The impact of ozone (O3) pollution events on the plant drought response needs special attention because spring O3 episodes are often followed by summer drought. By causing stomatal sluggishness, O3 could affect the stomatal dynamic during a subsequent drought event. In this context, we studied the impact of O3 exposure and water deficit (in the presence or in the absence of O3 episode) on the stomatal closure/opening mechanisms relative to irradiance or vapour pressure deficit (VPD) variation. Two genotypes of Populus nigra x deltoides were exposed to various treatments for 21 days. Saplings were exposed to 80 ppb/day O3 for 13 days, and then to moderate drought for 7 days. The curves of the stomatal response to irradiance and VPD changes were determined after 13 days of O3 exposure, and after 21 days in the case of subsequent water deficit, and then fitted using a sigmoidal model. The main responses under O3 exposure were stomatal closure and sluggishness, but the two genotypes showed contrasting responses. During stomatal closure induced by a change in irradiance, closure was slower for both genotypes. Nonetheless, the genotypes differed in stomatal opening under light. Carpaccio stomata opened more slowly than control stomata, whereas Robusta stomata tended to open faster. These effects could be of particular interest, as stomatal impairment was still present after O3 exposure and could result from imperfect recovery. Under water deficit alone, we observed slower stomatal closure in response to VPD and irradiance, but faster stomatal opening in response to irradiance, more marked in Carpaccio. Under the combined treatment, most of the parameters showed antagonistic responses. Our results highlight that it is important to take genotype-specific responses and interactive stress cross-talk into account to improve the prediction of stomatal conductance in response to various environmental modifications.

This study investigated the spatial and temporal distributions of particulate and gaseous air pollutants in a primary school in Beijing and assessed their health impact on the children. The results show that air quality inside the classroom was greatly affected by the input of outdoor pollutants; high levels of pollution were observed during both the heating and nonheating periods and indicate that indoor and outdoor air pollution posed a threat to the children's health. Traffic sources near the primary school were the main contributors to indoor and outdoor pollutants during both periods. Moreover, air quality in this primary school was affected by coal combustion and atmospheric reactions during the heating and nonheating periods, respectively. Based on the estimation by exposure-response functions and the weighting of indoor and outdoor pollutants during different periods, the levels of PM2.5, PM 10 and O3 at school had adverse respiratory health effects on children. Longer exposures during the nonheating period contributed to higher health risks. These results emphasized that emission sources nearby had a direct impact on air quality in school and children's respiratory health. Therefore, measures should be taken for double control on air pollution inside and outside the classroom to protect children from it.

Around the globe, worsening air pollution is spawning major public health and environmental concerns, especially in the poorest and most populous cities. As a major secondary air pollutant, ozone is a potential risk factor for exacerbated asthma, although the underlying mechanisms remain uncertain. In this study, we aim to investigate the role of ozone on asthma exacerbation using a classic asthmatic model with allergic airway inflammation by treating Balb/c mice with ovalbumin (OVA). Our study shows ozone exposure significantly exacerbated OVA-induced asthmatic phenotypes, including serum immunoglobulin, Th cytokines, inflammatory cell counts, mucus production, airway remodeling, and airway hyper-responsiveness (AHR). Interestingly, expression of transient receptor potential cation channel subfamily V member1 (TRPV1) was also significantly elevated in ozone-exacerbated asthmatic mice and that treatment with TRPV1 antagonist effectively suppressed AHR, airway inflammation and remodeling. The underlying mechanisms of these effects may be associated with suppression of neuropeptide calcitonin gene-related peptide (CGRP) and thymic stromal lymphopoietin (TSLP), an epithelial cell-derived cytokine. Base on the role of TRPV1 in allergic asthma, this study further revealed that inhibition of TRPV1 by TRPV1 antagonist has significant anti-inflammatory effects on ozone-induced asthma exacerbation in this study. Induction of TRPV1 expression may be an important mechanism underlying the increased risks for asthma after exposure to environmental pollutants.

Air pollution has been identified as a major cause of environmental and human health damage. O₃ is an oxidative pollutant that causes leaf symptoms in sensitive plants. This study aims to adjust a multilinear model for the monitoring of O₃ in subtropical climatic conditions by associating O₃ concentrations with measurements of morphological leaf traits in tobacco plants and different environmental variables. The plants were distributed into five areas (residential, urban or industrial) in the southern region of Brazil and exposed during 14 periods, of 14 days each, during the years of 2014 and 2015. The environmental variables and leaf traits during the exposure periods were described by mean, median, standard deviation and minimum and maximum values. Spearman correlation and multiple linear regression analyses were applied on data from exposure periods. Leaf injury index, leaf area, leaf dry mass, temperature, relative humidity, global solar radiation and accumulated rainfall were used in the regression analyses to select the best models for predicting O₃ concentrations. Leaf injury characteristically caused by O₃ was verified in all areas and periods of plant exposure. Higher values of leaf injury (24.5% and 27.7%) were registered in the 13th and 12th exposure periods during spring and in areas influenced by urban and industrial clutches. The VPD, temperature, global solar radiation and O₃ were correlated to leaf injury. Environmental variables [leaf area, leaf dry mass, global solar radiation and accumulated rainfall] and primarily the VPD were fundamental to improve the adjustments done in the bioindicator model (R² ≥ 0.73). Our research shows that biomonitoring employing the tobacco “Bel-W3” can be improved by measuring morphological leaf traits and meteorological parameters. Additionally, O₃ fumigation experiment should be performed with biomonitoring as conducted in this study, which are useful in understanding the role of other environmental factors.

