Excess Ozone Research Articles

Algae Removal and Release of Algal Organic Matter During Ozonation of Synechococcus sp.

Pre-ozonation can enhance the removal of algae in source water during cyanobacterial blooms; however, little is known about the influence of the co-existing allochthonous natural organic matter (NOM) on algal removal and algal organic matter (AOM) behavior during ozonation. This study aims to elucidate in the presence and absence of allochthonous NOM and the effects of varying ozone doses on Synechococcus sp. cell removal, membrane integrity, and dissolved organic matter (DOM) release and removal. The results indicate that ozone effectively disrupted algal cell membranes, reducing algal density; however, the presence of allochthonous NOM delayed cell rupture by competing for ozone due to aromatic humic-like substances. Pterin-like and protein-like fluorescent compounds were released upon cell disruption. Due to that, excess ozone led to the oxidation of the released pterin-like compounds, with characteristic fluorescence changes correlating to ozone dosage; these changes are potential to be used as an indicator to determine the optimized ozone dosage, avoiding more adverse release of intracellular AOM to form disinfection byproducts.

A practical clinical device for evaluating changes to the skin's sebum from ozone.

It is known that tropospheric ozone (O3) generated from pollutants reacting with UV forms lipid peroxidation products and induces oxidative stress to the skin. With the ever-increasing consumer awareness of the effects pollution has on skin, more testing methods will be needed to evaluate cosmetic ingredients. Recently, others have shown how antioxidants are able to reduce the effects from ozone on skin through in vitro, ex vivo and clinical studies where human subjects place their arms into large stationary chambers. To develop a small, easy to use ozone exposure module (OEM) that can be used on various sites of the body and to validate this device for use in testing the ability of topical products to mitigate the effects of ozone exposure on the skin. We have produced an OEM which can generate levels of ozone in excess of 1000 ppb and can be set to achieve the equivalent exposure to what is found in polluted environmental conditions. After exposure we used D-squame discs to remove the sebum and analytically quantitate squalene depletion. Squalene, which is very sensitive to ROS, easily oxidizes into early metabolite squalene monohydroperoxide (SQOOH) with ozone exposure. We were able to show decreases in squalene levels after exposure and protective effects from a topical formulation. This generator will be a useful tool for researchers to easily create a small and safe exposure from ozone for clinical testing.

Development of a broad range of two-colour ozone indicator

The antiviral and antibacterial properties of ozone gas have been utilised for air and on-site disinfection. However, excess ozone gas exposure is toxic to humans, necessitating the monitoring of exposure levels. While this has been achieved using ozone indicators, determining exposure levels at intermediate time points during exposure remains challenging owing to the current ones being capable of measuring exposure only at endpoints. Shifts in the endpoint are also difficult as the coverage ranges of the indicators are dependent on a single colour dye. The indicator that covers a wide range is desirable to treat various pathogenic microorganisms. The aim of this study was to develop a two-colour ozone indicator with a broad coverage range that does not compromise the performance of the individual dyes. Exposure levels were indicated by visible changes in colour density and phase, aiding the measurement of exposure at the endpoints and during the exposure period, thereby maintaining better safety profiles for exposed individuals. Additionally, a theoretical approach for the development of two-colour indicators has been described.

Large Ozone Hole in 2023 and the Hunga Tonga Volcanic Eruption

AbstractPolar stratospheric chemistry is highly sensitive to changes in water vapor content and temperature. We identified an unusual behavior of water vapor and temperature in the southern polar winter stratosphere in 2023. The relationships between the Hunga-Tonga eruption injection of water vapor (detected in the tropics) and its transport to SH high latitudes, temperature changes and ozone anomalies at southern high latitudes are discussed, as well as the roles of zonal wind and the meridional flux of zonal mean zonal momentum. These parameters exhibit a consistent pattern in anomalous year 2023. In the winter of 2023 in the Southern Hemisphere, an unexpected decrease in ozone levels and the emergence of an excessive ozone hole were observed. This event marked one of the deepest Antarctic ozone holes with the largest area since 2011. This appears to be associated with the Hunga Tonga eruption anomalous water vapor injection. This study highlights importance of water vapor for evolution of the Antarctic stratosphere.

