Measured Water Concentrations Research Articles

Using the fish plasma model to evaluate potential effects of pharmaceuticals in effluent from a large urban wastewater treatment plant

Several pharmaceuticals and personal care products (PPCPs) were evaluated using the fish plasma model (FPM) for juvenile Chinook salmon exposed to effluent from a large urban wastewater treatment plant. The FPM compares fish plasma concentrations to therapeutic values determined in human plasma as an indication of potential adverse effects. We used human Cmax values, which are the maximum plasma concentration for a minimum therapeutic dose. Observed and predicted plasma concentrations from juvenile Chinook salmon exposed to a dilution series of whole wastewater effluent were compared to 1%Cmax values to determine Response Ratios (RR) ([plasma]/1%Cmax) for assessment of possible adverse effects. Several PPCPs were found to approach or exceed an RR of 1, indicating potential effects in fish. We also predicted plasma concentrations from measured water concentrations and determined that several of the values were close to or below the analytical reporting limit (RL) indicating potential plasma concentrations for a large number of PPCPs that were below detection. Additionally, the 1%Cmax was less than the RL for several analytes, which could impede predictions of possible effect concentrations. A comparison of observed and predicted plasma concentrations found that observed values were frequently much higher than values predicted with water concentrations, especially for low log10Dow compounds. The observed versus predicted values using the human volume of distribution (Vd), were generally much closer in agreement. These data appear to support the selection of whole-body concentrations to predict plasma values, which relies more on estimating simple partitioning within the fish instead of uptake via water. Overall, these observations highlight the frequently underestimated predicted plasma concentrations and potential to cause adverse effects in fish. Using measured plasma concentrations or predicted values from whole-body concentrations along with improved prediction models and reductions in analytical detection limits will foster more accurate risk assessments of pharmaceutical exposure for fish.

Kinetic description of water transport during spontaneous emulsification induced by Span 80.

Spontaneous emulsification is a phenomenon that forms nanometer-sized droplets (nanodroplets) without the application of any external force, and the mechanism has been actively studied for application to various technologies. In this study, we analyzed the kinetics of spontaneous emulsification induced by Span 80. The measurement of water concentration in Span 80 hexadecane solution indicated that the chemical potential of water in the nanodroplets decreased as the amount of water in the nanodroplets decreased. Based on this result, water transport between the aqueous phase and nanodroplets in which the chemical potential of water was controlled was quantitatively investigated by using a microfluidic device. The results demonstrate that the kinetics of water transport during spontaneous emulsification induced by Span 80 was described by a model of osmotic transport through an organic liquid film between the aqueous phase and nanodroplets.

Detection of dilution due to turbulent mixing vs. precipitation scavenging effects on biomass burning aerosol concentrations using stable water isotope ratios during ORACLES

Abstract. The interaction between biomass burning aerosols and clouds remains challenging to accurately determine, in part because of difficulties using direct observations to account for influences on aerosol concentrations from precipitation scavenging and dilution due to air mass mixing and separating those signals from source contributions. The prevalence of mixing versus precipitation processes in air laden with biomass burning aerosol (BBA) in the southeast Atlantic lower free troposphere (FT) and marine boundary layer (MBL) is assessed during three observation periods (September 2016, August 2017, and October 2018) during the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) campaign. Significant sources of BBAs over the African continent combined with regional circulation patterns result in BBA-laden air flowing from the continent over the southeast Atlantic in the lower FT, then subsiding onto the semi-permanent stratocumulus cloud deck, and entraining into the MBL. This study is broken into two parts, first analyzing hydrologic histories of the BBA air in the lower FT and then carrying out a similar assessment in the underlying MBL. Both analyses leverage joint measurements of water concentration and its heavy isotope ratio, interpreted in the previously established (q, δD) phase space framework. For the lower-FT analysis, in situ observations (water concentration, water isotope ratios) in the lower FT are combined with satellite and Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), global reanalysis data into simple analytical models to constrain hydrologic histories. We find that even simple models are capable of detecting and constraining the primary processes at play, e.g., distinguishing air masses that experienced moist convection and precipitation (likely over the continent) from those that underwent dry convection and turbulent mixing. Regression of the aircraft data onto a simple model of convective detrainment is used to develop a metric of total precipitation for the in situ measurements and then compared to an aerosol metric of black carbon scavenging also derived from the in situ measurements (the ratio of black carbon to carbon monoxide, BC/CO). There is a strong correlation between the two, suggesting black carbon scavenging has been detected and partially quantified, if only in a relative manner. In comparison, weak correlation is found between BC/CO and the total water concentration itself. The above method is expanded to test for entrainment and precipitation influences on BBA concentrations in the MBL. This is more difficult than the FT analysis since signals are subtle and limited by imperfect knowledge of the water and isotope ratios of the entrained air mass at cloud top. For some of the MBLs observed during 2016 and 2018, lower cloud condensation nuclei (CCN) concentrations occur in the sub-cloud layer coincident with isotopic evidence of precipitation, indicating aerosol scavenging, but more complex models are needed to produce definitive conclusions. For the 2017 observation period, with the highest sub-cloud CCN concentrations, there is no connection between precipitation signals and CCN concentrations, likely indicating the importance of different geographic sampling and air mass history in that year. Nonetheless, these findings along with the FT analysis suggest that utilizing isotope ratio signals may be an aid in addressing cloud–aerosol challenges. Especially for the FT case, these findings support the pursuit of more complex models combined with targeted in situ data to constrain BC scavenging coefficients in a manner which can guide model parameterizations, leading to improvements in the accuracy of simulated BC concentrations and lifetimes in climate models.

