High O2 Concentrations Research Articles

Establishing a self-supporting system of H2S production from SO2 with induced catalytic reduction process for mercury capture with super-large enrichment

Various sulfur (S) species in the environment possess different functions or adverse impacts, which highly depend on their existing states and forms. In a typical nonferrous smelting industry, the high concentration of SO2 is excrescent and needs further field upcycling, while such industry encounters a desperate shortage of sulfidation reagents (e.g., H2S or CuS) that are used for Hg0 capture in flue gas. Therefore, on-site reduction of SO2 to H2S or CuS for Hg0 capture is a feasible method to realize simultaneous SO2 upcycling and Hg0 immobilization. However, the low activity and rapid deactivation in direct reduction of SO2 with CO (DCRP) restrict actual application. To resolve the problems, an induced catalytic reduction process (ICRP) is established by refluxed partial COS to form nascent sulfurs (Sx*, x < 8), then Sx* is reduced to COS with CO. Subsequently, the obtained COS can be readily hydrolyzed to H2S. Results indicated that COS reduced SO2 showed five times higher rate than CO, which can significantly decrease the ramp from 400 to 375 °C. Moreover, it also can alleviate sulfation poison by COS induced effect because of preferential reaction sequence of SO2 with COS. Thus, the mechanism in ICRP was reasonablely transformed to mixed Mvk and E-R mechanism while DCRP was Mvk mechanism. Then, COS was readily hydrolyzed to H2S at 300 °C. Finally, the yielded H2S in-situ activated CuS exhibit a superior Hg0 capture performance with an adsorption capacity about 32.4 mg/g(CuS), which is 80 times higher than primitive CuS because of generated Sn2- in the presence of SO2 and H2O. This ICRP proved to be helpful in establishing a self-supporting system of H2S for SO2 reuse and Hg0 immobilization with super-large enrichment in nonferrous smelting industries.

Investigating the hygroscopicities of calcium and magnesium salt particles aged with SO2 using surface plasmon resonance microscopy

The hygroscopicities of calcium and magnesium salts strongly affect the environment and climate, but the aging products of these salts at high relative humidities (RHs) are still poorly understood. In this study, surface plasmon resonance microscopy (SPRM) was used to determine the hygroscopic growth factors (GFs) of Ca(NO3)2 and Mg(NO3)2 separately or mixed with galactose at different mass ratios at different RHs before and after aging. For all particles, the measured GFs showed no indication of deliquescence across the range of RHs tested, and overall hygroscopicity was clearly lower after than before aging. The Ca(NO3)2 and Mg(NO3)2 GFs at 90 % RH were 1.80 and 1.66, respectively, before aging and 1.33 and 1.42, respectively, after 4 h aging, meaning aging decreased the GFs by 26.11 % and 14.46 %, respectively. Aging decreased the hygroscopicity because insoluble or sparingly soluble substances (CaSO3, CaSO4, MgSO3) formed and strongly changed the overall hygroscopicity. For bicomponent aerosols with different mass ratios, the GFs (calculated using the Zdanovskii-Stokes-Robinson method) of the other components except galactose at 90 % RH after 1 h aging were all lower, respectively, than the measured GFs of pure Ca(NO3)2 and Mg(NO3)2 after aging for 1 h, especially with the mass ratio of 1:2, their GFs have decreased by 14.63 % and 7.50 %, respectively. Subsequently, Ion chromatograms indicated that the peak area ratio of SO42− to NO3− ratios were higher for the aged bicomponent particles than aged single-component particles, possibly because adding galactose improved the gas–liquid state stability during drying after the aging process and therefore promoted nitrate consumption and sulfate formation. The results indicated that organic components may play important roles in heterogeneous reactions between trace gases and multicomponent aerosols and should be considered in evaluating the impacts on submicron aerosol composition of high atmospheric SO2 concentrations at high humidities.

