High Ozone Levels Research Articles

Hourly ozone level prediction based on the characterization of its periodic behavior via deep learning

Surface ozone has become one of the most important air pollutants in recent years, posing a huge threaten to human health. The accurate prediction of ozone pollution, especially when ozone concentration exceeds permissible standard, has become an important research topic in the field of air quality management, where data-driven methods are widely used. Among these methods, the long short-term memory neural network (LSTM) has received significant attention in ozone forecasting for its ability in modeling long-term time dependence. However, from the time series perspective, short-term nonstationary characteristics resulted from periodic trends of ozone data have not been sufficiently considered by LSTM. To address this issue, we propose a novel deep learning-based prediction method named multi-order difference embedded LSTM (MDELSTM). Through statistical analysis of ozone time series, a multi-order difference strategy is employed to extract the periodic information. By embedding it into LSTM layers, a brand-new deep learning prediction model with the ability to extract both long-term stationary information and short-term periodic information is constructed for ozone forecasting. The proposed method is verified through the Los Angeles air quality dataset between 2013 and 2017. The prediction accuracy of ozone concentration over the next hour is improved compared to other state-or-the-art methods in terms of mean absolute error (MAE), root mean square error (RMSE), and coefficient of determination (R2). To further illustrate the ability of the proposed method in predicting high-level ozone concentration, new evaluation indicators oriented on situations where the ozone concentration exceeds permissible standard are proposed. The results demonstrate its application prospect in hourly ozone pollution prediction and prevention.

Air pollution and the onset of balance problems: The Canadian longitudinal study on aging.

To understand the relationship between ambient air pollution and the onset of balance problems. Population-based prospective cohort study. Baseline and 3-year follow-up data were used from the Canadian Longitudinal Study on Aging. The Comprehensive Cohort included adults aged 45-85 years old recruited from 11 sites across 7 provinces. Data on air pollution came from the Canadian Urban Environmental Health Research Consortium. Annual mean levels of ozone, fine particulate matter (PM2.5), and sulfur dioxide for each participant's postal code were estimated from satellite data. Balance was measured at both time points using the one-leg balance test with those who could not stand on one leg for at least 60s defined as failing the balance test. Our outcome was the new development of failing the balance test at follow-up in those who passed the balance test at baseline. Logistic regression was used. Of the 12,158 people who could stand for 60s on one leg at baseline, 18% were unable to do so 3 years later. In single pollutant models, living in an area with higher ozone levels was associated with the 3-year onset of balance problems (odds ratio (OR)=1.13 per interquartile range of ozone, 95% CI 1.02, 1.24) after adjustment for demographic, lifestyle, and health variables. In a multipollutant model, the association with ozone increased slightly (OR=1.16, 95% CI 1.04, 1.30). There were no associations with PM2.5 or sulfur dioxide. Our findings provide longitudinal evidence that higher ozone levels are associated with the odds of developing balance problems over a 3-year period. Further work should attempt to confirm our findings and explore the potential mechanism of action.

A Geo-AI-based ensemble mixed spatial prediction model with fine spatial-temporal resolution for estimating daytime/nighttime/daily average ozone concentrations variations in Taiwan

High levels of ground level ozone (O3) are associated with detrimental health concerns. Most of the studies only focused on daily average and daytime trends due to the presence of sunlight that initiates its formation. However, atmospheric chemical reactions occur all day, thus, nighttime concentrations should be given equal importance. In this study, geospatial-artificial intelligence (Geo-AI) which combined kriging, land use regression (LUR), machine learning, an ensemble learning, was applied to develop ensemble mixed spatial models (EMSMs) for daily, daytime, and nighttime periods. These models were used to estimate the long-term O3 spatio-temporal variations using a two-decade worth of in-situ measurements, meteorological parameters, geospatial predictors, and social and season-dependent factors. From the traditional LUR approach, the performance of EMSMs improved by 60% (daytime), 49% (nighttime), and 57% (daily). The resulting daily, daytime, and nighttime EMSMs had a high explanatory power with and adjusted R2 of 0.91, 0.91, and 0.88, respectively. Estimation maps were produced to examine the changes before and during the implementation of nationwide COVID-19 restrictions. These results provide accurate estimates and its diurnal variation that will support pollution control measure and epidemiological studies.

