nécessité de développer des approches scientifiques pluridisciplinaires intégrant une large variété d’échelles de temps et d’espace. En tant que lien entre les différents compartiments de la Zone Critique (Atmosphère, Biosphère, Hydrosphère, Lithosphère et Pédosphère), l’eau est une molécule essentielle aux échanges d’énergie et de matière dont la dynamique requiert une attention particulière. Compte tenu de la diversité et de la variabilité spatiotemporelle des transferts d’eau et de matière dissoute dans les milieux aquatiques, de nouvelles méthodes d'investigations sont nécessaires. L'objectif général de cette thèse est de décrire l’intérêt et le potentiel qui résident dans l’utilisation des gaz dissous, en particulier lorsqu’ils sont mesurés à haute fréquence sur le terrain, afin de caractériser la dynamique hydrobiogéochimique des eaux naturelles de la Zone Critique à différentes échelles spatiales et temporelles. Pour parfaire cette ambition, ce travail s’est tout d’abord attaché au développement d'une instrumentation innovante puis, à la mise en place de nouveaux traceurs intégrés dans des dispositifs expérimentaux originaux et enfin, à l'acquisition, au traitement et à l'analyse de différents jeux de données de gaz dissous en se focalisant sur les eaux souterraines.

This manual is to be used with the SBE 63 Digital Optical Dissolved Oxygen Sensor. It is organized to guide the user from installation through operation and data collection. We’ve included detailed specifications, command descriptions, maintenance and calibration information, and helpful notes throughout the manual. Published Current Oxygen Mature Multi-organisational International Dissolved oxygen sensor Method Specification of criteria

Mass spectrometers are versatile sensor systems, owing to their high sensitivity and ability to simultaneously measure multiple chemical species. Over the last two decades, traditional laboratory-based membrane inlet mass spectrometers have been adapted for underwater use. Underwater mass spectrometry has drastically improved our capability to monitor a broad suite of gaseous compounds (e.g., dissolved atmospheric gases, light hydrocarbons, and volatile organic compounds) in the aquatic environment. Here we provide an overview of the progress made in the field of underwater mass spectrometry since its inception in the 1990s to the present. In particular, we discuss the approaches undertaken by various research groups in developing in situ mass spectrometers. We also provide examples to illustrate how underwater mass spectrometers have been used in the field. Finally, we present future trends in the field of in situ mass spectrometry. Most of these efforts are aimed at improving the quality and spatial and temporal scales of chemical measurements in the ocean. By providing up-to-date information on underwater mass spectrometry, this review offers guidance for researchers interested in adapting this technology as well as goals for future progress in the field.

Groundwater helium sources and residence times were investigated using groundwater discharging from springs surrounding Mount St. Helens in the Cascades region of the United States. Significant contributions of mantle helium were found in all samples and are attributable to interaction between groundwater and magmatic gases. Bounding calculations for residence times were made on the basis of helium isotope mixing plots and historical tritium data.

peer-reviewed The objective of the study was to evaluate the different headspace equilibration methods for the quantification of dissolved greenhouse gases in groundwater. Groundwater samples were collected from wells with contrasting hydrogeochemical properties and degassed using the headspace equilibration method. One hundred samples from each well were randomly selected, treatments were applied and headspace gases analysed by gas chromatography. Headspace equilibration treatments varied helium (He):water ratio, shaking time and standing time. Mean groundwater N2O, CO2 and CH4 concentrations were 0.024 mg N L−1, 13.71 mg C L−1 and 1.63 μg C L−1, respectively. All treatments were found to significantly influence dissolved gas concentrations. Considerable differences in the optimal He:water ratio and standing time were observed between the three gases. For N2O, CO2 and CH4 the optimum operating points for He:water ratio was 4.4:1, 3:1 and 3.4:1; shaking time was 13, 12 and 13 min; and standing time was 63, 17 and 108 min, respectively. The headspace equilibration method needs to be harmonised to ensure comparability between studies. The experiment reveals that He:water ratio 3:1 and shaking time 13 min give better estimation of dissolved gases than any lower or higher ratios and shaking times. The standing time 63, 17 and 108 min should be applied for N2O, CO2 and CH4, respectively. Department of Agriculture, Food and Fisheries, Ireland - Research Stimulus Fund Programme (Grant RSF 06383); Department of Civil, Structural and Environmental Engineering, Trinity College Dublin

