Atmospheric Gas Composition Research Articles

Experimental and analytical study on liquid and vapor penetration of high-reactivity gasoline using a high-pressure gasoline multi-hole injector

Spray penetration length is an important parameter which is of great interest to both experimentalists and modelers. As it affects engine efficiency and emissions, measurement and prediction of spray penetration can significantly benefit engine optimization under various operating conditions. In this study, penetration length was investigated in a pre-burn constant volume combustion chamber using a gasoline multi-hole injector with high reactivity gasoline-like fuel designed explicitly for gasoline compression ignition (GCI) engines. Diffused back illumination (DBI) and shadowgraph were implemented for liquid and vapor phase penetration measurements, respectively. Different pre-burn gas mixtures are compared to investigate the influence of ambient gas properties on gasoline spray penetration under evaporating conditions. The liquid penetration under the gas composition of higher molecular weight tends to be longer. However, the vapor penetration showed insignificant effect under different gas compositions. Ambient gas temperature and gas composition were found to be an essential parameter for liquid phase penetration. Pressure difference was found to affect the vapor penetration length while its influence on liquid phase steady state penetration length at high ambient gas temperature is marginal. Statistical analysis was performed for both liquid and vapor phase penetration lengths, and a prediction model was developed with good agreement to the data under all test conditions.

DETERMINATION OF THE PROBABILITY FACTOR OF PARTICLES MOVEMENT IN A GAS-DISPERSED TURBULENT FLOW

The goal of the work is to define the probability factor of particles movement in a gas-dispersed turbulent flow. The object of the research is the description of harmful impurities transfer process in the atmosphere with the help of mathematical modelling of variability of gas and aerosol composition of atmosphere. Another object is assessment atmospheric impurities on the environment. The novelty of the research is that probability-statistical approach is used in modelling the transfer of harmful impurities from anthropogenic sources into the atmosphere.

Predicting soybean losses using carbon dioxide monitoring during storage in silo bags

The rapid increase of the overall grain production of Argentina resulted with a storage capacity deficit in permanent structures of 40–50 million tons, and this context favored the rapid adoption of the silo bag technology. Silo bag allows differing grain selling from harvest time, taking advantage of the seasonal price changes and, hence, improving farmers’ income. However, storing grain in silo bag could be risky if inadequate planning, handling or monitoring is implemented. Thus, the objective of this article was to develop a prediction model for soybean losses in silo bag storage based on monitoring CO2 concentration and other sensible variables. During 2013, an experiment was conducted in 13 soybean silo bags placed at farms and grain elevators in Balcarce area, South East of Buenos Aires province, Argentina, since May to December. Grain samples were collected and grain quality was evaluated. Storage variables, such as moisture content and interstitial atmosphere gas composition were also recorded, and at the end of storage, physical grain losses were quantified for each silo bag (kg of spoiled grain not commercialized). The results showed that there was not generalized quality loss in any silo bag, but localized losses were observed. These losses occurred due to water entrance in the silo bag through openings which resulted in spoiled grain from 140 to 4320 kg, representing from 0.07% to 2.16% in a 200 ton silo bag. Next, a correlation to predict grain losses was developed, which considered grain moisture and a predictor related to the CO2 concentration at the silo bag closing end as independent variables. This correlation explained 73% of the grain losses variability, allowed to model different levels of losses, and was consistent with biological concepts.

Nutritional and quality changes of minimally processed faba (Vicia faba L.) beans during storage: Effects of domestic microwaving

The present study evaluated the effect of different sanitizers (an edible coating (EC) based on sucrose fatty acid esters, and UV–C (3 kJ m–2), compared with a control consisting of a conventional NaOCl washing (CTRL)) on the quality changes of fresh–cut (FC) faba (Vicia faba L.) seeds stored for 10 d at 4 °C. Additionally, domestic cooking of samples was assessed by periodically microwaving (3 min, 700 W) during FC samples storage to obtain a ready–to–eat product. The modified atmosphere gas composition at the steady was the same for all treatments. The EC treatment better retained vitamin C, total phenolics content (TPC) and tannins, while UV–C better maintained the sugars levels of samples. EC and UV–C controlled mesophilic and enterobacteria growth with 1 and 2–log units lower contents than CTRL after 10 d at 4 °C. Microwaving reduced the microbial loads below detection limits. EC or UV–C treatments extended the shelf–life of fresh–cut faba seeds from 7 to 10 d at 4 °C comparing with CTRL. As expected, microwaving decreased the bioactive compounds contents, but retained the quality of faba seeds allowing to obtain a ready–to–eat tasteful food.