The perfect storm: temporal analysis of air during the world's most deadly epidemic thunderstorm asthma (ETSA) event in Melbourne.

There have been 26 epidemic thunderstorm asthma (ETSA) events worldwide, with Melbourne at the epicentre of ETSA with 7 recorded events, and in 2016 experienced the deadliest ETSA event ever recorded. Health services and emergency departments were overwhelmed with thousands requiring medical care for acute asthma and 10 people died. This multidisciplinary study was conducted across various health and science departments with the aim of improving our collective understanding of the mechanism behind ETSA. This study involved time-resolved analysis of atmospheric sampling of the air for pollen and fungal spores, and intact and ruptured pollen compared with different weather parameters, pollution levels and clinical asthma presentations. Time-resolved pollen and fungal spore data collected by Deakin AirWATCH Burwood, underwent 3-h analysis, to better reflect the 'before', 'during' and 'after' ETSA time points, on the days leading up to and following the Melbourne 2016 event. Linear correlations were conducted with atmospheric pollution data provided by the Environment Protection Authority (EPA) of Victoria, weather data sourced from Bureau of Meteorology (BOM) and clinical asthma presentation data from the Victorian Agency for Health Information (VAHI) of Department of Health. Counts of ruptured grass pollen grains increased 250% when the thunderstorm outflow reached Burwood. Increased PM10, high relative humidity, decreased temperature and low ozone concentrations observed in the storm outflow were correlated with increased levels of ruptured grass pollen. In particular, high ozone levels observed 6 h prior to this ETSA event may be a critical early indicator of impending ETSA event, since high ozone levels have been linked to increasing pollen allergen content and reducing pollen integrity, which may in turn contribute to enhanced pollen rupture. The findings presented in this article highlight the importance of including ruptured pollen and time-resolved analysis to forecast ETSA events and thus save lives.

Using mobile air quality station data to identify critical areas in the city of Rio de Janeiro regarding pollutant concentrations

Recent studies have shown that tropospheric ozone, fine particulate matter and nitrogen dioxide are the urban air pollutants of major concern regarding human health effects. Monitoring air quality is a challenge in several cities, such as Rio de Janeiro, where the number of fixed-site air quality monitoring stations and their spatial distribution are insufficient to assess the extent of atmospheric pollutants. However, despite this lack of resources, the data obtained by mobile stations are a valuable means of determining which areas are experiencing critical air quality conditions, and provide key information for an air quality management program. The main purpose of this study was to conduct a critical analysis of data obtained by the Municipal Department of Environment and Climate (SMAC) mobile station in the period 2010–2018. Concentrations determined for particulate matter with a diameter ≤2.5 µm (PM2.5), O3, NO2, SO2 and CO showed that PM2.5 and O3 are the pollutants of major concern, and that the north of the city has higher air quality indices for these compounds. In addition, the south-west district had relatively high ozone levels, probably owing to low concentrations of NO2 in a volatile organic compound (VOC)-limited ozone formation regime. These factors should be considered by the municipal government in future discussions of control strategies for managing the city’s air quality. This study also shows the value of mobile stations in making a preliminary survey of pollutant concentrations, mainly in countries with limited financial investment in air quality management.

