Average O3 Concentrations Research Articles

Impact of Differents in the Concentrations of Ozone on the Chemical Composition of Single Particles

To investigate the effect of high concentration of ozone (O3) on the aerosol formation and aging process, this study made observations using a single-particle aerosol mass spectrometer (SPAMS) at Heshan Atmospheric Environment Supervision Station in Guangdong Province in October 2018. During the observation period, a high ozone concentration period (PH) and a low ozone concentration period (PL) were defined according to the level of O3 concentration. The average O3 concentration during PH was 117 μg·m-3, and that of PL was 25 μg·m-3. According to the difference in chemical composition, single particles mainly included aging element carbon particles (EC-aged), secondary particles (Sec), and aging organic carbon particles (OC-aged) during the observation period. The total number of single particles in PH (348085) was higher than in PL (224797), and the proportion of Sec particles (37.1%) in PH was significantly higher than in PL (27.8%), whereas the proportion of EC-aged particles in PH (32.1%) was lower than in PL (44.1%). The proportion of OC-aged particles in PH (13.5%) was slightly higher than in PL (10.4%). The concentration of particles containing nitrate and sulfate showed significant diurnal changes during PH, but no diurnal changes during PL. The peak area of nitrate and sulfate in the Sec particles and EC-aged particles in PH was higher than in PL, which indicates that the amount of nitrate and sulfate produced by the secondary reaction process in PH was more than in PL. In addition, the peak areas of nitrate and sulfate in the Sec particles were significantly higher than those in the EC-aged particles, indicating that the age of the Sec particles was greater. In this study, acetate (59CH3CO2-) and glyoxal (73C2HO3-) were selected to represent the changing characteristics of aldehyde and ketone compounds in single-particle aerosols. The number concentration and peak area of 59CH3CO2- and 73C2HO3- in Sec and OC-aged particles in PH were significantly higher than those in PL, and showed significant diurnal variation characteristic during PH. The peak appeared 2 h after the peak of O3 concentration. In PL, the peak value was significantly reduced, and the change trend was the same as that of the number concentration of Sec and OC-aged particles, indicating that high concentration of O3 is beneficial to the oxidation of VOCs to 59CH3CO2- and 73C2HO3-. In summary, high concentration of O3 and enhancement of secondary species in single particles were due to the strong photochemical reactions during PH.

Characteristics of Spatial and Temporal Evolution and Investigation of Air Pollution in Guangdong-Hong Kong-Macao Greater Bay Area Based on Ground-Space Observation Data

The temporal and spatial distribution characteristics, evolution trend and potential climatic effects of air pollution in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) were analyzed on different time scales and spatial spaces, based on ground environment observation data from June 2014 to December 2018 and satellite remote sensing inversion products from 2000 to 2018. The results show that:① From the in-situ observed daily average concentration of PM2.5, good or mild to moderate pollution occurred in January, February, October, November, and December every year, and the rest of the time was excellent. ② Based on the annual average PM2.5 concentration obtained by satellite for the past 20 years, the spatial characteristics showed that the external radiation is centered on Guangzhou and Foshan. The time evolution shows the characteristics of an Ω shape, which increases gradually from 2000 to 2009, is highest in 2008, and then gradually decreases. ③ The monthly average aerosol optical thickness (AOT) value from the Multi-angle Imaging Spectro Radiometer satellite reversion every 10 years for a period (2000-2009 for a period, 2010-2018 for a period) was used to see the monthly variation. The monthly average AOT value in the first period was larger than that in the second period of the same month, the maximum value was in March and April, and the minimum value was in November and December. It is envisaged to draw a line along the north-south direction of the Pearl River Port, which basically shows that the AOT value in the west is greater than that in the east. ④ According to the observed daily average concentration data of O3-8h, the main concentration level of O3-8h in the GBA is excellent. The cities with good ozone concentration were most numerous in 2014, with five cities, and least in 2018, with only one city. The highest ozone concentration was in September, followed by June and November, and then May and July. In the past 20 years, the spatial distribution of the average concentration of O3 monitored by satellite remote sensing showed a characteristic Ω shape, increasing initially and then decreasing. The maximum value was in May, and the north-south boundary line appeared in space. ⑤ There is a good linear relationship between the interannual variation of monthly mean temperature and radiation, whereas the relationship between AOT and radiation cannot be described by a simple linear relationship.

