Atmospheric Chemistry Research Articles

A Comparative Theoretical Study of the Atmospheric Chemistry of Dimethyl and Bis(trifluoromethyl) Sulfides.

Dimethyl sulfide (CH3SCH3) is the largest natural source of atmospheric sulfur. Bis(trifluoromethyl) sulfides (CF3SCF3) are one of the perfluorinated thioethers with great interest as the new refrigerant fluid and dielectric replacement gas for the sake of environmental concern. In order to clarify the effect of fluorine substitution, degradation mechanisms and kinetics for the reactions of CH3SCH3 and CF3SCF3 with OH radicals in the atmosphere have been calculated comprehensively in a comparative manner using various high-level ab initio methods. It is revealed that the CH3SCH3 + OH reaction is predominated by addition/elimination and hydrogen abstraction mechanisms. A stable van der Waals complex exists via the long-range S···O interaction with a binding energy 9.1 kcal/mol, which decomposes straightforwardly by the S-C bond rupture. The collisional deactivation of the complex competes with two distinct hydrogen-abstraction paths. Theoretical rate coefficients are in good agreement with the available experimental data. In contrast, CF3SCF3 reacts with OH through the shallow wells (0.7 kcal/mol) to form the less stable tricoordinated S (III) covalent intermediates before the endothermic S-C bond fission. The room-temperature rate coefficient for the CF3SCF3 + OH reaction is 4 orders of magnitude lower than that for the CH3SCH3 + OH reaction. It is demonstrated that the atmospheric loss of CF3SCF3 has been retarded considerably with the lifetime around 300 years. The radiative efficiency is 0.463 W m2- ppb-1 and the global warming potential of CF3SCF3 is predicted to be approximately 14,000, indicative of a new super greenhouse gas. The present theoretical results will stimulate experimental studies of the dramatic impact on the reactivity of thioethers due to fluorination.

MORPHOLOGY AND PRESERVATION OF GAOJIASHANIA, AN ENIGMATIC TUBULAR FOSSIL FROM THE UPPER EDIACARAN DUNFEE MEMBER, DEEP SPRING FORMATION, NEVADA, USA

Abstract The upper Ediacaran stratigraphic record hosts fossil assemblages of Earth’s earliest communities of complex, macroscopic, multicellular life. Tubular fossils are a common and diverse, though frequently undercharacterized, component of many of these assemblages. Gaojiashania cyclus is an enigmatic tubular fossil and candidate index fossil found in upper Ediacaran strata globally and is best known from the Gaojiashan Lagerstätte of South China. Here we describe a recently discovered assemblage of Gaojiashania fossils from the Ediacaran Dunfee Member of the Deep Spring Formation of Nevada, USA. Both body and trace fossil affinities have been proposed for Gaojiashania; we present morphological and biostratinomic evidence for a body fossil affinity for the Dunfee specimens. Additionally, previous studies have highlighted that Ediacaran tubular fossils are characterized by a wide range of preservational modes, including association with pyrite, apatite, or clay minerals and preservation as carbonaceous compressions. Petrographic, SEM, and EDS data indicate that the Dunfee Gaojiashania specimens are preserved as ‘Ediacara-style’ external, internal and composite molds, in siltstone and sandstone with a clay mineral-rich matrix of both aluminosilicates and non-aluminous Mg- and Fe-rich silicate minerals that we interpret as authigenic clays. Authigenic clay-mediated fossilization of unmineralized tissues, including moldic preservation in heterolithic siliciclastic strata, as indicated by the Dunfee Gaojiashania, may be linked to the prevalence of both silica-rich and ferruginous seawater conditions prior to both the radiation of silica-biomineralizing organisms and the rise of ocean and atmospheric oxygen to modern levels. In this light, clay authigenesis may have played a critical role in facilitating multiple modes of Ediacaran and Cambrian exceptional fossilization, thus shaping the stratigraphic distribution of a range of Ediacara macrofossil taxa.

