SO2 Gas Research Articles

Influence of flue gas components on SO2 adsorption by activated carbon at low temperature

Activated carbon can adsorb SO2 in flue gas, whose performance is significantly enhanced when lowering the adsorption temperature; however, the characteristics and mechanism of SO2 adsorption under the action of complex flue gas components at low temperatures remain unclear. In this study, adsorption experiments were conducted to investigate the characteristics of SO2 adsorption on activated carbon and the impact of O2, H2O, and NO within −20 to 20 °C. The saturated adsorption of SO2 showed a 2.21-fold increase when the temperature was lowered from 20 °C to −20 °C. Within this temperature range, physical adsorption was dominant, accounting for 73.7–91.0 %. O2 and H2O inhibited the physical adsorption of SO2 and promoted its chemical adsorption. As the temperature was lowered, the promoting effect of O2 increased, while the influence of H2O shifted from promotion to inhibition. NO affects SO2 adsorption only when co-existing with O2. As the temperature decreased, the promoting effect of NO on both physical and chemical adsorption strengthened and was significantly higher than that of O2 and H2O. Based on desorption experiments and quantum chemical calculations, the mechanisms by which H2O and NO affect SO2 adsorption were proposed·H2O and SO2 share the same physical adsorption sites, with H2O being more strongly adsorbed, thus significantly inhibiting the SO2 physical adsorption. When NO coexists with O2, gaseous SO2 reacts with the NOx adsorption configurations to form C-SO3 and C-HSO3. Active atoms near C-SO3 and C-HSO3 can adsorb NO2, forming a co-adsorption configuration, which in turn enhances the nearby physical adsorption of SO2. Enhancing the catalytic oxidation and adsorption of NO through surface modification of activated carbon can improve the low-temperature adsorption performance of SO2.

Reversible MOF-Based mixed matrix membranes for SO2/N2 separation: A photo-responsive approach

Fuel consumption for industrial development, SO2 gas emissions are increasing year by year and have become a focal point of air pollution. Membrane separation method photo-responsive materials and MOFs have attracted more and more attention in a variety of fields. This is because the membrane separation method uses less energy and is an uncomplicated process; MOFs have superior gas adsorption capabilities; and the photo-responsive materials are controllable. In this study, mixed matrix membranes are prepared using Uio-66-NH2 and photo-responsive materials CE-Azo-Uio-66 as fillers and Pebax as base membranes. By improving the dissolution-diffusion mechanism for SO2 gas molecules, SO2/N2 gas separation is accomplished. More channels for the mass transport of SO2 gas through the membrane can be created by MOFs increased porosity and larger specific surface area. Secondly, the SO2 adsorption and dissolution-diffusion mechanism of the mixed matrix membrane are strengthened by the grafted SO2 affinity groups on the MOF. Moreover, Pebax/CE-Azo-Uio-66 membranes is not only significantly more permeation selective than Pebax/Uio-66-NH2 membranes, but also shows photo-responsive characteristic. The SO2 permeability and selectivity of Pebax/CE-Azo-Uio-66 mixed matrix membranes at CE-Azo-Uio-66 content of 20 % are increased by 191 % and 179 %, respectively, compared to pure Pebax membranes. It is also found that the SO2 permeability and SO2/N2 selectivity of the membranes show regularly reversible changes at the UV–Vis photoconversion conditions of Pebax/CE-Azo-Uio-66-20 % membranes, indicating the photo-responsive characteristics of mixed matrix membranes that include Azo groups. The SO2 permeability of the Pebax/CE-Azo-Uio-66 membrane is increased by 1300 Barrer and the SO2/N2 selectivity is increased by 350 when the light source is changed from UV to Vis light, achieving a controlled separation of SO2/N2. Besides, the addition of MOF particles significantly enhances the mechanical properties and stability of the membrane.

