Passive Gas Research Articles

Reducing corrosion and hydrogen gas release inside an alkaline zinc-air battery by employing ionic liquid

Zn–air batteries are a promising route that might be used in a range of energy sectors. Significant disadvantages, such as passive film and hydrogen gas evolution (HGE) in alkaline corrosive medium; restrict the possible usage of Zn–air batteries. To address these problems and increase the performance of zinc-air batteries, an ionic liquid (tris(2hydroxyethyl) hydroxymethylammonium methyl sulfate [IL]+[MS]-) has been used in this study. The usage of [IL]+[MS]- in 7.0 M KOH solution has a considerable effect on suppressing hydrogen gas creation, with an effectiveness of 86.2 %. Increasing the depth of the Bode-phase angle and the charge transfer resistance by adding [IL]+[MS]- also indicates a slower hydrogen gas production rate. The application of the [IL]+[MS]- additive improves the zinc-air battery's specific discharge capacity and capacity retention. To support these findings, SEM/EDX has been used to analyze the morphological features of Zn anodes in various electrolytes.

The Effect of Manual Maneuver on Shoulder Pain of Laparoscopic Gynecology Surgery, a Randomized Clinical Trial Study

Background: Shoulder pain following gynecological laparoscopy is a common complication that requires treatment. Objectives: This study aimed to evaluate the effect of manual maneuvers on shoulder pain following laparoscopic surgery in women. Methods: This parallel clinical trial was conducted with 77 female laparoscopy candidates referred to Yas Hospital in Tehran in 2023. After the laparoscopic procedure, the intervention group had CO2 gas actively removed from the abdomen during a two-handed abdominal massage, while the control group received only traditional passive gas evacuation. The intensity of pain was assessed 6- and 24-hours post-operation using the Visual Analogue Scale (VAS), and the number of painkillers and anti-nausea medications used was recorded in each patient's chart. All data were entered into SPSS software and analyzed using appropriate statistical tests. Results: The average age of the women was 39.4 ± 10.1 years, and the average body mass index (BMI) was 27.5 ± 2.5 kg/m². No significant difference was observed between the two groups in these characteristics. Six hours after the operation, the pain intensity was 4.6 ± 0.86 in the intervention group and 6.2 ± 1.1 in the control group, with a significant reduction in the intervention group (P = 0.001). Twenty-four hours post-operation, pain intensity was 2.7 ± 0.79 in the intervention group and 4.2 ± 1.1 in the control group, again showing a significant decrease in the intervention group (P = 0.001). Additionally, the need for analgesics was significantly lower in the intervention group (P = 0.001). Conclusions: The results of this study indicate that manual abdominal massage following laparoscopic surgery can significantly reduce shoulder pain, decrease the need for analgesics, and enhance patient satisfaction.

The effects of F-500 Encapsulator Agent on canine alerts and laboratory analysis using passive headspace concentration and gas chromatography-mass spectrometry

F-500 Encapsulator Agent (EA) is a fire suppression agent that is an alternative to traditional firefighting foams. It is marketed as having the capability to act on all four parts of the fire tetrahedron as well as being environmentally friendly and non-toxic. An internal survey of the use of F-500 EA by fire departments encountered by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) ignitable liquid detection canine (ILDC) handlers in 2022 showed that this product is not yet in widespread use across the country, but where it has been implemented, it is frequently utilized on a variety of types of fires. Additional agencies are researching the product to determine if it should be adopted. As this product appears to be growing in popularity, it is important to understand whether the use of the product would affect a canine’s ability to detect ignitable liquids or a forensic laboratory’s ability to identify the presence of an ignitable liquid. Burned wood and burned carpet, two commonly encountered substrates, were spiked with gasoline or a heavy petroleum distillate (HPD) and F-500 EA was applied. At various time intervals, ILDC teams surveyed the samples and laboratory analysis was conducted. Results showed that the presence of F-500 EA can negatively affect canine alerts and the laboratory’s ability to identify ignitable liquids.

Active gas camera mass flow quantification (qOGI): Application in a biogas plant and comparison to state-of-the-art gas cams.

