Low Ozone Research Articles

Exceptionally Low Arctic Stratospheric Ozone in Spring 2020 as Seen in the CAMS Reanalysis

AbstractA reanalysis data set produced by the Copernicus Atmosphere Monitoring service (CAMS reanalysis, 2003 to present day) augmented by ERA5 data for the years before 2003 is used to describe the evolution of the 2020 Arctic ozone season and to compare it with years back to 1979. Ozone columns over large parts of the Arctic reached record low values in March and April 2020 because of an exceptionally strong, cold, and persistent Arctic polar vortex. Minimum ozone columns were below 250 DU for most of March and the first half of April, with the lowest values of 211 DU in the CAMS reanalysis found on 18 March. Such low values are extremely unusual for the Arctic. The previous years with similarly strong Arctic ozone depletion were 2011 and 1997 with minimum values of 232 and 217 DU, respectively. The performance of the CAMS ozone analysis is assessed by comparison with ozonesonde data and found to agree well with the independent observations. We find a clear sign of chemical ozone destruction with ozone severely depleted in a layer between 80 and 50 hPa in late March and early April when partial pressure values below 2 mPa were observed. Profiles from the limb sounders Atmospheric Chemistry Experiment‐Fourier Transform Spectrometer (ACE‐FTS) and Microwave Limb Sounder (MLS) show clear signs of chlorine activation and the presence of polar stratospheric clouds. Monthly mean ozone columns in March 2020 were up to 180 DU or 40% lower than the CAMS climatology (2003–2019) while values for 2011 and 1997 were lower by 31% and 35%, respectively.

Identification of Sea Breeze Recirculation and Its Effects on Ozone in Houston, TX, During DISCOVER‐AQ 2013

AbstractIn coastal environments, sea breeze recirculation has been found to be an important mesoscale meteorological phenomenon that causes high ozone episodes, yet the identification of this small‐scale circulation pattern remains difficult. In this study, a new method was developed to automatically identify sea breeze recirculation in Houston, TX, by applying K‐Means clustering algorithm to surface winds measurements at near‐coast sites during the DISCOVER‐AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) field campaign period from August to October 2013. The key to the clustering algorithm is seven features derived from site‐based surface winds on each day, including zonal (U) and meridional (V) winds in the morning and afternoon, 24‐hr transport direction (θ) and the recirculation factor, which is the ratio of net transport distance (L) to wind run distance (S). For comparison, the same clustering was applied to San Antonio, TX, a noncoastal city yet within the synoptic‐scale distance from Houston. Four clusters were obtained for each region, including three synoptic patterns common to both regions and one mesoscale pattern that differs by region, classified as Stagnation and Sea Breeze Cluster for San Antonio and Houston, respectively. The clustering outputs were verified by wind profiler data in Houston. By linking the wind clusters with surface and aircraft ozone measurements, we revealed a clear connection between circulation patterns and daily ozone variability showing that maximum daily average 8‐hr (MDA8) ozone levels and spatial distributions differed by cluster type (e.g., the highest ozone found in the Stagnation/Sea Breeze Cluster and the lowest ozone in the Southerly Cluster). This automatable method of sea breeze identification we developed can be potentially applied to other coastal cities because it has low data requirement and no ad hoc location‐specific adjustments.

Simultaneously promoted reactive manganese species and hydroxyl radical generation by electro-permanganate with low additive ozone

A novel water treatment process combining electrolysis, permanganate and ozone was tested in the laboratory. The combination showed synergistic effects in degrading various organic contaminants (like diclofenac, sulfamethoxazole, carbamazepine, etc.). A small amount of O3 (1 mg L−1, 60 mL min−1) significantly improved the oxidation and mineralization ability of an electro-permanganate process by generating more reactive manganese species and hydroxyl radicals. The combination required less energy consumption than comparable processes. Mechanism experiments showed that the ·OH involved was mainly generated by cathode reduction, homogeneous manganese catalysis, and heterogeneous manganese catalysis of O3 decomposition. Reactive Mn species were generated by electro-reduction, ·OH oxidation or/and O3 activation. In situ generated Mn (Ⅳ)s plays a vital role in generating ·OH and reactive Mn species. ·OH generated by O3 catalysis could transfer colloid Mn (Ⅳ)s to free Mn (Ⅴ)aq and Mn (Ⅵ) aq. And both the ·OH and RMnS played the dominant role for DCF removal. Increasing permanganate dosage, O3 concentration, the current density, Cl−, or humic acid, and decreasing the pH all enhanced the degradation of diclofenac, but the presence of PO43− or HCO3− inhibited it. Supplementing electrolysis with permanganate and O3 might be a practical, sustainable, and economical technology for treating refractory organics in natural waters.

