Fourier-transform Spectroscopy Research Articles

Differentiation and prediction of the in vitro antifungal activity of Brazilian propolis against Fonsecaea pedrosoi using chemometrics and diffuse reflectance infrared Fourier Transform spectroscopy

The in vitro antifungal activity of ethanolic extracts of propolis was evaluated at five different concentrations in twelve Fonsecaea pedrosoi strains using agar dilution. Eight propolis extracts were collected from towns located in the central region of the state of Rio Grande do Sul, Brazil. Diffuse reflectance infrared Fourier Transform spectroscopy (DRIFTS) was employed to analyze the spectra of lyophilized propolis extracts. The use of chemometric tools allowed for the development of models with more relevant factors and with fewer variables. Partial least squares (PLS) regression was applied, allowing for the development of PLS-DRIFTS models to predict antifungal activity of all fungal strains with root mean square error of cross validation (RMSECV) lower to 5.00 mm2 and coefficient correlation of cross-validation (R2) upper to 0.99 with five to eight latent variables at 4000-2400 and 2200-600 cm-1. Concluding, DRIFTS models associated with chemometrics are powerful screening tools of propolis samples with fungistatic properties against Fonsecaea pedrosoi.

Sorption Preconcentration of Quercetin Using Molecularly Imprinted Phloroglucinol–Melamine–Formaldehyde Resins

Hydrophilic quercetin-imprinted phloroglucinol–melamine–formaldehyde resins are obtained. The obtained samples are studied by Fourier-transform IR spectroscopy and laser diffraction. The phloroglucinol–melamine ratio (3 : 1) is optimized at the sorption capacity of the molecularly imprinted resin (1.7 μmol/g) with respect to quercetin 2.6 times higher than that of the non-imprinted resin. It is shown that the kinetics of quercetin rebinding by both molecularly imprinted and non-imprinted resins obeys the pseudo-second order model, and the isotherms follow the Freundlich model, which indicates the inhomogeneity of the resin surface. The resin imprinted with quercetin demonstrated high selectivity to morine (a structural analogue of quercetin of the flavonol class) and caffeine. At that it is shown that quercetin can be used as a pseudotemplate for the separation and preconcentration of naringenin (a representative of flavanones) and rutin (a representative of flavonols).

Detection of Atmospheric Hydrofluorocarbon-22 with Ground-Based Remote High-Resolution Fourier Transform Spectroscopy over Hefei and an Estimation of Emissions in the Yangtze River Delta

Under the control of the Montreal Protocol and its amendments, hydrofluorocarbons (HCFCs) are used as temporary substitutes for ozone-depleting substances, such as chlorofluorocarbons, and are regulated for consumption and production. China plans to phase out HCFCs by 2030, and HCFC-22 (CHClF2) is currently the most abundant HCFC in the atmosphere. This study measures the vertical profiles and total columns of atmospheric HCFC-22 from January 2017 to December 2022, based on the mid-infrared solar spectra recorded by the ground-based high-resolution Fourier transform infrared (FTIR) spectrometer at the Hefei remote sensing station. The HCFC-22 total columns over Hefei increased from 2017–2018 and gradually decreased in 2018–2022, with an annual variation rate of 5.98% and −1.02% ± 0.02%, respectively. Compared with the ACE-FTS satellite independent dataset, the FTIR data indicate good consistency with the ACE-FTS data at a 5–25 km altitude, with an average relative difference of −4.38 ± 0.83% between the vertical profiles. HCFC-22 emissions in the Yangtze River Delta from 2017 to 2022 are estimated, derived from measured total columns combined with the Lagrangian transport model and the Bayesian inversion technique. In the Yangtze River Delta, HCFC-22 emissions were high in 2017, with a value of 33.3 ± 16.8 kt, and decreased from 2018 to 2022, with a minimum of 27.3 ± 13.6 kt in 2022 during the observations.