Independent LUMO Reactivity in Mesoionic N‐Heterocyclic Thiones: Synthesis of a Stable Radical Anion

Mesoionic compounds, with positive and negative charges, are expected to have dual‐site highest occupied molecular orbital (HOMO, donor) and lowest unoccupied molecular orbital (LUMO, acceptor) reactivity. Herein, we report a novel class of air‐stable mesoionic N‐heterocyclic thiones (mNHTs) synthesized from abnormal N‐heterocyclic carbenes (aNHCs). DFT studies revealed a highly polarized exocyclic thione moiety and computed Fukui function analysis suggests the dual‐site HOMO/LUMO reactivity of mNHTs predicting donor property at the negatively charged ‘S’ center while acceptor property at the cationic imidazole ring. The independent LUMO reactivity of the mNHT was realized by its chemical reduction to an elusive radical anion, which was characterized by a single crystal X‐diffraction study. Further, we explore the reactivity of radical anion for the activation of SO2 gas, C‐Br bonds of aryl bromide and photocatalytic functionalization of C‐X (X = F, Br) bonds. This work unlocks the independent LUMO reactivity of a mesoionic compound.

Sulfur dioxide gas sensor based on vanadium oxide doped TiO2 nanopaper

Abstract The gas sensor based on TiO2 nanomaterials is promising for both industry and daily life because of its simple fabrication, low cost, high sensitivity, and easy application to micro-devices. However, its selectivity is relatively low and strongly influenced by the environment, thus limiting its practical application. In this work, we prepared TiO2 nanopaper by methods of hydrothermal synthesis and conventional paper preparation. To improve the selectivity, we added V2O5 by immersing the as-prepared nanopaper in an ammonium metavanadate (NH4VO3) solution evenly dispersed in ethanol. Nanopaper is a random array of long nanowires and nanofibers, which retains its shape and structure at high temperature, unlike pure nanowires, due to its high porosity and mechanical stability. V2O5 leads to a selective sensing performance with high catalytic activity for SO2 gas. The surface structure of the sensing material and its porosity were characterized by SEM, XRD, XPS. The improved sensing material exhibited a high response of about 22.6 for 100 ppm SO2 and a fast response and recovery of 9 s and 14 s, respectively. It also exhibited good reproducibility and selectivity in other interfering gases. Furthermore, the long-term sensing performance in the atmospheric environment was maintained for about 50 days.

Spectroscopic, structural characterization, along with DFT calculation, of a new cadmium(II) acetato meso-arylporphyrin: Theoretical study on NO2, CO2, N2, NO2, and SO2 gas-sensing and analysis of electrical conductance and dielectric properties

The paper presents a combined experimental and computational investigation of the cadmium(II) (acetato)‑meso-tetra(para-methoxyphenyl)porphyrin ion complex [Cd(TMPP)(OAc)]- (complex 1), which was prepared by the reaction of [Cd(TMPP)] with an excess of NaOAc and crysptand-222 in chloroform. This new Cd(II) meso‑arylporphyrin was characterized by elementary analysis and UV–Vis, IR, and 1H NMR spectroscopic techniques along with single crystal X-ray diffraction. This later study shows that the Cd2+center ion adopts a distorted square pyramidal geometry and is coordinated by the four nitrogens of the TMPP porphyrinate and the oxygen atom of the acetato axial ligand. The intermolecular interactions in the crystal lattice of [Cd(TMPP)(OAc)]-, determined using the PLATON program and Hirshfeld surfaces analysis, are of types O__H…O, C__H…H, C__H…Cl, C__H…Cg and C__Cl…Cg (Cg is the centroid of a phenyl or a pyrrole ring) involving the [Cd(TMPP)(OAc)]- ion complex, the [Na(crypt-222)]+ counterion, and the chloroform and water molecules found in the crystal lattice of complex 1. Using DFT calculations at the DFT/B3LYP-D3/lanL2DZ level of theory HOMO–LUMO orbitals of 1 and several global reactive parameters of this compound were calculated. The 3D-MEP plots of [Cd(TMPP)(OAc)]- were also determined. This theoretical study includes the sensing properties of complex 1 and the NO2, CO2, N2, and SO2 gas molecules. Furthermore, experimental tests have been carried out concerning the impedance and dielectric spectroscopy of the InGa/[Cd(TMPP)(OAc)]/InGa device.