Глубина прогорания торфа и потери углерода при лесном подземном пожаре

Глубина прогорания торфа и потери углерода при лесном подземном пожаре

SRS-lidar for environmental monitoring atmospheric surface layers

Background: The development and implementation of new methods of environmental monitoring is an urgent problem due to the technogenic pollution of the Earth's biosphere. The remote control of the gas composition of the surface atmosphere layer in industrial zones of modern metropolis is important for determining penalties for enterprises whose emissions of pollutants exceed established norms. Objectives: Development of an ecological Spontaneous Raman Scattering (SRS) lidar for monitoring the gas composition in the air basin of large megacities. Theoretical verification of the lidar effectiveness for problem solving. Materials and methods: The developed lidar for environmental monitoring of the atmospheric surface layer is based on the SRS method which allows remote monitoring of the atmospheric gas composition at distances up to several kilometers with a fairly high resolution (up to 1 meter). The absolute concentration of detected polluting gases is determined by comparing the intensities of the satellite pollutant and nitrogen lines in the recorded SRS spectra. Results: The choice of the SRS method for remote laser monitoring of the atmosphere ground layer in large industrial centers is substantiated. The block diagram and the main technical characteristics of the developed SRS lidar are presented. Preliminary estimates of the lidar efficiency for the environmental monitoring were carried out. Conclusions: The simulation results have shown that the specifications of the SRS lidar allow detecting of following polluting gases: CO, NO2, SO2, CH4, H2S, C6H6 at distances up to 200 m with the maximum permissible concentration level. The simulation results were obtained when accumulation time varied from 10 s to 4 min. The specification of the SRS lidar allow its using for remote monitoring of air conditions in the cities and near industrial enterprises.

Parameterization of the Infrared Molecular Absorption in the Earth’s Lower and Middle Atmosphere

A new algorithm for parameterizations of molecular absorption in the Earth’s atmosphere is presented, which takes into account the change in atmospheric gas composition with altitude and has a number of other advantages, as well as a parameterization constructed using this algorithm, in the frequency region from 10 to 2000 cm−1 and altitude range from the Earth’s surface to 76 km. Comparison of the calculation results of the Earth’s atmospheric radiation field (carried out using this parameterization) with the results of reference calculations (line-by-line) shows that the parameterization suggested has good accuracy in the lower and middle atmosphere both in the absence and in the presence of cloud layers with a large optical thickness.

Colorado Plateau Coring Project, Phase I (CPCP-I): a continuously cored, globally exportable chronology of Triassic continental environmental change from western North America