New Insights into the Effect of Ce Doping on the Catalytic Performance and Hydrothermal Stability of Cu-USY Zeolite Catalysts for the Selective Catalytic Reduction of NO with NH3

5Cu-USY and Ce-doped 5Cu8Ce-USY zeolite catalysts were prepared by the conventional impregnation method. The obtained catalysts were subjected to the hydrothermal ageing process. The catalytic performance of the selective catalytic reduction of NOx with NH3 (NH3-SCR) was evaluated on both fresh and aged catalysts. Physical/chemical characterizations such as X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS) were performed, along with detailed in situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) experiments including CO adsorption, NH3 adsorption, and NO + O2 reactions. Results showed that, for the 5Cu-USY catalyst, hydrothermal ageing treatment could somehow improve the low-temperature SCR activity, but it also led to significant formation of unfavorable byproducts NO2 and N2O. Such an activity change can be attributed to hydrothermal ageing inducing the migration of isolated Cu+ species in the sodalite cavities towards the super cages of the USY zeolites. The increased content of Cu+ species in the super cages was beneficial for the low-temperature activity improvement, but, at the same time, it also facilitated ammonia oxidation at high temperatures. Ce doping after hydrothermal ageing has a “double-edged sword” effect on the catalytic performance. First of all, Ce doping can inhibit Cu species migration by self-occupying the internal cage sites; thus, the catalytic performance of 5Cu8Ce-USY-700H remains stable after ageing. Secondly, Ce doping introduces a CuOx–CeO2 strong interaction, which facilitates lattice oxygen mobility by forming more oxygen vacancies so as to increase the concentration of surface active oxygen. These changes, on the one hand, could help to promote further oxidative decomposition of nitrate/nitrite intermediates and improve the catalytic performance. But, on the other hand, it also causes the byproduct generation to become more severe.

Using machine learning to construct TOMCAT model and occultation measurement-based stratospheric methane (TCOM-CH4) and nitrous oxide (TCOM-N2O) profile data sets

Abstract. Monitoring the atmospheric concentrations of greenhouse gases (GHGs) is crucial to improve our understanding of their climate impact. However, there are no long-term profile data sets of important GHGs that can be used to gain a better insight into the processes controlling their variations in the atmosphere. In this study, we apply corrections to chemical transport model (CTM) output based on profile measurements from two solar occultation instruments: the HALogen Occultation Experiment (HALOE) and the Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS). The goal is to construct long-term (1991–2021), gap-free stratospheric profile data sets, hereafter referred to as TCOM, for two important GHGs. To estimate the corrections that need to be applied to the CTM profiles, we use the extreme gradient boosting (XGBoost) regression model. For methane (TCOM-CH4), we utilize both HALOE and ACE satellite profile measurements from 1992 to 2018 to train the XGBoost model, while profiles from 2019 to 2021 serve as an independent evaluation data set. As there are no nitrous oxide (N2O) profile measurements for earlier years, we derive XGBoost-derived correction terms to construct TCOM-N2O profiles using only ACE-FTS profiles from the 2004–2018 time period, with profiles from 2019–2021 used for the independent evaluation. Overall, both TCOM-CH4 and TCOM-N2O profiles exhibit excellent agreement with the available satellite-measurement-based data sets. We find that compared to evaluation profiles, biases in TCOM-CH4 and TCOM-N2O are generally less than 10 % and 50 %, respectively, throughout the stratosphere. The daily zonal mean profile data sets, covering altitude (15–60 km) and pressure (300–0.1 hPa) levels, are publicly available via the following links: https://doi.org/10.5281/zenodo.7293740 for TCOM-CH4 (Dhomse, 2022a) and https://doi.org/10.5281/zenodo.7386001 for TCOM-N2O (Dhomse, 2022b).

Su8-waveguide based phase corrected fourier transform spectrometer chip with low side ripples

Integrated Fourier transform spectrometer (FTS) chip is of great interest recently due to its small size, low cost, and inherent high throughput. Phase and intensity errors caused by fabrication imperfections can give rise to severe side ripples in the retrieving spectrum of an FTS chip. To suppress the side ripples poses a great challenge, especially for the spatial heterodyne spectrometer (SHS) chip constituted by numerous Mach-Zehnder interferemoters (MZI) and having a relatively large size. Pseudoinverse algorithm combined with apodization function is considered to be able to compensate the phase and intensity errors efficiently. However, recent researches show that it still has its limitations, some results illustrate the side ripples of the retrieving spectra can be as large as −6 dB. In this article, we design, fabricate and characterize an Su8-waveguide based SHS chip with 51 MZIs, each MZI is accompanied with a pair of heating electrodes to correct the phase error. Different factors that contribute to the side ripples of the retrieved spectrum are analyzed and simulated. Our experimental result shows that by means of physically heat-tuning the metal electrodes and mathematically compensating the transmissivity fluctuations, the side ripples can be suppressed to be in the range from −19 dB to −15 dB for monochromatic and doublet light in our Su8-waveguide based SHS chip.

