Increase In Ozone Research Articles

Climate implications of the sun transition to higher activity mode

We analyze the ozone and climate response to the solar irradiance changes caused by the switch of the Sun to higher activity mode which is characterized by the simultaneous decrease of the total and increase of the UV solar irradiance. The results obtained using a chemistry-climate model with an interactive ocean show increase in the stratospheric ozone and temperature caused by higher levels of shortwave (100–380 nm) UV radiation. For the surface climate, the results are not so trivial because we obtained annual mean cooling for most of the globe, but at the same time, we do not observe expected statistically significant cooling over the northern high latitudes. This can be explained by the influence of the stratospheric ozone increase which can enhance the positive phase of the North Atlantic Oscillation bringing more energy to high latitudes. In general, a possible switch of the Sun to a more active state can lead to a slightly cooler climate and some decrease in the surface UV. However, these changes cannot be considered as catastrophic.

Association between short-term exposure to ambient air pollution and heart failure: An updated systematic review and meta-analysis of more than 7 million participants.

Exposure to air pollution has been linked to the mortality of heart failure. In this study, we sought to update the existing systematic review and meta-analysis, published in 2013, to further assess the association between air pollution and acute decompensated heart failure, including hospitalization and heart failure mortality. PubMed, Web of Science, EMBASE, and OVID databases were systematically searched till April 2022. We enrolled the studies regarding air pollution exposure and heart failure and extracted the original data to combine and obtain an overall risk estimate for each pollutant. We analyzed 51 studies and 7,555,442 patients. Our results indicated that heart failure hospitalization or death was associated with increases in carbon monoxide (3.46% per 1 part per million; 95% CI 1.0233-1.046, P < 0.001), sulfur dioxide (2.20% per 10 parts per billion; 95% CI 1.0106-1.0335, P < 0.001), nitrogen dioxide (2.07% per 10 parts per billion; 95% CI 1.0106-1.0335, P < 0.001), and ozone (0.95% per 10 parts per billion; 95% CI 1.0024-1.0166, P < 0.001) concentrations. Increases in particulate matter concentration were related to heart failure hospitalization or death (PM2.5 1.29% per 10 μg/m3, 95% CI 1.0093-1.0165, P < 0.001; PM10 1.30% per 10 μg/m3, 95% CI 1.0102-1.0157, P < 0.001). The increase in the concentration of all pollutants, including gases (carbon monoxide, sulfur dioxide, nitrogen dioxide, ozone) and particulate matter [(PM2.5), (PM10)], is positively correlated with hospitalization rates and mortality of heart failure. https://www.crd.york.ac.uk/PROSPERO/, identifier: CRD42021256241.

Quantitative impacts of vertical transport on the long-term trend of nocturnal ozone increase over the Pearl River Delta region during 2006–2019

Abstract. The Pearl River Delta (PRD) region in southern China has been subject to severe ozone (O3) pollution during daytime and anomalous nocturnal O3 increase (NOI) during nighttime. In this study, the spatiotemporal variation of NOI events in the PRD region from 2006 to 2019 is comprehensively analysed, and the role of vertical transport in the occurrence of NOI events is quantified based on observed surface and vertical O3 and the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) dataset. The results show that the average annual frequency of NOI events in the whole PRD region during the 14 year period is estimated to be 53 ± 16 d yr−1, with an average of 58 ± 11 µg m−3 for the nocturnal O3 peak (NOP) concentration. Low-level jets (LLJs) are the main meteorological processes triggering NOI events, explaining on average 61 % of NOI events. Annual NOI events exhibit an upward trend before 2011 (4.70 d yr−1) and a downward trend thereafter (−0.72 d yr−1), which is consistent with the annual variation of LLJs (r=0.88, p&lt;0.01). Although the contribution of convective storms (Conv) to NOI events is relatively small with an average value of 11 %, Conv-induced NOI events steadily increased at a rate of 0.26 d yr−1 during this 14 year period due to the impact of urbanisation. Seasonally, a relatively higher frequency of NOI events is observed in spring and autumn, which is consistent with the seasonal pattern of LLJs and maximum daily 8 h average (MDA8) O3. Spatially, NOI events are frequent in the eastern PRD, which agrees well with the spatial distribution of the frequency of LLJs and partially overlaps with the distribution of MDA8 O3 concentration, suggesting that vertical transport plays a more important role in NOI events than daytime O3 concentration. The Weather Research and Forecasting (WRF) model coupled with the Community Multiscale Air Quality (CMAQ) model and the observed vertical O3 profiles are further applied to illustrate the mechanisms of NOI formation caused by LLJs and Conv. The results confirm that both LLJs and Conv trigger NOI events by inducing downdrafts with the difference being that LLJs induce downdrafts by wind shear, while Conv by compensating downdrafts. Through observational and modelling analysis, this study presents the long-term (2006–2019) trends of NOI events in the PRD region and quantifies the contribution of meteorological processes for the first time, emphasising the importance of vertical transport, as well as daytime O3 concentration for the occurrence of NOI events.