Gas cameras are primarily used to detect gas leaks, but their use has been increasingly extended to mass flow quantification (qOGI). We employ the previously published active illuminated gas camera [Bergau etal. "Real-time active-gas imaging of small gas leaks," J. Sens. Sens. Syst. 12, 61-68 (2023) and Bergau etal. "Flow rate quantification of small methane leaks using laser spectroscopy and deep learning," Process Saf. Environ. Prot. 182, 752-759 (2024)] in a real-world application for quantification, enhancing the camera with two new features: sensitivity adaptation and camera-gas distance detection. This technology was applied to a gas leak found in the pressure swing adsorption room of a biogas plant in Germany. We compare its performance with state-of-the-art quantification gas cameras (qOGI), such as Sensia Mileva 33. Such a comparison between active and passive gas cameras is possible for the first time due to the introduced sensitivity tuning. Additionally, we enclosed the gas leak and measure the methane concentration with a flame ionization detector, providing a gold standard for comparison. Our findings revealed relative offsets to our gold standard of -57% and +319% for the DAS-camera and the Sensia, respectively, suggesting that the accuracy of mass flow quantification could be improved through the use of active gas cameras.

Numerical investigation and optimal design of capillary barrier cover with passive gas collection pipes on the performance at limiting landfill gas emissions

Relying solely on soil properties may not fully ensure the performance of capillary barrier covers at limiting landfill gas (LFG) emissions. This study proposed to install passive gas collection pipes in the coarse-grained soil layers of capillary barrier covers to enhance their performance at limiting LFG emissions. First, the LFG generation rate of municipal solid waste and its influencing factors were analyzed based on empirical formulas. This information provided necessary bottom boundary conditions for the analyses of LFG transport through capillary barrier covers with passive gas collection pipes (CBCPPs). Then, numerical simulations were conducted to investigate the LFG transport properties through CBCPPs and reveal relevant influencing factors. Finally, practical suggestions were proposed to optimize the design of CBCPPs. The results indicated that the maximum whole-site LFG generation rate occurred at the end of landfilling operation. The gas collection efficiency (E) of CBCPPs was mainly controlled by the ratio of the intrinsic permeability between the coarse- and fine-grained soil (K2/K1) and the laying spacing between gas collection pipes (D). E increased as K2/K1 increased but decreased as D increased. An empirical expression for estimating E based on K2/K1 and D was proposed. In practice, CBCPPs were supposed to be constructed once the landfilling operation finished. It is best to select the fine- and coarse-grained soils with K2/K1 exceeding 10,000 to construct CBCPPs.

Active gas aspiration in reducing pain after laparoscopic cholecystectomy: a systematic review and meta-analysis of randomized controlled trials.

Postoperative pain is a common issue following laparoscopic cholecystectomy. This meta-analysis aimed to determine if active gas aspiration is more effective than passive gas aspiration in reducing postoperative pain and analgesic requirements. The study conducted a systematic search of various databases, including Embase, Medline, and Cochrane Central Register of Controlled Trials (CENTRAL) via Ovid. It also searched trial registries and reference lists of included studies, with no date restrictions but limited to English language, up to December 21, 2022. The study included all randomized clinical trials that had documented elective laparoscopic cholecystectomy procedure and reported at least one relevant outcome. Articles that included subdiaphragmatic drain, intraperitoneal normal saline infusion, or pulmonary recruitment maneuver were excluded from the analysis. Two reviewers independently and in duplicate assessed the eligibility of studies and extracted data. The study reported findings according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. The risk of bias of the included trials was assessed using the Revised Cochrane Risk of Bias Assessment Tool. The study used a random-effects model to pool data. This meta-analysis included 5 randomized clinical trials with 367 participants and found that active gas aspiration resulted in significantly lower residual gas volume and total analgesia requirements compared to passive gas aspiration. Active gas aspiration also led to significantly lower shoulder pain scores at 24h postoperatively. However, no significant differences were observed in hospital stay duration or abdominal pain scores. The study found that active gas aspiration can be effective in reducing postoperative shoulder pain and analgesic requirements after laparoscopic cholecystectomy, which has important implications for patient care and healthcare costs. Importantly, this intervention does not impose any additional time or financial burden. However, further research is needed to evaluate its impact on other laparoscopic procedures.

