Methane Absorption Research Articles

Phytoremediation of Formaldehyde in Indoor Environment With Common House Plants and Pseudomonas Chlororaphis

Low light survivor house plants were assessed for their formaldehyde removal capacity from indoor environment. Low ventilation leading to poor air circulation in indoor environment has become a matter of grave concern as it leads to health issues. Phytoremediation technology is being studied in such situations. The capacity of plants in absorbing indoor pollutants can be enhanced through use of bacteria helping phytoremediation process. The gaseous formaldehyde of about 5 ppm was released into the static chamber of volume 1 m3 . Selected test plants were Aglaonema commutatum, Chlorophytum comosum, Sansevieria trifasciata and Epipremnum aureum. Medium in which plants were growing was inoculated with Pseudomonas chlororaphis, which helps the process of phytoremediation. Activated charcoal was also added in the medium, to increase the absorptive surface. The exposure given was for 24 hours. Experiment was replicated for three times. Air quality in the chamber was monitored on advanced Formaldehyde meter, at the start of the experiment and after 24 hours. Leaves of the plants were analysed by DNPH on LCMS method for quantification of Formaldehyde. Quantification of Formaldehyde from leaves ranged between 0.03–4.7 ppm. Formaldehyde meter showed reduction in formaldehyde quantity ranges from 1.999 to 0 ppm in 24 hours. This clearly indicates that selected plants have enhanced limited capacity of formaldehyde absorption in synergy with Pseudomonas chlororaphis.

Low cost equipment for astronomical spectroscopy

The purpose of this paper is to show how we can obtain spectra for different astronomical objects using low coat equipment. Where a high-efficiency diffraction grating named “The Star Analyzer” was used by the International Astronomical Center (IAC) in Abu Dhabi, UAE to get the spectrum of different astronomical objects. Balmer series was readily visible when observing an “A” type star. TiO absorptions lines were distinguished by observing an “M” type star. Methane absorption lines were visible by observing Uranus and Neptune. Whereas HI and HeI emission lines were detected by observing a blue hypergiant. In addition, C2 Swan band absorption lines were identified by observing a red giant carbon star. This type of observation is very interesting for public outreach as well as university students, because it shows astrophysical principles for public and students practically and by using low cost equipment.

Study on the application of sulfonation catalysis in a new formaldehyde recovery process

This study proposed a new catalytic conversion process using a sulfonated catalyst to promote the condensation reaction of methanol and formaldehyde (FA) to form methylal (DMM). This method can remove FA while generating the valuable chemical product DMM. A series of SiO 2 -xSO 3 H catalysts were developed, and the synergistic effect of the sulfonic acid group vacancy and hydroxyl vacancy contents was evaluated by adjusting the activation temperature and sulfonation ratio. When the activation temperature was 60 °C, the FA yield reached 82.3%, and DMM selectivity was 80.4%. The FA recovery rate was much higher than in other studies. A series of characterization studies revealed that when there were few -SO 3 H groups, the hydroxyl content increased, providing more activation centers for forming the formic acid by-product from FA. The dehydration and condensation of formic acid and methanol formed methyl formate (MF). However, when there were too many -SO 3 H groups, side reactions of methanol and FA occurred preferentially. Therefore, the synergistic effect of the -SO 3 H group and hydroxyl group content was the fundamental reason for the exceptional catalytic performance. Furthermore, in-situ infrared spectroscopy revealed the possible reaction mechanism of methanol and FA on sulfonated silica gel and verified the conclusion drawn from the catalyst characterization. This approach overcomes the disadvantages of the high cost of FA absorption and difficulty of industrialization due to the high reaction temperature and provides the potential to “turn waste into treasure” during FA recovery while providing new avenues to solving the problem of FA pollution.