Impacts of deep boundary layer on near-surface ozone concentration over the Tibetan Plateau

The deep atmospheric boundary layer in winter and spring over the Tibetan Plateau (TP) facilitates the exchange of mass and chemical species between the troposphere and stratosphere. Using ERA5 reanalysis data (1979–2018), this paper analyzes the atmospheric process over the TP when the dynamical tropopause (1.5 PVU surface) approaches the top of the deep boundary layer, which would affect the concentration of near-surface ozone. The result shows that the near-surface (at the height about 500–550 hPa) ozone concentration increases when the tropopause descends and adjoins the top of the deep boundary layer. The influence mechanism of the deep boundary layer on the increase of surface ozone on February 27, 2008 is studied by the WRF-Chem model. It is found that the calculated (using Reynolds average method) near-surface ozone increases by about 8 ppb per hour due to the vertical transport when the ozone-rich air from the stratosphere penetrates into the troposphere. Furthermore, a large eddy simulation (LEM model) is used to investigate the turbulence structure and development during the formation of the deep atmospheric boundary layer in the same case. It is found that a separate weak-turbulence layer forms at the height of about 6000 m AGL at 1300 LT below the tropopause fold. The upper-level turbulence couples with the boundary-layer turbulence after 1900 LT. As a result, the strong boundary layer turbulence causes the ozone-rich air from the stratosphere to mix with air near the surface layer.

The historical ozone trends simulated with the SOCOLv4 and their comparison with observations and reanalyses

Abstract. There is evidence that the ozone layer has begun to recover owing to the ban on the production of halogenated ozone-depleting substances (hODS) accomplished by the Montreal Protocol and its amendments and adjustments (MPA). However, recent studies, while reporting an increase in tropospheric ozone from the anthropogenic NOx and CH4 and confirming the ozone recovery in the upper stratosphere from the effects of hODS, also indicate a continuing decline in the lower tropical and mid-latitudinal stratospheric ozone. While these are indications derived from observations, they are not reproduced by current global chemistry–climate models (CCMs), which show positive or near-zero trends for ozone in the lower stratosphere. This makes it difficult to robustly establish ozone evolution and has sparked debate about the ability of contemporary CCMs to simulate future ozone trends. We applied the new Earth system model (ESM) SOCOLv4 (SOlar Climate Ozone Links, version 4) to calculate long-term ozone trends between 1985–2018 and compare them with trends derived from the BAyeSian Integrated and Consolidated (BASIC) ozone composite and MERRA-2, ERA-5, and MSRv2 reanalyses. We designed the model experiment with a six-member ensemble to account for the uncertainty of the natural variability. The trend analysis is performed separately for the ozone depletion (1985–1997) and ozone recovery (1998–2018) phases of the ozone evolution. Within the 1998–2018 period, SOCOLv4 shows statistically significant positive ozone trends in the mesosphere, upper and middle stratosphere, and a steady increase in the tropospheric ozone. The SOCOLv4 results also suggest slightly negative trends in the extra-polar lower stratosphere, yet they barely agree with the BASIC ozone composite in terms of magnitude and statistical significance. However, in some realizations of the SOCOLv4 experiment, the pattern of ozone trends in the lower stratosphere resembles much of what is observed, suggesting that SOCOLv4 may be able to reproduce the observed trends in this region. Thus, the model results reveal marginally significant negative ozone changes in parts of the low-latitude lower stratosphere, which agrees in general with the negative tendencies extracted from the satellite data composite. Despite the slightly smaller significance and magnitude of the simulated ensemble mean, we confirm that modern CCMs such as SOCOLv4 are generally capable of simulating the observed ozone changes, justifying their use to project the future evolution of the ozone layer.