Room-temperature self-calibrating sensor based on CsPbBr3/SnO2 for detecting low-concentration sulfur dioxide

Sulfur dioxide (SO2) is a colorless toxic gas, and accurate monitoring of its concentration is important for safety. However, accuracy is often interfered by humidity. To address the issues, in this work, a self-calibrating SO2 sensor based on CsPbBr3/SnO2 was prepared, the sensor exhibited an excellent response to parts per billion (ppb) levels of SO2 at room temperature, which is rarely achieved by other SO2 sensors. The response sensitivity of the sensor to 600 ppb SO2 reached up to 0.53 with response/recovery times of 17/285 s. In addition, the CsPbBr3/SnO2-based SO2 gas sensor showed a low detection limit, good reproducibility, and high selectivity. Moreover, theoretical calculations show that the gas recognition mechanism is attributed to the significant changes in the band structure and density of states of the heterojunction materials CsPbBr3/SnO2 after gas adsorption, thereby altering the charge carrier transport behavior and electrical properties. A self-calibrating algorithm MobileNetV2 was employed to eliminate humidity interference and effectively identify low-concentration SO2 in humid environments, and the recognition accuracy rate is 0.85. This work demonstrates the production of a high-performance SO2 gas sensor, and provides an effective method to eliminate the interference of humidity, making it significant in environmental monitoring and air quality control.

Association of SO2-Generating Pads before Packaging and during Cold Storage to Extend the Conservation of 'Italia' Table Grapes.

The SO2-generating pads contain different concentrations of sodium metabisulfite, which absorbs water from the grapes' transpiration, releasing SO2 gas, and there are slow-(SlowSO2) and dual (DualSO2)-releasing pads (fast release in the first 48 h and slow for up to 60 days). The ultra-fast SO2-generating pad (FieldSO2) releases the SO2 quickly for up to 6 h, and it was designed to be used soon after the harvest and until the grapes' packaging. The goal was to study the effect of FieldSO2 associated with SlowSO2 and DualSO2 pads on gray mold incidence and physicochemical and appearance characteristics of 'Italia' table grapes. Grapes were harvested from a commercial vineyard in Parana, Brazil, in 2020 and 2021, and packaged in cardboard boxes, and the treatments were as follows: control (without SO2-generating pads); FieldSO2 + SlowSO2; and FieldSO2 + DualSO2. After 30, 45, 60, 75, and 90 days of cold storage (1 ± 1 °C), the grapes were assessed for gray mold incidence, mass loss, shattered berries, stem browning, and filamentous fungi on the surface. The use of FieldSO2 associated with SO2-generating pads is effective in controlling gray mold on 'Italia' table grapes, especially the treatment FieldSO2 + DualSO2, which provides the lowest incidence of the disease up to 90 days of cold storage, while the combination with SlowSO2 results in intermediate efficacy. Treatments combining these SO2-generating pads extend the postharvest shelf life of 'Italia' grapes, with few shattered berries, low mass loss and freshness of the rachis without impairing the bunch's appearance.

Simultaneous measurement of SO2 and CO2 for sulfur content detection in marine diesel fuel using QCL absorption spectroscopy

Simultaneous measurement of CO2 and SO2 in ship exhaust gases is a common method for assessing compliance with sulfur emission standards. This study develops a new ship exhaust gas analyzer using time-division multiplexing of two quantum cascade lasers for simultaneous detection of the two gas species. A digital circuit integrated with a dual-channel waveform generator and a lock-in amplifier is developed to implement wavelength modulation spectroscopy (WMS) scheme. To enhance the measurement accuracy of SO2 with broadband absorption feature, a novel WMS approach that combines first-harmonic and normalized second-harmonic detection is introduced. A Kalman filter algorithm is employed to further refine the measurement precision. Experimental results show a 30.76% increase in detection accuracy. With a 1 s time resolution, the sensitivities of 13.4 ppb for SO2 and 9.81 ppm for CO2 are achieved. The effectiveness of the prototype for sulfur content detection is demonstrated, aiding emission management of water transport emissions.

