Peak Ozone Concentrations Research Articles

Sensitivity analysis of PM2.5 and O3 co-pollution in Beijing based on GRAPES-CUACE adjoint model

In recent years, incidents of simultaneous exceedance of PM2.5 and O3 concentrations, termed PM2.5 and O3 co-pollution events, have frequently occurred in China. This study conducted atmospheric circulation analysis on two typical co-pollution events in Beijing, occurring from July 22 to July 28, 2019, and from April 25 to May 2, 2020. These events were categorized into pre-trough southerly airflow type (Type 1) and post-trough northwest flow type (Type 2). Subsequently, sensitivity analyses using the GRAPES-CUACE adjoint model were performed to quantify the contributions of precursor emissions from Beijing and surrounding areas to PM2.5 and O3 concentrations in Beijing for two types of co-pollution. The results indicated that the spatiotemporal distribution of sensitive source region varied among different circulation types. Primary PM2.5 (PPM2.5) emissions from Hebei contributed the most to the 24-hour average PM2.5 (24-h PM2.5) peak concentration (41.6 %-45.4 %), followed by Beijing emissions (31 %-35.7 %). The maximum daily 8-hour average ozone peak concentration was primarily influenced by the emissions from Hebei and Beijing, with contribution ratios respectively of 32.8 %-44.8 % and 29 %-42.1 %. Additionally, NOx emissions were the main contributors in Type 1, while both NOx and VOCs emissions contributed similarly in Type 2. The iterative emission reduction experiments for two types of co-pollution indicated that Type 1 required emission reductions in NOx (52.4 %-71.8 %) and VOCs (14.1 %-33.8 %) only. In contrast, Type 2 required combined emission reductions in NOx (37.0 %-65.1 %), VOCs (30.7 %-56.2 %), and PPM2.5 (31 %-46.9 %). This study provided a reference for controlling co-pollution events and improving air quality in Beijing.

Determination of Ozone Concentration Levels in Urban Environments Using a Laser Spectroscopy System

In urban areas, there has been a recent rise in ground-level ozone. Given its toxicity to both humans and the environment, the investigation of ozone pollution demands attention and should not be overlooked. Therefore, we conducted a study on ozone concentration in three distinct locations within the city of Magurele, Romania. This investigation considered variations in both structure and location during the spring and summer seasons, specifically at a breathing level of 1.5 m above the ground. Our analysis aimed to explore the impact of different locations and meteorological variables on ozone levels. The three measurement points were strategically positioned in diverse settings: within the city, in a forest, and within an industrial area. For these measurements, we used a laser spectroscopy system to determine the system’s sensitivity and selectivity and the influence of humidity in the detection of ozone in ambient air, which is a mixture of trace gases and water vapor. During the March–August campaign, the mean values in the three measuring points were 24.45 ± 16.44 ppb, 11.96 ± 3.80 ppb, and 95.01 ± 37.11 ppb. The peak concentrations of ozone were observed during the summer season. A diurnal analysis revealed that the atmospheric ozone levels were higher in the latter part of the day compared to the earlier part. These measurements suggest that the atmospheric temperature plays a significant role in tropospheric ozone production. Additionally, meteorological variables such as wind speed and direction were found to influence the ozone concentration. Remarkably, despite substantial traffic, the ozone levels remained consistently low throughout the entire period within the forested area. This observation may suggest the remarkable ability of trees to mitigate pollution levels.

Integrated analysis of the transport process and source attribution of an extreme ozone pollution event in Hefei at different vertical heights: A case of study

The Yangtze River Delta (YRD) region frequently experiences ozone pollution events during the summer and autumn seasons. High-concentration events are typically related to synoptic weather patterns, which impact the transport and photochemical production of ozone at multiple scales, ranging from the local to regional scale. To better understand the regional ozone pollution problem, studies on ozone source attribution are needed, especially regarding the contributions of sources at different vertical heights based on tagging the region or time periods. Between September 3 and 8, 2020, an episode of ozone concentration anomaly high was observed in Hefei through ground-based stations and ozone Lidar. The mechanism behind this event was uncovered through synoptic weather pattern analysis and using the Weather Research and Forecasting Chemistry model (WRF-Chem). Because an approaching typhoon caused variable wind direction, the O3-rich air masses (ORMs) arising from the YRD region were transported to Hefei via the nocturnal residual layer and descended to the ground through horizontal advection and vertical mixing processes the next day. Based on geographic source tagging, the anthropogenic NOx emissions (ANEs) from local and regional sources were the main contributors to the heavy ozone pollution over Hefei on September 6. Furthermore, the intra-regional transported ozone from southern Jiangsu (SJS), southern Anhui (SAH), and Zhejiang (ZJ) in the YRD was the main driving factor of the surface and upper atmosphere ozone pollution. Based on time period tagging, The ozone generated due to ANEs from September 3 to 5 significantly contributed to this episode. It is important to pay attention to the impact of ANEs on September 5 on the surface peak ozone concentration the following day (i.e., September 6). Our findings provide significant insights into the regional ozone transport mechanism in the YRD and optimization of measures to prevent and control heavy ozone pollution on spatiotemporal scales.