El Niño Impacts on the Ozone Column Over Mato Grosso Do Sul

The El Niño-South Oscillation (ENSO), a dominant factor in interannual climate variations worldwide, is characterized in the Pacific by anomalous sea surface heating during the El Niño phase and cooling during the La Niña phase. Although ENSO strongly affects atmospheric circulation, its effects on tropospheric ozone are not fully explored. We used satellite measurements of the tropospheric column of ozone to assess the effects of atmospheric circulations driven by ENSO on tropospheric column ozone levels in Mato Grosso do Sul (MS). The objective of this work is to analyze the annual variation and the effects of the El Niño atmospheric variability mode in the Total Ozone Column (TCO) on MS between 2005 and 2020 using data from the AUREA satellite and the \Ozone Monitoring Instrument (OMI) sensor. We found that observed ozone tends to increase in the troposphere after the La Niña peak, corresponding to anomalous downward motions and suppressed convection. The model also reveals that the La Niña-related ozone increase in MS is largely due to intensified transport of ozone-rich air from higher latitudes. This suggests that ENSO should be considered for estimating the ozone concentration in MS, requiring close attention to the properties of ENSO in a changing climate.

The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms

Abstract. Surface ozone concentrations typically peak during the daytime, driven by active photochemical production, and decrease gradually after sunset, due to chemical destruction and dry deposition. Here, we report that nocturnal ozone enhancement (NOE, defined as an ozone increase of more than 5 ppbv h−1 in 1 of any 2 adjacent hours between 20:00 and 06:00 LT, local time) events are observed at multiple monitoring sites in China at a high frequency, which has not been recognized in previous studies. We present an overview of the general characteristics of NOE events in China and explore the possible mechanisms based on 6 years of observations from the national monitoring network. We find that the mean annual frequency of NOE events is 41±10 % (i.e., about 140 d would experience an NOE event per year) averaged over all 814 Chinese sites between 2014 and 2019, which is 46 % larger than that over Europe or the United States. The NOE event frequency is higher in industrialized city clusters (&gt;50 %) than in regions with lighter ozone pollution, and it is higher in the warm season (46 %) than in the cold season (36 %), consistent with the spatiotemporal evolution of ozone levels. The mean ozone peak during NOE events reaches 37±6 ppbv in the warm season. The ozone enhancements are within 5–15 ppbv h−1 during 85 % of the NOE events; however, in about 10 % of cases, the ozone increases can exceed 20 ppbv h−1. We propose that high photochemistry-induced ozone during the daytime provides a rich ozone source in the nighttime residual layer, determining the overall high frequency of NOE events in China, and that enhanced atmospheric mixing then triggers NOE events by allowing the ozone-rich air in the residual layer to mix into the nighttime boundary layer. This is supported by our analyses which show that 70 % (65 %) of the NOE events are associated with increases in friction velocity (planetary boundary layer height), indicative of enhanced atmospheric mixing, and also supported by the observed sharp decreases in surface NO2 and CO concentrations with ozone increases in NOE events, a typical signal of mixing with air in the residual layer. Three case studies in Beijing and Guangzhou show that synoptic processes such as convective storms and low-level jets can lead to NOE events by aggravating vertical mixing. Horizontal transport of ozone-rich plumes may also be a supplementary driver of NOE events. Our results summarize, for the first time, the characteristics and mechanism of NOE events in China based on nationwide and long-term observations, and our findings emphasize the need for more direct measurements and modeling studies on the nighttime ozone evolution from the surface to the residual layer.