The Hubble PanCET program: Transit and Eclipse Spectroscopy of the Hot-Jupiter WASP-74b

Abstract Planets are like children with each one being unique and special. A better understanding of their collective properties requires a deeper understanding of each planet. Here we add the transit and eclipse spectra of hot-Jupiter WASP-74b into the ever growing data set of exoplanet atmosphere spectral library. With six transits and three eclipses using the Hubble Space Telescope and Spitzer Space Telescope (Spitzer), we present the most complete and precise atmospheric spectra of WASP-74b. We found no evidence for TiO/VO nor super-Rayleigh scattering reported in previous studies. The transit shows a muted water feature with strong Rayleigh scattering extending into the infrared. The eclipse shows a featureless blackbody-like WFC3/G141 spectrum and a weak methane absorption feature in the Spitzer 3.6 μm band. Future James Webb Space Telescope follow-up observations are needed to confirm these results.

Characteristics of greenhouse gas emissions from farmland soils based on a structural equation model: Regulation mechanism of biochar

Greenhouse gas (GHG) emissions from soil carbon and nitrogen cycles during freeze-thaw cycles (FTCs) provide positive feedback to climate warming. Biochar is a new type of soil conditioner that shows potential in soil GHG emissions reduction. To explore the mechanisms of the effects of biochar on soil GHG emissions in seasonally frozen soil areas, this study focused on farmland soil in the Songnen Plain. Variations in soil environmental factors, available carbon and nitrogen and microbial biomass were analyzed using an indoor simulation of soil FTCs. A structural equation model (SEM) was established to reveal the key driving factors and potential mechanism of biochar on soil GHG emissions under FTCs. The results showed that biochar increased carbon dioxide (CO2) emissions by 3.40% and methane (CH4) absorption by 2.52% and decreased nitrous oxide (N2O) emissions by 35.90%. SEM showed that soil temperature (ST) was the main environmental factor determining CO2 emissions and that soil moisture (SM) was the main environmental factor determining CH4 and N2O emissions. Soil available carbon and nitrogen and microbial biomass are important for soil GHG emissions as the reaction substrates and main participants in the biochemical transformation of soil carbon and nitrogen, respectively. This study showed that the application of biochar in farmland is a feasible choice to address climate change in the long term via soil carbon sequestration and GHG emissions reduction. The research results provide a theoretical basis and scientific guidance for soil GHG emissions reduction during FTCs in middle to high latitudes.

An all-optical off-beam quartz-enhanced photoacoustic spectroscopy employing double-pass acoustic microresonators

An all-optical off-beam quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor employing double-pass acoustic microresonators was proposed and experimentally investigated. An optical fiber Fabry–Perot interferometric sensor with quadrature point self-stabilization was employed for the detection of quartz prong vibration. A commercial quartz tuning fork with a resonant frequency of 30.72 kHz was employed as an acoustic transducer. Water vapor as the catalyst was added for improving the vibrational energy transfer. The minimum detection limit of ∼2.41 ppmv was obtained with a 1 s averaging time, which corresponded to a normalized noise equivalent absorption coefficient of 7.76×10−8 cm−1 W Hz−1/2 at the methane absorption line of 6046.95 cm −1 with an optimized modulation depth of 0.172 cm −1. The detection sensitivity was enhanced by a factor of ∼1.48 in comparison to the off-beam QEPAS employing a single-pass microresonator. An Allan deviation analysis indicated that the ultimate detection limit for the QEPAS-based sensor was ∼0.288 ppmv at the optimum averaging time of ∼125 s.

Seasonal Dynamics of Carbon-Containing Compounds under Different Effects of Natural and Anthropogenic Factors

It was found that the processes of exchange of carbon compounds between the soil and the atmosphere are characterized by high variation in different periods of the annual cycle. It has been proved that CO2 emission, as well as the release and absorption of methane from the soil, is the main expenditure item in the balance of organic matter, which significantly affects the fertility and the level of productivity of agrobiocenoses. Soil fertility management and carbon gas cycle processes largely overlap. With an increase in the content of organic carbon from 0.55 to 0.98%, the loss of carbon dioxin and the absorption of methane compounds increase 1.5–4.3 times. A weak correlation was established between the release of carbon dioxin and the degree of soil cultivation (Kendall coefficient r = 0.23 at p = 0.05), seasonal dynamics of soil moisture r = 0,23 at p = 0,05) and a strong one (r = 0,87 at p = 0.000,2) with methane release / uptake dynamics. The same relationship was found between the dynamics of carbon dioxide release and the temperature of the soil layer 0–5 (Pearson’s coefficient r = 0.82–0.84 at p = 0.003–0.04), and 0-20 cm (r = 0.68–0.71 at p = 0.003–0.006).