Relationship between the number of hospitalized cardiovascular and respiratory disease and the average concentration of criteria air pollutants (CAP) in Ahvaz.

This study aims to investigate the relationship between the number of hospitalized cardiovascular and respiratory patients and the average concentration of criteria air pollutants, including NO2, SO2, CO, O3 and PM10 in Ahvaz in the period of 10years (2007-2017). Data on referrals and the number of hospitalized cardiovascular and respiratory patients and also on air pollutants are obtained through Hospital Information System and air quality monitoring stations including Department of Environment Protection Station, Naderi Square Station, University Square Station and the Meteorological Organization Station. The data were analyzed by SPSS version 4 and Poisson distribution regression model to evaluate the effects of each pollutant and the rate of hospitalization. In this study, confidence interval and the significance level are considered at 95% and 5%, respectively. Changes in air pollution indices and number of patients with cardiovascular diseases were evaluated using Excel, Stata and ARIMA models. Based on the results of Poisson regression analysis, there was a significant relationship between the average concentration of NO2, O3, CO and SO2 and hospitalization of patients with cardiovascular disease, with a confidence level of less than 5%. This was the case with NO2 more than other pollutants. Furthermore, there was a significant relationship between the average concentrations of NO2, CO and O3 and the hospitalization rate of patients with respiratory problems and a confidence level of 5%. The effect of NO2 was also higher here. Due to the results, NO2, CO, and O3 had a significant direct correlation with cardiovascular and respiratory rates. The effect of NO2 has been higher than other pollutants. In the study of time intervals of patients with cardiovascular, the results of time-interval analysis indicate the relationship between cardiovascular clients with the "t" time of 7days earlier and NO2 as a pollutant. The results of this analysis also revealed the relationship between respiratory patients at the time "t" up to 7days before and O3.

Characteristic and Spatiotemporal Variation of Air Pollution in Northern China Based on Correlation Analysis and Clustering Analysis of Five Air Pollutants

AbstractAir quality in Northern China has become a global hot spot issue due to a series of air pollution events in the recent years. In this study, five representative air pollutants (PM2.5, SO2, NO2, CO, and O3) were employed to reveal the spatial and temporal distribution of air pollution in Northern China. Periodic decline in PM2.5, SO2, CO, and NO2 from 2016 to 2018 indicated that air pollution control measures have achieved desired results. In addition, PM2.5 was significantly positively correlated with SO2, CO, and NO2 (p < 0.001), and O3 had negative correlations with the other four pollutants. Furthermore, the heavy pollution phenomenon in Shijiazhuang, Anyang, Xingtai, and Handan was attributed to their industrial structures (e.g., steel industry) and geographical location based on clustering analysis. Contrary to above four pollutants, the annual average concentrations of O3 increased in all the nine cities (1.4–35.9%) from 2016 to 2018. It is necessary to plan mitigation strategy for O3 based on further investigation of source and formation mechanism of O3.

Modified regional biogenic VOC emissions with actual ozone stress and integrated land cover information: A case study in Yangtze River Delta, China

The biogenic volatile organic compounds (BVOCs) emissions are influenced by ambient ozone (O3) concentrations and vegetation cover. In most studies, however, the interaction between O3 and plants has not been considered and there are uncertainties in land cover input and emission factors (EFs) in BVOCs emission estimation, particularly at the regional scale. In this study, an O3 exposure-isoprene (ISOP) response function was developed using meta-analysis, and the EFs of ISOP and land cover inputs were updated by integrating local measurement and investigation data in the Yangtze River Delta (YRD) region. Five different cases were developed to explore the impacts of O3 and input variables on the BVOCs emissions using the Model of Emissions of Gases and Aerosols from Nature (MEGAN). The impacts of those variables on O3 simulation were further examined with air quality modeling. We found that the ISOP emissions were restrained in the city cluster along the Yangtze River during the growing season due to their negative feedback to O3 exposure for deciduous broadleaf forests. The estimation of BVOCs emissions strongly depended on EFs, and the global EFs underestimated the ISOP emissions in July by 37%, mostly in southern YRD. Different land cover datasets with various fractions and spatial distributions of plant function types resulted in a variation of 200–400 Gg in ISOP emissions in July across YRD. Air quality modeling indicated that BVOCs contributed 10%, 12%, and 11% to the 1-h mean, the maximum daily 1-h average, and the maximum daily 8-h average O3 concentrations, respectively, for July across the YRD region. Due to the NOx restriction, the spatial distribution of BVOCs emissions was inconsistent with that of their contribution to O3 formation. The O3 simulation was more sensitive to the changed BVOCs emissions in the area with relatively large contribution of BVOCs to O3 formation.