This study sought to improve the understanding of methane ebullition from wetlands by measuring total dissolved gas pressure (Ptdg), volumetric gas content, water pressure, and methane flux from surface chambers between July and September in the shallow part of a wetland. Capillary pressure, which is often ignored in estimating bubbling pressure, contributed up to 5% of the Pbub at shallow depths. Estimated bubbling pressure (Pbub(est)) was a better estimate of free-phase gas than Pbub(ave) given observed variations in Patm and Pw of up to 20 mm Hg. Although Ptdg increased with depth, free-phase gas presence did not vary with depth or time suggesting differential rates of production, retention, and release of gas with depth. Heterogeneities in the peat structure, most significantly the presence of a dense peat layer (~50 cm), contributed to limited agreement between gas-monitoring methods used.

Water is the elementary component of life on Earth, and quantifying this resource is critical to understanding ecosystem viability on planetary, continental, and local scales. In a simplified partition of the Earth's freshwater resources, 75% is ice at the north and south poles, 25% is groundwater, and 0.01% exists in lakes and streams. Mean transit time is a robust description of groundwater volume within the discrete aquifers that together make up the 25% of Earth's freshwater. Mean transit time can be estimated using environmental tracer concentrations in springs and gaining streams. That is because springs and streams are locations where groundwater flow paths naturally converge. Converging flowpaths create discharge that is a flow‐weighted mixture of water from the contributing aquifer. The age of that flow-weighted mixture is a good measure of the mean transit time of water as it discharges from the contributing aquifer. Mean transit time can be directly used to estimate the volume of groundwater storage in the aquifer. Although simple in principle, there are several important topics that need to be considered when collecting and dating a broad mixture of flow paths. They include 1) the necessity for a basic conceptual perception of the investigated aquifer, 2) the nonconservative aspect of most age-dating environmental tracers once exposed to the atmosphere, and 3) the importance of estimating a transit-time distribution. These specific topics are discussed in this dissertation.

This paper focuses on the chemical and isotopic features of dissolved gases (CH4 and CO2) from four meromictic lakes hosted in volcanic systems of Central-Southern Italy: Lake Albano (Alban Hills), Lake Averno Phlegrean Fields), and Monticchio Grande and Piccolo lakes (Mt. Vulture). Deep waters in these lakes are characterized by the presence of a significant reservoir of extra-atmospheric dissolved gases mainly consisting of CH4 and CO2. The delta C-13-CH4 and dD-CH4 values of dissolved gas samples from the maximum depths of the investigated lakes (from -66.8 to -55.6% V-PDB and from -279 to -195% V-SMOW, respectively) suggest that CH4 is mainly produced by microbial activity. The delta C-13-CO2 values of Lake Grande, Lake Piccolo, and Lake Albano (ranging from -5.8 to -0.4% V-PDB) indicate a significant CO2 contribution from sublacustrine vents originating from (1) mantle degassing and (2) thermometamorphic reactions involving limestone, i.e., the same CO2 source feeding the regional thermal and cold CO2-rich fluid emissions. In contrast, the relatively low delta C-13-CO2 values (from -13.4 to -8.2% V-PDB) of Lake Averno indicate a prevalent organic CO2. Chemical and isotopic compositions of dissolved CO2 and CH4 at different depths are mainly depending on (1) CO2 inputs from external sources (hydrothermal and/or anthropogenic); (2) CO2-CH4 isotopic exchange; and (3) methanogenic and methanotrophic activity. In the epilimnion, vertical water mixing, free oxygen availability, and photosynthesis cause the dramatic decrease of both CO2 and CH4 concentrations. In the hypolimnion, where the delta C-13-CO2 values progressively increase with depth and the delta C-13-CH4 values show an opposite trend, biogenic CO2 production from CH4 using different electron donor species, such as sulfate, tend to counteract the methanogenesis process whose efficiency achieves its climax at the water-bottom sediment interface. Theoretical values, calculated on the basis of delta C-13-CO2 values, and measured delta C-13(TDIC) values are not consistent, indicating that CO2 and the main carbon-bearing ion species (HCO3-) are not in isotopic equilibrium, likely due to the fast kinetics of biochemical processes involving both CO2 and CH4. This study demonstrates that the vertical patterns of the CO2/CH4 ratio and of delta C-13-CO2 and delta C-13-CH4 are to be regarded as promising tools to detect perturbations, related to different causes, such as changes in the CO2 input from sublacustrine springs, that may affect aerobic and anaerobic layers of meromictic volcanic lakes.