Modeling of polycyclic aromatic hydrocarbons (PAHs) from global to regional scales: model development (IAP-AACM_PAH v1.0) and investigation of health risks in 2013 and 2018 in China

Abstract. Polycyclic aromatic hydrocarbons (PAHs) significantly impact human health due to their persistence, toxicity, and potential carcinogenicity. Their global distribution and regional changes caused by emission changes, especially over areas in developing countries, remain to be understood along with their health impacts. This study implemented a PAH module in the global–regional nested Atmospheric Aerosol and Chemistry Model of the Institute of Atmospheric Physics (IAP-AACM) to investigate the global distribution of PAHs and the change in their health risks from 2013 to 2018 in China. An evaluation against observations showed that the model could capture well the spatial distribution and seasonal variation in Benzo[a]pyrene (BaP), the typical indicator species of PAHs. On a global scale, the annual mean concentrations are the highest in China followed by Europe and India, with high values exceeding the target values of 1 ng m−3 over some areas. Compared with 2013, the concentration of BaP in China decreased in 2018 due to emission reductions, whereas it increased in India and southern Africa. However, the decline is much smaller than for PM2.5 during the same period. The concentration of BaP decreased by 8.5 % in Beijing–Tianjin–Hebei (BTH) and 9.4 % in the Yangtze River Delta (YRD). It even increased over areas in the Sichuan Basin due to changes in meteorological conditions. The total incremental lifetime cancer risk (ILCR) posed by BaP only showed a slight decrease in 2018, and the population in east China still faced significant potential health risks. The results indicate that strict additional control measures should be taken to reduce the pollution and health risks of PAHs effectively. The study also highlights the importance of considering changes in meteorological conditions when evaluating emission changes from concentration monitoring.

Retrievals on NIRCam Transmission and Emission Spectra of HD 189733b with PLATON 6, a GPU Code for the JWST Era

We present the 2.4–5.0 μm JWST/NIRCam emission spectrum of HD 189733b, along with an independent re-reduction of the previously published transmission spectrum at the same wavelengths. We use an upgraded version of PLanetary Atmospheric Tool for Observer Noobs (PLATON) to retrieve atmospheric parameters from both geometries. In transit, we obtain [M/H] = 0.53−0.12+0.13 and C/O = 0.41−0.12+0.13 , assuming a power-law haze and equilibrium chemistry with methane depletion. In eclipse, we obtain [M/H] = 0.68−0.11+0.15 and C/O = 0.43−0.05+0.06 , assuming a clear atmosphere and equilibrium chemistry without methane depletion. These results are consistent with each other, and with a rerun of our previously published joint retrieval of Hubble Space Telescope and Spitzer transmission and emission spectra. Accounting for methane depletion decreases the C/O ratio by 0.14/0.04 (transmission/emission), but changing the limb cloud parameterization does not affect the C/O ratio by more than 0.06. We detect H2O, CO2, CO, and H2S in both the NIRCam transmission and emission spectra, find that methane is depleted on the terminator, and confirm with VULCAN that photochemistry is a potential cause of this depletion. We also find tentative (1.8σ) evidence of a dayside thermal inversion at millibar pressures. Finally, we take this opportunity to introduce a new version of PLATON. PLATON 6 supports GPU computation, speeding up the code up to 10×. It also supports free retrievals using both volume mixing ratio and centered-log ratio priors; emission from planetary surfaces of different compositions; updated opacities at improved resolution; and Pareto smoothed importance sampling leave-one-out cross-validation.