Ambient air pollution and male fecundity: A retrospective analysis of longitudinal data from a Chinese human sperm bank (2013–2018)

Ambient air pollution has adverse effects on human health and reproduction. A number of studies have suggested a significant association between ambient air pollution and human fecundity, with most studies focusing on cross-sectional data from the general male population with single semen samples. We conducted a retrospective study in China using longitudinal analysis of repeated semen samples to investigate the association between environmental exposure parameters (e.g., PM2.5, PM10, SO2, NO2, CO, ground temperature, and relative humidity) and sperm quality parameters (e.g., semen volume, sperm concentration, forward motility concentration, and percentage of progressive rate) during different exposure windows (current day, 90-day preceding). Data from 686 males and 4841 semen samples collected between 2013 and 2018 at Sichuan Provincial Sperm Bank were included in a mixed-effects model analysis. The study population was young, healthy, and well-educated. The results indicate that 90-day average concentrations of PM2.5, PM10, and CO were negatively associated with sperm concentration and forward motility concentration, whereas 90-day average concentration of O3 was positively associated with forward motility concentration. Between-subject variability played the dominant role in overall model variance. Our results suggest that chronic exposure to particulate matter and CO may interfere with spermatogenesis.

Effects of cool roofs on turbulent coherent structures and ozone air quality in Seoul

Abstract The cool-roof strategy is an effective way of mitigating severe urban heat islands, and its impacts on urban flow and air quality deserve in-depth investigations. This study examines the effects of cool roofs on turbulent coherent structures and ozone air quality in Seoul, South Korea using the Weather Research and Forecasting-Community Multiscale Air Quality (WRF-CMAQ) model with a 50 m horizontal grid spacing. Cool roofs decrease the daily average air temperature, planetary boundary layer (PBL) height, and wind speed in the urban area of Seoul by 0.80 °C, 230 m, and 0.17 m s−1, respectively. Due to the lowered air temperature by cool roofs, the sea breeze and convective structures weaken and eddies at the PBL top appear less frequently. Since high O3 concentration air flows into Seoul by the sea breeze, the weakened sea breeze decreases the daily average O3 concentration near the surface by 3.3 ppb. Air at lower level is transported upward across the PBL top by convective structures and eddies at the PBL top. The transported air at lower level has lower O3 concentration and higher concentrations of O3 precursors than air at upper level. Therefore, the weakened convective structures and less-frequent appearance of eddies at the PBL top by cool roofs weaken the upward transport of O3 precursors at lower level across the PBL top. As a result, the chemical production of O3 and O3 concentration slightly above the PBL top are decreased. An integrated process rate analysis shows that cool roofs weaken the effects of turbulent coherent structures on O3 concentration.

Estimating Ground-Level Ozone Concentrations in Eastern China Using Satellite-Based Precursors

The monthly ground-level ozone (O3) concentrations in eastern China (EC) are estimated using the surface NO2 and CH2O concentrations derived from the ozone monitoring instrument (OMI) according to the geographically weighted regression (GWR) method. The accuracy assessment shows that the proposed GWR model performed well for estimating monthly O3 concentrations ( ${R} ^{2} =0.81$ , absolute error (AE) $= 7.38~\mu \text{g}/\text{m}^{3}$ for the fitted results, and ${R} ^{2}= 0.77$ , AE $= 8.20~\mu \text{g}/\text{m}^{3}$ ). The estimated yearly average O3 concentration is $56.20~\mu \text{g}/\text{m}^{3}$ , with a standard deviation of $3.68~\mu \text{g}/\text{m}^{3}$ in 2014 across EC. The O3 concentrations show great spatial variation, with hotspots extending from north-EC to the Yangtze River Delta and the Pearl River Delta. The monthly O3 concentrations are generally low during the cold season and high during the warm season, but local areas show different seasonal variations.