Meso-scale simulation of Li–O2 battery discharge process by an improved lattice Boltzmann method

The discharge process of lithium–oxygen battery (LOB) is a highly complicated multi-physics coupling phenomenon. Moreover, the cathode morphology presents a complex multi-scale structure with pore size ranging from nanometers to micronmeters, and plays a crucial role in determining the discharge performance. In this work, the cathodes consisting of carbon paper, electrode material, and electrolyte are first numerically reconstructed using a two-step reconstruction method considering the multi-scale morphology. A lattice Boltzmann model with an improved partial bounce-back scheme is proposed for modeling the discharge process given that the electrode porosity changes with the progress of discharge. The effects of micron-scale electrode spatial distribution on the O2 diffusion and LOB discharge performance are investigated. Results show that the increment of the electrode dispersion degree increases the O2 diffusion resistance due to the increase of electrolyte-electrode specific interface area. A large local electrode load near O2 inlet leads to a high O2 diffusion resistance and low O2 concentration owing to the large specific interface area and electrode volume. Cathodes with the minimum electrode load and maximum electrode dispersion degree present the optimal specific capacity of LOB. However, the specific capacity first increases significantly and then slightly decreases with the increase of local electrode load.

Ce–Fe bimetallic oxide catalysts for CO catalytic oxidation at a high concentration of SO2

The doping of Fe into the CeO2 lattice played a positive role in enhancing the CO oxidation activity and SO2-poisoning resistance of Ce0.7Fe0.3.

Validation of a rapid test to dose SO&lt;sub&gt;2&lt;/sub&gt; in vinegar

&lt;abstract&gt; &lt;p&gt;Sulfur dioxide is generally used in wine and vinegar production. It is employed to decrease the bacteria' growth, improve the wines' aroma (since it supports the extraction of polyphenols during maceration), protect the wines from chemical oxidation and the musts from chemical and enzymatic oxidation (blocking free radicals and oxidase enzymes such as tyrosinase and laccase). The composition and storage conditions (i.e., pH, temperature, and alcohol levels) affect oenological results. In various countries, competent authorities have imposed legal limits since it can have toxic effects on humans. It is crucial to dose SO&lt;sub&gt;2&lt;/sub&gt; levels to allow vinegar production and compliance with legal limits. The iodometric titration named "Ripper test" is the legal method used to dose it in vinegar. In this work, an automatized colorimetric test was validated using the international guidelines ISO/IEC (2017) to allow its use instead of the Ripper test. The test reliability was verified on white, red, and balsamic vinegar with low or high SO&lt;sub&gt;2&lt;/sub&gt; content. The automatized test showed linearity, precision, and reproducibility similar to the Ripper test, but the accuracy parameter was not respected for the vinegar with a low concentration of SO&lt;sub&gt;2&lt;/sub&gt;. Therefore, the automatized colorimetric test can be helpful to dose SO&lt;sub&gt;2&lt;/sub&gt; in vinegar with high concentrations of SO&lt;sub&gt;2&lt;/sub&gt;.&lt;/p&gt; &lt;/abstract&gt;

Analysis of The Effect of Deforestation Rates on Air Pollution Concentration and Land Surface Temperature Using Landsat-8 Imagery with Google Earth Engine (Case Study: East Kalimantan Province, 2019-2020)

The increase in population triggers an increase in deforestation rates. According to data from Ministry of Environment and Forestry, East Kalimantan’s highest deforestation rate reached 54.8 thousand hectares in 2018-2019. This study analyzed the effect of deforestation rates on air pollutant concentrations (SO2 and NO2) and land surface temperature (LST) in East Kalimantan in 2019-2020 with Google Earth Engine (GEE) platform using Landsat 8 Level 2 surface reflectance imagery. The TIR channel was converted into brightness temperature which further used as the input in LST estimation using Mono-Window Algorithm, SO2 estimation using Hasan Algorithm (2014), and NO2 estimation using Alseroury Algorithm (2015). During 2019-2020, the average LST value was 24.2 °C, which was increased by 2.0 °C from the previous year. The maximum NO2 concentration was 189.771 g/m3. The annual average NO2 concentration increased by 0.757 g/m³ from the previous year. The maximum concentration of SO2 was 0.521 ppm. The annual average SO2 concentration increased by 0.011 ppm from the previous year. To determine the effect of deforestation rates on the concentration of SO2, NO2 and LST, the Pearson correlation test was carried out. The correlation coefficient between deforestation rates and SO2 is R = 0.949 (very strong correlation); correlation coefficient between deforestation rates and NO2 is R = 0.889 (very strong correlation); and the correlation coefficient between the deforestation rates and the LST is R = 0.887 (very strong correlation). This shows that the higher deforestation rates, will caused in the higher concentration of SO2, NO2, and LST.