Abstract. Phase 1 of the Colorado Plateau Coring Project (CPCP-I) recovered a total of over 850 m of stratigraphically overlapping core from three coreholes at two sites in the Early to Middle and Late Triassic age largely fluvial Moenkopi and Chinle formations in Petrified Forest National Park (PFNP), northeastern Arizona, USA. Coring took place during November and December of 2013 and the project is now in its post-drilling science phase. The CPCP cores have abundant detrital zircon-producing layers (with survey LA-ICP-MS dates selectively resampled for CA-ID-TIMS U-Pb ages ranging in age from at least 210 to 241 Ma), which together with their magnetic polarity stratigraphy demonstrate that a globally exportable timescale can be produced from these continental sequences and in the process show that a prominent gap in the calibrated Phanerozoic record can be filled. The portion of core CPCP-PFNP13-1A for which the polarity stratigraphy has been completed thus far spans ∼215 to 209 Ma of the Late Triassic age, and strongly validates the longer Newark-Hartford Astrochronostratigraphic-calibrated magnetic Polarity Time-Scale (APTS) based on cores recovered in the 1990s during the Newark Basin Coring Project (NBCP). Core recovery was ∼100 % in all holes (Table 1). The coreholes were inclined ∼60–75∘ approximately to the south to ensure azimuthal orientation in the nearly flat-lying bedding, critical to the interpretation of paleomagentic polarity stratigraphy. The two longest of the cores (CPCP-PFNP13-1A and 2B) were CT-scanned in their entirety at the University of Texas High Resolution X-ray CT Facility in Austin, TX, and subsequently along with 2A, all cores were split and processed at the CSDCO/LacCore Facility, in Minneapolis, MN, where they were scanned for physical property logs and imaging. While remaining the property of the Federal Government, the archive half of each core is curated at the NSF-sponsored LacCore Core Repository and the working half is stored at the Rutgers University Core Repository in Piscataway, NJ, where the initial sampling party was held in 2015 with several additional sampling events following. Additional planned study will recover the rest of the polarity stratigraphy of the cores as additional zircon ages, sedimentary structure and paleosol facies analysis, stable isotope geochemistry, and calibrated XRF core scanning are accomplished. Together with strategic outcrop studies in Petrified Forest National Park and environs, these cores will allow the vast amount of surface paleontological and paleoenvironmental information recorded in the continental Triassic of western North America to be confidently placed in a secure context along with important events such as the giant Manicouagan impact at ∼215.5 Ma (Ramezani et al., 2005) and long wavelength astronomical cycles pacing global environmental change and trends in atmospheric gas composition during the dawn of the dinosaurs.

Numerical Simulation of Heat Transfer and Scale Formation in a Reheat Furnace

In steel rolling mills, reheat furnaces are used to reheat slabs to high temperatures in a highly oxidizing environment; this results in the formation of iron oxide scale on the slab surface. Scale formation poses an ongoing material and economic loss to industry and should be minimized where feasible. The kinetics of scale growth are complex and still not fully understood. Previous studies that modeled scale formation with mathematical methods are limited to simple case studies. Here, computational fluid dynamics (CFD) is used to simulate slab reheat furnace operations and to investigate complicated physical phenomenon. This paper proposes a new numerical method to model scale growth under varying conditions/characteristics including temperature, gas atmosphere composition, and steel grade. This method uses a mixed linear‐parabolic equation to model both the initial surface reaction (and scale formation) and the subsequent solid‐state ion diffusion through the developed scale. This model can be used to predict the amount of scale that will form on a slab under certain conditions. Model predictions were found to be consistent with experimental data.

Simulation of Reflected Solar Radiation for Atmosphere Gas Composition Evaluation for Optical Remote Sensing from Space

At present, in optical remote sensing of atmosphere from space, a new problem class appears: to determine little gas components (carbon dioxide, methane, etc.), which cause greenhouse effect. Concentration of these gases in atmosphere is less than one percent, which rigidly limits accuracy of satellite measurements and of simulating spatial concentration of the radiation (signal) flow reflected by Earth. In the article, a description of simulating signals received by satellite spectrometer in nearinfrared spectrum region is given. The signals are solar radiation passed through an atmosphere layer and reflected from Earth surface. It is calculated based on parametrical radiation atmosphere scattering and absorption model, which takes into consideration both multidimensional atmosphere parameter structure and Earth surface relief. Accounting such information allows you to go from measurement of spatial radiation flux to calculations of gas concentration for an arbitrary geographical Earth surface point and for any time point. As an example, calculations for Fourier spectrometer for spectrum measurement near IR region with an average spectral resolution are presented. The spectrometer was installed on the GOSAT satellite of the Space Agency of Japan. A comparison of computed and of really measured values of the signal received by the satellite shows that deviation for the Sun zenith angle equal to 30o does not exceed 3 %.