Efficiency of Ozone Quenching Agents at Different Temperature, pH, and Hydrodynamic Conditions

ABSTRACT Quenching of excess aqueous ozone (O3) residual is needed to avoid off-gassing and oxidative damage to downstream components. Eight quenching agents (QAs), calcium thiosulfate (Ca-Thio), sodium bisulfite (Na-Bi), hydrogen peroxide (H2O2), sodium thiosulfate (Na-Thio), sodium metabisulfite (Na-Metabi), potassium metabisulfite (K-Metabi), sodium sulfite (Na-S), and ascorbic acid (AscAcid) were tested at varying pHs (7.5, 7.9, and 8.5) and temperatures (4°C, 15°C, and 23°C). Temperature had significant effects on initial quenching (≤30 s), with less occurring at 4°C than 23°C; but with extended contact time this trend reversed. Quenching efficiency was not substantially affected by pH. Ca-Thio and Na-Thio were inefficient but quick, had lower mass requirements, and minimal handling concerns. Na-Metabi, Na-Bi, and Na-S were quick and efficient, but K-Metabi was the only QA that quenched (26–31%) less O3 than stoichiometry at all conditions. These sulfite-based QAs had more handling concerns and greater mass requirements. H2O2 was slower than other QAs but 2–9× quicker than predicted by rate coefficients and efficient when given longer contact time (≤5 min). H2O2 had some handling concerns but the lowest mass requirements (assuming 5 min contact time) and creates desirable AOP conditions. AscAcid consistently quenched (22–113%) more O3 than the stoichiometric ratio but had higher mass requirements, except in colder temperatures. Hydrodynamics, QA-diffuser design, and supply chain were also important considerations.

A Study on a Health Impact Assessment and Healthcare Cost Calculation of Beijing–Tianjin–Hebei Residents under PM2.5 and O3 Pollution

Excessive fine particulate matter (PM2.5) and ozone (O3) are invisible killers affecting our wellbeing and safety, which cause great harm to people’s health, cause serious healthcare and economic losses, and affect the sustainable development of the social economy. The effective evaluation of the impact of pollutants on the human body, the associated costs, and the reduction of regional compound air pollution is an important research direction. Taking Beijing–Tianjin–Hebei (BTH) as the research area, this study constructs a comprehensive model for measuring the healthcare costs of PM2.5 and O3 using the Environmental Benefits Mapping and Analysis Program (BenMAP) as its basis. First, this study establishes a health impact assessment model and calculates the number of people affected by PM2.5 and O3 exposure using the health impact function in the BTH region. Then, the willingness to pay (WTP) and cost of illness (COI) methods are used to estimate the healthcare costs inflicted by the two pollutants upon residents from 2018 to 2021. The calculation results show that the total healthcare costs caused by PM2.5 and O3 pollution in BTH accounted for 1%, 0.7%, 0.5%, and 0.3% of the regional GDP in 2018, 2019, 2020, and 2021, respectively. Based on the research results, to further reduce these high healthcare costs, we propose policy suggestions for PM2.5 and O3 control in the BTH region.

Synergistic oxidation of toluene through bimetal/cordierite monolithic catalysts with ozone