Effect of Superhydrophobic Catalyst Layers on PEMFC Durability

High durability of proton exchange membrane fuel cells (PEMFCs) is one main objective of this technology nowadays. Among different ways, the use of a superhydrophobic catalyst layer in the cathode may help to increase the stability of the cell under operation. Superhydrophobic cathodic layers improve water management in the cell by enhancing the back-diffusion transport from cathode to anode. As a consequence, anode humidification is favored whereas flooding of the cathode is avoided, leading to higher cell response at intermediate and high current densities [1]. Superhydrophobic catalyst layers can be obtained by adding specific agents to the precursor ink that is later deposited together with the catalyst and the ionomer. Another possibility is the use of electrospray deposition, which does not require additives. Electrospray is a dry deposition method where the ink is deposited under an electric field, yielding particular ionomer distribution inside the pores of the layer as a consequence of electrostatic interactions.Accelerated stress tests (AST) are well stablished protocols to analyze durability of PEMFCs in a systematic and reduced time frame [2]. Protocols for stressing different components of the cell have been proposed. In this work, different cell configurations have been mounted, using electrosprayed catalyst layers in cathode, anode, and both. The cells have been submitted to an AST that affects mainly the cathodic catalyst layer. The study is complemented with microscopy analysis (cross-sectional) and local mechanical properties (small-punch) (Fig. 1).The results show the effect of superhydrophobic cathodic catalyst layers on the durability of a PEMFC.AcknowledgementsFunding by PORHYDRO2 project (TED2021-131620B-C22, ‘Preparation and characterisation of catalyst layers fabricated by electrospray for proton exchange fuel cells with passive gas feed’) by the Spanish Ministry of Science and Innovation.[1] M.A. Folgado, J.J. Conde, P. Ferreira-Aparicio, A.M. Chaparro, Single Cell Study of Water Transport in PEMFCs with Electrosprayed Catalyst Layers, Fuel Cells. 18 (2018) 602–612. https://doi.org/10.1002/fuce.201700217.[2] S. Stariha, N. Macauley, B.T. Sneed, D. Langlois, K.L. More, R. Mukundan, R.L. Borup, Recent Advances in Catalyst Accelerated Stress Tests for Polymer Electrolyte Membrane Fuel Cells, J. Electrochem. Soc. 165 (2018) F492–F501. https://doi.org/10.1149/2.0881807jes.[3] R. Hernández, S. Merino, D. Plaza, L. Duque, M.A. Folgado, A.M. Chaparro, M. Serrano, G. de Diego, Study of Mechanical Properties of Membrane-Electrode Assemblies for Proton Exchange Membrane Fuel Cells By the Small-Punch Technique, ECS Meet. Abstr. MA2022-02 (2022) 1426–1426. https://doi.org/10.1149/ma2022-02391426mtgabs. Figure 1