Flaring is a common and necessary operation for chemical industries, which is designed to manage dangerous process overpressure scenarios or to release and destroy off-spec products during chemical plant upsets or turnarounds. However, excessive flaring can emit large quantities of VOCs and NOx into the atmosphere, which will cause transient and localized ozone pollution events in the presence of sunlight. The objective of this study was to quantify the impact to regional air-quality due to flare emissions from chemical plant start-up operations through the coupling of dynamic process simulations via Aspen Plus and air-quality simulations via CAMx. Simulation results from case studies have indicated that the corresponding ozone increments can vary significantly from 0.2 ppb to 17.8 ppb under different temporal and spatial factors, including the start-up starting hour, starting day, and plant location. Additional ozone sensitivity simulations have also indicated that the corresponding ozone increments are higher when the plant is located in a VOC-limited area than that in a NOx-limited area. The results from this study have delivered a cost-effective air-quality control practice for plant start-ups with a minimum air-quality impact through selecting the optimal starting time within the allowable ranges. The practice has significant potential to benefit all stakeholders, including environmental agencies, chemical industries, and local communities.

Alternative transportation fuels (ATFs) can reduce air pollution. However, the influence of conventional fuels—diesel and gasoline, and particularly ATFs on photochemical air pollution is not well-characterized, limiting assessments of ATFs and air quality. This is mainly due to frequent use of lumped chemical mechanisms by related atmospheric modeling. Here we hypothesized that applying a chemical mechanism that is specifically developed according to both emission fractions and photochemical ozone creation potential of volatile organic compounds (VOCs) is key to gaining reliable insights into the impact of transportation fuels on photochemistry. We used a heterogeneous chemical mechanism with 927 reactions and relatively detailed emission inventories to specifically meet the requirements for reliable simulation of the effect of exhaust emissions from vehicles fueled by selected model fuels—diesel, gasoline, and mixtures of 15% gasoline with 85% ethanol (E85) or 85% methanol (M85)—on photochemistry. These dispersion-box model simulations revealed a strong influence of atmospheric background balance between VOCs and nitrogen oxides (NOX = [NO] + [NO2]) on the impact of exhaust emissions on photochemistry, with higher tendency toward ozone (O3) formation or destruction for more VOC-limited or NOX-limited conditions, respectively. Accordingly, higher [NOX]/[VOC] exhaust emission, such as from diesel and M85, resulted in lower O3, not only locally but also downwind of the emission. This offers a new perspective and measure for transportation fuel assessment. Rapid conversion of O3 to hydroxyl and hydroperoxyl radicals downwind of the exhaust emission indicates the importance of simulating the impact of road transportation on photochemistry at high spatial and temporal resolution. Peroxyacetyl nitrate formation was more sensitive to VOC emission under VOC-limited conditions than to NOX emission under NOX-limited conditions. Secondary formaldehyde dominated over primary emitted formaldehyde several minutes after emission. These findings should be verified using a 3D modeling study under varying meteorological conditions.

Tropospheric ozone in the surface air has become the primary atmospheric pollutant in Hangzhou, China, in recent years. Previous analysis is not enough to decode it for better regulation. Therefore, we use the traditional atmospheric model, Weather Research and Forecasting coupled with Community Multi-scale Air Quality (WRF-CMAQ), and machine learning models, Extreme Learning Machine (ELM), Multi-layer Perceptron (MLP), Random Forest (RF) and Recurrent Neural Network (RNN) to analyze and predict the ozone in the surface air in Hangzhou, China, using meteorology and air pollutants as input. We firstly quantitatively demonstrate that the dew-point deficit, instead of temperature and relative humidity, is the predominant meteorological factor in shaping tropospheric ozone. Urban heat island, daily direct solar radiation time, wind speed and wind direction play trivial role in impacting tropospheric ozone. NO₂ is the primary influential factors both for hourly ozone and daily O₃-8 h due to the titration effect. The most environmental-friendly way to mitigate the ozone pollution is to lower the volatile organic compounds (VOCs) with the highest ozone formation potentials. We deduce that the tropospheric ozone formation process tends to be not only non-linear but also non-smooth. Compared with the traditional atmospheric models, machine learning, whose characteristics are rapid convergence, short calculating time, adaptation of forecasting episodes, small program memory, higher accuracy and less cost, is able to predict tropospheric ozone more accurately.