Convective shutdown in the atmospheres of lava worlds

Abstract Atmospheric energy transport is central to the cooling of primordial magma oceans. Theoretical studies of atmospheres on lava planets have assumed that convection is the only process involved in setting the atmospheric temperature structure. This significantly influences the ability for a magma ocean to cool. It has been suggested that convective stability in these atmospheres could preclude permanent magma oceans. We develop a new 1D radiative-convective model in order to investigate when the atmospheres overlying magma oceans are convectively stable. Using a coupled interior-atmosphere framework, we simulate the early evolution of two terrestrial-mass exoplanets: TRAPPIST-1 c and HD 63433 d. Our simulations suggest that the atmosphere of HD 63433 d exhibits deep isothermal layers which are convectively stable. However, it is able to maintain a permanent magma ocean and an atmosphere depleted in H2O. It is possible to maintain permanent magma oceans underneath atmospheres without convection. Absorption features of CO2 and SO2 within synthetic emission spectra are associated with mantle redox state, meaning that future observations of HD 63433 d may provide constraints on the geochemical properties of a magma ocean analogous with the early Earth. Simulations of TRAPPIST-1 c indicate that it is expected to have solidified within 100 Myr outgassing a thick atmosphere in the process. Cool isothermal stratospheres generated by low molecular-weight atmospheres can mimic the emission of an atmosphere-less body. Future work should consider how atmospheric escape and chemistry modulates the lifetime of magma oceans, and the role of tidal heating in sustaining atmospheric convection.

Ambient air pollution undermines chemosensory sensitivity – a global perspective

This study offers insights into the complex relationship between chemical species constituting air pollution and chemosensory function. We examined the relationship between chemical species known to contribute to air pollution and assault human health and chemosensory sensitivity. Chemosensory sensitivity data was retrieved from a large-scale study involving 711 urban-dwelling participants inhabiting 10 different regions of the globe. Their olfactory threshold towards phenyl ethyl alcohol (PEA) and olfactory/trigeminal threshold towards Eucalyptol was measured in a multicentre study. We matched the individual chemosensory data with the levels of PM2.5, PM10, O3, NO2, SO2, CO at the location of testing sites, on the exact date of the test, using EMAC (ECHAM5/MESSy for Atmospheric Chemistry) model. Our findings indicate that air pollution negatively affects olfactory function and has cumulative negative effects with aging. The reported patterns are seasonal and increase during Autumn and Winter, and interact with medical conditions related to poorer olfactory function. We extend the current knowledge by demonstrating that olfactory/trigeminal perception is also disrupted by toxic air, albeit in a slightly different manner. The analyzed models promote a more complex perspective on the relationship between air composition and chemosensory sensitivity, but delineate problems related to the interdependence of the levels of chemical species constituting air pollution and using them together to predict chemosensory sensitivity. Conclusions point to the need to investigate the problem of air pollution and chemosensory health from a global perspective, as air quality partly accounts for the differences in chemosensory perception in different regions of the world.

Mineralogy, geochemistry and genesis of low-grade manganese ores of Anujurhi area, Eastern Ghats, India

The Anujurhi manganese ores occur in the high-grade gneisses of the Precambrian Eastern Ghats Supergroup in Odisha, India. They are characterized by conformable lenses containing minerals such as cryptomelane, romanechite, pyrolusite, todorokite, and pyrophanite, along with other opaque minerals like graphite, goethite and ilmenite. The gangue minerals associated with these ores include quartz, feldspar, garnet, kaolinite, apatite, sillimanite, zircon, biotite, alunite, and gorceixite. The primary elements present in the ore, Si, Mn, Fe, and Al, average at 16.20 %, 15.06 %, 11.94 %, and 6.6 % respectively. Additionally, trace amounts of P, K, Ti, Mg, Ca, and Na were detected. The average Fe/Mn ratio of 0.81 and the Si versus Al plot of the Anujurhi manganese ores suggest a hydrogenous-hydrothermal mixed source for the ferromanganese sediments. The characteristics of the manganese ore bands, absence of carbonate facies of ore, and geochemical association of Mn-Ba together with Na/Mg ratios and CaO-Na2O-MgO ternary plot of the manganese ores strongly indicate that the mineralization is a metamorphosed shallow marine-lacustrine deposit. Following deposition and diagenesis, the manganese minerals underwent at least two phases of Ultra High Temperature (UHT) and granulite facies metamorphism along with the host rocks. Tectonic uplift, erosion, extended exposure to atmospheric oxygen and percolation of meteoric water led to the supergene alteration and remobilization of the primary manganese minerals in a colloidal state, followed by epigenetic replacement along the structural weak planes of the granulite facies rocks, resulting in the formation of the current deposits. This is evidenced by the observed secondary replacement and colloidal textures in the Mn oxides.