H2S adsorbed by bismuth oxychloride under room temperature

Bismuth oxychloride (BiOCl) with controllable morphologies is synthesized for room-temperature removal of hydrogen sulfide (H2S) by a facile one-step hydrothermal methodology. Kinetic experiments demonstrated that the obtained BiOCl has a much better sulfur adsorption capacity than that of bismuth oxide. At room temperature, S atoms replaced O atoms in the first few atomic layers of BiOCl to form a passivation layer on its surface, preventing further erosion of the BiOCl material by H2S molecules. In the presence of oxygen, BiOCl can continue to oxidize the H2S molecules to sulfur. The diffuse reflection infrared Fourier transformation spectroscopy (DRIFTS) and spin-polarized density functional theory (DFT) calculations further verify the adsorption behaviors of H2S molecules on the surface of BiOCl. The comprehensive insight into the adsorption behavior of H2S on the BiOCl surface provides a reference for the development of novel room-temperature desulfurization materials and applications in anti-H2S corrosion.

Multiple cobalt species on HZSM-5 cooperative catalyzing N2O decomposition

As a strong greenhouse gas with a wide lifespan, nitrous oxide (N2O) reduction emissions are imperative. Transition metal oxides, especially cobalt oxides, possess superior N2O catalytic decomposition properties. A series of cobalt-incorporated HZSM-5 (Co/HZ) catalysts were synthesized by citric acid-complexion impregnation and were systematically investigated by N2O decomposition and characterizations. Co content and calcination temperature influenced cobalt species distribution and active site amount. Multiple cobalt species were found and cooperatively catalyzed N2O decomposition. Co2+ ions in cobalt species are regarded as active sites in N2O decomposition and the 10Co/HZ-800 catalyst showed better N2O catalytic decomposition performance, O2, and NO tolerance. The 10Co/HZ-800 catalyst was subjected to in situ diffuse reflectance infrared Fourier-transform spectroscopy (in situ DRIFTS) for surveying N2O adsorption patterns on the surface under different temperatures and atmospheres.

Interaction mechanisms of typical collectors with zircon surfaces and their influence on surface morphology and hydrophobicity for selective flotation

Zircon is the primary mineral that contains the critical metals zirconium and hafnium. However, the extraction of pure zircon from its natural ore is challenging. The inadequate understanding of the interaction mechanisms between traditional flotation collectors, namely n-octyl phosphonic acid (nOPA), octyl-hydroxamic acids (OHA), and oleic acid (OL), with zircon, has hindered the development of highly selective flotation reagents. Therefore, a combination of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Zeta potential tests, contact angle measurements, and flotation tests was employed to elucidate the mechanism of collector adsorption on surface morphology and the chemical bonding interactions at the interface. The AFM, XPS, and DRIFTS results consistently demonstrate that all three reagents can chemically bond with zircon surfaces. nOPA exhibits stronger interactions with zircon compared to OL and OHA, as it coordinates with two zirconium sites to form a monolayer. Zeta potential and contact angle measurements reveal that the surface morphology and weak adsorption, which is driven by weak interactions, contribute to an improvement in hydrophobicity. Flotation results further validate that the three reagents can selectively float zircon in specific pH ranges. The interfacial bonding interactions, which are influenced by weak interactions, play significant roles in the flotation of zircon.