Environmentally persistent free radicals (EPFRs) are a new class of environmental risk substances that can stably exist in atmospheric particles and pose a potential threat to human health. In this study, electron paramagnetic resonance (EPR) spectroscopy was used to study the concentration levels, species characteristics, and sources of EPFRs in PM₂.₅ in Xi'an in 2017. The results showed that the concentrations of EPFRs in PM₂.₅ in Xi'an in 2017 ranged from 9.8 × 10¹¹ to 6.9 × 10¹⁴ spins/m³. The highest concentration of EPFRs occurred in winter when the average concentration was 2.1 × 10¹⁴ spins/m³. The lowest concentration of EPFRs occurred in autumn when the average concentration was 7.0 × 10¹³ spins/m³. According to the annual average atmospheric concentration of EPFRs, the amount of EPFRs inhaled by people in Xi'an is equivalent to approximately 5 cigarettes per person per day and approximately 23 cigarettes per person per day in winter when haze occurs. The results of the study on the EPFR characteristics show that the EPFRs in PM₂.₅ in Xi'an are mainly C-center organic radicals that are primarily non-decaying types, accounting for approximately 75% and 85% of total concentration of EPFRs in autumn and winter, respectively. Finally, a correlation analysis was used to explore the origins of EPFRs in PM₂.₅. Significant positive correlations were found between EPFRs and SO₂, NO₂ and the thermally derived OC3 and OC4 carbonaceous components. The results suggested that coal-fired and traffic may be important sources of EPFRs in PM₂.₅ in Xi'an. In addition, EPFRs are significantly positively correlated with O₃ in summer, suggesting that some EPFRs may also originate from secondary processes. This study provides important basic data and evidence for further assessments of the potential health risks of EPFRs in PM₂.₅ and the development of effective air pollution control measures.

Previous studies have suggested a change of birth weight linked with elevated ambient air pollutant concentrations during the pregnancy. However, investigations of the influence of higher pollutant levels on birth weight change are limited. The goal of this study is to evaluate whether the air pollution of Ningbo is associated with birth weight, and which trimester could be a window period for maternal exposure to air pollution. A total of 170,008 live births were selected in the Ningbo city of Zhejiang, China, from 2015 to 2017. We estimated the association between the decreased birth weight and the increased air pollutant concentrations in the three trimesters and full gestation. The effects of interaction among pollutants were identified using a co-pollutant adjustment model. An interquartile range increases in PM2.5 (10.55 μg/m3), SO2(4.6 μg/m3), CO (125.59 μg/m3), and O3 (14.54 μg/m3) concentrations during the entire gestation were associated with 3.65 g (95% confidence interval: −6.02 g, −1.29 g), 5.02 g (−6.89 g, −3.14 g), 2.64 g (−4.65 g, −0.63 g) and 2.9 g (−4.8 g, 1 g) decreases, respectively, in birth weight. With each interquartile range increment in NO2 concentration was associated with an 8.05 g (6.24 g, 9.85 g) increase in birth weight. In the first trimester, only the PM2.5 exposure seemed to be associated with the greatest decline in birth weight. After adjustment for co-pollutant, both PM2.5 and SO2 were still associated with birth weight, except for CO for O3 adjustment, O3 for SO2 adjustment, and O3 for NO2 adjustment. Maternal exposure to air pollution may be associated with a decrease of birth weight, but the contribution of various pollutants is necessary to verify by future research.

As the frequency, intensity, and duration of heatwaves increases, emergency health serviceutilization, including ambulance service, has correspondingly increased across the world. The negative effects of air pollution on health complicate these adverse health effects. This research work is the first known study to analyze the joint effects of heatwaves and air quality on the ambulance service in Western Australia (WA). The main objective is to investigate the potential joint effects of heatwaves and air quality on the ambulance service for vulnerable populations in the Perth metropolitan area. A time series design was used. Daily data on ambulance callouts, temperature and air pollutants (CO, SO₂, NO₂, O₃, PM₁₀ and PM₂.₅) were collected for the Perth metropolitan area, WA from 2006 to 2015. Poisson regression modeling was used to assess the association between heatwaves, air quality, and ambulance callouts. Risk assessments on age, gender, socio-economic status (SES), and joint effects between heatwaves and air quality on ambulance callouts were conducted. The ambulance callout rate was higher during heatwave days (14.20/100,000/day) compared to non-heatwave days (13.95/100,000/day) with a rate ratio of 1.017 (95% confidence interval 1.012, 1.023). The ambulance callout rate was higher in males, people over 60 years old, people with low SES, and those living in coastal areas during period of heatwaves. Exposure to CO, SO₂, O₃ and PM₂.₅ increased risk on ambulance callouts and exposure to NO₂ showed joint effect with heatwave and increased risk of ambulance callouts by 3% after adjustment of all other risk factors. Ambulance callouts are an important indicator for evaluating heatwave-related emergency morbidity in WA. As the median concentrations of air pollutants in WA were lower than the Australian National Standards, the interactive effects of heatwaves and air quality on ambulance service need to be further examined, especially when air pollutants exceed the standards.