An investigation of petrochemical emissions during KORUS-AQ: Ozone production, reactive nitrogen evolution, and aerosol production

Emissions and secondary photochemical products from the Daesan petrochemical complex (DPCC), on the west coast of South Korea, were measured from the NASA DC-8 research aircraft during the Korea-United States Air Quality campaign in 2016. The chemical evolution of petrochemical emissions was examined utilizing near-source and downwind plume transects. Small alkenes, such as ethene (C2H4), propene (C3H6), and 1,3-butadiene (C4H6), dominated the hydroxyl (OH) radical reactivity near the source region. The oxidation of these alkenes in the petrochemical plumes led to efficient conversion of nitrogen oxides (NOx) to nitric acid (HNO3), peroxycarboxylic nitric anhydrides (PANs), and alkyl nitrates (ANs), where the sum of the speciated reactive nitrogen contributes more than 80% of NOy within a few hours. Large enhancements of short-lived NOx oxidation products, such as hydroxy nitrates (HNs) and peroxyacrylic nitric anhydride, were observed, in conjunction with high ozone levels of up to 250 ppb, which are attributed to oxidation of alkenes such as 1,3-butadiene. Instantaneous ozone production rates, P(O3), near and downwind of the DPCC ranged from 9 to 24 ppb h−1, which were higher than those over Seoul. Ozone production efficiencies ranged from 6 to 10 downwind of the DPCC and were lower than 10 over Seoul. The contributions of alkenes to the instantaneous secondary organic aerosol (SOA) production rate, P(SOA), were estimated to be comparable to those of more common SOA precursors such as aromatics at intermediate distances from the DPCC. A model case study constrained to an extensive set of observations provided a diagnostic of petrochemical plume chemistry. The simulated plume chemistry reproduced the observed evolution of ozone and short-lived reactive nitrogen compounds, such as PANs and HNs as well as the rate and efficiency of ozone production. The simulated peroxy nitrates (PNs) budget included large contributions (approximately 30%) from unmeasured PNs including peroxyhydroxyacetic nitric anhydride and peroxybenzoic nitric anhydride. The large, predicted levels of these PAN compounds suggest their potential importance in chemical evolution of petrochemical plumes. One unique feature of the DPCC plumes is the substantial contribution of 1,3-butadiene to ozone and potentially SOA production. This work suggests that reductions in small alkene, especially 1,3-butadiene, emissions from the DPCC should be a priority for reducing downwind ozone.

Low-to-moderate atmospheric ozone levels are negatively correlated with hospital visits by asthma patients.

Asthma is a chronic illness of the airways that affects approximately 300 million individuals worldwide. While it is commonly accepted that high ozone levels exacerbate asthma symptoms, the impact of low to moderate ozone levels on asthma symptoms has received little attention. The purpose of this research was to determine the relationship between hospital visits by asthma patients showing the severity of their symptoms and moderate ozone levels. Statistical analyses were performed on hospital visit big data for asthma patients in Seoul, Korea, collected between 2013 and 2017. The data set includes outpatient hospital visits (n = 17,787,982), hospital admissions (n = 215,696), and emergency department visits (n = 85,482). The frequency of hospital visits by asthma patients was evaluated in relation to low ozone levels (< 0.03 ppm) and moderate ozone levels (0.03-0.06 ppm) in the Seoul environment. In comparison to low ozone levels, moderate ozone levels resulted in a reduction in outpatient hospital visits (t = 7.052, P < .001). When ozone levels were low to moderate, there was a negative correlation between ozone levels and outpatient visits (r = -0.281, 95% CI: -0.331 to -0.228). Negative associations were also identified between ozone levels and new hospital admissions (t = 2.909, P < .01; r = -0.125, 95% CI: -0.179 to -0.070) and emergency treatments (t = 2.679, P < .01; r = -0.132, 95% CI: -0.186 to -0.076). Additionally, it was verified that moderate ozone levels one day before the visits resulted in a reduction in outpatient visits (t = 5.614, P < .001; r = -0.207, 95% CI: -0.259 to -0.153). A strong relationship was identified between moderate atmospheric ozone levels and a reduction in asthma patient hospital visits.