High-pressure vapor-liquid equilibrium measurements of methane + water mixtures by nuclear magnetic resonance spectroscopy

The vapor-liquid equilibrium (VLE) of methane + water mixtures has been studied with nuclear magnetic resonance (NMR) spectroscopy. This work had two primary goals. The first goal was to develop methods that broaden the utility of NMR spectroscopy for VLE measurements. In this regard, we report a method by which the liquid-phase and vapor-phase compositions are measured in separate experiments by adjusting the height of the liquid phase in the sample tube. We also report a method for hastening phase equilibration by adding glass beads to the sample and repeatedly inverting the sample tube. The second goal of this work was to collect VLE data on a challenging mixture with real-world importance. Mixtures of methane + water are a useful test case because of their challenging characteristics, including the widely differing vapor pressures of the two components. One use for accurate VLE data on methane + water mixtures is to better predict the formation of harmful liquid phases in natural gas pipelines. Herein we utilize 1H NMR spectroscopy to measure the VLE of methane + water mixtures at temperatures of 299.73, 307.98, and 323.25 K, and pressures ranging from 0.69 MPa to 13.89 MPa. Experiments were carried out with a 600 MHz spectrometer. Mixtures were prepared and equilibrated in a high-pressure zirconia sample tube with an integrated needle valve. NMR-based VLE measurements on the liquid phase are in good agreement with available literature data and with Henry's Law predictions at low pressures. However, the commonly used GERG-2008 model for natural gas systems deviates dramatically from the experimental data for the liquid phase. NMR-based VLE measurements on the vapor-phase resulted in measured water concentrations that are systematically lower than available literature data and models. This systematic offset is likely caused by peak overlap in the NMR spectra.

Simultaneous measurement of temperature and water concentration using a novel laser dispersion spectrum extraction method immune to carrier phase variation

Quantitative measurement of temperature and concentration is of wide interest in combustion diagnostics. In this paper, simultaneous temperature and water concentration measurements in a combustion flame were realized by using a novel laser dispersion spectrum extraction method immune to carrier phase variation. The laser dispersion phase signal obtained in the frequency domain was converted into the molecular free induction decay (FID) signal in the time domain by inverse Fourier transform. Then the FID signals of the dispersion phase and the carrier phase were separated in the time domain. The optimal temperature and concentration values were efficiently searched by an improved simulated annealing algorithm through the FID signal in the window function. Numerical simulations verified the noise immunity of the proposed method at different noise levels. Experiments were implemented on a methane-air laminar premixed flame, and the results showed that the proposed method performed better in measurement stability and accuracy than laser absorption spectrometry, especially in the presence of incident laser power fluctuations. This method is proven promising in the field of combustion diagnosis.

Numerical Study and Experimental Verification of Biomass Conversion and Potassium Release in a 140 kW Entrained Flow Gasifier.