Prediction of Northern Hemisphere Regional Sea Ice Extent and Snow Depth Using Stratospheric Ozone Information

AbstractThe forecast potential of springtime ozone on April surface temperatures at particular locations in the Northern Hemisphere has been previously reported. Evidence suggests that early springtime Arctic stratospheric ozone acts as a proxy for extreme events in the winter polar vortex. Here, using a state‐of‐the‐art chemistry‐climate model, reanalysis and observations, we extend the forecast potential of ozone on surface temperatures to aspects of the Northern Hemisphere cryosphere. Sea ice fraction and sea ice extent differences between years of March high and low Arctic stratospheric ozone extremes show excellent agreement between an ensemble of chemistry‐climate model simulations and observations, with differences occurring not just in April but extending through to the following winter season in some locations. Large snow depth differences are also obtained in regional locations in Russia and along the southeast coast of Alaska. These differences remain elevated until early summer, when snow cover diminishes. Using a conditional empirical model in a leave‐three‐out cross validation method, March total column ozone is able to accurately predict the sign of the observed sea ice extent and snow depth anomalies over 70% of the time during an ozone extreme year, especially in the region of the Bering strait and the Greenland Sea, which could be useful for shipping routes and for testing climate models.

Effects of tropospheric ozone and elevated nitrogen input on the temperate grassland forbs Leontodon hispidus and Succisa pratensis

Atmospheric ozone (O3) and nitrogen (N) pollution have increased since pre-industrial times and pose a threat to natural vegetation. The implications of these pollutants for the perennial temperate grassland species Leontodon hispidus (Rough Hawkbit) and Succisa pratensis (Devil’s-bit Scabious) are largely unknown. Both species are important for pollinators and Succisa pratensis is the host plant for the threatened marsh fritillary butterfly (Euphydryas aurinia).We examine growth and physiological responses (leaf cover, leaf litter, flowering, chlorophyll index [Leontodon hispidus and Succisa pratensis]; photosynthesis and stomatal conductance [Succisa pratensis]) using an outdoor Free Air Ozone Enrichment system. Plants were exposed to Low, Medium and High ozone treatments over three growing seasons (treatment means: 24, 40 and 57 ppb, respectively), with and without the addition of nitrogen (40 kg ha−1 yr−1) during the first year.Decreases in leaf cover (p < 0.001) and chlorophyll index (p < 0.01) were observed with increased O3 for Leontodon hispidus. The addition of N resulted in a higher chlorophyll index only at the uppermost O3 level and also led to an overall increase in litter production of 6%. However, a stronger effect of both O3 and N treatments was observed with Succisa pratensis. Litter production increased with increasing O3 (p < 0.001) and an overall rise of 31% was recorded with added N (p < 0.05). However, O3 had the biggest impact on Succisa pratensis foliage leading to more damaged leaves (p < 0.05). During summer resources were prioritised to new leaves, maintaining stomatal conductance and photosynthesis rates. However, this was not sustained during autumn and accelerated senescence occurred with higher ozone, and rates declined faster with added nitrogen (p < 0.05). Elevated O3 also reduced Succisa pratensis flowering (p < 0.01).These effects have implications for inter- and intra-specific competition, seed establishment, nutrient cycling, as well as the provision of general pollinator resources with specific issues for butterfly larvae. Results highlight the need for concerted action to reduce pre-cursor ozone emissions to go alongside habitat management efforts to protect biodiversity.