Utilizing Armchair and Zigzag Nanoribbons for Improved Detection of SO2 Toxicity with Graphene Biosensor

Graphene nanoribbons (GNRs), with their distinctive structural and electronic characteristics, offer significant potential for use as biosensors in the detection of sulfur dioxide (SO₂) levels. This study employs Density Functional Theory (DFT) to evaluate the sensitivity of armchair graphene nanoribbons (AGNRs) to SO₂ gas. Specifically, we investigate the influence of SO₂ molecules on the electronic and transport characteristics of both pure and Cr-doped zigzag graphene nanoribbons (ZGNRs) and Cr-doped AGNRs. Key electronic properties, including band structure, adsorption energy, and density of states (DOS), were analyzed following SO₂ adsorption. The results indicate that Cr doping leads to significant changes in the electronic properties of AGNRs upon SO₂ exposure, including alterations in the Fermi surface that result in band separation and the formation of a forbidden band. The adsorption energy of Cr-doped AGNR increased from 0.07 eV (pristine AGNR) to 0.55 eV (Cr-doped AGNR), nearly eight times higher, indicating strong chemisorption of SO₂. These findings suggest that Cr-doped AGNRs exhibit high sensitivity to SO₂, making them promising candidates for gas detection. Furthermore, this study reveals that SO₂ adsorption in the armchair direction results in a more pronounced peak-to-valley ratio compared to the zigzag direction, highlighting distinct characteristics in SO₂ adsorption behavior. These findings could facilitate the development of advanced sensors with improved sensitivity and selectivity for environmental monitoring and safety applications.

Nanoscale Synergy: Unveiling Gas Sensing Paradigms Through First Principles Exploration of Vertical Hexagonal Boron Nitride/Graphene Heterostructures

Modern civilization relies on rapid and accurate gas molecule identification at low concentrations for environmental surveillance, civilian security, healthcare evaluation, and inside atmospheric control. Density functional theory simulations are used to study the adsorption of CH4, CO2, PH3, N2O, NH3, O3, and SO2 gas molecules on a vertical hexagonal boron nitride/graphene heterostructure using the CASTEP code. Negative adsorption energy is only detected for NH3, O3, and SO2 gases. Our adsorption energy measurements show that the heterostructure is sensitive to NH3, O3, and SO2 gas molecules but insensitive to other gas molecules, as shown by the positive results. Further electrical and optical properties are only performed on gas‐adsorbed structures. It is found that the pure heterostructure acts like a semiconductor and has a band gap of 1.742 eV, which changes when gas is absorbed. Each of the structures has high absorption coefficients in the UV region, making them promising candidates for optoelectronic devices. The determination of the adsorbed gas type can be achieved by measuring the peak intensity and peak position of reflection or absorption. Heterostructures exhibit superior sensing capabilities for NH3 compared to other gases because of their enhanced adsorption energy, distinctive electrical band gap, and notable optical characteristics.

Comparison of Gas-sensitive response of three metal-doped GaNNT with Pb, Pd and Pt after adsorption of hazardous gases

In this paper, we comparatively analyze the gas-sensing ability of Pb, Pd and Pt metal-doped GaNNT (M-GaNNT) materials for the hazardous H2S, SO2, NH3 and Cl2 gases. The adsorption structure, adsorption energy (Eads), density of states (DOS), differential charge density and frontier molecular orbital of the M-GaNNT adsorbed hazardous gas have been studied based on the density functional theory (DFT) calculations. The results show that the energy gap of Pb-GaNNT performs the largest change with an increasing percentage change of 358 % after the Cl2 adsorption compared with that before the Cl2 adsorption, while the energy gap of Pt-GaNNT has the least change with an average value of 20.8 %. The doping of metal atoms can effectively improve the gas-sensitivity of M-GaNNT, and the gas-sensitivity follows the order of Pb-GaNNT> Pd-GaNNT> Pt-GaNNT. The potential applications of M-GaNNT in gas sensor and adsorbent are then predicted through the analysis of the adsorption energy, sensitive response (SR) and recovery time (τ). Pb-GaNNT performs the best Cl2 gas removal since the largest Eads (-5.883 eV), largest SR (4.4 × 1015) and largest τ (2.9 × 1087s) can be determined for Cl2 adsorption on Pb-GaNNT. Furthermore, Pb-GaNNT is a good NH3 gas sensor since the related τ is only 2.9 s at 498 K, and a small Eads (-1.232 eV) with large SR (9.7 × 105) can be determined as well. The research findings in this paper provide a new sensor material option for both the detection and the removal of harmful gases, and the systematically theoretical method can spread to other systems.