Measurements of H2O-O2 line shape parameters and the determination of the intermolecular potential for modified complex Robert-Bonamy calculations

A series of spectra, one pure H2O and four H2O-O2 mixtures, were measured for the ν2 band in the 1200–1950 cm−1 region at room temperature using a single-pass copper cell housed in the Bruker 125HR high-resolution Fourier transform spectrometer (FTS) at Jet Propulsion Laboratory (JPL). All the five spectra were fit simultaneously using a multispectrum non-linear least-squares fitting software, Labfit programme suite, which adopts a speed-dependent Voigt line shape profile using full line mixing taken into account through a relaxation matrix operation. O2-broadened half-width and O2-induced frequency shift coefficients were determined for more than 350 transitions of H2 16O. These data were then checked using the smooth variation and paring rules [Brown et al. J Mol Spectrosc. 2007;246:1-21, Ma et al. Mol Phys. 2011;109:1925-41] and 186 transitions that obey the rules with less than 3% difference were chosen. Using these selected data, Modified Complex Robert-Bonamy calculations were made to determine the intermolecular potential for the H2O-O2 collision system. Some 93 potential were investigated resulting in a final potential (potential 74) that agrees with the selected half-width measurements having an average percent difference of 0.052 and a standard deviation of 5.108% between measurement and calculations.

Enhancement of Fe-Nb interaction by acid modification over SO42--FeOx-Nb2O5 catalyst for NH3 selective catalytic reduction of NOx

A series of iron-based composite oxide catalysts, modified with acid and niobium, were produced for the purpose of selective catalytic reduction of NOx with NH3 (NH3-SCR) via co-precipitation. The obtained SO42--FeOx-Nb2O5 (S-FeNbOx) catalyst exhibited significantly better SCR performance than the unmodified FeOx catalyst, with a NOx conversion above 90% and N2 selectivity higher than 95% in the temperature range of 275–450 °C. The characterization results suggest that the addition of Nb not only modifies the electronic structure and alleviates the reducibility but also enhances the surface acidity of the catalysts. The sulfuric acid modification of FeOx-Nb2O5 catalyst promotes the formation of redox-acid sites. The in situ Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFTs) results revealed that the combining sulfuric acid and niobium modifications resulted in a significant increase in the amount of Brønsted acid sites, and also led to a blue shift of the band related to the Lewis acid sites, implying the existence of a synergistic effect of the two modification methods. The creation of redox-acid sites significantly enhances the adsorption and activation capacity of NH3 on the catalyst surface. These results suggest that the NH3-SCR reaction to primarily follow the Eley-Rideal (E-R) mechanism on the catalyst.

α-Mangostin and lawsone methyl ether in tooth gel synergistically increase its antimicrobial and antibiofilm formation effects in vitro

Objectivesα-Mangostin (α-MG) and lawsone methyl ether (LME) show antimicrobial and anti-biofilm activities. The objectives of this study were to develop a herbal tooth gel containing α-MG and LME plus fluoride and determine its antimicrobial, anti-biofilm formation, anti-cancer, anti-inflammatory, wound healing, and enamel microhardness effects.MethodsAntimicrobial assays against Streptococcus mutans, Porphyromonas gingivalis, and Candida albicans were performed. The microbes’ ultrastructural morphology was assessed using Transmission Electron Microscopy. The effect on microbial biofilm formation was tested by a broth microdilution. Cell viability was assessed with MTT assay. The anti-inflammatory effect was investigated by measuring inhibition of nitric oxide production. Enamel microhardness was measured via Vickers microhardness testing. The enamel chemical composition was investigated with Fourier Transform Spectrometer. The enamel surface morphology and fluoride content were examined by Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy.ResultsThe results show synergistic effects of α-MG and LME on antimicrobial activity and antibiofilm formation without cytotoxicity at a therapeutic dose. At a higher dose, the tooth gel inhibited proliferation of cancer cell line. Enamel microhardness was increased after brushing with the tooth gel plus fluoride. A large amount of fluoride was detected on the enamel surface.ConclusionThe tooth gel containing α-MG and LME synergized its antimicrobial activity and antibiofilm formation and inhibited oral cancer cell proliferation. Incorporating fluoride into the tooth gel increased enamel microhardness. Thus, the herbal tooth gel containing α-MG and LME plus fluoride may be useful for preventing dental caries and promoting oral health.