Ozone structure in Caribbean hurricanes

Using ozone data from model-assimilated satellite measurements in the eastern Caribbean 15–20N, 60–68W, cases were studied when upper tropospheric O3 values declined below 60 ppb. Secondary criteria on convection and circulation isolated two hurricanes for analysis (Irma and Maria 2017). Winds at 150 hPa (14 km) show divergence over the vortex characterized by ozone <50 ppb. Upper tropospheric O3 concentrations >100 ppb appear west of hurricanes, where sinking motions interact with vortex outflow. Past work suggests that high values are important, but here low ozone concentrations near the core are more conspicuous. The low O3 layer formed over the ocean and lifted by the hurricane circulation and convection, indicates vortex – environment interaction, vertical motion and storm intensity. Upper tropospheric O3 concentrations <50 ppb cover an area about double the radius of heavy rainfall >10 mm/h, appearing as a protective envelope around the core.

Stomatal conductance influences interannual variability and long-term changes in regional cumulative plant uptake of ozone

Ambient ozone uptake by plant stomata degrades ecosystem and crop health and alters local-to-global carbon and water cycling. Metrics for ozone plant damage are often based solely on ambient ozone concentrations, overlooking the role of variations in stomatal activity. A better metric is the cumulative stomatal uptake of ozone (CUO), which indicates the amount of ozone entering the leaf over time available to cause physiological damage. Here we apply the NOAA GFDL global earth system model to assess the importance of capturing interannual variations and 21st century changes in surface ozone versus stomatal conductance for regional mean CUO using 20-year time-slice simulations at the 2010s and 2090s for a high-warming climate and emissions scenario. The GFDL model includes chemistry-climate interactions and couples atmospheric and land components through not only carbon, water, and energy exchanges, but also reactive trace gases—in particular, ozone dry deposition simulated by the land influences surface ozone concentrations. Our 20-year time slice simulations hold anthropogenic precursor emissions, well-mixed greenhouse gases, and land use distributions fixed at either 2010 or 2090 values. We find that CUO responds much more strongly to interannual and daily variability in stomatal conductance than in ozone. On the other hand, long-term changes in ozone explain 44%–90% of the annual CUO change in regions with decreases, largely driven by the impact of 21st century anthropogenic NOx emission trends on summer surface ozone. In some regions, increases in stomatal conductance from the 2010s to 2090s counteract the influence of lower ozone on CUO. We also find that summertime stomatal closure under high carbon dioxide levels can offset the impacts of higher springtime leaf area (e.g. earlier leaf out) and associated stomatal conductance on CUO. Our findings underscore the importance of considering plant physiology in assessing ozone vegetation damage, particularly in quantifying year-to-year changes.

Assessment of Vertical Ozone Profiles from INSAT-3D Sounder Over The Central Himalaya

Vertical distribution of ozone has been obtained for the first time using INSAT-3D for the period 2013-2017 over the central Himalaya and validated utilizing balloon-borne observations from a high-altitude site in Nainital (29.4°N, 79.5°E, 1793 m amsl). The INSAT-3D retrieved ozone profiles captured ozone gradient and ozone peak altitude successfully, despite only one IR channel for ozone. This demonstrates the capability of the INSAT-3D Sounder in capturing the observed features, with a smaller bias in the stratosphere and somewhat larger bias in the troposphere. Total ozone column from INSAT-3D showed maximum difference of 8% with ozonesonde-derived total ozone column. Larger ozone bias in the lower troposphere could be attributed to lower reliability of regression coefficient and INSAT-3D channel constraints itself, whereas high variability near the tropopause is possibly due to low ozone, poor temperature retrieval near the tropo-pause and stratosphere–troposphere transport process in the Himalayan region.