Delayed Impact of Biomass Burning in the Indochinese Peninsula on the Bay of Bengal Monsoon

Abstract The Indochinese Peninsula experiences a dry season with extensive biomass burning peaking from March to April. As the monsoon arrives, rainfall significantly removes aerosols through deposition, ending the emission season. However, the biomass burning aerosols exert an influence on the atmospheric circulation prior to the monsoon onset. This study employed statistical methods and a regional atmosphere–chemistry model [WRF Model coupled with chemistry (WRF-Chem)] to investigate the delayed impact of biomass burning from the Indochinese Peninsula on the monsoon onset. The results indicate that the cold sea surface temperature anomaly caused by the aerosols during the emission season can be stored in the ocean and inhibit convective activities over the adjacent sea regions in the postemission season, suppressing the southwestward cross-equatorial flow over the southern Bay of Bengal. This suppression delays the westward extension and northward shift of the upper-level South Asian high pressure system, along with its divergence and subsidence effects, thereby postponing the breakdown and retreat of the subtropical high-pressure belt. Simultaneously, the cold sea temperature also suppresses the development of a warm pool in the southeastern Bay of Bengal, which is associated with the generation of a monsoon onset vortex. Consequently, the onset of the Bay of Bengal monsoon is delayed. Due to the decreasing delayed effects of aerosols over time and the counteractive warming from the accelerated abnormal anticyclonic circulation in the upper-level Bay of Bengal, which results in accelerated disappearance of the cold signal in sea surface, the delayed influence of aerosols diminishes gradually after the onset of the Bay of Bengal monsoon until it disappears. Significance Statement This study explores the correlation between spring biomass burning in the Indochinese Peninsula and the onset of the Bay of Bengal and South China Sea monsoons. The research reveals that biomass burning during the emission season might postpone the initiation of the Bay of Bengal monsoon, while it has minimal influence on the South China Sea monsoon. By employing sensitivity experiments using models, the study elucidates the underlying mechanisms responsible for these observed effects.

Ion Effects on Terahertz Spectra of Microsolvated Clusters.

Water clusters containing Na+ and Cl- ions play a key role in the atmospheric chemistry of sea salt aerosols. While Na+ is clearly buried deep inside, Cl- appears to be a chameleon since evidence for both surface-localized and interior solvation states are reported. Thus, disclosing the preferred location of Cl- within clusters remains challenging. Here, we investigate whether THz spectroscopy, a powerful tool for directly probing hydrogen bonds in water, provides insights into the location of Cl- ions in water clusters. We performed ab initio molecular dynamics simulations on water clusters containing a single Cl- ion and up to 64 water molecules to compute the THz spectra with reference to Na+ and bulk. The THz spectrum of the 64-water Cl- cluster closely agrees with that of the bulk solution. Surprisingly, this match is not caused by bulk-like solvation of Cl- as suggested by phenomenological line shape analyses. Instead, the similarity stems from Cl- being mostly located at the cluster surface, thus leaving the water-water interactions largely unperturbed.