Toluene treatment has received extensive attention, and ozone synergistic catalytic oxidation was thought to be a potential method to degrade VOCs (violate organic compounds) due to its low reaction temperature and high catalytic efficiency. A series of bimetal/Cord monolithic catalysts were prepared by impregnation with cordierite, including MnxCu5−x/Cord, MnxCo5−x/Cord and CuxCo5−x/Cord (x = 1, 2, 3, 4). Analysis of textural properties, structures and morphology characteristics on the prepared catalysts were conducted to evaluate their performance on toluene conversion. Effects of active component ratio, ozone addition and space velocity on the catalytic oxidation of toluene were investigated. Results showed that MnxCo5−x/Cord was the best among the three bimetal catalysts, and toluene conversion and mineralization rates reached 100 and 96% under the condition of Mn2Co3/Cord with 3.0 g/m3 O3 at the space velocity of 12,000 h−1. Ozone addition in the catalytic oxidation of toluene by MnxCo5−x/Cord could efficiently avoid the 40% reduction of the specific surface area of catalysts, because it could lower the optimal temperature from 300 to 100 °C. (Co/Mn)(Co/Mn)2O4 diffraction peaks in XRD spectra indicated all the four MnxCo1−x/Cord catalysts had a spinel structure, and diffraction peak intensity of spinel reached the largest at the ratio of Mn:Co = 2:3. Toluene conversion rate increased with rising ozone concentration because intermediate products generated by toluene degradation might react with excess ozone to generate free radicals like ·OH, which would improve the toluene mineralization rate of Mn2Co3/Cord catalyst. This study would provide a theoretical support for its industrial application.

Breathing on the job: investigating predictors of air quality protective actions and information seeking among outdoor workers

ABSTRACT Background Air quality issues, exacerbated by wildfire smoke and excessive ozone that is worsened by climate change, pose significant health risks to outdoor workers, who are often overlooked in regulatory protection and communication efforts. This study examined how outdoor worker demographics, risk perceptions, and efficacy beliefs predict air quality protective actions and information seeking. Additionally, it investigates the sources of information that this population relies on for understanding air quality. Method A survey was conducted with 256 outdoor workers in Colorado, a state regularly affected by wildfire smoke and ozone. Measures included demographics, perceived risk, efficacy beliefs, air quality actions, and information seeking behavior. Results Both perceived risk and efficacy beliefs influenced health-protective actions during poor air quality events. Interestingly, efficacy beliefs were found to be a more reliable predictor of air quality information seeking than perceived risk. The top sources of air quality information among outdoor workers were local news media, The Weather Channel, mobile apps, state public health authorities, and the National Weather Service. Conclusions These findings enhance our understanding of how perceived risk and efficacy beliefs promote health-protective behaviors among outdoor workers. They lay the groundwork for future research and initiatives to improve air quality communication and promote health-protective actions for this population group. Promoting the efficacy of health-protective actions and seeking information are important components of air quality communication.

Enhancing ozone nowcasting over East Asia using a data-to-data translation approach with observations from a geostationary environment monitoring spectrometer

The degradation of air quality caused by excessive anthropogenic ozone (O3) concentrations negatively affects ecosystems and the atmosphere. To monitor this issue, the Geostationary Environment Monitoring Spectrometer (GEMS) aboard the Geostationary Korea Multi-Purpose Satellite (GK)-2B provides ozone products over Asia-centered circular regions based on the ozone algorithm derived from representative polar-orbit atmospheric environmental satellites. In this study, we developed a few-hour GEMS O3 nowcasting model using data-to-data (D2D) translation with a conditional generative adversarial network. This model is based on hourly GEMS O3 time-series products and can be used to predict ozone concentrations. The D2D model underwent training and testing employing paired input and output datasets of GEMS O3, with data collected from March 22, 2020, to June 21, 2020, and from March 22, 2021, to June 18, 2021, respectively. The resulting D2D ozone nowcasting model was used to determine ozone concentrations in time zones where GEMS O3 products were unavailable. Test results of the D2D model demonstrated excellent statistical scores, including a bias of 2.162 Dobson Units (DU, where 1 DU corresponds to 2.687 × 1016 molecules/cm2), root-mean-square error (RMSE) of 5.606 DU, a correlation coefficient (CC) of 0.994 for 1-h prediction, a bias of 1.421 DU, RMSE of 5.903 DU, and CC of 0.992 for 2-h prediction, and a bias of 1.169 DU, RMSE of 6.797 DU, and CC of 0.988 for 3-h prediction. Despite the dataset pairing and number limitations, the D2D prediction model accurately forecasted GEMS O3 within 3 h in East Asia.