This report presents a high-accuracy Winkler titration method that has been developed for determination of dissolved oxygen concentration. Careful analysis of uncertainty sources relevant to the Winkler method was carried out and the method was optimized for minimizing all uncertainty sources as far as practical. The most important improvements were: gravimetric measurement of all solutions, pre-titration to minimize the effect of iodine volatilization, accurate amperometric end point detection and careful accounting for dissolved oxygen in the reagents. As a result, the developed method is possibly the most accurate method of determination of dissolved oxygen available. Depending on measurement conditions and on the dissolved oxygen concentration the combined standard uncertainties of the method are in the range of 0.012 – 0.018 mg dm-3 corresponding to the k = 2 expanded uncertainty in the range of 0.023 – 0.035 mg dm-3 (0.27 – 0.38%, relative). This development enables more accurate calibration of electrochemical and optical dissolved oxygen sensors for routine analysis than has been possible before. Most of this report is based on the article I.Helm, L.Jalukse, I. Leito, Anal. Chim. Acta. 741 (2012) 21-31. European Metrology Research Programme (EMRP) Published Current 14.a Oxygen Validated (tested by third parties) Method Description of a metrology standard

In this paper the very first geochemical and isotopic data related to surface and spring waters and dissolved gases in the area of Hontomín-Huermeces (Burgos, Spain) are presented and discussed. Hontomín-Huermeces has been selected as a pilot site for the injection of pure (>99%) CO2. Injection and monitoring wells are planned to be drilled close to 6 oil wells completed in the 1980s for which detailed stratigraphical logs are available, indicating the presence of a confined saline aquifer at the depth of about 1500 m into which less than 100,000 tons of liquid CO2 will be injected, possibly starting in 2013. The chemical and features of the spring waters suggest that they are related to a shallow hydrogeological system as the concentration of the Total Dissolved Solids approaches 800 mg/L with a Ca2+(Mg2+)-HCO3- composition, similar to that of the surface waters. This is also supported by the oxygen and hydrogen isotopic ratios that have values lying between those of the Global and the Mediterranean Meteoric Water Lines. Some spring waters close to the oil wells are characterized by relatively high concentrations of NO3- (up to 123 mg/L), unequivocally suggesting an anthropogenic source that adds to the main water-rock interaction processes. The latter can be referred to Ca-Mg-carbonate and, at a minor extent, Al-silicate dissolution, being the outcropping sedimentary rocks characterized by Palaeozoic to Quaternary rocks. Anomalous concentrations of Cl-, SO42-, As, B and Ba were measured in two springs discharging a few hundred meters from the oil wells and in the Rio Ubierna. These contents are significantly higher than those of the whole set of the studied waters and are possibly indicative of mixing processes, although at very low extent, between deep and shallow aquifers. No evidence of deep-seated gases interacting with the Hontomín-Huermeces waters was recognized in the chemistry of the dissolved gases. This is likely due to the fact that they are mainly characterized by an atmospheric source as highlighted by the high contents of N2, O2 and Ar and by N2/Ar ratios that approach that of ASW (Air Saturated Water) and possibly masking any contribution related to a deep source. Nevertheless, significant concentrations (up to 63% by vol.) of isotopically negative CO2 (

Aims: During wine making, oxygen and carbon dioxide are often simultaneously present in the liquid phase. We propose a simple rational approach, based on usual chemical engineering and thermodynamic principles, to provide understanding and practical rules for controlling the effects of these two dissolved gases, and especially their inter-relationship. Furthermore, this study proposes an explanation for the “protective” effect against oxidation, which is reported when high concentrations of carbon dioxide are present in musts and wines.Methods and results: The theoretical quantitative relation, termed “binary gas equilibrium line”, between the maximum possible concentration of dissolved oxygen in respect to dissolved carbon dioxide was derived and, in our experiments, corresponded to CO2max ≅ -0,005 CCO2 + 7,9 mg.L-1. Specific saturation experiments using simultaneous injection of air and gaseous carbon dioxide were performed and the experimental results allowed us to validate this theory in the case of gas bubbling in a liquid.Conclusion: It is shown that complete protection is only obtained when carbon dioxide is generated by the fermentation in the liquid. An interesting parallel conclusion is that micro-oxygenation is totally inefficient in such periods. In the case where there is no production of CO2 but where a high initial dissolved carbon dioxide concentration is present, the “protective” effect acts only by reducing the rate of oxygen transfer.Significance and impact of the study: The physical understanding of this phenomenon can be found in the fact that as soon as a gaseous air or pure oxygen phase is in contact with a carbon dioxide saturated liquid, the dissolved carbon dioxide, which is not at equilibrium with the gaseous phase, tends to escape into this gaseous phase. This study points out the complexity of the gas-liquid equilibrium when two dissolved gases are simultaneously present in a liquid and its implication in the winemaking process.