Influence of forest fire episodes on the distribution of gaseous air pollutants over Uttarakhand, India

ABSTRACTWidespread forest fire events occurred in the foothills of North Western Himalaya during 24 April to 2 May 2016 (Event-1) and 20–30 May 2018 (Event-2). Their impacts were investigated on the distribution of pollutant gases ozone (O3), carbon monoxide (CO), and oxides of nitrogen (NOx) over Uttarakhand using simulations of Weather Research and Forecasting model coupled with chemistry (WRF-Chem) and in-situ observations of these gases over Dehradun, the capital of Uttarakhand. During Event-1, the observed CO mixing ratio over Dehradun increased from 25 April 2016 onwards, attained maximum (705.8 ± 258 ppbv) on 2 May 2016 and subsequently decreased. The rate of increase of daily baseline CO was 29 ppbv/day during HFAP (High Fire Activity Period). During Event-2, daily average concentrations of CO, O3, and NOx showed systematic increase over Dehradun during HFAP period. The rate of increase of CO was 9 ppbv/day, while it was very small for NOx and O3. To quantitatively estimate the influence of forest fire emissions, two WRF-Chem simulations were made: one with biomass burning (BB) emissions and other without BB emissions. These simulations showed 52% (34%) enhancement in CO, 52% (32%) enhancement in NOx, and 11% (9%) enhancement in O3 during HFAP for Event-1 (Event-2). A clear positive correlation (r = 0.89 for Event-1, r = 0.69 for Event-2) was found between ∆O3 (O3with BB minus O3without BB) and ∆CO (COwith BB minus COwithout BB), indicating rapid production of ozone in the fire plumes. For both the events, the vertical distribution of ∆O3, ∆CO, and ∆NOx showed that forest fire emissions influenced the air quality upto 6.5 km altitude. Peaks in ∆O3, ∆CO, and ∆NOx during different days suggested the role of varying dispersion and horizontal mixing of fire plumes.

Characteristic of Surface Ozone and Meteorological Parameters Analysis in Anyang City

This study uses the national ambient air quality station data of Anyang City from 2014 to 2017 to analyze the characteristics and variation rules of ozone (O3) in different functional zones (urban, suburban, and industrial), and also studies meteorological influencing factors and potential source distributions of O3 pollution. The results showed that the O3 concentration in Anyang increased significantly between 2014 and 2017, whereby pollution started to advance from 2015 and the earliest occurrence of an O3 pollution episode was in April 2017. The 90th percentile and average concentrations of O3 in the industrial zone increased at faster rates (average annual growth of 16.0 μg·m-3 and 13.0 μg·m-3, respectively) than of those in the urban and suburban zones. The O3 concentrations at the suburban site showed the fastest increase of all zones at the 5th percentile (average annual growth of 13.2 μg·m-3). The monthly variation in O3 concentrations in Anyang showed an "M" pattern that varied spatially depending on the zone. Temperature played a leading role in O3 concentrations; air temperatures >23℃, relative humidity <58%, and a wind speed of 5 m·s-1 in a south-southwesterly direction were closely related to the occurrence of high O3 concentrations. Potential sources of O3 in different seasons were significantly different, and mainly distributed in southern Hebei, northern Hubei, and northern Shenyang in summer. The first heavy O3 pollution day in the studied period was in May 2017, at which time the highest O3 concentration was found in the industrial zone (up to 405 μg·m-3). This heavy O3 pollution episode was related to the continuous high temperature that was caused by the transfer of a dry, hot air mass in western China.