Spatial characteristics of change trends of air pollutants in Chinese urban areas during 2016–2020: The impact of air pollution controls and the COVID-19 pandemic

Air pollution is a threat to public health in China, and several actions and plans have been implemented by Chinese authorities in recent years to mitigate it. This study examined the spatial distribution of changes in urban air pollutants (UAP) in 336 Chinese cities from 2016 to 2020 and their responses to air pollution controls and the COVID-19 pandemic. Based on the harmonic model, decreases in fine particles (PM2.5), inhalable particles (PM10), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO) levels were found in 90.7%, 91.9%, 75.2%, 94.3%, and 88.7% of cities, respectively, while an increase in ozone (O3) was found in 87.2% of cities. Notable spatial heterogeneity was observed in the air pollution trends. The greatest improvement in air quality occurred mainly in areas with poor air quality, such as Hebei province and its surrounding cities. However, some areas (i.e., Yunnan and Hainan provinces) with good air quality showed a worsening trend. During the 13th Five-Year Plan period (2016–2020), the remarkable effects of PM2.5 and SO2 pollution control plans were confirmed. Additionally, economic growth in 74.2% of the Chinese provinces decoupled from air quality after implementing pollution control measures. In 2020, several Chinese cities were locked down to reduce the spread of COVID-19. Except for SO2, the national air pollution in 2020 improved to a greater extent than that in 2016–2019; In particularly, the contribution of simulated COVID-19 pandemic to NO2 reduction was 66.7%. Overall, air pollution control actions improved urban PM2.5, PM10, SO2, and CO, whereas NO2 was reduced primarily because of the COVID-19 pandemic.

Chemistry-driven changes strongly influence climate forcing from vegetation emissions

Biogenic volatile organic compounds (BVOCs) affect climate via changes to aerosols, aerosol-cloud interactions (ACI), ozone and methane. BVOCs exhibit dependence on climate (causing a feedback) and land use but there remains uncertainty in their net climatic impact. One factor is the description of BVOC chemistry. Here, using the earth-system model UKESM1, we quantify chemistry’s influence by comparing the response to doubling BVOC emissions in the pre-industrial with standard and state-of-science chemistry. The net forcing (feedback) is positive: ozone and methane increases and ACI changes outweigh enhanced aerosol scattering. Contrary to prior studies, the ACI response is driven by cloud droplet number concentration (CDNC) reductions from suppression of gas-phase SO2 oxidation. With state-of-science chemistry the feedback is 43% smaller as lower oxidant depletion yields smaller methane increases and CDNC decreases. This illustrates chemistry’s significant influence on BVOC’s climatic impact and the more complex pathways by which BVOCs influence climate than currently recognised.

Multidecadal increases in global tropospheric ozone derived from ozonesonde and surface site observations: can models reproduce ozone trends?