Ozone source attribution in polluted European areas during summer 2017 as simulated with MECO(n)

Abstract. Emissions of land transport and anthropogenic non-traffic emissions (e.g. industry, households and power generation) are significant sources of nitrogen oxides, carbon monoxide and volatile organic compounds (VOCs). These emissions are important precursors of tropospheric ozone and affect air quality. The contribution of the emission sectors to ozone cannot be measured directly but can only be calculated using sophisticated atmospheric chemistry models. For this study we apply the MECO(n) model system (MESSy-fied ECHAM and COSMO models nested n times) equipped with a source attribution method to investigate the contribution of various sources to ground-level ozone in Europe. Compared to previous source apportionment studies for Europe, for the first time we apply a combined NOx–VOC tagging implemented in an online nested global–regional chemistry–climate model to achieve a finer resolution over central Europe (12 km) but concurrently incorporating the effect of long-range transport. We distinguish 10 different source sectors and 4 geographical source regions, analysing especially the contribution from the land transport sector. Our analysis focuses on large ozone events during summer in four different regions, two major polluted regions (Po Valley and Benelux) and two more remote regions (Iberian Peninsula and Ireland). The analysis concentrates on results for summer 2017, during which measurement campaign EMeRGe took place. Measurement data from this campaign are used for model evaluation. Our analysis shows that European land transport emissions contribute largely (42 % and 44 %, respectively) to ground-level NOy mixing ratios over Benelux and the Po Valley. Due to the overall lower ozone production efficiency over Benelux compared to the Po Valley, however, the contributions to ground-level ozone are larger in the Po Valley (12 %) compared to Benelux (8 %). In line with previous publications using different source apportionment methods, our results underline the large importance of long-range transport of ozone, especially from North America (Benelux, Ireland), but also from Africa (Iberian Peninsula), and provide additional information about the sectoral contribution not available before. Our analysis shows that the contributions of European emissions from land transport and anthropogenic non-traffic sectors strongly increase with increasing values of MDA8 (daily maximum 8 h average) ozone over the Po Valley and in the Benelux region. Accordingly, these two sectors drive large MDA8 values in these regions. Inter-comparisons of results for 2018 and with a coarser model resolution (50 instead of 12 km) show that these results are robust with respect to inter-annual variability and model resolution. Comparing our results with results from other source attribution methods we find that the contributions to ozone from individual sectors, which have large NOx but rather low VOC emissions, are estimated to be lower, if their emissions of NOx and VOCs are regarded concurrently.

Impacts of O2/(O2+Ar) Flow Ratio on the Properties of Li‐Doped NiO Thin Films Fabricated by Pressure‐Gradient Radiofrequency Magnetron Sputtering

Herein, Li‐doped NiO thin films are deposited on glass substrates using pressure‐gradient radiofrequency magnetron sputtering, with Ar and O2 as sputtering gases. Following film fabrication, their crystal structures, optical features, and electrical properties are investigated as functions of O2 flow rate to the total flow rate (O2/(O2 + Ar)) of 10 sccm. The deposited films are also annealed at 600 °C for 1 h in an oxygen atmosphere. Notably, the resistivity of the as‐deposited films decreases significantly by three orders of magnitude from 106 to 0.0232 Ω cm when the sputtering gas is changed from pure Ar to pure O2. However, the transmittance decreases with increasing oxygen flow rate. Investigations on the temperature dependence of conductivity reveal hole conduction in the range of ≈320–420 K owing to small polaron hopping.

Electron-Beam-Evaporated Nickel Oxide Thin Films for Application as a Hole Transport Layer in Photovoltaics

We present the growth of nickel oxide (NiO) thin films as a hole transport material in photovoltaic devices using the e-beam evaporation technique. The metal oxide layers were reactively deposited at a substrate temperature of 200 °C using an electron beam evaporator under an oxygen atmosphere. The oxide films reactively grown through electron-beam evaporation were optimized for carrier transport layers. Optical and structural characterizations were performed using ultraviolet–visible (UV–Vis) spectrometry, X-ray diffraction, contact angle measurements, scanning electron microscopy, and Hall effect measurements. The study of these films confirmed that the NiO layer is a suitable candidate for use as a hole transport layer based on Hall effect measurements. A morphological study using field-emission scanning electron microscopy confirmed the growth of compact, uniform, and defect-free metal oxide layers. Contact angle measurements revealed that the films possessed semi-hydrophilic properties, contributing to improved stability by repelling water from their surfaces. The stoichiometry of the films was influenced by the oxygen pressure during deposition, which affected both their morphological and optical features. The NiO films exhibited a transmittance exceeding 80% in the visible spectrum. These findings highlight the potential applications of such nickel oxide films as hole transport material layers.