Based on the Feedforward Inputs Obtained by the Intelligent Algorithm the Moving Mirror Control System of the Fourier Transform Spectrometer

A moving mirror control system of the Fourier transform spectrometer (FTS) based on the feedforward inputs obtained by the intelligent algorithm is proposed in this paper. Feedforward control is an important part of the moving mirror speed control system of the FTS. And it is always difficult to quantitatively calculate the feedforward inputs through a precise mathematical model of the controlled object. Therefore, based on the expected motion law, an intelligent adaptive algorithm for obtaining feedforward inputs of the moving mirror system was designed. The algorithm decomposed the motion stroke into several position points, iteratively obtained the driving quantity of the moving mirror that met the expected instantaneous speed of each position point, and finally obtained the feedforward inputs of the whole motion stroke. The feedforward inputs obtained by the intelligent algorithm combined with the speed loop PID control constitute the complete moving mirror speed control system. Then, we applied the control system to the moving mirror of the FTS and acquired the velocity of the moving mirror. The experimental results show that the control system is feasible, the error of the peak-to-peak velocity is 0.047, and the error of the root mean square (RMS) velocity is 0.003. Compared with the single-speed-loop control system without feedforward inputs, the error of the peak-to-peak velocity is reduced by 43.3%, and the error of the RMS velocity is reduced by 67.7%, realizing a more accurate control of the moving mirror. Therefore, the control system based on the feedforward inputs obtained by the intelligent algorithm is a feasible and effective moving mirror speed control scheme of the FTS.

A portable reflected-sunlight spectrometer for CO2 and CH4

Abstract. Mapping the greenhouse gases (GHGs) carbon dioxide (CO2) and methane (CH4) above source regions such as urban areas can deliver insights into the distribution and dynamics of local emission patterns. Here, we present the prototype development and an initial performance evaluation of a portable spectrometer that allows for measuring CO2 and CH4 concentrations integrated along a long (>10 km) horizontal path component through the atmospheric boundary layer above a target region. To this end, the spectrometer is positioned at an elevated site from which it points downward at reflection targets in the region, collecting the reflected sunlight at shallow viewing angles. The path-integrated CO2 and CH4 concentrations are inferred from the absorption fingerprint in the shortwave–infrared (SWIR) spectral range. While mimicking the concept of the stationary California Laboratory for Atmospheric Remote Sensing – Fourier Transform Spectrometer (CLARS-FTS) in Los Angeles, our portable setup requires minimal infrastructure and is straightforward to duplicate and to operate in various locations. For performance evaluation, we deployed the instrument, termed EM27/SCA, side by side with the CLARS-FTS at the Mt. Wilson Observatory (1670 m a.s.l.) above Los Angeles for a 1-month period in April/May 2022. We determined the relative precision of the retrieved slant column densities (SCDs) for urban reflection targets to be 0.36 %–0.55 % for O2, CO2 and CH4, where O2 is relevant for light path estimation. For the partial vertical column (VCD) below instrument level, which is the quantity carrying emission information, the propagated precision errors amount to 0.75 %–2 % for the three gases depending on the distance to the reflection target and solar zenith angle. The comparison to simultaneous CLARS-FTS measurements shows good consistency, but the observed diurnal patterns highlight the need to take light scattering into account to enable detection of emission patterns.

A comprehensive study on the influence of Mg doping on structural, AC conductivity, and dielectric behavior of ZnONPs