Abstract. Despite decades of effort, the drivers of global long-term trends in tropospheric ozone are not well understood, impacting estimates of ozone radiative forcing and the global ozone budget. We analyze tropospheric ozone trends since 1980 using ozonesondes and remote surface measurements around the globe and investigate the ability of two atmospheric chemical transport models, GEOS-Chem and MERRA2-GMI, to reproduce these trends. Global tropospheric ozone trends measured at 25 ozonesonde sites from 1990–2017 (nine sites since 1980s) show increasing trends averaging 1.8 ± 1.3 ppb per decade across sites in the free troposphere (800–400 hPa). Relative trends in sondes are more pronounced closer to the surface (3.5 % per decade above 700 hPa, 4.3 % per decade below 700 hPa on average), suggesting the importance of surface emissions (anthropogenic, soil NOx, impacts on biogenic volatile organic compounds (VOCs) from land use changes, etc.) in observed changes. While most surface sites (148 of 238) in the United States and Europe exhibit decreases in high daytime ozone values due to regulatory efforts, 73 % of global sites outside these regions (24 of 33 sites) show increases from 1990–2014 that average 1.4 ± 0.9 ppb per decade. In all regions, increasing ozone trends both at the surface and aloft are at least partially attributable to increases in 5th percentile ozone, which average 1.8 ± 1.3 ppb per decade and reflect the global increase of baseline ozone in rural areas. Observed ozone percentile distributions at the surface have shifted notably across the globe: all regions show increases in low tails (i.e., below 25th percentile), North America and Europe show decreases in high tails (above 75th percentile), and the Southern Hemisphere and Japan show increases across the entire distribution. Three model simulations comprising different emissions inventories, chemical schemes, and resolutions, sampled at the same locations and times of observations, are not able to replicate long-term ozone trends either at the surface or free troposphere, often underestimating trends. We find that ∼75 % of the average ozone trend from 800–400 hPa across the 25 ozonesonde sites is captured by MERRA2-GMI, and &lt;20 % is captured by GEOS-Chem. MERRA2-GMI performs better than GEOS-Chem in the northern midlatitude free troposphere, reproducing nearly half of increasing trends since 1990 and capturing stratosphere–troposphere exchange (STE) determined via a stratospheric ozone tracer. While all models tend to capture the direction of shifts in the ozone distribution and typically capture changes in high and low tails, they tend to underestimate the magnitude of the shift in medians. However, each model shows an 8 %–12 % (or 23–32 Tg) increase in total tropospheric ozone burden from 1980 to 2017. Sensitivity simulations using GEOS-Chem and the stratospheric ozone tracer in MERRA2-GMI suggest that in the northern midlatitudes and high latitudes, dynamics such as STE are most important for reproducing ozone trends in models in the middle and upper troposphere, while emissions are more important closer to the surface. Our model evaluation for the last 4 decades reveals that the recent version of the GEOS-Chem model underpredicts free tropospheric ozone across this long time period, particularly in winter and spring over midlatitudes to high latitudes. Such widespread model underestimation of tropospheric ozone highlights the need for better understanding of the processes that transport ozone and promote its production.

Understanding the nocturnal ozone increase in Nanjing, China: Insights from observations and numerical simulations

Surface ozone (O3) is mainly photochemically formed by nitrogen oxides (NOX) and volatile organic compounds (VOCs), and therefore O3 usually has a distinct diurnal variation with high concentrations in the afternoon and low values at night. However, eight nocturnal O3 increase (NOI) events were identified in Nanjing in June 2021. To understand the mechanism of NOI events, we selected two events (June 6–7, and 24–25) for observational data analysis. The Community Multiscale Air Quality (CMAQ) model was employed for the process analysis (PA) and regional transport of O3. By analyzing the O3 observation data and meteorological factors, we found that there were clear southeastward O3 transport paths. The O3 peak clearly moved from the upwind to the downwind cities in both events. Model simulations showed that when nocturnal O3 enhancement occurred, horizontal transport resulted in a negative to positive net O3 production rate. O3 continued to get accumulated in Nanjing. Nocturnal O3 in the first event was dominated by long-range transport, with the top two contributing cities being Huzhou (5.6 %) and Jiaxing (4.7 %). NOI during the second event was from the nearby upwind cities. The top three contributing cities were Shanghai (18.3 %), Wuxi (9.1 %), and Suzhou (8.8 %). We conclude that the June NOI events in Nanjing were mainly driven by the horizontal transport of southeasterly winds. This study provides scientific support for O3 prevention and control in Nanjing in the summer.