A new method to correct the electrochemical concentration cell (ECC) ozonesonde time response and its implications for “background current” and pump efficiency

Abstract. The electrochemical concentration cell (ECC) ozonesonde has been the main instrument for in situ profiling of ozone worldwide; yet, some details of its operation, which contribute to the ozone uncertainty budget, are not well understood. Here, we investigate the time response of the chemical reactions inside the ECC and how corrections can be used to remove some systematic biases. The analysis is based on the understanding that two reaction pathways involving ozone occur inside the ECC that generate electrical currents on two very different timescales. The main fast-reaction pathway with a time constant of about 20 s is due the conversion of iodide to molecular iodine and the generation of two free electrons per ozone molecule. A secondary slow-reaction pathway involving the buffer generates an excess current of about 2 %–10 % with a time constant of about 25 min. This excess current can be interpreted as what has conventionally been considered the “background current”. This contribution can be calculated and removed from the measured current instead of the background current. Here we provide an algorithm to calculate and remove the contribution of the slow-reaction pathway and to correct for the time lag of the fast-reaction pathway. This processing algorithm has been applied to ozonesonde profiles at Costa Rica and during the Central Equatorial Pacific Experiment (CEPEX) as well as to laboratory experiments evaluating the performance of ECC ozonesondes. At Costa Rica, where a 1 % KI, 1/10th buffer solution is used, there is no change in the derived total ozone column; however, in the upper troposphere and lower stratosphere, average reported ozone concentrations increase by up to 7 % and above 30 km decrease by up to 7 %. During CEPEX, where a 1 % KI, full-buffer solution was used, ozone concentrations are increased mostly in the upper troposphere, with no change near the top of the profile. In the laboratory measurements, the processing algorithms have been applied to measurements using the majority of current sensing solutions and using only the stronger pump efficiency correction reported by Johnson et al. (2002). This improves the accuracy of the ECC sonde ozone profiles, especially for low ozone concentrations or large ozone gradients and removes systematic biases relative to the reference instruments. In the surface layer, operational procedures prior to launch, in particular the use of filters, influence how typical gradients above the surface are detected. The correction algorithm may report gradients that are steeper than originally reported, but their uncertainty is strongly influenced by the prelaunch procedures.

Ozone Activates the Nrf2 Pathway and Improves Preservation of Explanted Adipose Tissue In Vitro.

In clinical practice, administration of low ozone (O3) dosages is a complementary therapy for many diseases, due to the capability of O3 to elicit an antioxidant response through the Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2)-dependent pathway. Nrf2 is also involved in the adipogenic differentiation of mesenchymal stem cells, and low O3 concentrations have been shown to stimulate lipid accumulation in human adipose-derived adult stem cells in vitro. Thus, O3 treatment is a promising procedure to improve the survival of explanted adipose tissue, whose reabsorption after fat grafting is a major problem in regenerative medicine. In this context, we carried out a pilot study to explore the potential of mild O3 treatment in preserving explanted murine adipose tissue in vitro. Scanning and transmission electron microscopy, Western blot, real-time polymerase chain reaction and nuclear magnetic resonance spectroscopy were used. Exposure to low O3 concentrations down in the degradation of the explanted adipose tissue and induced a concomitant increase in the protein abundance of Nrf2 and in the expression of its target gene Hmox1. These findings provide a promising background for further studies aimed at the clinical application of O3 as an adjuvant treatment to improve fat engraftment.

Comparison of AOPs at pilot scale: Energy costs for micro-pollutants oxidation, disinfection by-products formation and pathogens inactivation

This work evaluated different advanced oxidation processes (AOPs) operated at pilot-scale as tertiary treatment of municipal wastewater in terms of energy efficiency, disinfection by-products formation and pathogens inactivation. Investigated AOPs included UV/H2O2, UV/Cl2, O3, O3/UV, H2O2/O3/UV, Cl2/O3/UV. AOPs were operated using various ozone doses (1.5–9 mg L−1), and UV fluences (191–981 mJ cm−2). Electrical energy costs necessary for the oxidation of contaminants of emerging concern (CEC) (i.e., carbamazepine, fluoxetine, gemfibrozil, primidone, sulfamethoxazole, trimethoprim) were calculated using the electrical energy per order (EEO) parameter. Ozonation resulted by far the most energy efficient process, whereas UV/H2O2 and UV/Cl2 showed the highest energy costs. Energy costs for AOPs based on the combination of UV and ozone were in the order O3/UV ≈ Cl2/O3/UV > H2O2/O3/UV, and they were significantly lower than energy costs of UV/H2O2 and UV/Cl2 processes. Cl2/O3/UV increased bromate formation, O3/UV and O3 had same levels of bromate formation, whereas H2O2/O3/UV did not form bromate. In addition, UV photolysis resulted an effective treatment for NDMA mitigation even in combination with ozone and chlorine in AOP technologies. Ozonation (doses of 1.5–6 mg L−1) was the least effective process to inactivate somatic coliphages, total coliform, escherichia coli, and enterococci. UV irradiation was able to completely inactivate somatic coliphages, total coliform, escherichia coli at low fluence (191 mJ cm−2), whereas enterococci were UV resistant. AOPs that utilized UV irradiation were the most effective processes for wastewater disinfection resulting in a complete inactivation of selected indicator organisms by low ozone dose (1.5 mg L−1) and UV fluence (191–465 mJ cm−2).