Mass Transport Impedance in a PEMFC with Superhydrophobic Catalyst Layers

Electrosprayed catalyst layers improve liquid water management in PEMFCs thanks to their superhydrophobic character [1]. Using appropriate parameters, the electrospray deposition of a suspension of Pt/C powder and ionomer (Nafion solution) gives rise to a macroporous layer with superhydrophobic pores. Under current generation in a PEMFC, superhydrophobicity of the cathodic catalyst layer minimizes water interaction with pores walls, and enhances water transport towards the anode. As a consequence, water distribution inside the cell is more homogeneous, which makes cathode flooding less severe and improves anode humidification. PEMFCs with cathodic electrosprayed catalyst layer have shown higher power production rate at intermediate and high current densities, with peak power densities above 20%-25% compared with conventional, more hydrophilic, catalyst layer under standard testing conditions. We have studied in previous works the transport properties of electrosprayed catalyst layers with a number of techniques, like polarization curves, electrochemical impedance spectroscopy, and hydrogen transport.In this communication, catalyst layer transport properties in a PEMFC with electrosprayed electrodes are studied with 'Current Modulated Hydrogen Flow Rate Spectroscopy' (CH2S) [2], which is a transport impedance technique relating hydrogen flow rate with faradaic current. With this aim, PEMFCs have been mounted with electrosprayed catalyts layers in anode and in cathode. When in anode, the electrosprayed catalyst layer gives rise to significant differences in the CH2S Nyquist plots and dependent on cell humidification (Fig. 1). The CH2S signals resolve transport kinetics having different characteristic times, that can be assigned to transport in different parts of the anode, like flow-field, gas diffusion layer, microporous layer and catalyst layer. The study is completed with CH2S measurements on PEMFCs with different configurations, having electrosprayed electrodes in anode and cathode. It is concluded that CH2S provides new insights into mass transport properties of gas diffusion electrodes.AcknowledgementsFunding by PORHYDRO2 project (TED2021-131620B-C22, ‘Preparation and characterisation of catalyst layers fabricated by electrospray for proton exchange fuel cells with passive gas feed’) by the Spanish Ministry of Science and Innovation.[1] M.A. Folgado, J.J. Conde, P. Ferreira-Aparicio, A.M. Chaparro, Single Cell Study of Water Transport in PEMFCs with Electrosprayed Catalyst Layers, Fuel Cells. 18 (2018) 602–612. https://doi.org/10.1002/fuce.201700217.[2] L. Duque, A. Molinero, J.C. Oller, J.M. Barcala, M.A. Folgado, A.M. Chaparro, Analysis of Hydrogen Feeding to the Anode of a PEMFC By a Transport Impedance Technique, ECS Meet. Abstr. MA2022-02 (2022) 1406–1406. https://doi.org/10.1149/ma2022-02391406mtgabs. Figure 1

The role of SVOCs in the initial film formation and soiling of unvarnished paintings

In recent years increased research efforts and environmental improvements have been directed towards the preventive conservation of the monumental, unvarnished oil paintings on canvas (1909–1916) by Edvard Munch (1863–1944) housed in the University of Oslo Aula. Surface soiling of the paintings has been a documented issue since their display, and the modern-day effect of air-borne particulates and gases on the painting surfaces remains hitherto undocumented. For the first time in the Aula, this study has measured the in-situ time-dependent mass deposit of air pollution onto vertical surfaces over the period of one year (2021–2022). Concomitant measurements of the concentrations of ozone (O3) and nitrogen dioxide (NO2) were also taken, to complement periodic data from 2020. The mass deposit was measured through incremental weight changes of Teflon membrane filters, and quartz filters for analysis of elemental/organic carbon (EC/OC), whilst the gaseous pollutants were measured using passive gas samplers. Indoor-to-outdoor ratios (I/O) for O3 were noted to be higher than those suggested by earlier data, whereas NO2 I/O ratios were found to be lower, indicating a stronger oxidising atmosphere in the Aula. Just over half of the deposited mass on the quartz filters was found to be OC, with no EC detected. Surprisingly, an overall decrease in the mass deposit from three to twelve months was measured on the Teflon membrane filters. It was hypothesised, based on models reported in the literature, that the source of the OC on the filters was mainly gaseous, semi-volatile organic compounds (SVOCs), which were present in an adsorption/desorption equilibrium that was dependent on possible SVOC emission episodes, relative humidity levels, gaseous oxidative reactions and the particulate matter deposit. A simple mathematical model is proposed to rationalise the observed mass deposits on the filters, together with a discussion of uncertainties affecting the measurements. The hypothesis preliminarily indicates the possible and previously unconsidered role of SVOCs on the initial film formation of soiling layers on the Aula paintings, and could bear implications for their monitoring in the preventive care of unvarnished oil paintings on canvas.

Accessible sampling methodologies to quantify the net methane emission from landfill cells