Elucidating the reaction mechanism of SO2 with Cu-CHA catalysts for NH3-SCR by X-ray absorption spectroscopy.

The application of Cu-CHA catalysts for the selective catalytic reduction of NOx by ammonia (NH3-SCR) in exhaust systems of diesel vehicles requires the use of fuel with low sulfur content, because the Cu-CHA catalysts are poisoned by higher concentrations of SO2. Understanding the mechanism of the interaction between the Cu-CHA catalyst and SO2 is crucial for elucidating the SO2 poisoning and development of efficient catalysts for SCR reactions. Earlier we have shown that SO2 reacts with the [Cu2II(NH3)4O2]2+ complex that is formed in the pores of Cu-CHA upon activation of O2 in the NH3-SCR cycle. In order to determine the products of this reaction, we use X-ray absorption spectroscopy (XAS) at the Cu K-edge and S K-edge, and X-ray emission spectroscopy (XES) for Cu-CHA catalysts with 0.8 wt% Cu and 3.2 wt% Cu loadings. We find that the mechanism for SO2 uptake is similar for catalysts with low and high Cu content. We show that the SO2 uptake proceeds via an oxidation of SO2 by the [Cu2II(NH3)4O2]2+ complex, resulting in the formation of different CuI species, which do not react with SO2, and a sulfated CuII complex that is accumulated in the pores of the zeolite. The increase of the SO2 uptake upon addition of oxygen to the SO2-containing feed, evidenced by X-ray adsorbate quantification (XAQ) and temperature-programmed desorption of SO2, is explained by the re-oxidation of the CuI species into the [Cu2II(NH3)4O2]2+ complexes, which makes them available for reaction with SO2.

Evaluation of reaction between SO2 and CH2OO in MCM mechanism against smog chamber data from ethylene ozonolysis

Environmental context The process of ethylene ozonolysis is an essential source of CH2OO radicals, and the latter is an important oxidant for the atmospheric pollutant SO2. The accuracy of a widely used atmospheric chemistry model (Master Chemical Mechanism, MCM) in quantifying SO2 oxidation has not been evaluated. In this study, this accuracy was evaluated, and optimal parameters underpinned by data from smog chamber experiments. Rationale The oxidation of SO2 by CH2OO radicals in the ethylene-O3 system is one of the important pathways of sulfate aerosol formation, but the accuracy of Master Chemical Mechanism (MCM) simulation for this reaction was not evaluated, although the MCM has been widely used in previous studies. Methodology The oxidation of SO2 in the ethylene-O3 system was performed in detail under different conditions, which were used to evaluate the accuracy of MCM simulation for the reactions in this study. Results The experimental conditions of low RH and high initial SO2 concentration favour the SO2 oxidation in the ethylene ozonolysis, and the yield of CH2OO in the ethylene ozonolysis without irradiations was determined to be 0.43. The n-hexane (C6H14) oxidation intermediates can promote the SO2 oxidation rate by generating sulfur-containing organics in the aerosol water. The original MCM simulated SO2 consumption after 4-h reaction was more than 70% smaller than the measured results. By adjusting the yield of CH2OO and updating the reaction rate constants of CH2OO-related reactions (e.g. with SO2, H2O and organic acid), the difference between experiments and simulations decreased from 70% to 6.6%. Discussion The promotion effects of n-hexane on the oxidation of SO2 suggest that alkanes may be the precursors of sulfur-containing organics in the atmospheric environment. This study further confirms the effect of CH2OO on the oxidation of SO2 in the atmospheric environment and provides information on the performance of MCM simulation.