Methodical Aspects of the Determination of Carbon Dioxide in Atmosphere Using FTIR Spectroscopy

Monitoring the state of ground-based spectroscopic systems ensures high accuracy of atmospheric gas composition measurements and the possibility of using measurement data for validating satellite measurements and numerical models. Column-averaged carbon dioxide mixing ratios (XCO2) can be used to assess the quality of spectroscopic measurements because its content is stable in the atmosphere. The XCO2 values were retrieved from spectra measured by Fourier transform IR spectrometry (FTIR) using a Bruker 125HR instrument between 2009 and 2017 at the Peterhof station (St. Petersburg, Russia). The total error of the FTIR CO2 columns retrieval was 4.18 ± 0.02%, with 0.36 ± 0.06% and 4.16 ± 0.02% for random and systematic errors, respectively. The data obtained are compared with model calculations based on long-term observations at the Mauna Loa station. Various schemes solving for the inverse problem were analyzed and compared among themselves, and estimates of empirical random errors in the determination of XCO2 were obtained. To improve the accuracy of XCO2 measurements, it is recommended to determine the error of the Fourier-spectrometer phase and the slope of the zero line of the spectrum simultaneously with the atmospheric gas composition measurements taking into account various continuum sources of error.

Long open-path measurements of greenhouse gases in air using near-infrared Fourier transform spectroscopy

Abstract. In complex and urban environments, atmospheric trace gas composition is highly variable in time and space. Point measurement techniques for trace gases with in situ instruments are well established and accurate, but do not provide spatial averaging to compare against developing high-resolution atmospheric models of composition and meteorology with resolutions of the order of a kilometre. Open-path measurement techniques provide path average concentrations and spatial averaging which, if sufficiently accurate, may be better suited to assessment and interpretation with such models. Open-path Fourier transform spectroscopy (FTS) in the mid-infrared region, and differential optical absorption spectroscopy (DOAS) in the UV and visible, have been used for many years for open-path spectroscopic measurements of selected species in both clean air and in polluted environments. Near infrared instrumentation allows measurements over longer paths than mid-infrared FTS for species such as greenhouse gases which are not easily accessible to DOAS.In this pilot study we present the first open-path near-infrared (4000–10 000 cm−1, 1.0–2.5 µm) FTS measurements of CO2, CH4, O2, H2O and HDO over a 1.5 km path in urban Heidelberg, Germany. We describe the construction of the open-path FTS system, the analysis of the collected spectra, several measures of precision and accuracy of the measurements, and the results a four-month trial measurement period in July–November 2014. The open-path measurements are compared to calibrated in situ measurements made at one end of the open path. We observe significant differences of the order of a few ppm for CO2 and a few tens of ppb for CH4 between the open-path and point measurements which are 2 to 4 times the measurement repeatability, but we cannot unequivocally assign the differences to specific local sources or sinks. We conclude that open-path FTS may provide a valuable new tool for investigations of atmospheric trace gas composition in complex, small-scale environments such as cities.

Global transcriptomic analysis suggests carbon dioxide as an environmental stressor in spaceflight: A systems biology GeneLab case study

Spaceflight introduces a combination of environmental stressors, including microgravity, ionizing radiation, changes in diet and altered atmospheric gas composition. In order to understand the impact of each environmental component on astronauts it is important to investigate potential influences in isolation. Rodent spaceflight experiments involve both standard vivarium cages and animal enclosure modules (AEMs), which are cages used to house rodents in spaceflight. Ground control AEMs are engineered to match the spaceflight environment. There are limited studies examining the biological response invariably due to the configuration of AEM and vivarium housing. To investigate the innate global transcriptomic patterns of rodents housed in spaceflight-matched AEM compared to standard vivarium cages we utilized publicly available data from the NASA GeneLab repository. Using a systems biology approach, we observed that AEM housing was associated with significant transcriptomic differences, including reduced metabolism, altered immune responses, and activation of possible tumorigenic pathways. Although we did not perform any functional studies, our findings revealed a mild hypoxic phenotype in AEM, possibly due to atmospheric carbon dioxide that was increased to match conditions in spaceflight. Our investigation illustrates the process of generating new hypotheses and informing future experimental research by repurposing multiple space-flown datasets.