Temporal Variations in the Air Quality Index and the Impact of the COVID-19 Event on Air Quality in Western China

This study investigated the AQI (air quality index) and atmospheric pollutants including PM2.5, PM10, CO, SO2, NO2 and O3 in Chongqing, Luzhou and Chengdu from 2017 to 2019. In addition, the impacts of the COVID-19 event on the air quality in the three cities in 2020 were compared and discussed. For the combined AQIs for the three cities, in spring, the daily AQIs ranged between 25 and 182 and averaged 72.1. In summer, the daily AQIs ranged between 24 and 206 and averaged 77.5. In autumn, the daily AQIs ranged between 22 and 170 and averaged 61.1, and in winter, the daily AQIs ranged between 28 and 375 and averaged 99.6. The distributions of the six AQI classes in spring were 3%, 94%, 3%, 0%, 0%, and 0%; in summer, they were 11%, 74%, 15%, 0%, 0% and 0%; in autumn, they were 29%, 70%, 1%, 0%, 0%, and 0%, and in winter, they were 1%, 52%, 44%, 3%, 0%, and 0%, respectively. The average AQIs, in order, were Chengdu (85.4) > Chongqing (73.8) > Luzhou (73.2). Both the highest AQIs and PM2.5 (as the major indicatory air pollutant) occurred mainly in the low temperature season (January, December, and February), while O3 was the main air pollutant in June and August when the weather was hot. In February 2020, during the epidemic prevention and control actions taken in response to COVID-19 for the three cities, the combined AQIs for the top five days with the highest AQIs in February 2020 was 79.4, which was 23.6% lower than that from 2017–2019 (AQI = 100.7), and the average concentrations of PM2.5, PM10, SO2, CO, and NO2 were 89.4 µg m–3, 106 µg m–3, 2.31 ppb, 0.72 ppm, and 12.3 ppb, respectively, and were 17.9%, 30.8%, 83.8%, 19.8%, and 62.1%, lower than those in February 2017–2019. However, the average O3 concentration (31.8 ppb) in February 2020 rather than decreasing, increased by 6.2%. This is because a lower NO2 concentration hindered the NO + O3 reaction and led to increase O3 concentration in the ambient air.

Impact of the COVID-19 Event on Air Quality in Central China

In early 2020, the COVID-19 epidemic spread globally. This study investigated the air quality of three cities in Hubei Province, Wuhan, Jingmen, and Enshi, central China, from January to March 2017–2020 to analyze the impact of the epidemic prevention and control actions on air quality. The results indicated that in the three cities, during February 2020, when the epidemic prevention and control actions were taken, the average concentrations of atmospheric PM2.5, PM10, SO2, CO, and NO2 in the three cities were 46.1 µg m–3, 50.8 µg m–3, 2.56 ppb, 0.60 ppm, and 6.70 ppb, and were 30.1%, 40.5%, 33.4%, 27.9%, and 61.4% lower than the levels in February 2017–2019, respectively. However, the average O3 concentration (23.1, 32.4, and 40.2 ppb) in 2020 did not show a significant decrease, and even increased by 12.7%, 14.3%, and 11.6% in January, February, and March, respectively. This is because a lower concentration of NO2 resulted in constraints on the NO + O3 reaction, and the O3 could not be effectively further depleted. In addition, the average air quality index (AQI) for the three cities in January, February, and March 2020 were 32.2%, 27.7%, and 14.9% lower than the levels in 2017–2019, respectively. Based on the AQIs for the three cities, the combined proportions of Class I and Class Ⅱ in January, February, and March 2020 increased by 27.9%, 24.8%, and 4.3%, respectively, while the combined proportion of AQI Classes III, IV, V, and VI was reduced from 34.8% to 15.8%. In addition, in the first three months of 2020, the indicatory air pollutants in the three cities for the AQIs were predominant in the following order: PM2.5 (72.0%), O3 (16.4%), PM10 (8.3%), NO2 (2.9%), and CO (0.4%). This study provides useful information for establishing a scientific air pollution control strategy and is a valuable reference for future research on improving urban air quality.

Urban ozone sink inferred from surface measurements in China

This study detected the spatial variations in the surface O3 concentrations along the urban-suburban-rural-background land use gradient and strived to identify the driving factors of these spatial differences. The average O3 concentrations exhibited an increasing gradient from urban cores to background areas with values of 43.5 μg/m3 in urban areas, 50.1 μg/m3 in the green regions of urban areas, 50.6 μg/m3 in suburban towns, 53.9 μg/m3 in rural areas, and 69.1 μg/m3 at background sites. The differences in the annual O3 concentrations between urban and background areas were strongly negatively correlated with the differences in NO2 and PM10 (particulate matter 10 μm or less in diameter) across China. Moreover, the monthly O3 differences between urban and background sites were generally large when the O3 concentration at the background site was at a high level. At the hourly scale, the O3 differences were larger during the night than during the day, and the O3 differences were significantly negatively correlated with the differences in the NO2 and PM10 concentrations but positively correlated with those in the CO and SO2 concentrations. In particular, SO2 had a positive effect on the O3 concentration when SO2 was at a high level. These results provide a scientific basis for enacting policies to control O3 pollution.