Insights from ozone and particulate matter pollution control in New York City applied to Beijing

Strict emission control policies implemented in two megacities of New York City (NYC) and Beijing show impacts on the non-linear relationship of their ozone (O3) and fine particulate matter (PM2.5) during summertime. Here we show these non-linear O3-PM2.5 relationships including a positive linear part reflecting the O3/PM2.5 co-occurrence and a negative power function part reflecting the O3 formation suppression by PM2.5 based on the multiyear surface observations. The control policies targeting sulfur dioxide and PM2.5, then volatile organic compounds and nitrogen oxides, changed the PM2.5 chemical composition which resulted in an increased linear slope that indicates a weaker O3 control effect than occurred for PM2.5. These policies also enhanced the relative PM2.5 suppression effect as shown by an increase in the power function coefficient. Model simulations suggest that regional equal percentage emission reductions for Beijing and other Chinese megacities will be necessary to avoid further increase in the O3/PM2.5 linear slope and continuing occurrences of high levels of ozone.

Building an oxidation reactor in Taiwan: From volatile organic compounds to secondary organic aerosols

AbstractLarge amounts of volatile organic compounds (VOCs) are emitted into the atmosphere from both human and natural sources. A significant portion of VOCs would be oxidized via their reactions with atmospheric oxidants like OH, NO3, ozone, etc. The products of the oxidation reactions are often of low volatility and may condense to form secondary organic aerosols (SOA). To study the effect of VOC oxidation in aerosol formation, we are building an oxidation flow reactor system, which consists of (1) a 22‐l aluminum chamber, (2) an ozone source with an ozone detector, (3) a UV‐C (254 nm) lamp, (4) a photoionization detector to measure the effective VOC concentration, (5) various flow/concentration controlling apparatuses, and (6) a scanning mobility particle sizer to monitor the generated particles. Under the conditions of high UV and ozone levels, the oxidation process can be speeded up by orders of magnitude in this reactor. We hope to use this reactor: (i) to learn the “potential” mass of SOA that can be formed from a given VOC source like a traffic or industry site; (ii) to trace back the SOA source by utilizing the shortened reaction times; (iii) to learn the trends from VOC to SOA.

Air quality assessment in biosphere reserves close to emission sources. The case of the Spanish “Tablas de Daimiel” national park

This work shows that biosphere reserves, national parks and other protected natural areas require in situ tools to monitor and detect local and remote air pollution sources which are a threat to flora, fauna water and soil. Industries in surrounding areas, traffic and long-range transport of air pollution, can change with time and meteorology and so each national park should also have a historical database of the air quality in the site. This study reports surface measurements of ozone, NO, NO2, CO, SO2 and PM2.5 acquired from March 2020 to July 2021 in “Las Tablas de Daimiel”, a wetland Mediterranean National Park bordered by different cities and new industries in the field of the revalorization of agricultural wastes. Simultaneous data from a background station in a rural area isolated from air pollution are considered as reference.Twelve campaigns of one week duration were also performed to sample air in sorbent tubes to analyse volatile organic compounds from anthropogenic sources. Data are discussed considering meteorology, especially wind speed and direction together with the assessment of back-trajectories of air masses from distant sources. The results show that the effects of pollution from local and faraway sources on air quality in the park were weak. Thus, except for the high levels of ozone, with a mean value of 71 μg.m−3, measured mass loadings for pollutants were low and not in exceedance of the air quality standards. Saharan dust events were frequent and contributed to PM2.5 levels in the site. NOx and SO2 average concentrations (3.2 and 0.4 μg.m−3, respectively) were below the recommended critical levels for vegetation and all the quantified VOCs were found in average concentration levels below 0.5 μg.m−3.

Evaluation of Ambient Ozone Effect in Bean and Petunia at Two Different Sites under Natural Conditions: Impact on Antioxidant Enzymes and Stress Injury

Tropospheric ozone is a harmful air pollutant and greenhouse gas that adversely affects living organisms. The effect of long-term ozone stress on the activity of SOD, APX, and GuPX, as well as lipid peroxidation and membrane injury in bean and petunia growing at a city site and in a forest, characterised by different ozone concentrations, was examined. The experiments were conducted in three growing seasons with different tropospheric ozone concentrations and meteorological conditions. Plants’ exposition to increased ozone concentration resulted in enhanced activity of antioxidant enzymes, level of lipid peroxidation, and membrane injury. In all years, higher ozone levels and solar radiation were observed at the forest site. The pattern of the changes in enzyme activity was dependent on ozone concentrations as well as on environmental conditions and varied from year to year. In the second year with the highest ozone concentration, the activity of GuPX and SOD increased the most. However, despite higher ozone concentration in the forest, a larger increase in APX and SOD activity in both species and GuPX activity in bean was recorded at the city site. The present results revealed that plant response to ozone might vary in different locations not only due to differences in ozone concentration but also because of the impact of other environmental factors, such as solar radiation and temperature.