Impact of air pollution on reproductive health in Afghanistan

The presence of one or more contaminants (harmful substances) in the atmosphere in a specific quantity, for such duration, which is injurious or tends to be injurious to human health, welfare, animal, or plant life is called air pollution. Air pollutants are of commonly two types, which are produced through natural pollutants; they include dust (crustal material), sea salts, biological material, pollen, spores or plant-animal debris, volcanic eruptions (which release a very large quantity of gases and particles into the atmosphere), periodic forest fires, thunderbolts, wind erosion, and low concentration ozone. Other types of pollutants are produced in human-made (technical) environments, like mobile sources (cars, trucks, airplanes, marine engines, etc.) or point sources (factories, electric power plants, etc.). The high level of air pollution is a big problem all over the world and also in Afghanistan, and all residents of this country are severely exposed to this ever-worsening situation. Air pollution and other extraordinary environmental problems are factors that threaten the livelihood of millions of Afghans, as a study report shows that 60% of Kabul’s residents are exposed to increased levels of harmful toxins, such as, nitrous oxides and sulfur dioxide. According to the State of Global Air report, more than 26,000 afghan deaths could be attributed to pollution in 2007, but United Nations Assistance Mission in Afghanistan (UNAMA) documented nearly 3,500 civilian casualties from the war for the same time period, so air pollution is killing more Afghans than war because they burn anything possible to get energy and heat they need. Result of air sampling in major urban centers of Afghanistan shows high amounts of particulate matters (PM), benzo-a-pyrene, and polycyclic aromatic hydrocarbons (PAHs) originating from vehicle exhaust emission. The highest concentrations were founded in Kabul and Mazar-e-Sharif (13.6 ng/m3 ). The absence of industrial parks, nonconformity of environmental protection rules, especially by industries, urbanization, degradation of fertile lands, deforestation, seasonal winds, drought, internal migration, and low knowledge about pesticides and herbicides use, are factors that boost the severity of air pollution in Afghanistan. In Afghanistan, women are more exposed to high levels of indoor air pollution because they spend more time at home due to their cultural rules; also, women have responsibility for household activities, working in the kitchen to prepare food, they are exposed to poor sanitation and contaminated water supplies, they clean and sweep rooms and yards with inadequate protection equipment, which are significant sources of dust, so they are often exposed to high levels of smoke and dust for long periods.

Pesticides removal from industrial wastewater by a membrane bioreactor and post-treatment with either activated carbon, reverse osmosis or ozonation

The purpose of this study was to evaluate the potential of a pilot membrane bioreactor (MBR) to treat effluents from a fruit processing factory, for the removal of pesticides, on its own, and combined with other treatment technologies. The stability of the MBR was monitored by the parameters chemical oxygen demand (COD), pH, total suspended solids (TSS) and permeability. The addition of pesticides was established to generate concentrations of 20 μg.L−1 for 2,4-D, carbendazim and diuron, and 1.5 μg.L−1 for atrazine in the bioreactor. The removal of pesticides by the MBR was evaluated by two experiments with variations in HDT (20 and 25 h) and operation of post-treatments with either activated carbon (AC), reverse osmosis (RO) or ozonation (O3). The MBR demonstrated robustness and stability in maintaining the quality of the permeate even under high variations of COD and biomass content. However, the removal of the pesticides was only partial. Among the hybrid systems, comprising a combination of the MBR and a post-treatment, the MBR/AC and MBR/RO presented excellent results, proving to be efficient for pesticides removal. The MBR/O3 system, however, did not perform as well as the others, which can be explained by the low ozone doses applied.