In this research magnesium (Mg) doped zinc oxide nanoparticles (Zn1-x MgxO, where x = 0 for pure ZnO) were synthesized using a simple chemical route. Their structure and morphology was characterized using different methods, such as X-ray diffraction, scanning electron microscopy, Fourier Transform spectroscopy, photoluminescence. Nanoparticles (NPs) were synthesized and analyzed for their structure, shape, chemical content, and optical and dielectric activity with Zn1-x MgxO (where x = 5,15,50 wt%). The crystalline, hexagonal ZnO was verified by X-ray diffraction, with an average grain size of 45 nm for ZnO and 28 nm for Mg doping and a more interplane spacing that ranges from 2.9 nm to 18 nm. In the nanoscale domain, with a hexagonal crystalline shape between 30 and 80 nm, Zn1-x MgxO were analyzed in scanning electron microscopy (SEM) pictures. Transmittance rises with doping, as shown by optical characterization, and UV–vis spectroscopy reveals low absorbance in the visible area. Absorption values drop dramatically for all samples in the UV region, and when magnesium content rises, the absorption peak moves to shorter wavelengths. As the Mg content increased from 5 % to 50 %, the optical absorption spectra of ZnO switched to red. The UV emission peak in PL spectra was seen between 389 and 700 nm. It revealed that up to 50 % Mg doping, the strength of the emission bands at 405 and 525 nm decreases. According to fluorescence emission, zinc oxide has interaction with porphyrin, which results in a new peak at 389 nm. This 389 nm peak is thus specific to ZnO and Zn1-x MgxO nanoparticles as a result of the electron transport between the two materials. The Zn1-x MgxO samples show low dielectric losses and high dielectric constants in the middle and high-frequency ranges. The Mg doping at 5 % concentration is particularly intriguing since it shows enormous dielectric constant across a broad frequency range. At low frequencies, all the samples suffer from a significant loss factor. In the high-frequency range, it stabilizes.

Observation and assignment of a high-resolution FTIR-spectrum of T[formula omitted]O, DT16O and HT16O in the range of 4300 to [formula omitted

In the range of 4300 to 4700cm−1, we present analysis of the 2ν1, 2ν2+ν3 and ν1+ν3 bands of T216O, the 2ν1 and ν1+2ν2 of DT16O and the 2ν1 of HT16O. The analysed high-resolution spectrum has been obtained from a Bruker IFS 125HR Fourier-transform spectrometer with a resolution of 0.025cm−1 using an optical cell with an activity of 10GBq. For the in total 2436 lines an individual positional uncertainty of up to 3.4×10-5cm−1 and a systematic uncertainty of 7.5×10-4cm−1 could be achieved. Four of the six bands have been analysed for the first time, the ν1+ν3 band of T216O and the 2ν1 of HT16O have been analysed in previous works of our group. These datasets are extended by 527 new lines and a cross check is confirming the consistency between both works. A comparison of the assigned line positions to the variationally calculated predictions from the Tomsk database agrees with previous findings indicating that band-specific shifts and shifts depending on the rotational quantum numbers are observed leading to an overall difference of up to 0.3cm−1.

Solar Observation with the Fourier Transform Spectrometer. II. Preliminary Results of Solar Spectrum near the CO 4.66 μm and Mg i 12.32 μm

An infrared solar spectrum observed by ground-based telescopes is seriously affected by the background radiation both from the telescope and sky, relative to the visible wavelengths. Its accuracy is also influenced by the spectral resolution of the Fourier transform spectrometer. In the paper, we developed a CO2 gas cell and installed it in the sample compartment to calibrate the spectral resolution of the Bruker IFS-125HR at infrared wavelengths. The measured spectral resolution is 0.00342 ± 0.00086 cm−1 and 0.0059 ± 0.00024 cm−1 at the wavenumbers of 798 cm−1 and 2136 cm−1, respectively. We also updated a fully reflective sunlight feeding system to observe the solar spectrum near CO 4.66 μm and Mg i 12.32 μm. By quickly pointing the sunlight feeding system about 1 degree away from the solar disk center, we are able to measure the background radiation from the telescope and the sky at Huairou Solar Observing Station. After removing the background radiation, our observed solar spectrum at CO 4.66 μm is consistent with that from the National Solar Observatory. The Mg i 12.32 μm working line selected by the Accurate Infrared Magnetic Field Measurements of the Sun (AIMS) project is also identified. Our method is helpful not only for the spectral resolution calibration and background radiation correction of AIMS but also for other infrared astronomical telescopes.