Analisis Pengaruh Faktor Meteorologi Terhadap Konsentrasi Gas SO2 dan NO2 dari Cerobong Ketel Pabrik Gula X

The process of burning bagasse in a steam boiler produces pollutants in the form of exhaust gas emissions through the chimney, which can pollute air quality and harm health. The aim of this study is to determine the great influence of meteorological factors including exhaust gas temperature, air temperature, and flow speed in 4 areas of the boiler pipe that can affect the load of SO2 and NO2 gas pollutants through statistical data analysis. The ANOVA test used in this study was the ANOVA One Way test. The results of the study showed that there was a significant influence of the air temperature factor on SO2 in Boiler 4 / Cheng Chen with a value of F value 14,553 and a sig value of 0,032, as well as the influence that exists on the exhaust gas temperature factor and air temperature on NO2 in Stork Boiler 2 with an F value of 15,358 ; 17,889 and a sig value of 0.030 ; 0.024. The results of the analysis can be used as monitoring to evaluate the success rate and operational efficiency of the boiler under the management that has been carried out.

Fabrication of modified Sb2O3 nanospheres for the removal of hazardous malachite green organic pollutant and selective NO2 gas sensor

Sb2O3 and Ni modified Sb2O3 (Ni–Sb2O3) nanospheres were synthesized using low cost co-precipitation method and characterised using various instrumental methods such as X-ray Powder Diffraction (XRD), High Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared (FT-IR) spectroscopy. The XRD pattern reveals cubic crystal lattice. The average size of Sb2O3 and Ni–Sb2O3 nanoparticles was calculated to be around 41 nm and 29 nm, respectively. The HR-TEM investigation of the Sb2O3 nanomaterial reveals homogeneous spherical balls with a fine dispersion. The random-shaped nanoparticles with porous surfaces and voids were revealed by SEM. EDS examination confirms the elemental composition of Sb (41.79 %) and O (58.21 %) in Sb2O3 and Sb (36.80 %), O (58.95 %), and Ni (4.25 %) in Ni–Sb2O3. Sb2O3 and Ni– Sb2O3 exhibit band gaps of 3.67 eV and 3.51 eV, respectively, according to UV–Vis analysis. The IR peaks 445.47, 642.18, and 745.18 in Sb2O3 and 438.72, 645.07, and 756.92 in Ni– Sb2O3 support the Sb–O bonding in the synthesized nanomaterials. The synthesized nanomaterials have been used for photocatalytic degradation of malachite green (MG) dye and sensing NO2, SO2, CO2, petroleum vapour and LPG gases. The MG dye was degraded 97.67 % in 120 min using Ni–Sb2O3 at optimized conditions (catalyst dose: 0.1 g/L to 0.3 g/L, pH: 7 and MG dye: 10 ppm). The gas sensing study showed that Ni–Sb2O3 sensor has greater sensitivity and selectivity for NO2 gas.

Investigating the Relationship between Urbanization and Air Pollution Using Google Earth Engine Platform: A Case Study of Istanbul

Rapid population growth in megacities such as Istanbul has led to various effects, such as industrialization, urbanization, loss of green areas, increasing vehicle traffic, and higher consumption of fossil fuels. These reasons, along with many other environmental factors, contribute to the rise of air pollution in urban life. This study aimed to examine the relationship between urbanization and air pollution in Istanbul. For this purpose, land cover maps covering Istanbul province were produced using Landsat-5 (TM), Landsat-8 (OLI), and Sentinel-2 (MSI) images for the years 1996 to 2021 at three-year intervals on the Google Earth Engine platform. Land cover for classification purposes was divided into five different classes: forest, water surface, urban area, and bare land, and classified using a random forest machine learning algorithm. To examine the impact of this urban area growth on air pollution, in the second step of the study, the column number density values of Sentinel 5P (TROPOMI) data for SO2, NO2, CO, and O3 gases for 2019, 2020, and 2021 were analyzed. The averages of the data from 39 air pollution monitoring stations across Istanbul were also examined. According to this classification, the urban area expanded from 491 km2 in 1996 to 1222 km2 by 2021. Considering the total surface area of Istanbul province, the urban area, which was 9% in 1996, reached 23% by 2021. The TROPOMI values were calculated as follows: the average column number density values for SO2, NO2, CO, and O3 were 0.0003538 mol/m², 0.0339514 mol/m², 0.0000984 mol/m², and 0.1453515 mol/m², respectively. Similarly, the gas concentrations of SO2, NO2, CO, and O3 measured from the ground stations were calculated as 6.603 µ/m3, 786,815 µ/m3, 43.763 µ/m3 and 45.773 µ/m3, respectively. Correlations between urbanization and TROPOMI values revealed a positive correlation of 0.39, 0.02, and 0.80 for SO2, NO2, and CO gases, while a negative correlation of 0.25 was found for O3 gas. The study also examined correlations between TROPOMI and ground station measurements, resulting in positive correlations of 0.55, 0.66, and 0.16 for SO2, NO2, and CO gases, respectively, while a negative correlation of 0.05 was found for O3 gas. Based on these findings, among the air pollutants studied both through TROPOMI and ground station data, the highest correlation was observed for CO gas.