Landfills are one of the main sources of anthropogenic methane (CH4) emissions in urban areas. The environmental conditions specific to each locality, the waste management and the infrastructure of each landfill will influence the emissions of this gas. By applying different methodologies, this study aims to investigate the total contribution of CH4 to the atmosphere from a landfill, as well as the surface fluxes within the cells and the passive gas vents. According to the results, mean atmospheric CH4 concentrations from landfills were measured up to 6 ppm higher than those recorded in urban areas and locations distant from CH4 fixed sources. Two closed cells were selected to study surface fluxes by static chamber technique. CH4 uptake (1.65E-08 to 2.04E-06 g m−2 d−1) was recorded in between 60% and 87.5% of the chambers, indicating that the surface acted as a sink for the gas, as compared to the mean uptake observed from a control site (1.72E-06 g m-2 d−1). CH4 emissions from gas vents were studied using a tracer technique with permeable capsules, a methodology used for the first time in a landfill. Relatively high emissions were detected, up to 1.20E+04 g d−1. Finally, from the net CH4 emission calculated, the energy produced if the emitted CH4 were captured was estimated to be 3.23 GJ. The results highlight the importance of these studies for decision-makers to plan future landfill infrastructure adequately, implement mitigation measures to reduce emissions of this potent greenhouse gas and contribute to the energy system resources.

Clouds of Theseus: long-lived molecular clouds are composed of short-lived H2 molecules

ABSTRACT We use passive gas tracer particles in an Arepo simulation of a dwarf spiral galaxy to relate the Lagrangian evolution of star-forming gas parcels and their H2 molecules to the evolution of their host giant molecular clouds. We find that the median chemical lifetime of H2 is 4 Myr, with an interquartile range between 2 and 9 Myr. This chemical lifetime is independent of the lifetime of the host molecular cloud, which may extend up to 90 Myr, with around 50 per cent of star formation occurring in longer lived clouds (>25 Myr). The rapid ejection of gas from around young massive stars by early stellar feedback is responsible for the short H2 survival time, driving down the density of the surrounding gas, so that its H2 molecules are dissociated by the interstellar radiation field. This ejection of gas from the H2-dominated state is balanced by the constant accretion of new gas from the galactic environment, constituting a ‘competition model’ for molecular cloud evolution. Gas ejection occurs at a rate that is proportional to the molecular cloud mass, so that the cloud lifetime is determined by the accretion rate, which may be as high as 4 × 104 M⊙ Myr−1 in the longest lived clouds. Our findings therefore resolve the conflict between observations of rapid gas ejection around young massive stars and observations of long-lived molecular clouds in galaxies. We show that the fastest-accreting, longest lived, highest mass clouds drive supernova clustering on sub-cloud scales, which in turn is a key driver of galactic outflows.

Muscle wobbling mass dynamics: eigenfrequency dependencies on activity, impact strength, and ground material

In legged locomotion, muscles undergo damped oscillations in response to the leg contacting the ground (an impact). How muscle oscillates varies depending on the impact situation. We used a custom-made frame in which we clamped an isolated rat muscle (M. gastrocnemius medialis and lateralis: GAS) and dropped it from three different heights and onto two different ground materials. In fully activated GAS, the dominant eigenfrequencies were 163 Hz, 265 Hz, and 399 Hz, which were signficantly higher (p < 0.05) compared to the dominant eigenfrequencies in passive GAS: 139 Hz, 215 Hz, and 286 Hz. In general, neither changing the falling height nor ground material led to any significant eigenfrequency changes in active nor passive GAS, respectively. To trace the eigenfrequency values back to GAS stiffness values, we developed a 3DoF model. The model-predicted GAS muscle eigenfrequencies matched well with the experimental values and deviated by − 3.8%, 9.0%, and 4.3% from the passive GAS eigenfrequencies and by − 1.8%, 13.3%, and − 1.5% from the active GAS eigenfrequencies. Differences between the frequencies found for active and passive muscle impact situations are dominantly due to the attachment of myosin heads to actin.

Multiplexed fiber-optic photoacoustic sensors for simultaneous detection of multi-point gases

A multiplexing scheme of fiber-optic photoacoustic (PA) gas sensors is demonstrated for simultaneous detection of multi-point gases. By sharing the PA demodulation device, the average cost of single point measurement can be significantly reduced. The passive fiber-optic PA gas sensing probe is integrated by a PA tube and a Fabry-Perot (F-P) interferometric (FPI) cantilever. The laser excited the PA signals is simultaneously incident into two sensing probes. The superimposed F-P interference spectrum containing multi-point gas concentration information is received by a high-speed spectrometer. For synchronous measurement of multi-point gases, a white-light interferometry (WLI) based frequency division multiplexing (FDM) spectral demodulation method is exploited. A multi-point acetylene gas remote monitoring system is established by two PA gas sensing probes with 3 km fiber cable. The experimental results show that the sensing probes have achieved the detection limit of sub-ppm. The crosstalk between the two sensors is characterized by the gas concentrations at the two points, indicating a crosstalk of about − 35 dB. This multiplexing scheme of fiber-optic PA sensing probes has the merits of remote monitoring, low crosstalk, high sensitivity, intrinsic safety and low cost. It can be applied for coal spontaneous combustion monitoring, dissolved gas analysis and gas micro-leakage monitoring.