In this study, a Eulerian-Lagrangian model is used to study biomass gasification and release of potassium species in a 140 kW atmospheric entrained flow gasifier (EFG). Experimental measurements of water concentration and temperature inside the reactor, together with the gas composition at the gasifier outlet, are used to validate the model. For the first time, a detailed K-release model is used to predict the concentrations of gas-phase K species inside the gasifier, and the results are compared with experimental measurements from an optical port in the EFG. The prediction errors for atomic potassium (K), potassium chloride (KCl), potassium hydroxide (KOH), and total potassium are 1.4%, 9.8%, 5.5%, and 5.7%, respectively, which are within the uncertainty limits of the measurements. The numerical model is used to identify and study the main phenomena that occur in different zones of the gasifier. Five zones are identified in which drying, pyrolysis, combustion, recirculation, and gasification are active. The model was then used to study the transformation and release of different K species from biomass particles. It was found that, for the forest residue fuel that was used in the present study, the organic part of K is released at the shortest residence time, followed by the release of inorganic K at higher residence times. The release of inorganic salts starts by evaporation of KCl and continues by dissociation of K2CO3 and K2SO4, which forms gas-phase KOH. The major fraction of K is released around the combustion zone (around 0.7-1.3 m downstream of the inlet) due to the high H2O concentration and temperature. These conditions lead to rapid dissociation of K2CO3 and K2SO4, which increases the total K concentration from 336 to 510 ppm in the combustion zone. The dissociation of the inorganic salts and KOH formation continues in the gasification zone at a lower rate; hence, the total K concentration slowly increases from 510 ppm at 1.3 m to 561 ppm at the outlet.

Aircraft measurements of water vapor heavy isotope ratios in the marine boundary layer and lower troposphere during ORACLES

Abstract. This paper presents aircraft in situ measurements of water concentration and heavy water isotope ratios D/H and 18O/16O during the NASA ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) project. The aircraft measurement system is also presented. The dataset is unique in that (1) it contains both total water and cloud condensed water isotope ratios; (2) it spans sufficient space and time to enable construction of spatially resolved climatology of isotope ratios in the lower troposphere; and (3) it is paired with a wealth of complementary measurements on atmospheric thermodynamic, chemical, aerosol, and radiative properties. Aircraft sampling took place in the southeast Atlantic marine boundary layer and lower troposphere (Equator to 22∘ S) over the months of September 2016, August 2017, and October 2018. Isotope measurements were made using cavity ring-down spectroscopic analyzers integrated into the Water Isotope System for Precipitation and Entrainment Research (WISPER). From an isotope perspective, the 300+ h of 1 Hz in situ data at levels in the atmosphere ranging from 70 m to 7 km represents a remarkably large and vertically resolved dataset. This paper provides a brief overview of the ORACLES mission and describes how water vapor heavy isotope ratios fit within the experimental design. Overviews of the sampling region and sampling strategy are presented, followed by the WISPER system setup and calibration details. The three data formats available to the users are each covered (latitude–altitude curtains, individual vertical profiles, and time series), with illustrative examples to highlight some features of the dataset and provide a plausibility check. The curtains and profiles demonstrate the dataset's potential to provide a comprehensive perspective on moisture transport and isotopic content in this region. Finally, measurement uncertainties are provided. Curtain and vertical profile data for all sampling periods can be accessed at https://doi.org/10.5281/zenodo.5748368 (see Henze et al., 2022). Time series data for the September 2016, August 2017, and October 2018 sampling periods can be accessed at https://doi.org/10.5067/Suborbital/ORACLES/P3/2016_V3, https://doi.org/10.5067/Suborbital/ORACLES/P3/2017_V3, and https://doi.org/10.5067/Suborbital/ORACLES/ P3/2018_V3, respectively (see references for ORACLES Science Team, 2020a–c, 2016 P3 data, 2017 P3 data, and 2018 P3 data).

Isotopic signatures of magmatic fluids and seawater within silicic submarine volcanic deposits