Insufficient Oxygen Supplementation During Cardiopulmonary Resuscitation Leads to Unfavorable Biological Response While Hyperoxygenation Contributes to Metabolic Compensation.

Sudden cardiac arrest (CA) is the third leading cause of death. Immediate reoxygenation with high concentrations of supplemental oxygen (O2) during cardiopulmonary resuscitation (CPR) is recommended according to the current guidelines for adult CA. However, a point in controversy exists because of the known harm of prolonged exposure to 100% O2. Therefore, there have been much debate on an optimal use of supplemental O2, yet little is known about the duration and dosage of O2 administration. To test whether supplying a high concentration of O2 during CPR and post resuscitation is beneficial or harmful, rats subjected to 10-minute asphyxia CA were administered either 100% O2 (n=8) or 30% O2 (n=8) for 2hours after CPR. Two hours after initiating CPR, the brain, lung, and heart tissues were collected to compare mRNA gene expression levels of inflammatory cytokines, apoptotic and oxidative stress-related markers. The 100% O2 group had significantly shorter time to return of spontaneous circulation (ROSC) than the 30% O2 group (62.9±2.2 and 77.5±5.9seconds, respectively, P<0.05). Arterial blood gas analysis revealed that the 100% O2 group had significantly higher PaCO2 (49.4±4.9mmHg and 43.0±3.0mmHg, P<0.01), TCO2 (29.8±2.7 and 26.6±1.1mmol/L, P<0.05), HCO3- (28.1±2.4 and 25.4±1.2mmol/L, P<0.05), and BE (2.6±2.3 and 0.1±1.4mmol/L, P<0.05) at 2hours after initiating CPR, but no changes in pH (7.37±0.03 and 7.38±0.03, ns). Inflammation- (Il6, Tnf) and apoptosis- (Casp3) related mRNA gene expression levels were significantly low in the 100% O2 group in the brain, however, oxidative stress moderator Hmox1 increased in the 100% O2 group. Likewise, mRNA gene expression of Icam1, Casp9, Bcl2, and Bax were low in the 100% O2 group in the lung. Contrarily, mRNA gene expression of Il1b and Icam1 were low in the 30% O2 group in the heart. Supplying 30% O2 during and after CPR significantly delayed the time to ROSC and increased inflammation-/apoptosis- related gene expression in the brain and lung, indicating that insufficient O2 was associated with unfavorable biological responses post CA, while prolonged exposure to high-concentration O2 should be still cautious in general.

The Role of Sulfur Emission from the Petroleum Industry on Ultrafine Particle Number Concentration in Singapore

Ultrafine particles, defined as particles with a diameter (dp) smaller than 100 nm, serve as an important component of cloud condensation nuclei, in addition to impacting human health. The dominant sources of ultrafine particles include traffic emissions and nucleation. Singapore is a tropical city that hosts petrochemical industries. To identify the sources of ultrafine particles, a year-long observation of the number size distribution was conducted in Singapore in 2018 and 2019. The concentrations of CO, CO2, CH4, and SO2 were also monitored. The particle number concentration during the southwest monsoon season was high, while that during the northeast monsoon period was relatively low. The CO concentration increased during the morning traffic rush hours, which was associated with relatively minor enhancements in ultrafine particle number concentration. The events for a high number concentration of the Aitken mode particles (dp < 50 nm) were identified during high SO2 concentration periods. The SO2 concentration was high during the afternoon because the sea breeze transported the emissions from the coastal industrial area to the observation site. The enhancements in CH4 from its background level (ΔCH4) and SO2 had a quasi-inverse relationship, as the major emission sources of these two chemical species were different. The particle number concentration (dp > 50 nm) correlated with the enhancements in CO concentration (ΔCO) for CH4-dominant air masses, suggesting that incomplete combustion processes, such as traffic emission, are important for the size range. Conversely, the number concentration of the Aitken mode particles (dp < 50 nm) increased for SO2-dominant air masses, suggesting the importance of industrial plume.