The passive sampler assisted human exposure risk characterization for tetrachloroethene soil vapor intrusion scenario

The potential human health risks associated with soil vapor intrusion and volatile organic compounds (VOCs) exposure were characterized at an industrialized site by the quantification of gaseous VOCs in soil pores using a passive sampling technique. The gaseous tetrachloroethene (PCE) in soil pores varied between 12 and 5,400 μg m−3 showing 3 orders of magnitude variation with dependence on groundwater PCE concentrations. Though the PCE concentration in the air only varied between 0.45 and 1.5 μg m−3 showing negligible variations compared to the variation observed in soil pores. The PCE concentration in the air varied between 0.45 and 1.5 μg m−3. The calculation of fugacity suggested that the PCE in the test site originated from groundwater. Measured PCE in groundwater ranged from 14 to 2,400 times higher than PCE in soil gas. This indicates that conducting a vapor intrusion risk assessment using passive soil gas sampling is critical for accurate risk characterization and assessment. Estimated PCE inhalation cancer risks for street cleaners and indoor residents varied between 10−6 and 10−4 with a low plausible hazard, and between 10−3 and 10−2 with a high risk, respectively. The results of this study demonstrate that passive sampling offers a significantly lower cost and labor-intensive approach compared to traditional methods for assessing pollution distribution in contaminated sites and characterizing risks. This highlights the potential for wider application of passive sampling techniques in environmental studies.

Integrated Passive Device-Based Gas Sensor Combined with PANI/SnO2 Composites for Ammonia Detection

Integrated Passive Device-Based Gas Sensor Combined with PANI/SnO₂ Composites for Ammonia Detection

Breakup of thin liquid films with viscous interfaces

Thin liquid films are ubiquitous in nature and have many practical applications. From biological films to the curtain coating process, thin films are present in both large and small scales. Despite their importance, understanding the stability of these films remains a significant challenge due to the fluid–fluid interface that is free to deform, affected by interfacial tension and complex rheological behavior. Instabilities in thin films are often caused by van der Waals attractions, which can lead to the rupture of the layer. To investigate the rupture dynamics, numerical methods are commonly used, such as asymptotic derivations of the lubrication theory or interface tracking methods. In this paper, we present a computational study of the breakup dynamics of a stationary thin liquid sheet bounded by a passive gas with a viscous interface, using the arbitrary Lagrangian–Eulerian method and the Boussinesq–Scriven constitutive law to model the rheological behavior. Our results demonstrate that the stability of thin liquid films is influenced by both surface rheology and disjoining effects and that the viscous character of the interface can delay sheet breakup, leading to more stable films.

A Novel-Structure LC Resonant Passive Wireless Sensor for NO2 Sensing

This work presents an LC resonant passive wireless gas sensor with a novel structure designed to mitigate the negative impact of substrate. The LC sensor antenna in the new structure, and the reader antenna, were designed and optimized utilizing HFSS software to improve the transfer efficiency. The superiority of the designed structure compared with general examples is highlighted and verified. The change in the substrate capacitance essentially makes no interference with the parameters of the LC sensor to be measured. The sensor for the new structure was prepared by combining etching and sputtering methods. The ZnO nanowires (NWs) were characterized to confirm their high purity and wurtzite crystal structure. The LC gas sensors demonstrated excellent wireless sensing performance, including a low detection limit of 0.5 ppm NO2, high response of 1.051 and outstanding stability at 180 °C. The newly developed sensor structure not only prevented interference from the substrate during gas sensing testing, but also expanded the choice of sensor substrates, playing a critical role in the development of sensors based on the LC resonance principle.