Addressing questions of magma ascent, volcanic eruption dynamics, and volatile fluxes requires accurate measurement of magmatic water concentrations in volcanic glass. Glass in volcanic rocks in the deep-sea environment can experience rehydration (addition of external water) across a range of temperatures, and from different sources (e.g., seawater and hydrothermal fluids), which can lead to overestimation of magmatic-H2O. This study used H and O isotopes (δD and δ18O) to identify sources of rehydration in pumice and lava from the deep-sea 2012 volcanic eruption of Havre volcano, Kermadec Arc, and from a variety of older (tens to thousands of years) silicic submarine deposits across the Izu-Bonin Arc and Lau Basin. We find that old seafloor pumices were rehydrated up to 6 wt.% H2O by the diffusion of cold seawater over 100s to 1000s of years, and thus, enriched in δD, bulk-δ18O, and water-in-glass (wig) δ18O up to −30‰, +9‰ and −5‰ respectively. By contrast, the young Havre deposits exhibit a much wider range of both isotopic enrichment and depletion with δD = −50 to −120‰, δ18Obulk = +5.7 to +6.2‰, and δ18Owig = −10 to +4‰, depending on the eruptive units. Using magmatic degassing and vapor δD-H2O modeling, a volatile-melt δ18O-geothermometer, and previous textural studies of Havre 2012 deposits, we identify multiple high-temperature rehydration sources, timescales, and mechanisms. δD-depleted pumices were likely rehydrated by vapor co-existing in bubbles and vesicles at temperatures around and below the glass transition (320–670 °C) over timescales of a few minutes during clast cooling above the eruptive vent. Conversely, δD-enriched Havre pumice and lava from different deposits were most likely rehydrated by heated, δD-enriched seawater at glass temperatures > 100 °C. These results provide a natural confirmation of recent experimental findings, which tackle the fundamentals of H and O diffusion and isotope exchange in silicate materials at temperatures of 100–400 °C. Addressing the effects of rehydration, and thus accuracy of H2O measurements, in volcanic glasses and crystals is important for improving our understanding of conduit processes during volcanic eruptions, and the kinetics of glass hydration and alteration.

Measurement of water concentration along the straight channel of proton exchange membrane fuel cell

Given that the ionic conductivity of a proton exchange membrane fuel cell is significantly influenced by water concentration in the channel, an elaborate water management strategy is crucial to ensure durability and performance of these types of fuel cells. In this study, the vapour concentration of a gas mixture was observed in the through-plane direction in a bipolar plate. The stainless steel bipolar plate used here has straight channels containing installed relative humidity/temperature micro-sensors such that the vapour flow behaviour can be observed. The vapour concentration in the anode channel is increased by the back diffusion of water vapour from the cathode. The vapour concentration at the cathode channel increases with the water produced during the electrochemical reaction. The distribution of the dew point temperature at the anode/cathode channel shows that water transport to the anode increases the vapour concentration of anode gases.

Multi-element isotopic evidence for monochlorobenzene and benzene degradation under anaerobic conditions in contaminated sediments

Industrial chemicals are frequently detected in sediments due to a legacy of chemical spills. Globally, site remedies for groundwater and sediment decontamination include natural attenuation by in situ abiotic and biotic processes. Compound-specific isotope analysis (CSIA) is a diagnostic tool to identify, quantify, and characterize degradation processes in situ, and in some cases can differentiate between abiotic degradation and biodegradation. This study reports high-resolution carbon, chlorine, and hydrogen stable isotope profiles for monochlorobenzene (MCB), and carbon and hydrogen stable isotope profiles for benzene, coupled with measurements of pore water concentrations in contaminated sediments. Multi-element isotopic analysis of δ13C and δ37Cl for MCB were used to generate dual-isotope plots, which for 2 locations at the study site resulted in ΛC/Cl(130) values of 1.42 ± 0.19 and ΛC/Cl(131) values of 1.70 ± 0.15, consistent with theoretical calculations for carbon-chlorine bond cleavage (ΛT = 1.80 ± 0.31) via microbial reductive dechlorination. For benzene, significant δ2H (122‰) and δ13C (6‰) depletion trends, followed by enrichment trends in δ13C (1.6‰) in the upper part of the sediment, were observed at the same location, indicating not only production of benzene due to biodegradation of MCB, but subsequent biotransformation of benzene itself to nontoxic end-products. Degradation rate constants calculated independently using chlorine isotopic data and carbon isotopic data, respectively, agreed within uncertainty thus providing multiple lines of evidence for in situ contaminant degradation via reductive dechlorination and providing the foundation for a novel approach to determine site-specific in situ rate estimates essential for the prediction of remediation outcomes and timelines.

A new approach for measuring water concentration in oil using copper sulfate powder and infrared spectroscopy

An approach for measuring water concentration in oil, based on the use of CuSO4 particles and infrared spectroscopy, is described. The particles interact with both dissolved water and water droplets to form the monohydrate, CuSO4·H2O. These particles are collected on an infrared transparent membrane and then an infrared spectrum in transmission mode is recorded. Strong interaction of the water with the CuSO4 shifts and intensifies the water bending mode to produce a unique band at 1743 cm−1. The method provided values which are equivalent to those measured by Karl Fischer titration over the range of 10 to 3500 mg L-1 with a linearity R2 value of > 0.99 and an average %RSD for all measurements was 6%. No matrix specific calibrations are required.