Long-term exposure to ozone and children's respiratory health: Results from the RESPOZE study

BackgroundAlthough there is evidence on the effects of short-term ozone (O3) exposures on children's respiratory health, few studies have reported results on the effects of long-term exposures. We report the effects of long-term exposure to O3 on respiratory health outcomes in 10–11-year old children. MethodsWe conducted a panel study in a sample of the general population of school children in two cities with high average O3 concentrations, Athens and Thessaloniki, Greece. All 186 participating students were followed up intensively for 5 weeks spreading across a school year. Data was collected through questionnaires, weekly personal O3 measurements, spirometry, FeNO and time-activity diaries. Long-term O3 exposure was assessed using fixed site measurements and modeling, calibrated for personal exposures. The associations between measured lung function parameters and lung function growth over the study period, as well as FeNO and the occurrence of symptoms with long-term O3 exposure were assessed through the application of multiple mixed effects 2-level regression models, adjusting for confounders and for short-term exposures. ResultsA 10 μg/m3 increase in calibrated long-term O3exposure, using measurements from fixed site monitors was associated with lower FVC and FEV1 by 17 mL (95% Confidence Interval: 5–28) and 13 mL (3–21) respectively and small decreases in lung growth: 0.008% (0.002–0.014%) for FVC and 0.006% (0.000–0.012%) in FEV1 over the study period. No association was observed with PEF, FeNO or the occurrence of symptoms. A similar pattern was observed when the exposure estimates from the dispersion models were employed. ConclusionsOur study provides evidence that long-term O3 exposure is associated with reduced lung volumes and growth.

Quantifying the impact of synoptic circulation patterns on ozone variability in northern China from April to October 2013–2017

Abstract. The characteristics of ozone variations and the impacts of synoptic and local meteorological factors in northern China were quantitatively analyzed during the warm season from 2013 to 2017 based on multi-city in situ ozone and meteorological data as well as meteorological reanalysis. The domain-averaged maximum daily 8 h running average O3 (MDA8 O3) concentration was 122±11 µg m−3, with an increase rate of 7.88 µg m−3 yr−1, and the three most polluted months were closely related to the variations in the synoptic circulation patterns, which occurred in June (149 µg m−3), May (138 µg m−3) and July (132 µg m−3). A total of 26 weather types (merged into five weather categories) were objectively identified using the Lamb–Jenkinson method. The highly polluted weather categories included the S–W–N directions (geostrophic wind direction diverts from south to north), low-pressure-related weather types (LP) and cyclone type, which the study area controlled by a low-pressure center (C), and the corresponding domain-averaged MDA8 O3 concentrations were 122, 126 and 128 µg m−3, respectively. Based on the frequency and intensity changes of the synoptic circulation patterns, 39.2 % of the interannual increase in the domain-averaged O3 from 2013 to 2017 was attributed to synoptic changes, and the intensity of the synoptic circulation patterns was the dominant factor. Using synoptic classification and local meteorological factors, the segmented synoptic-regression approach was established to evaluate and forecast daily ozone variability on an urban scale. The results showed that this method is practical in most cities, and the dominant factors are the maximum temperature, southerly winds, relative humidity on the previous day and on the same day, and total cloud cover. Overall, 41 %–63 % of the day-to-day variability in the MDA8 O3 concentrations was due to local meteorological variations in most cities over northern China, except for two cities: QHD (Qinhuangdao) at 34 % and ZZ (Zhengzhou) at 20 %. Our quantitative exploration of the influence of both synoptic and local meteorological factors on interannual and day-to-day ozone variability will provide a scientific basis for evaluating emission reduction measures that have been implemented by the national and local governments to mitigate air pollution in northern China.