Stepwise conversion of the Cys6[4Fe-3S] to a Cys4[4Fe-4S] cluster and its impact on the oxygen tolerance of [NiFe]-hydrogenase.

The membrane-bound [NiFe]-hydrogenase of Cupriavidus necator is a rare example of a truly O2-tolerant hydrogenase. It catalyzes the oxidation of H2 into 2e- and 2H+ in the presence of high O2 concentrations. This characteristic trait is intimately linked to the unique Cys6[4Fe-3S] cluster located in the proximal position to the catalytic center and coordinated by six cysteine residues. Two of these cysteines play an essential role in redox-dependent cluster plasticity, which bestows the cofactor with the capacity to mediate two redox transitions at physiological potentials. Here, we investigated the individual roles of the two additional cysteines by replacing them individually as well as simultaneously with glycine. The crystal structures of the corresponding MBH variants revealed the presence of Cys5[4Fe-4S] or Cys4[4Fe-4S] clusters of different architecture. The protein X-ray crystallography results were correlated with accompanying biochemical, spectroscopic and electrochemical data. The exchanges resulted in a diminished O2 tolerance of all MBH variants, which was attributed to the fact that the modified proximal clusters mediated only one redox transition. The previously proposed O2 protection mechanism that detoxifies O2 to H2O using four protons and four electrons supplied by the cofactor infrastructure, is extended by our results, which suggest efficient shutdown of enzyme function by formation of a hydroxy ligand in the active site that protects the enzyme from O2 binding under electron-deficient conditions.

Effects of oxygen concentration on devolatilization and combustion behavior of coal particles: A multi-parameter study

The devolatilization and volatile combustion of lignite coal (LC), sub-bituminous coal (SBC) and bituminous coal (BC) with different O2 concentrations (21%-50%) were investigated on a concentrating photothermal experiment platform. The characteristics and mechanism of different coal particle combustion were analyzed by using multiple diagnostics, including Planar Laser Induced Fluorescence (PLIF) of OH radicals and polycyclic aromatic hydrocarbons (PAHs), high-speed cinematography and FT-IR. The results showed that, with increasing O2 concentration, the ignition delay time (tign) of different ranks of coal decreased, which was associated with the increase of OH concentrations during the ignition stage. The good correlation between tign and OH concentration was observed. For the volatile combustion, the OH concentration, volatile release amount and volatile flame duration time (tvol) significantly increased with the increasing of O2 concentration at low O2 concentrations. In the higher O2 concentrations, coals with different PAHs generation amount responded differently on the increasing of O2 concentration. On one hand, for the coals with lower PAHs generation amount, the OH concentration increased with the increasing of O2 concentration, while the tvol was not sensitive to changes of the O2 concentration. On the other hand, for the coals with higher PAHs generation amount, the OH concentration decreased with the increasing of O2 concentration while the tvol increased with the increasing of O2 concentration. It can be concluded that PAHs inhibited the OH generation, and the generation characteristics of OH and PAHs affected the sustained state of volatile combustion. The higher PAHs concentration consumed higher amount of OH during the volatile combustion. Meanwhile, with the increasing of PAHs concentration, the reaction rate of H + O2+M→HO2+M in which PAHs participate was increased, inhibiting the reaction H + O2→OH+O, and the increasing of polymer soot of PAHs will reduce the flame temperature through thermal radiation, which further inhibited the OH formation.

Carrier-Free H2 O2 Self-Supplier for Amplified Synergistic Tumor Therapy.