Kinetic constants and transformation products of ornidazole during ozonation

Ornidazole (ONZ), a nitroimidazole antibiotic detected in water bodies, may negatively impact the aquatic ecosystem. Its reaction kinetics during ozonation which is a feasible and applicable technology to control the contamination of emerging contaminants, however, has not been reported in literature. In this study, we measured the apparent second-order kinetic constant of ONZ with ozone molecules via the excessive ozone method and the competing method which led to an average value of 103.8 ± 2.7 M−1 s−1 at pH 7. The apparent second-order kinetic constant of ONZ with HO• was calculated to be 4.65 × 109 M−1 s−1 with the concept of Rct measured via para-chlorobenzoic acid as a probe. The transformation products (TPs) of ONZ during ozonation at pH 3 and pH 11 were separately analyzed with HPLC-MS/MS and some unique products were found at pH 11, reflecting the influence of HO•. The toxicity of individual TPs was predicted with the tool of T.E.S.T. It was found that 62% of 21 identified TPs could be more toxic than ONZ in terms of at least one acute toxicity endpoint, including chlorinated amines and N-oxides. The analysis with a respirometer further revealed that the toxicity of mixing TPs generated at HO• rich conditions was slightly lower than O3 dominated conditions. In general, this study provides the basic kinetic data for designing ozonation processes to eliminate ONZ and the important reference for understanding the toxicity evolution of ONZ during ozonation.

Hydroxymethylbutenyl diphosphate accumulation reveals MEP pathway regulation for high CO2-induced suppression of isoprene emission

Isoprene is emitted by some plants and is the most abundant biogenic hydrocarbon entering the atmosphere. Multiple studies have elucidated protective roles of isoprene against several environmental stresses, including high temperature, excessive ozone, and herbivory attack. However, isoprene emission adversely affects atmospheric chemistry by contributing to ozone production and aerosol formation. Thus, understanding the regulation of isoprene emission in response to varying environmental conditions, for example, elevated CO2, is critical to comprehend how plants will respond to climate change. Isoprene emission decreases with increasing CO2 concentration; however, the underlying mechanism of this response is currently unknown. We demonstrated that high-CO2-mediated suppression of isoprene emission is independent of photosynthesis and light intensity, but it is reduced with increasing temperature. Furthermore, we measured methylerythritol 4-phosphate (MEP) pathway metabolites in poplar leaves harvested at ambient and high CO2 to identify why isoprene emission is reduced under high CO2. We found that hydroxymethylbutenyl diphosphate (HMBDP) was increased and dimethylallyl diphosphate (DMADP) decreased at high CO2. This implies that high CO2 impeded the conversion of HMBDP to DMADP, possibly through the inhibition of HMBDP reductase activity, resulting in reduced isoprene emission. We further demonstrated that although this phenomenon appears similar to abscisic acid (ABA)-dependent stomatal regulation, it is unrelated as ABA treatment did not alter the effect of elevated CO2 on the suppression of isoprene emission. Thus, this study provides a comprehensive understanding of the regulation of the MEP pathway and isoprene emission in the face of increasing CO2.

Tuning the properties of oxygen vacancy around Cu-Mn mixed oxides on dealumination Y zeolite by P-doping to achieve ultra-efficient catalytic ozonation of toluene with low ozone consumption