Spatiotemporal characteristics of ozone pollution and policy implications in Northeast China

The ground-level ozone (O3) pollution has become an emerging air quality issue in China. To effectively mitigate ozone pollution in Northeast China (NEC), this study focuses on its characteristics based on the surface ozone, meteorological data, and Ozone Monitoring Instrument (OMI) satellite data. Statistical methods are applied to analyze the effects of meteorology on O3 pollution. The results show that the area and annual averaged maximum 8-h average O3 concentrations rose from 81.3 to 87.4 μg/m3 during 2015–2018 and the nonattainment days kept increasing. The ground-observed O3 concentrations and OMI ozone vertical column densities (VCDs) displayed the pattern of highs in the southwest and lows the northeast of the NEC region with the exceedance areas mainly located over the Liaoning and Jilin provinces in spring and summer. The long-term series of O3, HCHO and NO2 VCDs averaged over NEC all exhibited annual upward trends. Indicated by the OMI HCHO/NO2 ratio, the seasonal and spatial O3-VOCs-NOx sensitivities in NEC provide the control measure guidance for government agencies. Also the ozone control measure needs to consider the biogenic emissions along with the anthropogenic VOCs emissions due to the vast forest areas and large-scale agricultural production in NEC. The ozone pollution episodes in NEC were correlated with weather conditions of high temperature, low relative humidity, long sunshine duration and southwesterly wind in summer and the impact of the East Asia summer monsoon cannot be ignored. Future investigation into VOCs’ measurements and emission inventories are much needed for ozone pollution control in NEC.

A WRF-Chem model-based future vehicle emission control policy simulation and assessment for the Beijing-Tianjin-Hebei region, China

Using 2025 as the target year, we quantitatively assessed the reduction potentials of emissions of primary pollutants (including CO, HC, NOx, PM2.5 and PM10) under different vehicle control policies and the impacts of vehicle emission control policies in the BTH region on the regional PM2.5 concentration in winter and the surface ozone (O3) concentration in summer. Comparing the different scenarios, we found that (1) vehicle control policies will bring significant reductions in the emissions of primary pollutants. Among the individual policies, upgrading new vehicle emission standards and fuel quality in Beijing, Tianjin, and Hebei will be the most effective policy, with emission reductions of primary pollutants of 26.3%–54.7%, 38.0%–70.3% and 46.0%–81.6% in 2025, respectively; (2) for PM2.5 in winter, the Combined Scenario (CS) will lead to a reduction of 0.5–3.9 μg m−3 (3.5%–11.6%) for the monthly average PM2.5 concentrations in most areas. The monthly nitrate and ammonium concentrations would reduce by 5.8% and 5.3%, respectively, in the whole BTH region, indicating that vehicle emission control policies may play an important role in the reduction of PM2.5 concentrations in winter, especially for nitrate aerosols; and (3) for O3 concentrations in summer, vehicle emission control policies will lead to significant decreases. Under the CS scenario, the maximum reduction of monthly average O3 concentrations in the summer is approximately 3.6 ppb (5.9%). Most areas in the BTH region have a decrease of 15 ppb (7.5%) in peak values compared to the base scenario. However, in some VOC-sensitive areas in the BTH region, such as the southern urban areas, significant reductions in NOx may lead to increases in ozone concentrations. Our results highlight that season- and location-specific vehicle emission control measures are needed to alleviate ambient PM2.5 and O3 pollution effectively in this region due to the complex meteorological conditions and atmospheric chemical reactions.

Short-term effects of Saharan dust intrusions and biomass combustion on birth outcomes in Spain

The objective of this study is to analyze the short-term effects of atmospheric pollutant concentrations (PM10, NO2 and O3) and heat and cold waves on the number of pre-term births and cases of low birth weight related to Saharan dust advection and biomass combustion. The dependent variables used in this analysis were the total number of births, births with low weight (>2.500 g) and pre-term births (<37 weeks), that occurred at the province level. Data provided by the NSI included: days with Saharan dust intrusion or biomass advection classified in terms of information provided by MITECO for each of the nine regions in Spain. A representative city was selected for reach region in which the registered average daily concentrations of PM10, NO2 and O3 (μg/m3) were used. These were also provided by MITECO. The daily maximum and daily minimum temperature (°C) used was those registered by the meteorological observatory station located in each province capital, provided by AEMET. Using Poisson log linear regression models, the associated relative risks (RR) were measured as well as the population attributable risk (PAR) corresponding to the variables that resulted statistically significant at p < 0.05 for days with and without intrusion of natural particulate matter.The results obtained show that the days with Saharan dust intrusion or advections due to biomass combustion- beyond the impact of PM10, primary pollutants such as NO2 (in Saharan intrusions), heat waves and O3 - are associated with the number of births, low birth weight and pre-term birth. The RR and percent PAR of the pollutants and the heat waves are greater than those obtained for PM10.The results of this study indicate that days with natural particulate matter due to biomass combustion or advection of Saharan dust put pregnant women at risk.