Change in Tropospheric Ozone in the Recent Decades and Its Contribution to Global Total Ozone

AbstractTropospheric ozone is a key chemically active trace gas and radiative forcer. Understanding its long‐term changes is important to properly interpret observed changes in total column ozone and stratospheric ozone recovery. We investigate global and regional tropospheric ozone changes and their impact on total column ozone during 2005–2018 using satellite measurements and the NASA Goddard Earth Observing System Chemistry Climate Model (GEOSCCM). Global total ozone increased ∼4 DU during 2005–2018 (+0.28 ± 0.06 DU yr−1) as inferred from Ozone Monitoring Instrument (OMI). Consistent with previous studies, the OMI/MLS (Microwave Limb Sounder) derived global tropospheric ozone increased 2.2 DU during this period, 60% of the global total column ozone increase. While GEOSCCM reproduces reasonably well the total column increase, it overestimates the stratospheric ozone increase and underestimates the tropospheric ozone increase. We find that the tropospheric ozone increases are likely attributed to a growth of regional emissions of key ozone precursors, especially volatile organic compounds as reflected by the positive trends in formaldehyde (CH2O). Although carbon monoxide (CO) has been decreasing everywhere around the globe, it has relatively small impact on the tropospheric ozone trend. Trends in nitrogen dioxide (NO2) vary with regions, and these changes counteract or reinforce the positive effects of CH2O on the tropospheric ozone increases. The model underestimates the observed tropospheric ozone increase, especially over the US and Europe, because of underestimated NO2 emissions changes used in the model. The stratospheric ozone contribution increases during this period in the Northern Hemisphere and contributes to the tropospheric ozone increase.

Simplifying network complexity of soil bacterial community exposed to short-term carbon dioxide and ozone enrichment in a paddy soil

Global atmospheric changes are characterized by increases in carbon dioxide (CO2) and ozone (O3) concentrations, with important consequences for the soil microbial community. However, the influences of CO2 and O3 enrichment on the biomass, diversity, composition, and functioning of the soil bacterial community remain unclear. We investigated the effects of short-term factorial combinations of CO2 (by 200 ppm) and O3 (by 40 ppb) enrichment on the dynamics of soil bacterial community in paddy soils with two rice varieties (Japonica, Nangeng 5055 (NG5055) vs. Wuyujing 3 (WYJ3)) in an open top chamber facility. When averaged both varieties, CO2 and O3 enrichment showed no individual or combined effect on the abundance or diversity of soil bacterial community. Similarly, CO2 enrichment did not exert any significant effect on the relative abundance of bacterial phyla. However, O3 enrichment significantly reduced the relative abundance of Myxococcota phylum by a mean of 37.5%, which negatively correlated to root N content. Compared to ambient conditions, soil bacterial community composition was separated by CO2 enrichment in NG5055, and by both CO2 and O3 enrichment in WYJ3, with root N content identified as the most influential factor. These results indicated that root N was the top direct predictor for the community composition of soil bacteria. The COG (cluster of orthologous groups) protein of cell motility was significantly reduced by 5.8% under CO2 enrichment, and the COG protein of cytoskeleton was significantly decreased by 14.7% under O3 enrichment. Furthermore, the co-occurrence network analysis indicated that both CO2 and O3 enrichment decreased the network complexity of the soil bacterial community. Overall, our results highlight that continuous CO2 and O3 enrichment would potentially damage the health of paddy soils through adverse impacts on the associations and functional composition of soil microbial communities.

Ground-level ozone in the Mekong Delta region: precursors, meteorological factors, and regional transport.

The Mekong Delta region (MDR), also known as Vietnam's rice bowl, produced a bountiful harvest of about 23.8 million tons in 2020, accounting for 55.7% of the country's total production, providing food security for 20% of the world population. With the rapid pace of industrialisation and urbanisation, the concentration of ozone in the lower atmosphere has risen to a level that reduces crop yields, especially rice, and is therefore the subject of research. This study aims to simulate the spatiotemporal distribution of ground-level ozone in the area and evaluate the impact of precursor emissions and meteorological factors on the spatiotemporal distributions of ozone concentrations. The study area was divided into seven zones, including six agro-ecological zones (AEZs) and one low-mountainous area, mainly to clarify the role of emissions in each AEZ. The simulation results showed that ground-level O3 in the MDR ranged from 40.39 to 52.13µg/m3. In six agro-ecological zones, the average annual ground-level O3 concentration was relatively high and was the highest in zone 6 (CPZ) and zone 3 (LXZ) with values of 96.18µg/m3 (exceeding 1.60 times the WHO Guidelines 2021) and 94.86µg/m3 (exceeding 1.58 times the WHO Guidelines 2021), respectively. In each zone, the annual average O3 concentration tended to gradually increase from the inner delta to coastal areas. Two types of precursors, NOx and NMVOCs, are the main contributors to O3 pollution, with the largest contribution coming from zone 1 (FAZ) with 91.5 thousand tons of NOx/year and 455.2 thousand tons of NMVOCs/year. Among the meteorological factors considered, temperature (T), relative humidity (RH), and surface pressure (P) were the three main factors that contributed to the increase in ground-level ozone. The spatio-temporal distribution of ground-level O3 in the MDR was influenced by emission precursors from different zones as well as meteorological factors. The present results can help policy-makers formulate plans for agro-industrial development in the entire region.