Changes in Oxygen Level Upon Cold Plasma Treatments: Consequences for RONS Production

Despite the large number of papers showing the biological effect of cold atmospheric plasmas (CAPs) on skin treatment and although their ability to produce a cocktail of reactive oxygen and nitrogen species (RONS) is largely known, the deep knowledge of these ionized gas sources is far to be uncovered. Many parameters take part in the complex mechanisms induced by plasma, such as voltage, frequency, feeding gas flow rate, temperature, air humidity, and atmospheric gas composition. In this paper, we focus our attention on the influence of oxygen dissolved in the medium in RONS generation during CAP treatment. We evaluate RONS production in Dulbecco’s phosphate-buffered saline equilibrated with two different percentages of oxygen: 18% and 3% O2. The former oxygen concentration is that usually used in most of cell culture and treatment (normoxia) while the latter is close to the physiological level measured inside human skin (physioxia). Intracellular RONS generation upon CAP treatment was also measured in two human skin cell lines maintained either in normoxic or in physioxic conditions. Our data suggest that RONS generation induced by plasma either in the medium or inside cells is influenced by oxygen dissolved in the treated target.

Photoluminescent properties of complex metal oxide nanopowders for gas sensing

This work carried out research on the features of photoluminescence of the mixed and complex metal oxide nanopowders (ZnO/TiO2, ZnO/SnO2, Zn2SiO4) in vacuum and gaseous ambient. The nanopowders were obtained using pulsed laser reactive technology. The synthesized nanoparticles were characterized by X-ray diffractometry, energy-dispersive X-ray analysis, and scanning and transmission electron microscopy analysis for their sizes, shapes and collocation. The influence of gas environment on the photoluminescence intensity was investigated. A change of ambient gas composition leads to a rather significant change in the intensity of the photoluminescence spectrum and its deformation. The most significant changes in the photoluminescent spectrum were observed for mixed ZnO/TiO2 nanopowders. This obviously is the result of a redistribution of existing centers of luminescence and the appearance of new adsorption centers of luminescence on the surface of nanopowders. The investigated nanopowders can be effectively used as sensing materials for the construction of the multi-component photoluminescent sensing matrix.

Effect of Feedstock and Gas Atmosphere Composition on Selectivity and Distribution of Hydrocarbon Groups in Gasoline Synthesis from Oxygenates

Gasoline has been synthesized from oxygenates (dimethyl ether and methanol) on a HZSM-5 zeolite catalyst, modified by palladium and zinc, in a micropilot unit operating in the continuous recycle flow mode. The influence of the gas atmosphere composition—synthesis gas, hydrogen, and methane—on the gasoline selectivity, and on-stream stability of the catalyst has been determined for dimethyl ether (DME) used as a feedstock. The hydrocarbon composition and the carbon distribution in the products have been compared using DME and methanol as the feedstock in the synthesis-gas atmosphere. It has been shown that the higher gasoline selectivity production in the case of methanol is due to the higher concentration of aromatic hydrocarbons, which is achieved by decreasing the intensity of their dealkylation.

Application of a planar falling film reactor for decomposition and mineralization of methylene blue in the aqueous media via ozonation, Fenton, photocatalysis and non-thermal plasma: A comparative study

Abstract The efficiencies of ozonation and different advanced oxidation processes (AOPs) including photocatalytic ozonation, Fenton, photo-Fenton, photocatalytic oxidation, UVA/TiO2/H2O2, and non-thermal plasma generated by a dielectric barrier discharge (DBD) were compared in terms of the energy yield (G₅₀) for decolorization of MB and total organic carbon (TOC) removal using a planar falling film reactor. Fenton oxidation and ozonation were found to be the most efficient methods for the decolorization of MB, although these techniques attained rather low mineralization. A combination treatment of the ozonation with the photocatalysis demonstrates a synergistic effect on the mineralization efficiency. The photocatalytic oxidation and UVA/TiO2/H2O2 provide only a moderate MB decolorization. The degradation efficiency of the DBD plasma is significantly dependent on the composition of gas atmosphere. The addition of Fe2+ to the solution in the DBD plasma under argon atmosphere improves the degradation efficiency due to the occurrence of Fenton reaction. The energy yield for 50% conversion of MB is calculated between 0.13 and 20.5 g/kWh, and the maximum and minimum values were obtained by the ozonation and photocatalytic oxidation, respectively. Ozonation with the highest energy yield provided a moderate mineralization by only 19%, while the DBD plasma obtained the highest TOC removal by 88%.