Chemodynamic therapy (CDT) utilizes Fenton or Fenton-like reactions to convert hydrogen peroxide (H2 O2 ) into cytotoxic hydroxyl radicals (•OH) and draws extensive interest in tumor therapy. Nevertheless, high concentrations of glutathione (GSH) and insufficient endogenous H2 O2 often cause unsatisfactory therapeutic efficacy. Herein, a GSH-depleting and H2 O2 self-providing carrier-free nanomedicine that can efficiently loadindocyanine green (ICG),β-lapachone (LAP), and copper ion (Cu2+ ) (ICG-Cu2+ -LAP, LICN) to mediate synergetic photothermal and chemotherapy in enhanced chemodynamic therapy is designed. The results show that LICNs successfully enter tumors owing to the enhanced permeability and retention effect. Through the reductive intracellular environment, Cu2+ in LICN can react with intracellular GSH, alleviate the antioxidant capacity of tumor tissues, and trigger the release of drugs. When LICN is subjected to near-infrared (NIR) irradiation, enhanced photothermal effect and upregulated expression of NAD(P)H quinone oxidoreductase-1 (NQO1) are observed. Meanwhile, the released LAP not only supports chemotherapy but also catalyzes NQO1 and produces sufficient endogenous H2 O2 , thereby increasing the efficiency of Cu+ -based Fenton-like reaction. Notably, GSH depletion and H2 O2 self-sufficiency generate sufficient •OH and kill tumor cells with high specificity. Overall, the study provides an innovative strategy to self-regulate GSH and H2 O2 levels for effective anticancer therapy.

Increased fire activity under high atmospheric oxygen concentrations is compatible with the presence of forests

Throughout Earth’s history, the abundance of oxygen in our atmosphere has varied, but by how much remains debated. Previously, an upper limit for atmospheric oxygen has been bounded by assumptions made regarding the fire window: atmospheric oxygen concentrations higher than 30–40% would threaten the regeneration of forests in the present world. Here we have tested these assumptions by adapting a Dynamic Global Vegetation Model to run over high atmospheric oxygen concentrations. Our results show that whilst global tree cover is significantly reduced under high O2 concentrations, forests persist in the wettest parts of the low and high latitudes and fire is more dependent on fuel moisture than O2 levels. This implies that the effect of fire on suppressing global vegetation under high O2 may be lower than previously assumed and questions our understanding of the mechanisms involved in regulating the abundance of oxygen in our atmosphere, with moisture as a potentially important factor.

Auto‐thermal chemical looping combustion of sulphur with Fe2O3 oxygen carriers for sulphuric acid production: Thermodynamics

AbstractChemical looping is a novel fuel conversion and material separation technology. It can be applied to obtain sulphur through selective oxidation of H2S. Further, chemical looping combustion (CLC) of sulphur can generate SO2 with a high concentration without NOx formation. The high SO2 concentration is adjustable and facilitates large‐scale H2SO4 production. In this study, we examined the thermodynamics of the CLC of sulphur for H2SO4 production, which has not been reported previously. We analyzed the effects of reactor temperature and sulphur to Fe2O3 oxygen carrier (OC) ratios on sulphur allotrope transformations and on the distributions of reaction products. Moreover, the reactors were operated auto‐thermally. Based on this design, we examined the effects of fuel reactor (FR) and air reactor temperatures on the minimum recirculation of the OC, as well as the gas and solid products and heat released from the air reactor. Our results showed that the CLC of sulphur with Fe2O3 OC could occur through an auto‐thermal process. The FR in a sulphur CLC system should be operated over a temperature range of 800–950°C, with an Fe2O3 OC recirculation between 45 and 143 kg/kgS(s). Furthermore, when the FR was operated in the auto‐thermal mode, we achieved 100% SO2 conversion. The findings of this study may be applied to reactor design for large‐scale H2SO4 production through CLC of sulphur.