Resonant Cavity–Enhanced Photodiodes for Spectroscopy of CH Bonds

Resonant cavity‐enhanced photodiodes targeted within the spectral region of absorption by CH bonds are demonstrated. The – region of the infrared spectrum contains many substances that are useful to measure spectroscopically. However, the measurement of individual substances requires a high spectral specificity, that is achieved by the resonant cavity photodiodes with spectral response widths of . Two material systems are investigated for detection at this wavelength range—an InAs absorber on an InAs substrate and an InAsSb absorber lattice‐matched to a GaSb substrate. The resonance wavelength of the InAs‐based device responds at , closely tuned to an absorption peak of methane to allow precise sensing of this gas. At a quantum efficiency of is achieved, with a specific detectivity of . The InAsSb‐based device is sensitive at , but the structure could be tuned to the methane absorption peak. Devices could be simply created to target other substances in the C−H absorption region by altering the layer thicknesses in the structure. Both structures can be used for spectrally specific gas sensing in this region of the infrared.

Development of a new high-capacity formaldehyde absorption unit for environmental problems solving and resource saving in formalin production

Ways of further intensification of formaldehyde absorption process and new constructions of more compact apparatuses have been developed on the basis of generalization of results of experimental study of regularities of mechanism and kinetics of formaldehyde absorption in conditions of formalin production. The most effective and for intensification of formaldehyde absorption process are vortex apparatuses in the form of a cascade of one-stage vortex apparatuses, or in the form of a vortex column including three vortex phase contact stages. A new splash trap with bag filtering elements was developed for effective fog catching.

Dual frequency comb absorption spectroscopy of CH4 up to 1000 Kelvin from 6770 to 7570 cm-1

As infrared telescopes are finding evidence of methane in hot exoplanet atmospheres, it is becoming increasingly important to have accurate high-temperature methane absorption models. To evaluate and update several spectroscopic databases (HITRAN2016, HITEMP, ExoMol), we collected laboratory spectra of the methane icosad (6770–7570 cm-1) using a 200 MHz (0.0067 cm-1) dual frequency comb spectrometer. The pure methane data span 18 to 300 Torr and 296 to 1000 K. We found good agreement with the HITRAN2016 model spectrum at room temperature, and substantial mismatch between our spectra and all absorption models at elevated temperature. We present several updates to HITRAN2016 to improve agreement with the measured high-temperature spectra. Specifically, we assign 4283 lower-state energies which had previously been given a default value in HITRAN2016 (EHIT″= 999 cm-1), update existing lower-state energies for 92 features, and add 293 new high-temperature features in order to improve HITRAN2016 above 300 K. Additionally, we update the band-wide line positions by ∼0.001 cm-1, the self-widths by +7%, and we estimate band-averaged temperature-dependence exponents for self-width (0.85) and self-shift (0.58). These measurements are an important step towards merging empirical and theoretical high-temperature methane databases, with the goal of enabling better understanding of exoplanet atmospheres.

Broadband, background-free methane absorption in the mid-infrared.

Rotationally resolved, broadband absorption spectra of the fundamental vibrational transition of the asymmetric C-H stretch mode of methane are measured under single-laser-shot conditions using time-resolved optically gated absorption (TOGA). The TOGA approach exploits the difference in timescales between a broadband, fs-duration excitation source and the ps-duration absorption features induced by molecular absorption to allow effective suppression of the broadband background spectrum, thereby allowing for sensitive detection of multi-transition molecular spectra. This work extends the TOGA approach into the mid-infrared (mid-IR) spectral regime, allowing access to fundamental vibrational transitions while providing broadband access to multiple mid-IR transitions spanning ∼150 cm-1 (∼160 nm) near 3.3 μm, thereby highlighting the robustness of this technique beyond previously demonstrated electronic spectroscopy. Measurements are conducted in a heated gas cell to determine the accuracy of the simultaneous temperature and species-concentration measurements afforded by this single-shot approach in a well-characterized environment. Application of this approach toward fuel-rich methane-nitrogen-oxygen flames is also demonstrated.