Evolution of the composition of nanoparticles formed by the nanosecond Nd:YAG laser irradiation of an aluminium target in N2–O2 gas mixtures

Laser ablation of metallic targets in gas atmospheres gives rise to the formation of nanoparticle (NP) powders when high laser irradiances (i.e., > 1 GW/cm² for aluminium targets) are used. The properties of the NPs so formed vary as a function of the laser irradiation parameters and the pressure and composition of the ambient gas. Here, we studied the composition and structure of NPs formed by laser ablation of Al targets with a nanosecond Nd:YAG laser emitting at 1064 nm. The laser irradiance was 2.5 GW/cm2. N2–O2 gas mixtures containing different amounts of nitrogen (100–80 vol% N2) were used as ambient gas at atmospheric pressure. The influence of the ambient gas composition on the morphology and the structure of the NPs was studied ex-situ by scanning and transmission electron microscopy, X-ray diffraction and micro-Raman spectroscopy. Their composition of light elements was determined by ion beam analysis. It was shown that together with metallic aluminium, different amounts of aluminium nitride and aluminium oxynitride were formed in the NPs as a function of the nitrogen concentration in the ambient gas. Below 95 vol% N2, the concentration of nitride phases decreases strongly. However, the formation of aluminium oxide (Al2O3) was not observed, whereas it was detected in NPs formed in air. A discussion of these results that takes into account the dynamics of the plasma plume is proposed.

From in-Situ to in-Operando Evaluation of SOFC Cathodes for Enhanced ORR Activity and Durability

To study the SOFC cathode oxygen reduction reaction (ORR) mechanism and the effects of ambient gas composition on ORR, we used in-situ 18O isotope exchange techniques to probe the exchange of H2O and CO2 with two of the most common SOFC cathode materials, (La0.8Sr0.2)0.95MnO3-x (LSM) and La0.6Sr0.4Co0.2Fe0.8O3-x (LSCF). A series of temperature programmed isotope exchange measurements were performed to comprehensively study the interaction of H2O and CO2 with the cathode surface as a function of temperature, oxygen partial pressure, and contaminant gas concentration. The experimental data are summarized in a Temperature-PO2 diagram to visualize the dominant reactions at each temperature and PO2 for the two cathode materials. We further report on the development of a novel in-operando 18O isotope exchange technique by modifying our heterogeneous catalysis system for operation and measurement under electrochemical polarization. The system allows ORR investigations under real time, real life, operating conditions. We will present our studies on the effect of cathodic polarization on LSM and LSCF. The studies show the effects of operating voltage, temperature, and oxygen partial pressure on the oxygen exchange coefficient. We will also present our model for the understanding and analysis of the isotope oxygen exchange profiles under in-operando conditions.

The deep atmosphere of Venus and the possible role of density-driven separation of CO2 and N2

With temperatures around 700 K and pressures of around 75 bar, the deepest 12 km of the atmosphere of Venus are so hot and dense that the atmosphere behaves like a supercritical fluid. The Soviet VeGa-2 probe descended through the atmosphere in 1985 and obtained the only reliable temperature profile for the deep Venusian atmosphere thus far. In this temperature profile, the atmosphere appears to be highly unstable at altitudes below 7 km, contrary to expectations. We argue that the VeGa-2 temperature profile could be explained by a change in the atmospheric gas composition, and thus molecular mass, with depth. We propose that the deep atmosphere consists of a non-homogeneous layer in which the abundance of N2—the second most abundant constituent of the Venusian atmosphere after CO2—gradually decreases to near-zero at the surface. It is difficult to explain a decline in N2 towards the surface with known nitrogen sources and sinks for Venus. Instead we suggest, partly based on experiments on supercritical fluids, that density-driven separation of N2 from CO2 can occur under the high pressures of Venus’s deep atmosphere, possibly by molecular diffusion, or by natural density-driven convection. If so, the amount of nitrogen in the atmosphere of Venus is 15% lower than commonly assumed. We suggest that similar density-driven separation could occur in other massive planetary atmospheres. The only temperature profile of the lowermost Venusian atmosphere appears unstable. Compositional heterogeneity due to density-driven separation of N2 from CO2 gas in the lower atmosphere of Venus may be a viable explanation.