Effects of elevated ozone on physiological, biochemical and morphological characteristics of eggplant

Air pollutants are emitted from various anthropogenic sources into the atmosphere. Especially, ozone (O3) has become a critical problem since the average O3 concentration is increasing every year by about 0.5–2% across the world. O3 in the air affects plant growth because it mainly passes through the stomata of leaves into plants. This experiment was designed to identify the physiological, morphological, and biochemical responses of plants to O3. For the purposes of this study, eggplant (Solanum melongena L.), which is one of the most well-known crops produced in the world, was used. Eggplants were continuously subjected to 110 nmol mol−1 for 25 days using the phytotron. Following O3 treatment, the growth and biomass of the eggplant were reduced, and the photosynthetic rates were lower than those of the controls. In contrast, water use efficiency increased progressively on the leaves of the eggplant. Initial visible injures were observed at 15 days after O3 treatment. Stomatal density was reduced in response to the O3 treatment. With regard to biochemical responses, malondialdehyde content and relative ion leakage were higher than those of the control. Superoxide and hydrogen peroxide accumulation was observed on the leaf surface after 25 days of O3 treatment. These observations indicate that treatment with 110 nmol mol−1 O3 had negative effects on the physiological, morphological, and biochemical activities of eggplant. Further studies investigating the damage caused by exposure to different concentrations of O3 and for different periods of time are required.

Assessment of tropospheric ozone at an industrial site of Chennai megacity

ABSTRACTThis paper presents the temporal variation in surface-level ozone (O3) measured at Gummidipoondi near Chennai, Tamilnadu. The site chosen for the present study has high potential for ozone generation sources, such as vehicular traffic and industrial activities. The site is also located near a hazardous waste management facility. The key sources of nitrogen oxides (NOx), which are considered to be an important precursor of O3, include hazardous waste incineration, trucks bringing the hazardous wastes, and vehicles plying on the nearby National Highway 16 (NH 16). The measurements clearly showed diurnal variation, with maximum values observed during the noon hours and minimum values observed when solar radiation was less. The data showed a marked seasonal variation in O3, with the highest hourly average O3 concentration (497.2 µg/m3) in the summer season. Consequently, in order to identify the long-range transport sources adding to the increased O3 levels, backward trajectories were computed using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. It was found that the polluted air mass originated from the Southeast Asian region and the Indo-Gangetic Plain. The polluted air mass, which advected large amounts of carbon monoxide (CO) plumes, was analyzed using the Measurement of Pollution in the Troposphere (MOPITT) retrievals. The correlations of O3 with temperature (r = 0.746; P < 0.01) and solar radiation (r = 0.751; P < 0.01) were strongly positive, and that with NOx was found to be negative. Stronger correlation of O3 with NOx was observed during pre-monsoon months (r = 0.627; P < 0.01) and following hours of photochemical reactions. There were substantial differences in concentrations between weekdays and weekends, with higher nitric oxide (NO) and nitrogen dioxide (NO2), but lower O3, concentrations on weekdays. A substantial weekday-weekend difference in O3, which was higher on weekends, appears to be attributable to lower daytime traffic activity and hence reduced emissions of NOx to a “NOx-saturated” atmosphere.Implications: The assessment of ground-level ozone in an industrial area with hazardous waste management facility is very important, as there is high possibility for more generation of tropospheric ozone. Since the location of the study area is coastal, wind plays a major role in O3 transportation; hence, the effects of wind speed and wind direction have been studied in different seasons. When compared with the other studies carried out in different places across India, the present study area has recorded much greater O3 mixing ratio. This study can be useful for setting up control strategies in such industrial areas.