As a promising technology, ozone catalytic oxidation can effectively eliminate VOCs at low temperature. However, the excessive ozone consumption brings serious economic problems for industrial applications. Herein, Cu-Mn mixed oxides were supported on the dealumination Y zeolite, and the electronic metal-support interaction between the support and metal nanoparticles was enhanced through P-doping. Satisfyingly, the optimized catalyst P2-CuMn/DY achieved over 90% conversion of toluene even at a very harsh catalytic condition (30 °C, GHSV=240,000 h−1). Moreover, this high toluene conversion accompanying with lower ozone consumption. Compared to CuMn/DY, the ozone/toluene consumption ratio in P2-CuMn/DY decreased from ∼ 10:1 to ∼ 8.7:1. With the help of multiple various characterizations and DFT calculations, it can be found that the existence of pyrophosphate led more charge to accumulate on the surrounding metal oxides, improving the activity of oxygen vacancies. The change in the properties of oxygen vacancies enhanced the accumulation of O* species on the catalyst, improving the utilization of ozone in the catalytic reaction. This work provides a more economical strategy and guidance to design highly effective catalysts for industrial-scale VOCs eliminations.

Comprehensive computational study on reaction mechanism of N-Nitroso dimethyl amine formation from substituted hydrazine derivatives during ozonation

N- Nitrosodimethyl amine, the simplest member of the N-Nitrosamine family, is a carcinogenic and mutagenic agent that has gained considerable research interest owing to its toxic nature. Ozonation of industrially important hydrazines, such as unsymmetrical dimethylhydrazine (UDMH) or monomethylhydrazine (MMH), has been associated with NDMA formation and accumulation in the environment. UDMH/MMH - ozonation also leads to several other transformation products such as acetaldehyde dimethyl hydrazine (ADMH), tetramethyl tetra azene (TMT), diazomethane, methyl diazene, etc, which can be either precursors or competitors for NDMA formation. However, the relevant chemistry detailing the formation of these transformation products from UDMH/MMH -ozone reaction and their subsequent conversion to NDMA is not well understood. In this work, we explored the formation mechanism of ADMH and TMT from UDMH-ozonation and their further oxidation to NDMA using the second-order Moller Plesset perturbation theory employing the 6-311G(d) basis set. We have also investigated how MMH selectively forms methyl diazene and diazomethane under normal conditions and NDMA in the presence of excess ozone. Our calculations indicate that the reactions proceed via an initial H abstraction from the hydrazine –NH2 group, followed by the oxidation of the generated N-radical species. The formation of ADMH from the UDMH-ozone reaction involves an acetaldehyde intermediate, which then reacts with a second UDMH molecule to generate ADMH. The preferable attack of ozone molecule on N=C bond of ADMH generates DMAN intermediate, which subsequently undergoes oxidation to form NDMA. Unlike other transformation products, TMT formation occurs via the dimerization of DMAN. 1Though there exists an N=N bond in the TMT, which are preferable attacking sites for ozone, experimental studies show the lower yields of NDMA formation, which corroborates with the high activation barrier required for the process (42 kcal/mol). Overall, our calculated results agree well with the experimental observations and rate constants. Computational calculations bring new insights into the electronic nature and kinetics of the elementary reactions of this pathway, enabled by computed energies of structures that are not possible to access experimentally.

Estimation of Stratospheric Intrusions During Indian Cyclones

AbstractDeep convection associated with tropical cyclones leads to stratosphere‐troposphere exchange (STE), which affects the upper‐tropospheric ozone concentrations in the vicinity of the cyclones. This study estimates the ozone enhancements over India due to the North Indian Ocean (NIO) cyclones‐driven STE. Indicators such as stratospheric fraction and potential vorticity calculated using the reanalysis data sets suggest that roughly 70% of the cyclones show anomalously high stratospheric intrusions. Aircraft observations over different locations across India also show elevated ozone concentrations in the mid‐to‐upper troposphere on cyclone days. Further, ozone and stratospheric ozone tracer concentrations from Goddard Earth Observing System‐Chemistry simulations and the Copernicus Atmosphere Monitoring Service reanalysis data sets show up to 40 ppb of excess upper tropospheric ozone over India, of which stratospheric ozone accounts for roughly 60%. Stratospheric intrusion due to the Bay of Bengal and the Arabian Sea cyclones affected the upper tropospheric ozone amounts over North and South India, respectively. The stratospheric ozone was observed to propagate downwards into the troposphere, often reaching ∼600 hPa and, in some cases, even the surface.