A machine learning approach to investigate the build-up of surface ozone in Mexico-City

Ground-level ozone is an important pollutant regarding air quality and climate. Mexico City frequently experiences severe ozone episodes due to a combination of strong ozone precursor emissions and its specific topographical environment which critically impacts meteorological conditions. High ozone levels during these episodes cause harmful effects to the public health and the environment. This necessitates ranking air quality and meteorological variables according to their contributions towards the build-up of ozone. In this study, three machine learning models are used to learn a prediction function with hourly data of eight predictors as input and hourly ground-level ozone mixing ratios as output. One-year hourly data of eight predictors collected in Mexico-City from March 2015 to February 2016 is employed to train and test the models. The best model, capturing ozone peak levels with 92% accuracy during 6–18 March 2016, is used to rank the predictors according to their importance in the build-up of ozone applying a shapley additive explanations approach based on the game theory shapley values. This 6–18 March 2016 period encompassed different meteorological and emission conditions and included a severe ozone smog episode from 12 to 17 March 2016. Such ranking of the air quality and meteorological variables is crucial for policy-making decisions regarding the prevention and mitigation of ozone detrimental effects during severe ozone episodes and provides insight into the functional dependency of ozone on its predictors. The proposed approach showcases Mexico City, but its principles can be applied for ozone episodes at any other location.

Interactive effects of ozone and carbon dioxide on plant-pollinator interactions and yields in a legume crop

• Increasing greenhouse gas emissions is linked to disruption of ecosystem services. • How ozone and carbon dioxide impact pollination services is not well understood. • We report on the effects of elevated ozone and carbon dioxide on field bean plants. • Elevated ozone reversed the positive effects of enhanced carbon dioxide on yield. Recent studies link increased levels of ozone and carbon dioxide to plant performance and plant-herbivore interactions, but the interactive effects on plant-pollinator interactions and ecosystem services have rarely been studied. Here we experimentally tested whether elevated levels of these two gases alter plant growth, flower visitation, and yield in field bean crop ( Vicia faba : Fabaceae or Leguminosae) using a full-factorial experimental set-up. Plants were exposed to (i) clean air (control), (ii) carbon dioxide-enriched (900 ppm), (iii) ozone-enriched (120 ppb) or (iv) carbon dioxide (900 ppm) + ozone (120 ppb) - enriched treatments. We examined how flower visitation by two widespread bee pollinators, Bombus terrestris and Osmia cornuta , and consequent yields responded to the treatments. Increased carbon dioxide levels enhanced flower visitation by B. terrestris and O. cornuta, while an increase in ozone led to a decline in visitation rates. The seed set of field beans generally increased with flower visitation rates of pollinators, revealing a pollination-mediated effect of the increased greenhouse gas concentrations on plant reproduction. In addition to the pollinator-mediated effect, we found an interactive effect of ozone and carbon dioxide on the seeds set in plants visited by B. terrestris: while increases in carbon dioxide enhanced seed set, increases in ozone generally decreased seed set - overruling the effect of increased carbon dioxide. Our results suggest that negative impacts of high ozone levels on flower visitation and fruit set counteract potential increases of legume crop yields with enhanced carbon dioxide concentrations under future climates.

Environmental Factors in Northern Italy and Sickle Cell Disease Acute Complications: A Multicentric Study.