International audience; Membrane contactor is a new technology which enables implementing liquid-liquid, liquid-gas or liquid-gas-liquid separations. The main component of the system is a hydrophobic porous membrane system. Only gases with low molecular weight like O2 and CO2 can pass through the barrier. The system can be installed before the bottling line or in the winery in order to adjust the gas concentration of wine before storage in bulk or bottling. INRA carried out a first series of tests on an INOXPA WineBrane 2500 pilot unit. The results showed that it is possible to deoxygenize and adjust CO2 in only one passage on the unit (contrary to a gas injector), thanks to several operating processes which use the vacuum and/or an inert gas flow (Vacuum, Combo and Strip). A deoxygenation, [final dissolved O2] < 0.5 mg/L, of a white and a red wine (comparison with gas injector) didn't affect the higher alcohols. Only some esters underwent significant quantitative losses. However, a jury of 19 judges could not make the difference between the wines before and after deoxygenation whatever the technique.

The first geochemical data showing the existence of an active degassing activity over a large seismically active sector of the Southern Alps (Friuli Region, NE Italy) are presented. The dissolved gases, helium and carbon isotopic systematics of 46 water samples taken from 13 sites running along E–W and NE–SW faults besides the natural degassing of a 5000 km 2 wide area are investigated. The chemical composition of the dissolved gases revealed that a CO 2 -rich gas phase feeds the local groundwaters. 3 He/ 4 He ratios ( R ) normalized to the atmospheric 3 He/ 4 He ratio (Ra = 1.39 × 10 − 6 ) and corrected for the atmospheric contamination ( R /Ra c ), range from 0.29 to 1 as a result of a two component (radiogenic and atmospheric) mixing. The δ 13 C values of total dissolved inorganic carbon (TDIC) ranging from − 15.28 to − 0.75‰ vs. PDB, show the occurrence of multiple gas–water interactions. The mixing between the atmospheric air and a crustal source and the gas–water interactions occurring at various extents appears to be the main control on the observed He–C systematics. The natural CO 2 degassing was evaluated by a soil gas survey carried out by a grid of about 100 measuring sites located over the area that generated destructive seismic sequences (e.g. the Gemona sequence of 1976; main shocks M6.4 of 6th May and M6.1 of 11th and 15th September). The results obtained show that a significant amount of crustal-originated gases are released over the continental area of Eastern Southern Alps. The evidence that carbon dioxide is associated with radiogenic-type helium denotes the lack of the mantle as primary energy and degassing source, highlighting the possibility that CO 2 is produced by thermo-mechanical processes occurring at seismogenic depth. The information provided here may be used to start up a long-term geochemical monitoring of this seismically active area and could be able to detect the modifications occurring to the circulating fluids to gain a better insight on the relationships between the fluids' geochemistry and the activity of the local seismogenic faults.

Conventional industrial glass furnaces show broad glass melt residence time distributions in the melting tanks and average residence times may be up to more than two days for high quality glass products, such as float glass or TV glass, despite the minimum residence times of 8-10 hours (or even less than 4 hours for container glass furnaces). Long residence times are associated with large melt tank volume/pull rate ratios and high structural heat losses. The recirculation flows, necessary to supply the batch blanket with sufficient energy for the fusion processes of the batch materials, are often poorly controlled and cause these shown residence time differences. For each elementary process step the most relevant process parameters in terms of desired flow patterns, mixing behavior, temperature, chemistry and required time for completion of the process step are analyzed. From this analysis, it is concluded that the different steps need very different conditions comparing the processes with each other. Therefore glass furnace design modifications should be focused on the development of furnaces with segments, each of them dedicated and optimized for the a certain stage of the melting process: melting-in of batch, sand grain dissolution, removal of gases (bubbles and dissolved gases), re-absorption of residual bubbles and glass melt (chemical and thermal) homogenization. Some developments in fast fining and rapid melting-in of batch will be shown and shortly discussed.