Response surface methodology based modelling and optimisation of anionic dyes adsorption onto nitrate intercalated Zn2Al layer double hydroxide adsorbent

ABSTRACT In the present work, nitrate intercalated zinc aluminium layer double hydroxide (ZA-LDH) nanoparticles in the hydrodynamic particle size range between 210 and 530 nm were synthesised using co-precipitation method under reflux condition and nitrogen atmosphere. The pristine ZA-LDH nanoadsorbent was characterised using X-ray diffraction (XRD), Fourier transformation spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM). The results revealed the formation of single-phase ZA-LDH nanopowder with sheet-like morphology. The optimisation of adsorption kinetic parameters with the fixed dose of 10 mg for 50 ml of 0.03 mg/ml MO and AY dye solution was performed using the Box Behnken design model (BBD). The effects of three independent variables such as incubation time, temperature and pH of the suspended ZA-LDH nanoadsorbents in the MO and AY dye solution on the adsorption kinetics were studied. Optimum values for the maximum adsorption capacity were evaluated that included the incubation time of 52.4 min, the temperature of 35.45 ± 0.55°C, and the pH of 5.75 ± 0.75. According to the BBD model, ZA-LDH nanoadsorbent exhibited the maximum adsorption percentage of 99.84% and 99.99% of corresponding MO and AY dye, respectively. The ZA-LDH adsorbent retained up to 72.3% for the MO and 60.43% for the AY dye of regeneration capacity after 5 cycles of regeneration. The adsorption kinetic and isotherm of the MO and AY dyes onto the ZA-LDH nanoadsorbent were well fitted with pseudo second order kinetic model and Langmuir model, respectively. According to Langmuir isotherm, the maximum adsorption capacities of 601.62 mg/g for the MO dye and 462.48 mg/g for the AY dye onto the ZA-LDH were found and those confirmed the monolayer chemisorption mechanism in this case.

Intelligent pointing increases the fraction of cloud-free CO2 and CH4 observations from space

For most CO2 and CH4 satellites, only a small percentage (∼10%) of observations yield successful retrievals, with the remaining ∼90% rejected, primarily due to the effects of clouds. Discarding this large fraction of data is an inefficient strategy worth reconsidering due to the costs involved in developing, launching and operating the satellites to make these observations. However, if real-time cloud data are available together with pointing capability, cloud data can guide the instrument pointing in an “intelligent pointing” strategy for cloud avoidance. In this work, multiple intelligent pointing simulations were conducted, demonstrating the significant advantages of this approach for satellites in a highly elliptical orbit (HEO), from which nearly the whole Earth disk can be observed. Multiple factors are shown to contribute to intelligent pointing efficiency such as the size and shape (or aspect ratio) of the field of view (FOV). For the current baseline orbit and Imaging Fourier Transform Spectrometer (IFTS) observing characteristics for the proposed Arctic Observing Mission (AOM), the monthly fraction of cloud-free observations is roughly a factor of 2 (ranging from ∼1.5–2.5) more than obtained with standard pointing (in which cloud information is not used). A similar efficiency is expected in a geostationary orbit (GEO) with an IFTS, however, for a dispersive instrument in HEO or GEO, the gain is more modest. This result is primarily attributed to the ∼1:1 aspect ratio of the IFTS FOV, since it is more efficient for cloud avoidance and scanning irregularly-shaped land masses than the long and narrow slit projection of a typical dispersive spectrometer. These results have implications for the design of future CO2 or CH4 monitoring satellites and constellation architectures, as well as other fields of satellite earth observation in which clouds significantly impact observations.

N2O as a regression proxy for dynamical variability in stratospheric trace gas trends

Abstract. Trends in stratospheric trace gases like HCl, N2O, O3, and NOy show a hemispheric asymmetry over the last 2 decades, with trends having opposing signs in the Northern Hemisphere and Southern Hemisphere. Here we use N2O, a long-lived tracer with a tropospheric source, as a proxy for stratospheric circulation in the multiple linear regression model used to calculate stratospheric trace gas trends. This is done in an effort to isolate trends due to circulation changes from trends due to the chemical effects of ozone-depleting substances. Measurements from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) and the Optical Spectrograph and InfraRed Imager System (OSIRIS) are considered, along with model results from the Whole Atmosphere Community Climate Model (WACCM). Trends in HCl, O3, and NOy for 2004–2018 are examined. Using the N2O regression proxy, we show that observed HCl increases in the Northern Hemisphere are due to changes in the stratospheric circulation. We also show that negative O3 trends above 30 hPa in the Northern Hemisphere can be explained by a change in the circulation but that negative ozone trends at lower levels cannot. Trends in stratospheric NOy are found to be largely consistent with trends in N2O.