Background: Environmental factors seem to influence clinical manifestations of sickle cell disease (SCD), but few studies have shown consistent findings. We conducted a retrospective multicentric observational study to investigate the influence of environmental parameters on hospitalization for vaso-occlusive crises (VOC) or acute chest syndrome (ACS) in children with SCD. Methods: Hospital admissions were correlated with daily meteorological and air-quality data obtained from Environmental Regional Agencies in the period 2011–2015. The effect of different parameters was assessed on the day preceding the crisis up to ten days before. Statistical analysis was performed using a quasi-likelihood Poisson regression in a generalized linear model. Results: The risk of hospitalization was increased for low maximum temperature, low minimum relative humidity, and low atmospheric pressure and weakly for mean wind speed. The diurnal temperature range and temperature difference between two consecutive days were determined to be important causes of hospitalization. For air quality parameters, we found a correlation only for high levels of ozone and for low values at the tail corresponding to the lowest concentration of this pollutant. Conclusions: Temperature, atmospheric pressure, humidity and ozone levels influence acute complications of SCD. Patients’ education and the knowledge of the modes of actions of these factors could reduce hospitalizations.

Correlation between extreme/ unusual ozone events and corona effect from electric power transmission &amp;#x26; distribution grids. Assessing the health and environmental impact of high-voltage direct current (HVDC) grid on ozone ground levels in Sao Paulo metropolitan area, Brazil.

• BACKGROUND AND AIM 1- Ozone ground levels pose a risk for public health 2- The increasing ozone levels measured in parts of the metropolitan area of Sao Paulo have brought the attention of researchers. Proposed mechanisms do not provide a clear outcome for establishing root causes, and for clarifying sources of ozone. Spatial distribution of ozone also depends on wind patterns. 3- As an alternate hypothesis for explaining unusual high levels of ozone, the corona discharge from electric transmission grid, known as corona effect, can play a significative role in the absence of, or in coincidence with other concomitant factors, to explain ozone (O3) and nitric oxide (NO) unusual levels. Negative coronas emits more ozone than Positive coronas. 4- The Environmental Protection Agency- EPA, found in a report of 1973 (EPA-650/4-73-003), following a research carried out in areas of high concentration of transmission lines that &amp;#x22;under minimal wind conditions, such transmission line concentrations can produce sizeable local ozone levels.” 5- Research applies geospatial and statistical analysis with the aim of better understanding correlations between exposures and ozone levels. • METHODS Geographic Information System (GIS)-based systems with average grid cell edge length of 10 km minimum. Global InMAP (Intervention Model for Air Pollution) with a variable resolution grid (4 km horizontal grid cell widths) in combination with GEOS- Chem simulations. Data analysis by machine-learning model. • RESULTS Applying Predictive Machine Learning algorithm as regression models, research found that coronas could generate significant ozone levels downwind of the power line. • CONCLUSIONS Evidence of correlation between unusual ozone measurements and location of key power electric grid transmission lines and distribution centers with potential for corona effect are found in Sao Paulo state and Sao Paulo city metropolitan area. • KEYWORDS Corona effect, ozone, electric grids, spatial simulation, wind patterns, air pollution

A severe weather system accompanied by a stratospheric intrusion during unusual warm winter in 2015 over the South Africa: An initial synoptic analysis

This study aims to highlight the abnormally warm winter experienced in South Africa during 2015. This work also investigates the synoptic and dynamic aspects of the specific severe weather system (late July 2015) which affected the western, southern, and eastern provinces including some parts in the Northern Cape, Western Cape, Lesotho, KwaZulu-Natal, and Eastern Cape. This is followed by an investigation of the stratospheric-tropospheric transport of the high-level ozone associated with a deep cut-off low weather system over the southern and central regions of South Africa which occurred on 24–25 July 2015. The case characteristics of the dynamical analysis of the weather system associated with a stratospheric-tropospheric intrusion was also determined. This research illustrated that this system was accompanied by deep upper and mid-tropospheric troughs which developed over the eastern part of the country. This resulted in tropopause folding controlled by the upper meandered tropospheric jet stream axis in the east of the upper and mid-tropospheric troughs. This caused the strong downward injection of stratospheric ozone-rich air with a maximum ozone value of 320 ppb at a level of 300 hPa observed using MERRA reanalysis data in the north of the North Cape province together with very dry higher tropospheric air at 300 hPa. In the lower troposphere, ozone levels as high as 61 ppb at 850 hPa were found within these intrusions in the northern-central region during the active cut-off low weather system. Using the Aura-Microwave Limb Sounder (MLS) to determine the vertical ozone profile at different pressure levels over South Africa indicated that a maximum value of approximately 270 ppb ozone was recorded on 24 July 2015. The observational measurements from this study show good agreement with the findings from the reanalysis models together with the results taken from the MERRA database for the specific day of peak ozone activity.