DETECTION OF METHANE PLUMES IN HYPERSPECTRAL IMAGES FROM SENTINEL-5P BY COUPLING ANOMALY DETECTION AND PATTERN RECOGNITION

Abstract. Reducing methane emissions is essential to tackle climate change. Here, we address the problem of detecting large methane leaks using hyperspectral data from the Sentinel-5P satellite. For that we exploit the fine spectral sampling of Sentinel-5P data to detect methane absorption features visible in the shortwave infrared wavelength range (SWIR). Our method involves three separate steps: i) background subtraction, ii) detection of local maxima in the negative logarithmic spectrum of each pixel and iii) anomaly detection in the background-free image. In the first step, we remove the impact of the albedo using albedo maps and the impact of the atmosphere by using a principal component analysis (PCA) over a time series of past observations. In the second step, we count for each pixel the number of local maxima that correspond to a subset of local maxima in the methane absorption spectrum. This counting method allows us to set up a statistical a contrario test that controls the false alarm rate of our detections. In the last step we use an anomaly detector to isolate potential methane plumes and we intersect those potential plumes with what have been detected in the second step. This process strongly reduces the number of false alarms. We validate our method by comparing the detected plumes against a dataset of plumes manually annotated on the Sentinel-5P L2 methane product.

СРАВНИТЕЛЬНЫЙ АНАЛИЗ ПОВЕДЕНИЯ СЛАБЫХ ПОЛОС ПОГЛОЩЕНИЯ АММИАКА 552 И 645 НМ В СПЕКТРЕ ЮПИТЕРА

This article contains the first obtained results of measuring the latitudinal variations of the very weak ammonia (NH3) absorption band at 552 nm along the central Jupiter meridian based on spectral observations in 2019. This study is preliminary in nature as the first attempt to clarify the possibility and advisability of further detailed study of this weak ammonia band behavior on the Jupiter disk. We obtained the latitude variations of the equivalent widths and equivalent absorption paths for the 552 nm NH3 band and, for comparison, the same characteristics for the more intense, but also weak NH3 645 nm band. The absorption maximum in both bands is observed in the equatorial zone, where in the center of the disk their equivalent widths are: W (552 nm) = 2.58 ± 0.29 A and W (645 nm) = 6.77 ± 0.25 A. A feature that distinguishes the behavior of the 552 nm NH3 band from the 645 nm NH3 band is a steeper decrease in absorption towards high latitudes, as well as small differences in the positions of absorption extrema in latitudes. The effect of latitudinal differences in the position of the extrema of the methane absorption bands was discovered by us as early as 1999 observations and was later noted also in the ammonia absorption bands. These features reflect structural differences in the Jupiter cloud layer and its troposphere and can serve as one of the means for its (troposphere) optical sounding.

Longitudinal variations in the stratosphere of Uranus from the Spitzer infrared spectrometer