Effects of oxygen on the response of mitochondria to X-irradiation and reactive oxygen species-mediated fibroblast activation

Purpose In living organisms, sensitivity to radiation increases in the presence of oxygen (O2) compared with that under anoxic or hypoxic conditions. Here, we investigated whether O2 concentration affected the response of mitochondria to X-rays radiation, which is associated with tumor microenvironment formation via fibroblast activation in radiation-related tumors. Materials and methods O2 concentrations were controlled at <5% (internal environmental oxygen condition) or anoxic levels during culture of normal human diploid lung fibroblasts TIG-3 and MRC-5. Protein expression associated with the response of mitochondria to radiation was assessed using immunostaining or western blotting. Results Induction of DNA damage (marker: γ-H2A histone family member X) and mitochondrial signaling (AMP-activated protein kinase), suppression of mitochondrial metabolic activity, and generation of reactive oxygen species occurred with radiation in cells cultured under 5% and 20% O2 conditions. However, reducing O2 concentration mitigated the effects of radiation on cell growth, mitochondrial damage (parkin), induction of antioxidant responses (nuclear factor E2-related factor 2), and fibroblast activation (α-smooth muscle actin). Radiation did not affect the markers used in this study in the absence of O2. Conclusion O2 concentration affected the response of mitochondria to radiation and reactive oxygen species-mediated fibroblast activation. Higher O2 concentrations enhanced the effects of radiation on mitochondria in human fibroblasts. In vitro studies may overestimate in vivo radiation effects due to high O2 concentrations.

Chemistry of PM2.5 in haze events in two East Asian cities during winter–spring 2019

East Asian experiences frequent severe haze episodes (EPs) during winter–spring, and their causes are not fully understood. Two EPs (daily average PM2.5 > 35 μg m−3) occurred at Tianjin (TJ), China, and Daejeon (DJ), Korea, during late February (EP-1) and early March (EP-2) 2019. The mean total PM2.5 concentrations at the TJ and DJ sites during these events (82.9 and 66.2 μg m−3, respectively) were approximately three times higher than those observed during non-haze events (27.3 and 23.0 μg m−3, respectively). MODIS satellite RGB images suggested that aerosols were transported regionally from east Asian countries to the DJ site during EPs. After NO3−, the major contributors to PM2.5 during the EPs at both sites were NH4+, SO42−, and organic carbon (OC), indicating that secondary aerosols were important in severe haze formation. During the EPs, the distributions of secondary chemical species were similar at the two sites, with coefficient of divergence (COD) values of <0.2, whereas primary chemical species had dissimilar distributions with COD values of >0.2. This suggests that secondary aerosols may be impacted by regional influences, whereas primary aerosols are subject to more local influence. The average COD values in the first two days (27–28 February) relative to the remaining days (1–7 March) were <0.2 at the DJ site during EP-2, indicating no additional local production of secondary and primary species. Sulfur oxidation ratios (SOR) were lower at the TJ site than at the DJ site, while nitrogen oxidation ratios (NOR) were higher. Gradual increases observed in SOR and NOR at the TJ site early in the EPs imply significant secondary formation of SO42− and NO3−. Strong correlations between aerosol liquid-water content (ALWC) and SOR and NOR at the TJ site indicate that aqueous-phase reactions were important in the formation of SO42− and NO3−. Although high concentrations of SO42− and NO3− were observed at the DJ site, correlations between ALWC and SOR/NOR were weak with low regression gradients, implying that SO42− and NO3− may have been associated with regional transport. Low COD values, and SOR and NOR values similar to those at the beginning of EP-2, imply that additional formation of SO42− or NO3− at the DJ site is not active, with stagnant atmospheric conditions prevailing.

Mitochondria targeted and immobilized ratiometric NIR fluorescent probe for investigating SO2 phytotoxicity in plant mitochondria