Human skin gas profile of individuals with the people allergic to me phenomenon

Recent studies have shown that some people claim that their skin gases provoke allergy-like reactions in people in their near vicinity. Such a phenomenon or symptom is called ‘people allergic to me (PATM)’. Although numerous people suffer from PATM, the actual conditions are unknown. The aim of this study was to investigate the characteristics of human skin profiles in patients with PATM by measuring the dermal emission fluxes of 75 skin gases using passive flux sampler and gas chromatography/mass spectrometry. We found common features in the human skin gas profiles of 20 subjects with PATM, with a significant difference from those of 24 non-PATM subjects: greater emissions of petrochemicals, organosulfur compounds, and some aldehydes and lower emissions of aroma compounds and others. The ratio of toluene to benzaldehyde is considered a vital sign that suggests the fundamental of PATM. These findings indicate that PATM is a medically unexplained phenomenon or symptom worthy of further research, which requires an interdisciplinary approach.

Research on the Passivation Process of Iron Nanopowder as Catalyst for Ammonia Synthesis

This paper aims to study a passivation technology and process of iron nanopowder, and provides basic theory and experimental data for promoting the practical application of iron nanopowder as a high-efficiency catalyst in the production of ammonia. There are two specific objectives. The first one is to provide a nanometal powder passivation device to prevent the nano metal powder from being oxidized and deactivated. The second one is to provide a method for using the nano metal powder passivation device to passivate the nano metal powder. Meanwhile, the research on iron nano-powder passivation technology and process is also beneficial to the application of iron nano-materials in other fields. The metal nanopowder passivation equipment provided in this paper can control the passivation reaction speed by adjusting the ratio and flow rate of the passivation gas during the passivation process, and identify the occurrence and stop of the passivation reaction by detecting the composition of the passivation reactant. Overall, the technology has the advantages of easy operation, uniform powder passivation, adjustable reaction speed, high product purity, etc. Therefore, it is suitable for industrial production.

Quantification of CO2 degassing and atmospheric dispersion at Caldeiras da Ribeira Grande (São Miguel Island, Azores)

Caldeiras da Ribeira Grande is one of the degassing areas of Fogo, a trachytic central volcano located at São Miguel Island (Azores archipelago). Recently, new steam emissions, soil CO2 and temperature anomalies developed towards the inhabited area, causing high indoor CO2 values and affecting the vegetation and several small animals that were found dead in depressions and low-ventilated zones. During July–August 2021, a soil CO2 flux survey was carried out on the north flank of the volcano, estimating a soil gas release of at least 40 t d−1 (excluding the contribution of the fumaroles) over an area of ∼0.27 km2. Two populations for the CO2 released were found, highlighting the biogenic and volcanic-hydrothermal origins. General NW-SE diffuse degassing structures (DDS) were identified, in agreement with the tectonic lineaments previously recognized in the area. In this regard, we investigated the passive gas dispersion in the atmosphere at Caldeiras da Ribeira Grande performing a model validation aimed to estimate the fumarolic gas flux at source and the potential hazard for human and animal lives posed by CO2. Numerical simulations were carried out with the DISGAS-2.3, a 3D Eulerian advection-diffusion model, and the relative outputs processed through the VIGIL-1.3 workflow able to provide probabilistic long-term CO2 concentration maps, considering a meteorological variability over the last 30 years (1991–2020) taken from the ECMWF ERA5 reanalysis dataset. A best-fit between observed and simulated CO2 concentrations allowed us to estimate the total gas flux of the area (∼209 t d−1) obtained by scaling the soil CO2 gas flux by a factor 30. Such an estimate is composed of ∼174 t d−1 as unknown fumarolic and ∼ 35 td−1 as diffuse contribution, in a good agreement with measurements.Although the present-day CO2 concentration at 0.3 m height cannot be considered to raise serious concerns for human health, we reasonably infer that the death of small animals may be due to local conditions of CO2 accumulation or to the presence of H2S. The current study highlights the relevance of coupling gas flux maps, concentration data, and gas dispersion modeling to obtain robust estimation of gas fluxes, including the fumarolic contribution, and identify zones potentially impacted by dangerous concentrations of volcanic gases, which are relevant for land-use planning and hazard assessment in case of renewed escalations of volcanic activity.