Hotspots of Diffusive CO2 and CH4 Emission From Tropical Reservoirs Shift Through Time

AbstractThe patterns of spatial and temporal variability in CO2 and CH4 emission from reservoirs are still poorly studied, especially in tropical regions where hydropower is growing. We performed spatially resolved measurements of dissolved CO2 and CH4 surface water concentrations and their gas‐exchange coefficients (k) to compute diffusive carbon flux from four contrasting tropical reservoirs across Brazil during different hydrological seasons. We used an online equilibration system to measure dissolved CO2 and CH4 concentrations; we estimated k from floating chamber deployments in conjunction with discrete CO2 and CH4 water concentration measurements. Diffusive CO2 emissions were higher during dry season than during rainy season, whereas there were no consistent seasonal patterns for diffusive CH4 emissions. Our results reveal that the magnitude and the spatial within‐reservoir patterns of diffusive CO2 and CH4 flux varied strongly among hydrological seasons. River inflow areas were often characterized by high seasonality in diffusive flux. Areas close to the dam generally showed low seasonal variability in diffusive CH4 flux but high variability in CO2 flux. Overall, we found that reservoir areas exhibiting highest emission rates (“hotspots”) shifted substantially across hydrological seasons. Estimates of total diffusive carbon emission from the reservoir surfaces differed between hydrological seasons by a factor up to 7 in Chapéu D'Úvas, up to 13 in Curuá‐Una, up to 4 in Furnas, and up to 1.8 in Funil, indicating that spatially resolved measurements of CO2 and CH4 concentrations and k need to be performed at different hydrological seasons in order to constrain annual diffusive carbon emission.

Uego Sensor for Monitoring Humidity at the Cathode of PEM Stacks

One of the greatest challenges associated with PEMFCs is the water balance in thefuel cell stack. Depending upon the load and the operating conditions, the fuel cell membranes have a propensity to both flood and dry-out. If the PEM is not adequately humidified, the conductivity of the protons decreases, which causes reduced performance. Excess water also can create an issue by inhibiting the reactants from diffusing to the catalyst sites by flooding of the electrodes and gas channels if the water removal is insufficient. Current humidity sensing technologies are not capable of meeting the demands required for this harsh environment.Zirconia-based electrochemical sensors for measuring the oxygen concentration in the automotive exhaust have been used on vehicles for nearly 40 years. Single and double-zirconia-cell sensors have been developed which have high sensitivity and a wide range of operation (up to 25%). These are amperometric sensors are based on oxygen pumping which involves the transfer of oxygen from one side of a zirconia cell to the other by passing an electric current through the device. Since these sensors operate over a wide range, they are referred to as “wide-range oxygen” or “universal exhaust gas oxygen” (UEGO) sensors and can be used over a broad range of A/F measurement and control. All gasoline vehicles, as well as most diesel powertrains employ UEGO sensors to meet the emission requirements. The double-cell amperometric sensor also can be used to measure the concentration of other oxygen-containing molecules, e.g. H2O, CO2, SO2, and NOx [3]. In order to measure the H2O concentration for example, a voltage is applied across the pump-cell that is greater than the dissociation potential for H2O. The resulting oxygen generated from the decomposition of water is then measured via an increase in pumping current by the UEGO sensor and is proportional to the H2O concentration in the gas. If other oxygen-containing molecules are present in the measurement gas, the voltage across the pump cell can be varied over the dissociation potentials of these gases. For H2O/air mixtures, the concentration of oxygen can be measured at a lower potential. A second voltage larger than the dissociation potential of the measurement gas, H2O, is applied to measure the concentration of oxygen plus water. The water concentration can be determined by subtracting the pumping current due to oxygen from the pumping current due to the combination of the two gases. Other gases can also be measured in a similar fashion. These measurements can be achieved without any modification to the existing sensor hardware. A simple modification to the electronic control circuitry is all that is required to perform this type of measurement. Figure 1 shows the sensitivity of a commercially available UEGO sensor for the dissociation of H2O as a function of Nernst sensing voltage (Vs). Vs is a measurement of the oxygen concentration in the measurement cavity. A typical operating value for the sensing voltage Vs for oxygen measurement is 450 mV which corresponds to a concentration of ~ppm. The plot below was generated from data measured in the lab at various water concentrations in a carrier gas of dry nitrogen. From the plot it is evident that water dissociation is occurring at potentials less than 800 mV. Additionally, the output begins to saturate at a potential approaching 1100 mV, suggesting that full dissociation of the water has been achieved. Figure 2 shows the sensitivity (pumping current) of the same sensor as a function of water concentration for Vs = 1080 mV. Once again, the carrier gas is dry nitrogen. The output is linear in water concentration.The water balance at the cathode is particularly difficult to manage because water accumulates due to the reaction and the clogging of the small channels. Controlling this water balance requires accurate water concentration measurements at temperatures approaching 100°C and pressures up to 3 bar absolute. The application of this humidity sensing technology to measure the water concentration at the cathode of PEMFCs will be discussed. Figure 1