NASA's Spitzer Infrared Spectrometer (IRS) acquired mid-infrared (5–37 μm) disc-averaged spectra of Uranus very near to its equinox in December 2007. A mean spectrum was constructed from observations of multiple central meridian longitudes, spaced equally around the planet, which has provided the opportunity for the most comprehensive globally-averaged characterisation of Uranus' temperature and composition ever obtained (Orton et al., 2014a,b). In this work we analyse the disc-averaged spectra at four separate central meridian longitudes to reveal significant longitudinal variability in thermal emission occurring in Uranus' stratosphere during the 2007 equinox. We detect a variability of up to 15% at wavelengths sensitive to stratospheric methane, ethane and acetylene at the ~0.1-mbar level. The tropospheric hydrogen‑helium continuum and deuterated methane absorption exhibit a negligible variation (less than 2%), constraining the phenomenon to the stratosphere. Building on the forward-modelling analysis of the global average study, we present full optimal estimation inversions (using the NEMESIS retrieval algorithm, Irwin et al., 2008) of the Uranus-2007 spectra at each longitude to distinguish between thermal and compositional variability. We found that the variations can be explained by a temperature change of less than 3 K in the stratosphere. Near-infrared observations from Keck II NIRC2 in December 2007 (Sromovsky et al., 2009; de Pater et al., 2011), and mid-infrared observations from VLT/VISIR in 2009 (Roman et al., 2020), help to localise the potential sources to either large scale uplift or stratospheric wave phenomena.

THE CONTRIBUTION OF ROMANIA TO CLIMATE CHANGE – THE EFFECTS OF ACCOUNTING THE GHG EMISSIONS FROM LAND USE, LAND-USE CHANGE AND FORESTRY (LULUCF)

This study aimed to analyze Romanian (RO) involvement in the LULUCF sector by considering the Intergovernmental Panel on Climate Change (IPCC) good practice guidance (GPG). Trends were assessed using the Mann-Kendall (MK) test for trend estimation to determine the total greenhouse gas (GHG) (GHGCO₂-eq.) emissions/ removals. The results emphasized the increasing average annual levels of emissions/removals in both the EU-28 and RO when the subperiods from 1990-2005 and 2005-2017 were analyzed. Kendall’s analysis of GHG removal showed a positive trend in Romanian GHG removals, and no trend was observed for the EU-28. In comparison, the emissions indicated an increasing trend for RO and a decreasing trend for the EU-28. The GHGCO₂-eq. generated by the LULUCF sector decreased to an average annual rate of 0.5% per year in the EU-28. In Romania, these emissions increased by approximately 0.2% per year on average. Between 1990 and 2017, the CO2 total absorption increased to 0.9% per year. The methane absorption also increased by 11.7% per year, and no significant increasing trend was observed for methane. The dynamics of GHGCO₂-eq. emissions/removals in RO and LULUCF sectors showed that settlement had decreased in wetlands, and settlement of other land areas had increased. Assessing GHG gas emissions is essential for allowing each sector to promote specific strategies, policies and action plans. This will improve the national-level monitoring of the LULUCF sector and make this information more accessible to decision makers by raising awareness of the Romanian position within the EU-28

Synergistic enhanced catalysis of micro-reactor with nano MnO2/ZIF-8 immobilized in membrane pores by flowing synthesis

A catalytic membrane micro-reactor (CMMR) with nano MnO2/ZIF-8 immobilized in membrane pores has been fabricated by flowing synthesis and formaldehyde degradation was used to test its catalytic performance. The CMMR with deep-permeation nano structure (DPNS) has good stability, uniform nano MnO2/ZIF-8 dispersion and higher loading capacity. The MnO2 coated on the surface of nano ZIF-8 with the size in the range of 100–150 nm was obtained. The contact between formaldehyde and MnO2 is enhanced by the effect of even disperse of membrane pores. The enhanced mass transfer can be achieved in the micro-scale pores of the membrane by the confined space effect. A higher amount of MnO2 loading and higher formaldehyde absorption rate can be achieved by the effect of ZIF-8 in membrane pores. The formaldehyde degradation rate was increased from 82.6% to 94.0%, if the MnO2 loading capacity was increased from 98 mg g−1 to 344 mg g−1.