Halogen Radical-Enabled Dearomatization of N-Arylpropiolamides via Photoinduced Sequential Halogenation/Spirocyclization/Oxidation Process.

Here we report a strategy that eliminates the need for photocatalysts and external additives, which provides an operable and mild method for halogen radical-enabled dearomatization of N-arylpropiolamides under an oxygen atmosphere at room temperature. The method is applicable to a wide range of substrates, extending beyond the limited scope of p-methoxyl N-phenylpropynamides. Furthermore, several functional synthetic intermediates and anticancer bioactive molecules were successfully derived from 3-halogenated azaspiro[4.5]trienones.

Dual Role of Aerosols on Reactive Bromine Recycling in Extrapolar Marine and Continental Regions

AbstractReactive bromine species play important roles in atmospheric chemistry and influence the abundance of climate‐ and air quality‐relevant trace gases. While extensive studies have focused on bromine chemistry in polar regions, the bromine species in extrapolar regions, particularly regarding pollution‐related bromine recycling, have received less attention. In this study, we examine the factors influencing the bromine recycling at a clean marine site of the North Atlantic (Cape Verde, CVAO), a semipolluted coastal site of the South China Sea (Hok Tsui, HT), and a polluted continental site of North China (Wangdu, WD), using an observation‐based model combined with updated halogen chemistry. Our results indicate that aerosol‐related multiphase processes significantly affect bromine recycling in these extrapolar sites. Nitrate photodissociation efficiently recycled bromide into the gas phase in regions characterized by strong aerosol acidity (HT) or high aerosol concentrations (WD). Concurrently, bromine species are lost from the gas phase toward aerosol surfaces, with this process being more effective at higher liquid water content (WD > HT > CVAO). In semipolluted and polluted sites, the aerosol‐related processes resulted in elevated bromine levels in the daytime compared to nighttime, leading to larger effects of bromine species on ozone than previously thought. Our study suggests the need for a better understanding of the complex effects of aerosols on reactive halogen chemistry.

Viscosity of aqueous ammonium nitrate–organic particles: equilibrium partitioning may be a reasonable assumption for most tropospheric conditions

Abstract. The viscosity of aerosol particles determines the critical mixing time of gas–particle partitioning of volatile compounds in the atmosphere. The partitioning of the semi-volatile ammonium nitrate (NH4NO3) might alter the viscosity of highly viscous secondary organic aerosol particles during their lifetimes. In contrast to the viscosity of organic particles, data on the viscosity of internally mixed inorganic–organic aerosol particles are scarce. We determined the viscosity of an aqueous ternary inorganic–organic system consisting of NH4NO3 and a proxy compound for a highly viscous organic, sucrose. Three techniques were applied to cover the atmospherically relevant humidity range: viscometry, fluorescence recovery after photobleaching, and the poke-flow technique. We show that the viscosity of NH4NO3–sucrose–H2O with an organic to inorganic dry mass ratio of 4:1 is 4 orders of magnitude lower than the viscosity of the aqueous sucrose under low-humidity conditions (30 % relative humidity (RH), 293 K). By comparing viscosity predictions of mixing rules with those of the Aerosol Inorganic–Organic Mixtures Functional groups Activity Coefficients Viscosity (AIOMFAC-VISC) model, we found that a mixing rule based on mole fractions performs similarly when data from corresponding binary aqueous subsystems are available. Applying this mixing rule, we estimated the characteristic internal mixing time of aerosol particles, indicating significantly faster mixing for inorganic–organic mixtures compared to electrolyte-free particles, especially at lower RH. Hence, the assumption in global atmospheric chemistry models of quasi-instantaneous equilibrium gas–particle partitioning is reasonable for internally mixed single-phase particles containing dissolved electrolytes (but not necessarily for phase-separated particles), for most conditions in the planetary boundary layer. Further data are needed to see whether this assumption holds for the entire troposphere at midlatitudes and at RH > 35 %.