High-resolution modeling for criteria air pollutants and the associated air quality index in a metropolitan city

The Air Quality Index (AQI), which jointly accounts for levels of criteria air pollutants relative to their guidelines, is largely reported at the city level. Little is known about the spatial patterns of the AQI in terms of the magnitude, temporal variability, and predominant air pollutant contributions at the hyperlocal scale within a city. To fill this research gap, we developed spatiotemporal models for each criteria air pollutant based on an advanced geostatistical framework and estimated daily AQI levels at 100-meter resolution in a metropolitan city in 2019. The model prediction ability (cross-validation, CV, Coefficient of determination, R2, and root mean square error, RMSE) ranged from 0.43 and 1.86 µg/m3 for sulfur dioxide (SO2) to 0.92 and 6.25 µg/m3 for fine particulate matter (PM2.5) across the six air pollutants, leading to good performance in the subsequent AQI estimations (CV R2 = 0.86, RMSE = 10.05). The AQI varies substantially over space at a fine scale and differs from the distributions of individual air pollutants. The unhealthy air quality (AQI > 100 over 75 days) spatial pattern was dominated by excessive ground-level ozone exposure in a large area. Our research provides a useful tool for accurately estimating AQI spatiotemporal variations for population health studies.

Role of meteorology-driven regional transport on O3 pollution over the Chengdu Plain, southwestern China

Owing to the complex mesoscale meteorological dynamics, deep basin topography and pollutants emissions, the Chengdu Plain (CDP) situated at west border of the Sichuan Basin (SCB) have suffered excessive ozone (O3) pollution in the warm season. However, the meteorology-driven mechanism and associated dominant processes underlying the elevated O3 levels are not well elucidated due to limited ambient measurements. Here, we adopted trace gases data measured by basin-wide network in combination with a high-resolution chemical transport model for characterizing a regional continuous O3 episode occurred from 10 to 18 August 2019. The extensive monitoring network shapes a much-detailed evolution map of O3 concentrations which depicts that O3 hotspots extend from metropolitan areas to suburban areas across the CDP. It is found that both advection of O3-rich air masses in the residual layer (RL) and regional transport of O3 and its precursors under prevailing winds exert profound influences on the elevation of ambient O3 across the CDP. As the convective boundary layer is destroyed after sunrise, vertical mixing effects cause the entrainment of O3-rich air masses in RL to the surface, affecting the redistribution of surface O3 concentration. In addition, process analysis (PA) and integrated source apportionment method (ISAM) results of the CMAQ model indicated that vertical transport and gas-phase chemistry were the main sources of O3 during the day, while dry deposition and horizontal advection were the main sinks of surface O3. O3 transport by boundary condition (BCO) was the largest contributor to all urban O3 concentrations in the CDP. Our findings highlight the regional transport mechanism of O3 in SCB under complex topographic conditions and point out the physical and chemical causes and sources of typical summer O3 pollution episodes in the SCB.

Increasing the efficiency of ozone technology in air purification HVAC systems

The global problem of air pollution is exacerbated by large-scale pandemics and the catastrophic consequences of the war in Ukraine. To solve the problems of air purification, a technological scheme and equipment for plasma-chemical air treatment with a module for combined catalytic and thermal decomposition of excess ozone are proposed. Approbation of the scheme with the combined method of ozone destruction on oxide-cement catalysts showed an increase in ozone conversion by 10 - 15%. At the same time, the energy consumption for the implementation of the combined method of ozone destruction using heat pump recovery is 7-10 times less compared to the direct method of air heating.