Fluid Degradation Measurement Based on a Dual Coil Frequency Response Analysis.

Electrical industry uses oils for cooling and insulation of several machines, such as power transformers. In addition, it uses water for cooling some synchronous generators. To avoid malfunctions in these assets, fluid quality should be preserved. To contribute to this aim, a sensor that detects changes in fluid composition is presented. The designed sensor is like a single-phase transformer whose magnetic core is the fluid whose properties will be measured. The response of this device to a frequency sweep is recorded. Through a comparison between any measurement and a reference one corresponding to a healthy state, pollutants presence, such as water in oil or salt in water, can be measured. The performance of the sensor was analyzed through simulation. In addition, a prototype was built and tested measuring water concentration in oil and salt content in water. The correlation between pollutant concentration measured with the sensor and known pollutant concentrations is good.

Study of passive sampler calibration (Chemcatcher®) for environmental monitoring of organotin compounds: Matrix effect, concentration levels and laboratory vs in situ calibration

Application of Chemcatcher® to monitor organotin compounds [monobutyltin (MBT), dibutyltin (DBT) and tributlytin (TBT)] in sea water has been little developed. Prior to the measurement of the time-weighted average water concentrations (TWAC), a calibration step is required to determine sampling rates (Rs) which is usually assessed in a flow-through laboratory pilot where experimental conditions are well controlled. This paper investigates the effect of the water matrix (tap water vs real sea water from the harbor of Port Camargue in France) and organotin concentrations on the uptake rates of organotin compounds. Laboratory calibrations provided sampling rates in the range of 66–225 mL.day−1 in high concentration (usually used for laboratory calibrations) and in the range of 30–56 mL.day−1 at low concentrations (environmental range). When the tank is filled with real sea water, sampling rates were found to be in the range of 38–177 mL.day−1. In order to demonstrate the efficiency of Chemcatcher® in real conditions, in situ calibration was done in the harbor of Port Camargue. This calibration has been done in order to replicate environmental conditions: compounds concentrations, hydrodynamic and water matrix effects. To compare the impact of calibration procedures on TWAC determination, Chemcatcher® was deployed in the harbor of Port Camargue and spot sampling was performed to monitor the concentrations of organotins in water throughout the exposure period. Results obtained using the field Rs determined by in situ calibration were more reliable. In this case, TWAC is in agreement with spot sampling concentration.