A CuO/MoO3-based SO2 gas sensor with moisture resistance and ultra-fast response at 90°C

Sulfur dioxide (SO2) is a toxic and harmful decomposition product generated during arc discharge or partial discharge in sulfur hexafluoride (SF6) electrical equipment, which can corrode internal pipelines. Detecting SO2 is crucial for assessing the insulation condition of equipment and preventing faults. To overcome the challenges faced by traditional SO2 gas sensors, including high operating temperatures, slow response times, and poor moisture resistance, this paper proposes a novel SO2 gas sensor based on CuO/MoO3. The morphology, composition, and chemical states of the materials were analyzed using different characterization techniques. At 90°C, the S2 sensor (CuO: MoO3=1: 1) exhibited a fast response time (10 s) to 10 ppm SO2 and demonstrated good moisture resistance (a 1 % change in relative humidity (RH) has the same effect on the sensor as 25.9 ppb SO2). The response of the S2 sensor to 100 ppm SO2 was 26.5. Additionally, the voltage sensitivity of the S2 sensor at low (1–10 ppm) and high (10–100 ppm) concentrations are 658.74 mV/ppm and 33.43 mV/ppm, respectively. Therefore, the S2 sensor is more suitable for low concentration conditions. These good sensing characteristics of the S2 sensor are owing to the high content of oxygen vacancies (39.2 %) and the heterojunction effect in the composite material. Additionally, this sensor exhibits excellent anti-interference capabilities, including moisture resistance and high selectivity. Therefore, the CuO/MoO3-based SO2 gas sensor can be effectively applied to detect the decomposition of SF6.

DFT study of MoSe2 monolayers for cohesive adsorption of harmful gases CO, CO2, SO2, and NF3

DFT study of MoSe2 monolayers for cohesive adsorption of harmful gases CO, CO2, SO2, and NF3

First-Principles Study on Bi2Te2S Monolayer for Adsorption Performance and Sensing Capability.

In this study, a comprehensive investigation into the gas sensing capabilities of the two-dimensional (2D) Bi2Te2S was conducted using first-principles calculations based on density functional theory. A wide array of gas molecules, including CH4, Cl2, CO, CO2, H2, H2O, H2S, N2, NH3, NO, NO2, O2, and SO2, was encompassed in this work. Through the strategic placement of these gas molecules at different locations on the Bi2Te2S monolayer and taking into account a range of configurations, the adsorption process was thoroughly investigated, with a particular emphasis on the structures that are most thermodynamically stable. It was revealed that Cl2, O2, NO, and NO2 molecules exhibit a pronounced affinity for the Bi2Te2S monolayer. Notably, it was found that the Cl2@Bi2Te2S, O2@Bi2Te2S, and NO2@Bi2Te2S systems' gas adsorption capabilities are greatly enhanced by the introduction of an external electric field. Moreover, the addition of horizontal biaxial strain significantly impacts the gas adsorption properties of the O2@Bi2Te2S system, underscoring the tunability of the Bi2Te2S monolayer's sensing capabilities. In light of these theoretical results, the Bi2Te2S monolayer is proposed to have great potential as an extremely sensitive and selective gas sensing material, especially for identifying Cl2, O2, NO, and NO2. This study clarifies the intrinsic gas sensing capabilities of the Bi2Te2S monolayer, while highlighting how its performance can be tailored in response to external stimuli, setting the stage for the advancement of more sophisticated gas sensing devices.