Attributing Increases in Ozone to Accelerated Oxidation of Volatile Organic Compounds at Reduced Nitrogen Oxides Concentrations.

Surface ozone (O3) is an important secondary pollutant affecting climate change and air quality in the atmosphere. Observations during the COVID-19 lockdown in urban China show that the co-abatement of nitrogen oxides (NOx) and volatile organic compounds (VOCs) caused winter ground-level O3 increases, but the chemical mechanisms involved are unclear. Here we report field observations in the Shanghai lockdown that reveals increasing photochemical formation of O3 from VOC oxidation with decreasing NOx. Analyses of the VOC profiles and NO/NO2 indicate that the O3 increases by the NOx reduction counteracted the O3 decreases through the VOC emission reduction in the VOC-limited region, and this may have been the main mechanism for this net O3 increase. The mechanism may have involved accelerated OH-HO2-RO2 radical cycling. The NOx reductions for increasing O3 production could explain why O3 increased from 2014 to 2020 in response to NOx emission reduction even as VOC emissions have essentially remained unchanged. Model simulations suggest that aggressive VOC abatement, particularly for alkenes and aromatics, should help reverse the long-term O3 increase under current NOx abatement conditions.

Adverse associations of long-term exposure to ambient ozone with molecular biomarkers of aging alleviated by residential greenness in rural Chinese adults.

Both ambient ozone exposure and residential greenness are linked to the aging process. However, their interactive effect on molecular biomarkers of aging (telomere length (TL) and mitochondrial DNA copy number (mtDNA-CN)) remains unclear. This study was conducted among 6418 rural Chinese adults. The concentration of ambient ozone was assessed using a random forest model. Residential greenness was represented by the normalized difference vegetation index (NDVI). Molecular biomarkers of aging (relative TL and relative mtDNA-CN) were determined by quantitative real-time polymerase chain reaction. Generalized linear regression models were applied to investigate the independent and combined effects of ambient ozone and residential greenness on relative TL and relative mtDNA-CN. The estimated percent changes and 95% confidence intervals (CIs) of relative TL in response to per-unit increase in ambient ozone were -22.43% (-23.74%, -21.18%), -14.19% (-15.63%, -12.72%) and -4.50% (-6.57%, -2.27%) for participants with low (NDVI≤0.53), moderate (0.54-0.55) and high (≥0.56) residential greenness exposure, respectively, while the corresponding figures of relative mtDNA-CN were -12.63% (-13.84%, -11.31%), -9.52% (-10.60%, -8.33%) and 2.12% (0.20%, 4.19%). Furthermore, negative interactive effects between ambient ozone and residential greenness exposure on molecular biomarkers of aging were observed (Pfor interaction<0.001 for relative TL, and 0.098 for relative mtDNA-CN). Long-term exposure to high concentrations of ambient ozone and low residential greenness was associated with decreased mtDNA-CN and shortened TL. The adverse effect of ambient ozone exposure on molecular biomarkers of aging may be attenuated by increased residential greenness.