Estudo numérico e observacional de um evento de diminuição da coluna total de ozônio de origem tropical no Sul do Brasil

A depletion event of 11% of the total ozone column over South Brazil was analyzed from observational data and numerical simulations. The meteorological fields resulting from the simulation did not show the presence of subtropical or polar jets over the study region. The real and simulated soundings showed the dryness at high and low tropospheric levels, pointing a stratospheric intrusion. The total ozone column values from ERA-5 reanalyses showed the maintenance of a region with low total ozone values in tropical latitudes and its advance over the study region, before and during the depletion event. The isentropic retro-trajectories of air parcels at different levels, obtained with the Hybrid Single Lagrangian Integrated Trajectory Model (HYSPLIT), confirmed the zonal transport from the tropical region over Southern Brazil. A combination of a cyclonic circulation at the 850 K stratospheric isentropic level and an intense anticyclonic circulation at the 440 K tropospheric level, over the depletion region, was identified as responsible for the tropopause lift and horizontal transport of ozone-rich air out of the column.

Features of Lignin Destruction in Wood under the Action of Ozone

Samples of pine wood ozonated with different contents of water are studied via UV diffuse reflectance spectroscopy. It is shown that polyaromatic and stilbene structures, guaiacyl derivatives, and carbonyl- and carboxyl-containing aromatic structures of lignin are destroyed during ozonation of pine wood. The destruction of aromatic structures proceeds efficiently in wood with a moisture content of more than 60–65% in the 2–3 mmol/g range of ozone consumption. When the moisture content is below 40%, ozone treatment of pine wood at low ozone consumption allows us to obtain different modifications of oxygen-containing aromatic and polyaromatic structures on surfaces of lignocellulosic material (LCM). IR absorption spectra of dioxane lignin obtained from the initial and ozonated wood samples confirm the different direction of lignin transformations, depending on the content of moisture in the wood.

Comparison of phenol removal with ozonation in jet loop reactor and bubble column

This study aimed to remove phenol with ozonation in a jet loop reactor (JLR) and a bubble column (BC). In the first stage of the study, the mass transfer properties of JLR were determined and superiority over BC reactors were shown, and in the second stage, these reactors were used in phenol removal studies. At the same conditions, the volumetric mass transfer coefficient of JLR was 0.540 min-1, while this value was determined as 0.246 min-1 in the BC reactor. In phenol removal, the effects of initial phenol concentration, ozone dosage and pH on phenol and chemical oxygen demand (COD) removal were determined for both JLR and BC. While the pseudo-first rate constant for phenol removal in JLR at 221 mg/min ozone dosage was 0.1756 min-1, this value was only calculated as 0.1157 min-1 in the BC reactor. As a result, it has been shown that JLRs can achieve higher ozone gas transfer with lower energy consumption and perform more effective phenol and COD removal than BC reactors, especially at low pH and high ozone dosages.

Impacts of Stratospheric Ozone Extremes on Arctic High Cloud

AbstractStratospheric ozone depletion in the Antarctic is well known to cause changes in Southern Hemisphere tropospheric climate; however, because of its smaller magnitude in the Arctic, the effects of stratospheric ozone depletion on Northern Hemisphere tropospheric climate are not as obvious or well understood. Recent research using both global climate models and observational data has determined that the impact of ozone depletion on ozone extremes can affect interannual variability in tropospheric circulation in the Northern Hemisphere in spring. To further this work, we use a coupled chemistry–climate model to examine the difference in high cloud between years with anomalously low and high Arctic stratospheric ozone concentrations. We find that low ozone extremes during the late twentieth century, when ozone-depleting substances (ODS) emissions are higher, are related to a decrease in upper tropospheric stability and an increase in high cloud fraction, which may contribute to enhanced Arctic surface warming in spring through a positive longwave cloud radiative effect. A better understanding of how Arctic climate is affected by ODS emissions, ozone depletion, and ozone extremes will lead to improved predictions of Arctic climate and its associated feedbacks with atmospheric fields as ozone levels recover.