Water-in-olivine magma ascent chronometry: Every crystal is a clock

The syneruptive decompression rate of basaltic magma in volcanic conduits is thought to be a critical control on eruptive vigor. Recent efforts have constrained decompression rates using models of diffusive water loss from melt embayments, olivine-hosted melt inclusions and clinopyroxene phenocrysts; however, these techniques are difficult to apply because of the rarity of pyroxene crystals or melt embayments suitable for analysis and the complexities associated with modeling water loss from melt inclusions. We have developed a new magma ascent chronometer based on syneruptive diffusive water loss from olivine phenocrysts.We have found water zonation in every olivine phenocryst we have measured, from explosive eruptions of Seguam, Fuego, Kilauea and Cerro Negro volcanoes. The majority of the olivine phenocrysts were polished to expose a central plane normal to the crystallographic ‘b’ axis and volatile concentration profiles were measured along ‘a’ and ‘c’ axes by secondary ion mass spectrometry (SIMS). Profiles are compared to 1D and 3D finite-element models of diffusive water loss from olivine, whose boundaries are in equilibrium with a melt undergoing closed-system degassing.Least-squares fitting of measured water concentration gradients in olivine to a 1D Monte Carlo model produces constraints on magma decompression rates that are in good agreement with independent constraints from melt embayment studies and modeling of water loss from olivine-hosted melt inclusions at Fuego, Seguam, Kilauea, and Cerro Negro. Such agreement confirms the accuracy and sensitivity of the water-in-olivine chronometer over a range of decompression rates (dP/dt) spanning ~2 orders of magnitude (from 0.007 to 0.45 MPa/s). We find that the assumption of a zero-water boundary condition (in which the water concentration at the edges of the olivine phenocrysts is fixed at 0 ppm throughout their ascent) leads to an overestimation of the decompression rate by an order of magnitude compared to the closed-system degassing boundary condition assumed in our model, thereby highlighting the sensitivity of the water-in-olivine chronometer to the host magma degassing path.At Seguam, a wide range of best-fit values of dP/dt is obtained both from the water-in-olivine chronometer (0.04–0.23 MPa/s) and from melt embayments (0.02–0.13 MPa/s). We find systematically higher dP/dt values in the melt embayments that appear to have stalled or crystallized at the shallowest depths. Together, these observations are suggestive of magma acceleration during ascent.A strength of the water-in-olivine chronometer is the prevalence of olivine in mafic to intermediate magmas. This new technique yields many values of dP/dt from a single eruption, providing insight into the diversity of ascent records carried by the crystal cargo and possibly defining changes in dP/dt through time and space. This data density offers a more detailed window into syneruptive conduit processes than has been possible using other techniques for constraining dP/dt. In theory, each crystal is a clock, with the potential to record variable ascent in the conduit, over the course of an eruption, between eruptions, and among volcanic systems.

Influence of two‐phase behavior of ethylene ionomers on diffusion of water

ABSTRACTIn this study, diffusion of water into ethylene ionomers neutralized with sodium or zinc cations (Na‐ionomer and Zn‐ionomer, respectively) was studied by in situ Fourier transform near infrared (NIR) spectroscopy. Water ingress was measured by NIR from the edge of the laminated glass toward the center and the measured water concentration profiles were analyzed by Fick's second law or the modified Jacobs–Jones model, which describes diffusion into a two‐phase system of different density and polarity. It was found that the modified Jacobs–Jones model agrees well with the measured water concentration profiles of ionomers, while the Fickian model fits well to the poly(vinyl‐butyral) (PVB) results. The modified Jacobs–Jones model was also confirmed to apply to water vapor transmission rate (WVTR) data of another sodium ionomer (Na‐ionomer‐HTM) with a higher melting temperature than Na‐ionomer. The water diffusion coefficient for Na‐ionomer, Zn‐ionomer, and PVB are compared, and the diffusion parameters are discussed considering the higher‐ordered structures of ionomers studied by small‐angle X‐ray scattering (SAXS). Simulating conditions that PV modules encounter in field applications, model projections show that Zn‐ionomer and Na‐ionomer‐HTM give significantly lower water permeation than PVB, and due to its low diffusion coefficient, Na‐ionomer will have significantly less water ingress than PVB. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48929.

Noncontact high sensitivity chipless tag microwave resonator for bitumen concentration measurement at high temperatures

Real-time water concentration measurement in bitumen is critically important during all operating processes from extraction to refining. Having a low-cost, noncontact sensor that can operate in high temperatures is vital in terms of energy conservation, process optimization and elapsed time. This paper presents a specific design of a microwave coupled split ring resonator-based sensor, with a ground-gap-coupled transmission line as the reader. The tag is a metallic trace with the theoretical capability to sense in ultra-high temperatures far beyond the maximum temperature used in bitumen refineries and is electromagnetically coupled the reader, enhancing the coupling distance up to 60 mm. Therefore, the proposed sensor is well adapted to measure in harsh environmental conditions. Various simulations are conducted and compared against experimental results, verifying the features for the introduced sensor such as the capability to measure at temperatures higher than 200 °C, extremely high sensitivity of 500 kHz (1% of water concentration variation) and measurement in both steady-state and turbulent conditions.

Role of water in degradation of nitroplasticizer

The role of water in degradation of nitroplasticizer (NP) was studied using a set of NP samples aged inside confined containers between room temperature and 70∘C with their water concentrations monitored during the aging course. For the first 42 days at the temperatures 55∘C and below, simple Fickian diffusion dominates the monotonic decreases of the water concentrations with time. After about 60–80 days depending on temperatures, diffusion alone can no longer explain the water decreases, despite no significant NP degradation detectable using the FTIR spectroscopy. Starting at about 80–160 days, also depending on temperatures, the measured water concentrations fluctuated around mean values that decrease with increasing temperature, and the onset of NP degradation was detected using FTIR and TGA. It was found that NP contains an irreducible amount of water on the order of a few hundred ppms, which decreases with increasing temperature. Pristine NP does not exist with a water concentration lower than this amount. The diffusivity, the irreducible amount of water in NP, and the mean water production rate due to NP degradation are calculated from the water concentrations of the first aging stage and the mean water concentrations during the onset of NP degradation. They all change with the temperature following Arrhenius laws with different prefactors and activation energies. This study shows that trace water formation is an intrinsic property of the NP while it ages with the mechanistic details to be resolved.