Influence of ozone treatment on wheat (Triticumaestivum) germination during bulk storage

The currentexperiment was conductedto understandgaseous ozone exposure time and cycle effect on wheat seed germination during storage. The bulk storage of wheat grain hasa major issue of insects and pests which is controlled by gaseous ozone treatment in closed storage system. Ozone is the acceptable and economically viable technique for treating grains during storage for its residue-free and environment-friendly nature. In this research article, the ozone gas treatment givento the wheat grain during bulk storage and evaluated its influence on seed germination.A pilot-scale ozone disinfestation system for wheat grains was developed. The two-factorial experimental design on the influence of the parameters of the technological process of ozone treatment on the germination qualities of wheat seeds was carried out. Wheat grains were treated by gaseous ozone with various time durations (0 min, 30 min, 60 min, 90 min and 120 min) and at various frequency cycles (7 days, 14 days, 21 days). The experiment has recorded observation on the effect of ozone treatment time and the ozone frequency cycle on the germination percentage of wheat grain.The data demonstrated that ozone used in bulk storage enhances seed germination percentage. On the other hand, excess ozone can also cause some negative effects on germination. This study provided new insights into how stored wheat grain responds to ozone treatment and highlighted the impact of treatment time durations and frequency cycle for seed germination.

Ultraviolet disinfection of water in recirculating aquaculture system: a case study at sturgeon caviar fish farm

In this report, we present a practical example of ultraviolet (UV) water disinfection in an aquaculture facility for sturgeon caviar production. Among the methods of water disinfection in recirculating aquaculture systems, the technical approaches using ozonation or ultraviolet radiation in combination with other methods are the most effective. However, improper use of ozonation can result in excessive ozone concentrations that can cause serious harm to fish and be harmful to the environment and personnel. Therefore, we describe an example of a reagent-free ultraviolet water disinfection system. Preliminary results show that filtration followed by ultraviolet irradiation inactivates microorganisms in fish tank water. Total microbial count, total coliform bacteria, and E. coli (CFU/m3) did not exceed the permissible values. The described UV system provides an irradiance of 180 W/m2. For a pool with a water volume of 300 m3, bacteriological purity of the water was achieved with 480 W of UV-light.

Drivers of 2013–2020 ozone trends in the Sichuan Basin, China: Impacts of meteorology and precursor emission changes

The Sichuan Basin (SCB) of China is known for excessive ozone (O3) pollution owing to high anthropogenic emissions combined with terrain-induced poor ventilation and weak wind fields against the surrounding mountains. While O3 pollution has emerged as a prominent concern in southwestern China yet variations in O3 levels during 2013–2020 are still unclear and the dominant factor in explaining the long-term O3 trend throughout the SCB remains elusive due to uncertainties in emission inventory and variability associated with meteorological conditions. Here, we use extensive basin-wide ambient measurements to examine the spatial pattern and trend of O3 and leverage OMI and TROPOMI satellites in conjunction with MEIC emission inventory to track emission changes. Sensitivity simulations are conducted by using WRF-CMAQ model to investigate the impacts of meteorological variability and emission changes on O3 changes over 2013–2020. O3 concentrations exhibit obvious interannual increases during 2013–2019 and a slight decrease in 2020. Both decreases in the MEIC emission inventory (−2.9% yr−1) and OMI NO2 column density (−3.1% yr−1) reflects the declining trend in NOx emissions over 2013–2020, while anthropogenic VOCs were not adequately regulated during 2013–2017, which explained the majority of deteriorated O3 pollution from 2013 to 2017. Furthermore, attribution analysis based on CMAQ simulations indicate that the unexpected aggravated O3 levels in 2019 is not only modulated by disproportional reductions in VOCs and NOx emissions, but also associated with unfavorable meteorological conditions featured by profound heatwaves and frequent stagnant conditions. In 2020, the abnormal meteorological conditions in May leads to substantial increase of O3 by 26.8 μg m−3 as compared to May 2019, while the considerable enhancement was fully offset by low O3 levels over the whole period which attributes to substantial emission reductions. This study reveals the long-term trend of O3 levels and precursor emissions and highlights the effects of meteorological variability and emission changes on O3 pollution over the SCB, with strong implications for designing effective O3 control measures.