This paper describes the chemical and isotopic characterization of H 2 S-bearing groundwaters of the Fontevivo area, northern Italy. Groundwaters from Fontevivo (Parma Province) contain dissolved H 2 S and minor hydrocarbons, which are released from the truncated front of a buried geological structure (Calabrian– Miocene terrains) and through abandoned unsealed oil wells. H 2 S concentration is up to 5.54 mg/l in groundwaters from the topographical high of the village and its distribution in the investigated area is inversely related with those of NH 4 + and SO 4 2− . Groundwaters are dominantly Ca-HCO 3 type with lesser Ca-SO 4 and Na-Cl types and display two compositional trends: group A, waters from Ca-HCO 3 to Ca-SO 4 ; group B, waters from Ca-HCO 3 to Na-Cl. Group A water compositions are influenced by redox processes including the oxidation of H 2 S to SO 4 2− . Primary sulphate from dissolution of Messinian evaporite is rare. Group B waters represent mixing of meteoric water with small amounts of brine. The most Cl (Br, I)-rich groundwaters are located in the NE of the investigated area, where a Cl–Br–I-rich brine was encountered by an exploration well in the Calabrian stratum. Berner has provided a classification of redox environments starting from the observation of the sequence of reduction/oxidation processes as shown by groundwater composition. At Fontevivo the Berner redox zones show an areal distribution where the anoxic zones occur in the topographical high. The δ 2 H and δ 18 O values of groundwaters plot close to the Global Meteoric Water Line. They indicate that local precipitation recharges the shallow aquifer ( Dissolved H 2 S is depleted in 34 S consistent with biogenic sulphate reduction. Secondary origin from oxidation of H 2 S in shallow groundwater is invoked for depleted δ 34 S (SO 4 2− ). The studied saline sample (27.8 g/l TDS) show a δ 34 S (H 2 S) value of +24.9‰, suggesting a nearly complete reduction of Messinian sulphate within a system closed to H 2 S. A hydrogeological model is presented based on a chemical-thermodynamic, trace element statistical, and multi-isotope approach.

We used a dynamic mixed layer model to determine carbon export by the oxygen mass balance method from a time series of O2/Ar, N2/Ar and Ne measurements collected at station ALOHA near Hawaii from July 2000 to June 2001. The inert gas measurements constrain the flux of oxygen into the mixed layer from small, collapsing bubbles (injection) to be greater than or equal to the flux from larger bubbles (exchange), with mean estimates of the ratio in the range of 1–2. We also show that monthly observations of temperature and inert gases cannot constrain the rate of diapycnal mixing at this location, because of uncertainties in air-sea heat flux estimates and bubble dynamics. Organic carbon export from the mixed layer calculated from our dataset was 1.1 ± 0.5 mol C m–2 yr–1, with most of the error deriving from uncertainties in the parameterization of diffusive gas exchange with wind speed. Our estimates of carbon export from the zone beneath the mixed layer but still in the euphotic zone ranged from 0 to 0.6 mol C m–2 yr–1 as the rate of background diapycnal mixing was increased from 0.1 to 1.0 cm2 s–1. We conclude that the oxygen mass balance method has errors of about a factor of two in areas similar to the subtropical North Pacific, with the main uncertainties deriving from mixing rates and the parameterization of diffusive gas exchange.

We describe an analytical method with improved precision for measuring the concentration of neon dissolved in water. Measurements were calibrated by isotope dilution, with addition of a Ne-22 spike directly to the evacuated sample flask prior to water collection. The use of glass flasks for water sampling, with flushing of air from the system by CO2, greatly reduced the chance of contamination. Dissolved gases were extracted from the water sample by equilibration with a headspace and cryogenically processed to remove interferences. The Ne-22/Ne-20 ratio was then measured on a quadrupole mass spectrometer operated in static mode. Mass fractionation by the system was accounted for by frequent analyses of the Ne-22/Ne-20 ratio in air. We routinely obtained precisions of +/-0.13% based on the standard deviation of duplicate field samples. Accuracy of the method, in the form of possible systematic offsets that could skew all the data, was assessed to be +/-0.18%, excluding a possible +/-0.2% error in the estimate of the Ne concentration of air. (C) 2004 Elsevier B.V. All rights reserved.

The Laboratory of Lake Studies of the Academy of Sciences of the USSR in 1956 undertook this complicated study of Lake Ladoga. The plan of the laboratory made allowance for the detailed investigation of the phytoplankton of the lake during a series of years. In the present article are given the preliminary results of observations on the phytoplankton of the Yakimvarskii Bay from 1956 to 1957. Details are also given on the concentration of dissolved gases and biogenic substances of the bay. Translated from Russian into English