Volatile organic compounds in urban Lhasa: variations, sources, and potential risks

Lhasa is a typical high-altitude city with strong solar radiation and high background ozone levels. With the rapid development and urbanization, the emission of volatile organic compounds (VOCs) in Tibet has been increasing annually. However, VOCs activity and the impact on air quality and human health have scarcely been investigated. We conducted online measurement of VOCs in urban Lhasa during May 2019. The mean mixing ratio (with one standard deviation) of the total VOCs was 21.5 ± 18.6 ppb. Of the total VOCs, alkanes, alkenes, and aromatic hydrocarbons accounted for 57.7%, 20.9%, and 21.4%, respectively. On the basis of VOC atmospheric reactivity, the ozone formation potential (OFP) and hydroxyl radical loss rate (LOH) were 91.7 ppb and 3.1 s−1, respectively. Alkenes accounted for the largest proportion of the OFP and LOH, followed by aromatic hydrocarbons. The results of correlation analysis on the benzene series (BTEX), and the similarity of the diurnal changes in CO, NOy, BTEX, and TVOC mixing ratios indicated that Lhasa city strongly affected by motor vehicle emissions. Source apportionments using positive matrix factorization (PMF) model further confirmed that traffic related emissions, including gasoline automobiles, diesel vehicles, and public transportation vehicles fueled with liquid natural gas contributed the most in total VOCs concentration (44.5%–50.2%), LOH (41.6%–46.8%) and OFP (47.4%–52.3%). Biomass combustion, mainly from the traditional biomass fuel in the plateau, was the second contributor to ambient VOCs (41.3%), LOH (26.4%), and OFP (29.7%), and existed a less variation in diurnal changes with a feature of regional background. Plants contributed only about 1.5% to the VOCs concentration but a relatively high (approximately 14.6%) LOH. The noncarcinogenic risk of BTEX did not exceed the hazard quotient value, but the carcinogenic risk of benzene was 4.47 × 10–6, indicating a potential risk.

Influence of using different chemical mechanisms on simulations of ozone and its precursors in the troposphere of Shanghai, China

The implementation of different chemical mechanisms in air quality models can exert a significant impact on simulations of ozone and its precursors in the troposphere. In the present study, we applied three different chemical mechanisms (RADM2, SAPRC99 and CBMZ) in a three-dimensional mesoscale air quality model, WRF-Chem, to capture the spatiotemporal variation of the surface ozone and its precursors such as NOx and VOCs in Shanghai, China in May 2016, so that the influences on simulations exerted by using different chemical mechanisms can be clarified. Observational data from surface monitoring stations were also adopted for the comparison of the model simulations. By comparing the model predictions with the observational data, we found that the model with different chemical mechanisms can generally capture the temporal change of ozone in Shanghai during the simulated time period. However, it was found that SAPRC99 predicts a higher ozone than the other two mechanisms during a high-ozone period, while RADM2 gives a higher ozone level in other time periods. In the present study, CBMZ gives a closer ozone prediction to observations than the other two mechanisms. Regarding the nitrogen related species, in simulations using RADM2 and SAPRC99, NO2 is overestimated. In contrast, NO2 predicted by CBMZ is closer to the observational data. A comparison between simulations using different mechanisms also shows that SAPRC99 predicts higher OH, HO2 and NOx than the other two mechanisms. In contrast, RADM2 predicts the highest HNO3 and ozone among these three mechanisms. In addition, simulations using different mechanisms all indicate that Shanghai city is VOC-controlled. However, VOCs and NOx concentrations predicted by CBMZ were found to be mostly lower than those predicted by the other two mechanisms under a same condition.