Assessment of summertime ozone formation in the Sichuan Basin, southwestern China

The alarming increase of ambient ozone (O3) levels across China raises an urgent need in understanding underlying mechanisms of regional O3 events for highly urbanized city clusters. Sichuan Basin (SCB) situated in southwestern China has experienced severe O3 pollution at times in summer from 2013 to 2020. Here, we use the WRF-CMAQ model with the Integrated Source Apportionment Method (ISAM) to investigate the evolution mechanism and conduct source attribution of an extreme O3 episode in the SCB from June 1 to 8, 2019. This typical summer O3 episode is associated with the synoptic-driven meteorological phenomenon and transboundary flow of O3 and precursors across the SCB. Weak ventilation in combination with stagnant conditions triggered the basin-wide high O3 concentrations and enhanced BVOC emissions substantially contribute up to 57.9 μg/m3 MDA8 O3. CMAQ-ISAM indicates that precursor emissions from industrial and transportation have the largest impacts on elevating ambient O3 concentrations, while power plant emissions exhibit insignificant contributions to basin-wide O3 episodes. These results improve the understanding of the summertime O3 episode in the SCB and contribute insights into designing O3 mitigation policy.

Assessing the short-term effects of ozone exposure on the indicator of pharmacy visits in Nanjing based on mobile phone big data

Ozone pollution significantly impacts human health. However, less is known about the effects of ozone on pharmacy consumption affecting a wider population, especially in heavily polluted developing countries. Moreover, no studies reveal the community-level heterogeneity of these effects. Taking advantage of multi-sources big data, this study aimed to refine the short-term effects of ozone exposure on the indicator of pharmacy visits to community levels in Nanjing, China. Firstly, we established a random forest model to predict the high-resolution ozone exposure and extracted the indicator of pharmacy visits from mobile phone call detail records and Point of Interest data. Then, we applied a generalized additive model to estimate the percent increase of pharmacy visits per 10 μg/m3 increase in ozone exposure. The results showed that in the best lag model, the pharmacy visits in Nanjing increased by 0.822% (95% CI: 0.818%–0.826%) for each 10 μg/m3 increase in ozone. The exposure-response curve for maximum 8-h average ozone and pharmacy visits was nonlinear, with a rapid increase below 150 μg/m3 and then slightly decreased. The rural 1.210% (95% CI: 1.19%–1.23%) has a higher estimate than the urban 0.819% (95% CI: 0.813%–0.825%). The low temperature intensifies the ozone's effect on increasing pharmacy visits, while the high temperature does the opposite. On the one hand, our study proposed an innovative and promising method to apply multi-sources big data to overcome the health data lacking issues in environmental health studies. On the other hand, it also sheds light on previously unidentified heterogeneous effects of ozone on mild health outcomes, especially in heavily polluted developing countries.

Data for "Rapid increase in tropospheric ozone over Southeast Asia attributed to changes in precursor emission source regions and sectors"

Data for "Rapid increase in tropospheric ozone over Southeast Asia attributed to changes in precursor emission source regions and sectors"

Disentangling the complex impacts of urban digital transformation and environmental pollution: Evidence from smart city pilots in China

Existing studies are mixed about whether smart city construction (SCC) can alleviate urban environmental pollution. This study takes three batches of smart city pilots implemented by the Ministry of Housing and Urban-Rural Development of China as a quasi-natural experiment. We construct the panel dataset of 286 prefecture-level cities in China covering the period 2006 to 2018, then applies the multi-stage difference-in-differences method to investigate the environmental benefits of SCC policies. The results show that SCC can significantly reduce air pollution by 2.6% ∼ 18 %, except for ozone (increase by 13.9%), water pollution by 0.7%∼ 11.8%, and solid waste pollution by 5.8%∼ 19.7%. Meanwhile, SCC policy shows a more prominent reduction effect in eastern cities, megacities, young local officials and regions with high government capacity. The dynamic effect reveals that the environmental benefits take effect after 2∼4 years of SCC implementation, and then the benefit will increase significantly over time. The mechanism tests indicate that although the rebound effect will deteriorate the environmental quality, SCC can reduce pollution through industrial structure optimization and technological innovation. Overall, this finding inspires other emerging economies to solve the dilemma of economic development and environmental governance at the level of new infrastructure construction.