Effect of annealing on flexoelectricity in hafnium oxide (HfO2)

Flexoelectricity is universal in all dielectrics, effective at high temperatures, and a promising transduction technique for nanoelectromechanical systems (NEMS). However, as flexoelectricity is still in its early stages, many aspects require further investigation. Understanding how flexoelectricity depends on material parameters like crystallographic phase and how temperature might affect it is important for selecting and optimizing the right material for technological applications. This work studies the influence of high-temperature annealing (and the consequent crystallization) in the flexoelectricity of hafnium oxide (HfO2), a material with significant technological relevance. We measure the flexoelectric coefficient for amorphous (not annealed) and annealed (slightly crystalline) phases of HfO2, with samples annealed in nitrogen or oxygen atmospheres. Our results indicate that the amorphous phase of HfO2 exhibits the highest flexoelectric coefficient (105 ± 10 pC/m), while annealed samples show a significant decrease, with the lowest value in nitrogen-annealed samples (26 ± 4 pC/m). Samples annealed in an oxygen atmosphere improve flexoelectric properties (54 ± 6 pC/m) compared to those annealed in nitrogen. Using cross-sectional imaging, x-ray diffraction, resonance frequency characterization, and relative permittivity measurements, we find that annealing promotes crystallization into the tetragonal phase and increases internal stress within the HfO2 layer, while most other parameters remain constant. We attribute the differences in flexoelectricity from the annealed samples to the quantity of oxygen vacancies in hafnium oxide. These oxygen vacancies in hafnium oxide seem to negatively affect the flexoelectric coefficient. This finding can be applied to optimize materials to enhance their flexoelectric properties.

Opinion: Challenges and needs of tropospheric chemical mechanism development

Abstract. Chemical mechanisms form the core of atmospheric models to describe degradation pathways of pollutants and ultimately inform air quality and climate policymakers and other stakeholders. The accuracy of chemical mechanisms relies on the quality of their input data, which originate from experimental (laboratory, field, chamber) and theoretical (quantum chemistry, theoretical kinetics, machine learning) studies. The development of robust mechanisms requires rigorous and transparent procedures for data collection, mechanism construction and evaluation and the creation of reduced or operationally defined mechanisms. Developments in analytical techniques have led to a large number of identified chemical species in the atmospheric multiphase system that have proved invaluable for our understanding of atmospheric chemistry. At the same time, advances in software and machine learning tools have enabled automated mechanism generation. We discuss strategies for mechanism development, applying empirical or mechanistic approaches. We show the general workflows, how either approach can lead to robust mechanisms and that the two approaches complement each other, resulting in reliable predictions. Current challenges are discussed related to global change, including shifts in emission scenarios that result in new chemical regimes (e.g., low-NO scenarios, wildfires, mega- and gigacities) and that require the development of new or expanded gas- and aqueous-phase mechanisms. In addition, new mechanisms should be developed to also target oxidation capacity and aerosol chemistry impacting climate, human and ecosystem health.