Sensitivity Enhancement of Methane Detection Based On Hollow Core Photonic Crystal Fiber

Monitoring methane (CH4) concentration is essential in many industrial and environmental applications. Emission of such gases is indeed important to detect for health, safety and environmental reasons. The major risk in all these areas is an explosion hazard, which may occur if methane reaches its Lower Explosive Limit (LEL) of5% concentration in air. For that reason, it is necessary to develop gas sensors to monitor that methane levels below this value. Due to a weak absorption of methane, this gas is difficult to detect using conventional methods.Hollow core photonic crystal fibers (HC-PBF) have emerged as a promising technology in the field of gas sensing. The strong interaction achievable with these fibers are especially advantageous for the detection of weakly absorbing regions of methane. In this paper, we investigated, by full vectorial finite element method (FV-FEM) in Rsoft CAD environment, the dependency of relative sensitivity on the fiber parameters and wavelength. Consequently, we introduced the optimal structureof an index guiding hollow core photonic crystal fiber capable of measuring methane concentrations down to 0.1%in air. The simulations showed that the sensing sensitivity increased with an increase in the core diameter and a decrease in the distance between centers of two adjacent holes.

Development of a laser heterodyne spectroradiometer for high-resolution measurements of CO2, CH4, H2O and O2 in the atmospheric column.

We have developed a portable near-infrared laser heterodyne radiometer (LHR) for quasi-simultaneous measurements of atmospheric carbon dioxide (CO2), methane (CH4), water vapor (H2O) and oxygen (O2) column absorption by using three distributed-feedback diode lasers as the local oscillators of the heterodyne detection. The developed system shows good performance in terms of its high spectral resolution of 0.066 cm-1 and a low solar power detection noise which was about 2 times the theoretical quantum limit. Its measurement precision of the column-averaged mole fraction for CO2 and CH4 is within 1.1%, based on the standard deviation from the mean value of the retrieved results for a clean sky. The column abundance information of the O2 is used to correct for the variations and uncertainties of atmosphere pressure, the solar altitude angle, and the prior profiles of pressure and temperature. Comparison measurements of daily column-averaged atmospheric mole fractions of CO2, CH4 and H2O, between our developed LHR and a greenhouse gas observing satellite, show a good agreement, which proves the reliability of our developed system.

Features of methane emission into the atmosphere over buried landfill bodies in urbanized ecosystems of Moscow

On the outskirts of cities landfill bodies are formed, the territories of which are later used in urban planning. Over the buried landfill soils which represent construction and household garbage, methane flows are formed, which worsen the environmental conditions of the territories and negatively affect the psychosomatic health of residents. The goal was to study methane emissions from various buried landfills in Moscow. Our study on urbanized ecosystems in Moscow revealed different methane emissions in the soils. Thus, over young landfill bodies, the concentration of methane in the soils was 8 -16 ppm. This led to the release of methane into the atmosphere of the capital city. In the old landfill bodies, the concentration of methane in the soil was 1-2 ppm and did not cause methane emissions into the urban atmosphere. The analysis of the obtained data revealed the absorption of methane by soils on old landfill bodies at high and very high methane oxidation (Lobochevsky, Zyuzinskaya, Brateevskaya, Kashirskoe Highway and Ochakovka Streets). For organomineral horizons of replantozems with an increased content of organic matter and a loamy granulometric composition, increased methane formation and oxidation of autochthonous gas with undetected emission were detected.In technogenic and gray-humus horizons of urbanozems, methane formation and methane oxidation were reduced.

Accumulation of Natural Gas with a Prospective Material Based on Graphene Aerogel

The assessment of the possibility of effective use of graphene aerogels for the adsorption storage and transportation of methane is given. For the study, an aerogel based on reduced graphene oxide was synthesized using supercritical methods for processing a hydrogel in an isopropyl alcohol medium. A narrow distribution of micropores with a maximum at 0.8 nm, a narrow distribution of mesopores with a maximum at about 4.5 and 6.5 nm were revealed. The obtained graphene aerogel (GA) was used to study the adsorption of methane at pressures up to 10 MPa and temperatures of 298, 303, 313 K. The maximum gravimetric absorption of methane reaches 0.86 g/g (37 cm3 (STP)/cm3) and 2.6 g/g (109 m3 (STP)/m3) at corresponding pressures of 35 and 100 bar and a temperature of 298 K, which is the highest recorded value for porous carbon previously reported.