Detection of ultra-low concentration NH3, SO2, and NO using UV-DOAS combined with multidimensional spectral fusion

Since nitric oxide (NO), sulfur dioxide (SO2), and ammonia (NH3) in flue gas cause severe air pollution, accurate measurements of their concentrations are crucial for optimizing the efficiency of flue gas denitrification in coal-fired power plants and protecting the atmosphere. Due to their large absorption cross sections in the ultraviolet (UV) band, NH3, SO2, and NO in flue gas can be detected by UV Differential Optical Absorption Spectroscopy (UV-DOAS) techniques. However, spectral overlap and noise caused by short optical path limitations in the measurement are the main obstacles to achieve concentration inversion. Here, we propose a multidimensional spectral fusion method one-dimensional convolutional neural network combined with two-dimensional convolutional neural network (1D-2D-CNN) with the ability to invert concentration of NH3, SO2 and NO at ppb level with 0.5 m optical-length. To separate the absorption features, one-dimensional spectra are converted into two-dimensional time-frequency plots by continuous wavelet transform (CWT). After denoising the spectra by wavelet thresholding, one-dimensional and two-dimensional spectral features are extracted by 1D-2D-CNN model and fused for inversion. The experimental results show that the proposed system can effectively eliminate interferences from NH3, SO2, and NO, significantly improving the concentration inversion accuracy. The detection limits for NH3, SO2 and NO in the mixture are 0.95 ppb∙m, 6.31 ppb∙m, and 2.53 ppb∙m, respectively, demonstrating that our approach outperforms other reported methods for flue gas analysis. The proposed system is expected to be applied to ammonia slip monitoring of Selective Catalytic Reduction (SCR) in power plants.

SO2 and OCS toward high-mass protostars

Context. OCS and SO2 are both major carriers of gaseous sulfur and are the only sulfurated molecules detected in interstellar ices to date. They are thus the ideal candidates for exploring the evolution of the volatile sulfur content throughout the different stages of star formation. Aims. We aim to investigate the chemical history of interstellar OCS and SO2 by deriving a statistically significant sample of gas-phase column densities toward massive protostars and comparing them to observations of gas and ices toward other sources, from dark clouds to comets. Methods. We analyzed a subset of 26 line-rich massive protostars observed by ALMA in Band 6 as part of the High Mass Protocluster Formation in the Galaxy (ALMAGAL) survey. Column densities were derived for OCS and SO2 from their rare isotopologs O13CS and 34SO2 toward the compact gas around the hot cores. We compared the abundance ratios of gaseous OCS, SO2, and CH3OH with ice detections toward both high- and low-mass sources as well as dark clouds and comets. Results. We find that gas-phase column density ratios of OCS and SO2 with respect to methanol remain fairly constant as a function of luminosity between low- and high-mass sources, despite their very different physical conditions. In our dataset, OCS and SO2 are weakly correlated. The derived gaseous OCS and SO2 abundances relative to CH3OH are overall similar to protostellar ice values, with a significantly larger scatter for SO2 than for OCS. Cometary and dark-cloud ice values agree well with protostellar gas-phase ratios for OCS, whereas higher abundances of SO2 are generally seen in comets compared to the other sources. Gaseous SO2/OCS ratios are consistent with ices toward dark clouds, protostars, and comets, albeit with some scatter. Conclusions. The constant gas-phase column density ratios throughout low- and high-mass sources indicate an early-stage formation before intense environmental differentiation begins. Icy protostellar values are similar to the gas-phase medians and are compatible with an icy origin for these species followed by thermal sublimation. The larger spread in SO2 compared to OCS ratios with respect to CH3OH is likely due to a more water-rich chemical environment associated with the former, as opposed to a CO-rich origin for the latter. Post-sublimation gas-phase processing of SO2 can also contribute to the large spread. Comparisons to ices in dark clouds and comets point to a significant inheritance of OCS from earlier to later evolutionary stages.

A theoretical study on adsorption and sensing of SO2, CS2, CO2, CH2O, H2O, C2H2, and CF3H air pollutant gases by B3S monolayer

A theoretical study on adsorption and sensing of SO2, CS2, CO2, CH2O, H2O, C2H2, and CF3H air pollutant gases by B3S monolayer