Exposure to excessive SO 2 will induce severe phytotoxicity to plants. Dissecting mechanisms of SO 2 phytotoxicity is vital for preventing adverse effect of SO 2 . But unfortunately, the mechanisms of SO 2 phytotoxicity remain elusive. We speculated that interaction of SO 2 derivatives with mitochondria might be an important mechanism for SO 2 phytotoxicity. To authenticate this speculation, it is urgently need to detect SO 2 derivatives in plant mitochondria when it is suffering from SO 2 phytotoxicity. Herein, we presented a novel ratiometric NIR fluorescent probe for highly sensitive and selective detection of SO 2 derivatives in plant mitochondria. Notably, the probe not only could target into the mitochondria, but also can immobilize in the mitochondria to continue detecting SO 2 derivatives even when the mitochondrial membrane potential was collapsed by high concentration of SO 2 derivatives. Importantly, the probe has been successfully employed for monitoring high concentration of SO 2 derivatives in the plant mitochondria when the plant is suffering from SO 2 phytotoxicity. The results demonstrated that the SO 2 derivatives level in plant mitochondria is strictly associated with SO 2 phytotoxicity. Thus, the interaction of SO 2 derivatives with plant mitochondria could be considered as an important mechanism for SO 2 phytotoxicity. • The first fluorescent probe that can detect SO 2 derivatives in plant mitochondria has been rationally developed. • The probe not only targets into mitochondria, but also retains in mitochondria when membrane potential is collapsed. • The interaction of SO 2 derivatives with mitochondria was firstly proved as a key mechanism for SO 2 phytotoxicity.

Simultaneous detection of three chemical species (NO, O, O2) using a single broadband femtosecond laser

Simultaneous nitric oxide (NO) laser-induced fluorescence (LIF), atomic oxygen (O) two-photon LIF (TPLIF), and molecular oxygen (O2) LIF were demonstrated using a single broadband femtosecond (fs) laser in methane- and hydrogen-fueled flames. An amplified Ti:Sapphire laser with ∼80-fs pulse duration was used to pump an optical parametric amplifier (OPA) to generate 226.1-nm pulses having 2.3 nm (∼450 cm−1) bandwidth to excite all three species simultaneously. The specific excitation transitions are NO A-X (0,0) system, O 3p3P←←2p3P two-photon transition, and O2B3Σu−−X3Σg− Schumann-Runge system. Detailed emission characterization was performed using a 1D imaging spectrometer to identify suitable emission bands for interference-free detection of each species. A simultaneous detection system consisting of a visible and a UV camera provided the optimal detection of all three species. Imaging studies revealed high concentrations of NO, O, and O2 at the edge of the flame cone of Bunsen flames because NO and O are produced at the hot flame front. O2 LIF signal was present only at the flame front because of the strong temperature dependence of the O2 Schumann-Runge system. Direct imaging of O TPLIF enabled single-shot as well as high-fidelity shot-averaged line images in stable laminar flames. Equivalence ratio scans in the CH4/air Hencken flames showed good agreements for O and O2 with Cantera equilibrium predictions performed using GRI-Mech 3.0. Although the NO measurements deviated from the equilibrium calculations on the fuel-rich side, it agreed well with previously reported NO LIF measurements in a similar flame. This discrepancy is likely due to Prompt NO, which was not considered in the simulation. NO LIF measurements as a function of height-above-the-burner in the H2/air Hencken flames agreed well with calculated NO mole fractions using the UNICORN flame code. The present study lays the foundation for single-laser imaging of three critical flame species in NO formation pathways in combustion systems.

Resource utilization of high-concentration SO2 for sulfur production over La-Ce-Ox composite oxide catalyst.

Sulfur dioxide is one of the main causes of air pollution such as acid rain and photochemical smog, and its pollution control and resource utilization have become important research directions. La2O3 was incorporated into CeO2 to enhance the surface basicity of La-Ce-Ox catalyst and increase the concentration of chemisorbed oxygen, thereby promoting the improvement of catalytic performance of SO2 reduction by CO. Results have showed that the incorporation of La2O3 would not only increase the concentration of chemisorbed oxygen and hydroxyl on the catalyst surface, but also increase the basicity of the catalyst, thereby facilitating the adsorption of SO2 on the catalyst surface. The 12%La-Ce-Ox was the optimal catalyst, and its SO2 conversion at 350-400 ℃ reached close to 100%, and the sulfur yield at this temperature range was higher than 93%. Finally, according to the in situ infrared diffuse reflectance spectrum, it was found that the main reaction intermediates of 12%La-Ce-Ox in the catalytic reduction of SO2 were weakly adsorbed sulfate, SO32-, non-coordinating CO32-, monodentate carbonate, and CO, so the catalytic reaction followed the L-H and E-R mechanisms simultaneously.