(Invited) Zirconia-Based Electrochemical Oxygen Sensor for Monitoring Humidity at the Cathode of PEM Stacks

One of the greatest challenges associated with PEMFCs is the water balance in thefuel cell stack. Depending upon the load and the operating conditions, the fuel cell membranes have a propensity to both flood and dry-out. If the PEM is not adequately humidified, the conductivity of the protons decreases, which causes reduced performance. Excess water also can create an issue by inhibiting the reactants from diffusing to the catalyst sites by flooding of the electrodes and gas channels if the water removal is insufficient. Current humidity sensing technologies are not capable of meeting the demands required for this harsh environment. Zirconia-based electrochemical sensors for measuring the oxygen concentration in the automotive exhaust have been used on vehicles for nearly 40 years. This oxygen sensor is an electrochemical cell based on oxygen-ion conducting zirconia operated at elevated temperatures (> 400°C). The sensor is a simple Nernst cell that consists of a single electrochemical cell with one electrode exposed to a reference atmosphere (typically air) and the other electrode exposed to the measurement (exhaust) gas. Although successfully used for stoichiometric A/F control for many years, Nernst-type oxygen sensors are not useful for applications away from stoichiometry because of their weak logarithmic dependence of the emf on oxygen partial pressure. Single and double-zirconia-cell sensors have been developed which have much higher sensitivity and thus a wider range of operation. These are amperometric sensors are based on oxygen pumping, which involves the transfer of oxygen from one side of a zirconia cell to the other by passing an electric current through the device. Since these sensors operate over a wide range, they are referred to as “wide-range oxygen” or “universal exhaust gas oxygen” (UEGO) sensors and can be used over a broader range of A/F measurement and control. All gasoline vehicles, as well as diesel powertrains which operate lean, employ UEGO sensors to meet the emission requirements. The double-cell amperometric sensor also can be used to measu­re the concentration of other oxygen-containing molecules, e.g. H2O, CO2, SO2, and NOx. In order to mea­sure the H2O concentration for example, a voltage is applied across the pump-cell that is greater than the dissociation potential for H2O. The resulting oxygen generated from the decomposition of water is then measured via an increase in pumping current by the UEGO sensor and is proportional to the H2O concentration in the gas. If other oxygen-containing molecules are present in the measurement gas, the voltage across the pump cell can be varied over the dissociation potentials of these gases. For H2O/air mixtures, the concentration of oxygen can be measured at a lower potential. A second voltage larger than the dissociation potential of the measurement gas, H2O, is applied to measure the concentration of oxygen plus water. The water concentration can be determined by subtracting the pumping current due to oxygen from the pumping current due to the combination of the two gases. Other gases can also be measured in a similar fashion. These measurements can be achieved without any modification to the existing sensor hardware. A simple modification to the electronic control circuitry is all that is required to perform this type of measurement. Figure 1 shows the sensitivity of a commercially available UEGO sensor for the dissociation of H2O as a function of dissociation potential. A typical operating value for the sensing voltage Vs for oxygen measurement is 450 mV. The plot below was generated from data measured in the lab at various water concentrations in a carrier gas of dry nitrogen. From the plot it is evident that water dissociation is occurring at potentials less than 800 mV. Additionally, the output begin to saturate at a potential approaching 1100 mV, suggesting that full dissociation of the water has been achieved. Figure 2 shows the sensitivity (pumping current) of the same sensor as a function of water concentration for Vs = 1080 mV. Once again the carrier gas is dry nitrogen. The output is linear in water concentration. The water balance at the cathode is particularly difficult to manage because water accumulates due to the reaction and the clogging of the small channels. Controlling this water balance requires accurate water concentration measurements at temperatures approaching 100°C and pressures up to 3 bar absolute. The application of this humidity sensing technology to measure the water concentration at the cathode of PEMFCs will be discussed. Figure 1