Leaf trait plasticity and site-specific environmental variability modulate the severity of visible foliar ozone symptoms in Viburnum lantana.

The assessment of Visible Foliar Symptoms (VFS) is commonly adopted by forest monitoring programs to evaluate ozone impact on vegetation. The occurrence of ozone VFS may differ among individuals of the same species at the same site, and within leaves of the same individual. The aim of this study was to identify site and plant characteristics as well as functional leaf traits associated with the occurrence and severity of VFS in Viburnum lantana (an ozone-sensitive species) and at the scale of an individual site. V. lantana plants growing at one site of the ViburNeT monitoring network (Trentino, North Italy) experiencing high ozone levels were surveyed in relation to 1) sun exposure, 2) shading effect from neighbor vegetation, 3) plant height and 4) presence and severity of VFS. Leaves from three different sections of each plant were subjected to a phenotypic characterization of leaf area, dry weight, specific leaf area (SLA), chlorophyll content (ChlSPAD), percentage of VFS, and adaxial and abaxial trichome density (Tr). We showed that plants at high irradiation levels had significantly lower SLA (p<0.05), higher Tr (p<0.01) and greater ChlSPAD (p<0.01) when compared to shaded and/or west- and north-exposed plants, thus indicating a strong influence of site-specific characteristics on leaf trait plasticity. Similar differences were observed for taller vs. shorter plants and apical vs. basal branches (p<0.05). Ozone-induced VFS at leaf level were associated with lower SLA (p<0.001) and higher Tr in the abaxial leaf surface (p<0.05). Both leaf traits showed significant differences also within the south and east exposed plant category, thus suggesting the increase in leaf thickness and Tr as a potential adaptive strategy under multiple stress conditions. Our results provide evidence of a strong relationship between VFS, leaf traits and site-specific variables, offering new insights for interpreting data on the impact of ozone on vegetation.

Ambient ozone exposure and bone turnover markers in children: Results from the GINIplus and LISA birth cohorts

BackgroundMultiple environmental factors can regulate bone metabolism, and it is hypothesized that air pollution may be deleteriously involved in this regulation. However, only a few studies considered bone turnover markers (BTMs) - sensitive and specific markers of bone metabolism - as outcomes, and no study investigated the exposure to ambient ozone. Here, we intended to explore the associations between long-term exposure to ambient ozone and concentrations of two BTMs, osteocalcin and β-isomer of C-terminal telopeptide of type I collagen (CTx), amongst 10-year-old children. MethodsBased on the GINIplus and LISA birth cohorts, our cross-sectional analysis included 1848 children aged 10 years from Munich and Wesel. Serum osteocalcin and CTx concentrations were measured. We estimated ozone exposures by optimal interpolation, assessed nitrogen dioxide and particulate matter with an aerodynamic diameter <10 μm concentrations by land use regression models, and assigned the exposures to home addresses. Linear regression models were built and adjusted for covariates as well as co-pollutants. ResultsThe mean concentrations were 93.09 ng/mL and 663.66 ng/L for osteocalcin and CTx, respectively. In general, higher levels of ozone were associated with decreased concentrations of both BTMs. This held true for the two areas and different exposure metrics. The number of days per year with a maximum 8-h average concentration exceeding 120 μg/m³ showed consistent results across different models. Specifically, models adjusted for co-pollutants illustrated that the beta estimates and 95% confidence intervals on osteocalcin and CTx were −2.51 (−3.78, −1.14) and −44.53 (−57.12, −31.93), respectively, for an increase of 10 days. ConclusionsWe found that long-term exposure to ambient ozone was associated with decreased concentrations of BTMs in German children. This association might potentially affect bone metabolism. Nevertheless, unless other prospective studies confirm our results, the detrimental effects of ambient ozone on bone development in children should be interpreted cautiously.