Effect of Annealing Temperatures on Structural and Electrochemical Properties of Li[Ni0.5Co0.25Mn0.25]O2 Film Cathodes

Thin films of Li[Ni0.5Co0.25Mn0.25]O2 were prepared by RF-sputtering technique post-annealed the deposited films at various temperatures in a controlled oxygen atmosphere. The annealing temperature played an important role in the crystallinity of the films. The films post-annealed at optimized temperature displayed an X-ray diffraction peak at 18.29°, which can be ascribed to the Braggs reflection (003) of hexagonal Li[Ni0.5Co0.25Mn0.25]O2. The lattice parameters of the optimized films were a = 2.85 Å and c = 14.45 Å with c/a ratio equal to 5.070. The electrochemical activity of the post-annealed films was methodically investigated. The discharge capacity offered by the films is 40 μAh/cm2μm at 300 °C however this was further improved to 57.5 μAh/cm2.μm by post-annealing at 700 °C. Due to structural integrity of Li[Ni0.5Co0.25Mn0.25]O2 film may be used as cathode material for energy storage devices.

Development of the CMA-ChemRA: China Regional Weakly Coupled Chemical-Weather Reanalysis System with product since 2007.

The CMA-ChemRA (China Regional Weakly Coupled Chemical-Weather Reanalysis System) was developped using China's first-generation global atmospheric reanalysis product (CRA-40) as initial fields and boundary conditions, coupled with the WRF-Chem atmospheric chemical model and the WRFDA/3DVar assimilation system. By constructing a joint background error covariance matrix, CMA-ChemRA achieves weak coupling between atmospheric chemistry and meteorological variables, enabling simultaneous assimilation of diverse data sources, including hourly observations from ground stations, wind profilers, upper-air soundings, aircraft reports, and atmospheric composition measurements. To extend the dataset to periods before 2013 when China lacked PM2.5 observations, the system incorporates a reconstructed PM2.5 dataset derived by AI from visibility inversion alongside various emission inventories. The CMA-ChemRA system produces a reanalysis product from 2007 to the present, with a spatial resolution of 15km and an hourly temporal resolution. It includes three-dimensional isobaric and near-surface layers for 6 key elements PM2.5, PM10, O3, SO2, NO2, and CO, as well as meteorological variables. This product is updated in near real-time, with a 50-min lag for forecast updates. Evaluation of the system shows substantial improvements in accuracy, with significant reductions in root mean square error (RMSE) for the six elements in the near-surface atmospheric layer post-assimilation. The model's depiction of ground-level PM2.5 concentrations aligns well with independent observational data across five urban regions, showing a narrow RMSE range of 15.5 to 32.8μg/m3. Additionally, CMA-ChemRA demonstrates strong performance in capturing the evolution of dust storms and pollution events, particularly in accurately modeling PM2.5 concentrations during severe pollution episodes. Our innovative approach in constructing a joint background error covariance matrix and the resulting high-resolution, real-time updating CMA-ChemRA product. This represents significant advancement in the field of atmospheric and chemical weather reanalysis. The product serves as an crucial tool for environmental monitoring and forecasting in China.

From Space to Health: The Impact of Earth Observation Research on the Smart4COV19 Telemedicine project

Abstract This study investigates the potential of Earth observation research in improving air quality management and supporting telemedicine initiatives in response to the COVID-19 pandemic. Utilizing ground stations in Sofia and Burgas, we collected hourly measurements of NO2, CO, PM10, and PM2.5. Satellite data from TROPOMI-S5p and ground-based air quality observations were integrated to assess the spatial distribution of surface particulate matter concentrations. Our results demonstrate the feasibility of leveraging satellite-derived atmospheric chemistry data to enhance air pollution modeling and urban-scale air quality management. Furthermore, the technology developed for Burgas has the potential for expansion to other Bulgarian cities and replication in different urban centers. Overall, this research highlights the importance of Earth observation research in addressing critical environmental and public health challenges. Telemedicine via smartphones can help manage these risks by offering assistance to patients with mild symptoms, thereby minimizing their exposure to COVID-19 patients. The study also presents the findings of models used to convert TROPOMI – S5p aerosol data into PM concentrations in Burgas, Bulgaria.