Ozone elimination over oxygen-deficient MnOx based catalysts: Effect of different transition metal dopants

Ozone pollutant can be decomposed by catalysts at room temperature. In this study, pristine β-MnO2 and those doped with Co, Cu, and Ce were synthesized by a redox precipitation method. Their catalytic performance on ozone decomposition was further investigated at room temperature under both dry and humid (RH = 35%) gas conditions. Our results showed that Co and Cu doped MnO2 catalysts, especially the Co doped one, could enhance the room-temperature decomposition activity and improve the stability of catalyst. But Ce doped MnO2 catalyst exhibited lower ozone decomposition activity even than the pristine MnO2. To reveal their intrinsic promotion and inhibition mechanisms, those catalysts were characterized with XRD, N2 physisorption, TEM, SEM, XPS, Raman, H2-TPR, and O2-TPD. The introduction of dopants in MnO2 catalysts resulted in higher surface specific area and lower crystallinity than their pristine counterpart. Those dopants also helped tailor the number and type of the oxygen vacancies on the surface of catalysts. The appearance of isolated CeO2 in Ce doped MnO2, though have more oxygen vacancies, hindered the desorption of oxygen intermediates owing to their different nature of oxygen vacancies when compared to those Co or Cu doped catalysts.

The Status of Thermodynamic Data and Models for CF3I and its Mixtures ⋆.

There is a renewed interest in the use of the refrigerant CF3I for refrigeration and air-conditioning applications, driven by its low global warming potential (similar to that of CO2), low (but nonzero) ozone depletion potential, and its ability to suppress flammability. In this paper the existing thermodynamic data for this fluid are summarized. Furthermore, as CF3I has been proposed as a component in mixtures with other refrigerants, the emphasis of this paper is on the survey of existing mixture data and an assessment of the suitability of existing thermodynamic modeling approaches and estimation schemes to model the properties of these mixtures. For mixtures where sufficient data exist, interaction parameters have been optimized.

Impact of convection on the upper-tropospheric composition (water vapor and ozone) over a subtropical site (Réunion island; 21.1° S, 55.5° E) in the Indian Ocean

Abstract. Observations of ozonesonde measurements of the NDACC/SHADOZ (Network for the Detection of Atmospheric Composition Change and the Southern Hemisphere ADditional OZonesondes) program and humidity profiles from the daily Météo-France radiosondes at Réunion island (21.1∘ S, 55.5∘ E) from November 2013 to April 2016 were analyzed to identify the origin of wet upper-tropospheric air masses with low ozone mixing ratio observed above the island, located in the southwest Indian Ocean (SWIO). A seasonal variability in hydration events in the upper troposphere was found and linked to the convective activity within the SWIO basin. In the upper troposphere, ozone mixing ratios were lower (mean of 57 ppbv) in humid air masses (RH &gt; 50 %) compared to the background mean ozone mixing ratio (73.8 ppbv). A convective signature was identified in the ozone profile dataset by studying the probability of occurrence of different ozone thresholds. It was found that ozone mixing ratios lower than 45 to 50 ppbv had a local maximum of occurrence between 10 and 13 km in altitude, indicative of the mean level of convective outflow. Combining FLEXPART Lagrangian back trajectories with METEOSAT-7 infrared brightness temperature products, we established the origin of convective influence on the upper troposphere above Réunion island. It has been found that the upper troposphere above Réunion island is impacted by convective outflows in austral summer. Most of the time, deep convection is not observed in the direct vicinity of the island, but it is observed more than 1000 km away from the island, in the tropics, either from tropical storms or the Intertropical Convection Zone (ITCZ). In November and December, the air masses above Réunion island originate, on average, from central Africa and the Mozambique Channel. During January and February the source region is the northeast of Mozambique and Madagascar. Those results improve our understanding of the impact of the ITCZ and tropical cyclones on the hydration of the upper troposphere in the subtropics in the SWIO.