An Observational Constraint of VOC Emissions for Air Quality Modeling Study in the Pearl River Delta Region

AbstractVolatile organic compounds (VOCs) have crucial influences on atmospheric chemistry. Accurate quantification of the VOC emissions is critical for air pollution research, especially when applying to air quality models. However, current bottom‐up emission inventories have biases, making observational constraints of VOC emissions necessary. We conducted concurrent VOC measurements in the Pearl River Delta (PRD) region during the summer of 2018 and found large discrepancies in the spatiotemporal variations of VOCs between observations and model simulations when using the priori VOC emission inventory (Multi‐resolution Emission Inventory for China). The normalized biases of total VOC concentrations ranged from −55% to 85% across the PRD cities in the study period. To improve the simulations, we constrained the anthropogenic VOC emissions based on their measured concentrations. The observation‐constrained VOC emissions showed clear diurnal variations and resolved the spatially‐concentrated priori emissions by reducing the high emissions by 15%–36% in the central PRD cities while elevating the sparse emissions in other cities. After employing the observation‐constrained VOC emissions, the model better reproduced the spatiotemporal variations of VOCs in the PRD region, alleviating the biases to −13%–13%. Furthermore, simulations of peak ozone (O3) concentrations were amended to reduce the mean normalized bias by 5%–12% on high O3 days. Our work has effectively combined VOC field measurements with air quality modeling to achieve better simulations of VOCs and O3. Besides, the observational‐constrained emissions are flexible for studying short‐term emission changes and their subsequent impacts on air quality.

Future Ozone Levels Responses to Changes in Meteorological Conditions under RCP 4.5 and RCP 8.5 Scenarios over São Paulo, Brazil

Since the implementation of emission control policies in 1983, the Metropolitan Area of São Paulo (MASP) has experienced a significant decrease in the annual mean concentration of air pollutants, except for ozone, which has remained relatively stable. This work analyzes the future impact on surface ozone formation in the MASP caused by changes in atmospheric conditions. The authors performed air quality simulations using the weather research and forecasting with chemistry (WRF-Chem) model under two representative concentration pathway (RCP) atmospheric conditions. A base case simulation from September and October 2018 was compared to scenarios for the same months in 2030, using the same anthropogenic emissions. Results show an average increase in peak ozone concentrations (0.43% for RCP 4.5 and 5.92% for RCP 8.5) with variations depending on the month and location. However, under the RCP 4.5 scenario, peak ozone concentrations in October were higher in urban areas than under the RCP 8.5. These outcomes can assist decision-makers in understanding the potential future impacts of high ozone formation, which has historically occurred in September and October in São Paulo by considering the effects of changing meteorological conditions, such as increased temperatures, higher surface radiation, and reduced cloudiness.

Attribution of surface ozone to NOx and volatile organic compound sources during two different high ozone events

Abstract. Increased tropospheric ozone (O3) and high temperatures affect human health during heat waves. Here, we perform a source attribution that considers separately the formation of German surface ozone from emitted NOx and volatile organic compound (VOC) precursors during two peak ozone events that took place in 2015 and 2018 which were associated with elevated temperatures. Results showed that peak ozone concentrations can be primarily attributed to nearby emissions of anthropogenic NOx (from Germany and immediately neighboring countries) and biogenic VOC. Outside of these high ozone episodes, baseline ozone concentrations are attributed primarily to long-range transport, with ozone due to remote anthropogenic NOx emissions and methane oxidation adding to the tropospheric ozone background. We show that a significant contribution to modeled O3 coming from German NOx or VOC emissions occurs mostly in southern Germany, emphasizing that the production of ozone depends on the local interplay between NOx and VOC precursors. Shipping activities in the Baltic and North seas have a large impact on ozone predicted in coastal areas, yet a small amount of ozone from these sources can also be seen far inland, showing the importance of transported ozone on pollution levels. We have also shown that changes in circulation patterns during the peak O3 episodes observed in Germany during the 2015 and 2018 heat waves can affect the contribution of different NOx emission sources to total O3; thus, the possible influence of multiple upwind source regions should be accounted for when mitigation strategies are designed. Our study also highlights the good correlation between ozone coming from German biogenic VOC emissions and total ozone, although the diurnal variation in the ozone coming from biogenic sources is not dominated by the diurnal variation in biogenic emissions, and the peaks of ozone from biogenic sources are disconnected from local emission peaks. This suggests that the formation of O3 from local German biogenic VOC emissions is not the sole factor that influences the ozone formation, and other meteorological and chemical processes affect the diel variation of ozone with a biogenic origin. Overall, this study helps to demonstrate the importance of a source attribution method to understand the sources of O3 in Germany and can be a useful tool that will help to design effective mitigation strategies.

Separating emissions and meteorological impacts on peak ozone concentrations in Southern California using generalized additive modeling

Ozone levels have been declining in the Los Angeles, CA, USA area for the last four decades, but there was a recent uptick in the 4th highest daily maximum 8-h (MDA8) ozone concentrations from 2014 to 2018 despite continued reductions in the estimated precursor emissions. In this study, we assess the emissions and meteorological impacts on the 4th highest MDA8 ozone concentrations to better understand the factors affecting the observed MDA8 ozone using a two-step generalized additive model (GAM)/least squares approach applied to the South Coast Air Basin (SoCAB) for the 1990 to 2019 period. The GAM model includes emissions, meteorological factors, large-scale climate variables, date, and the interactions between meteorology and emissions. A least squares method was applied to the GAM output to better capture the 4th highest MDA8 ozone. The resulting two-step model had an R2 of 0.98 and a slope of 1 between the observed and predicted 4th highest MDA8 ozone. Emissions and the interactions between the maximum temperature and emissions explain most of the variation in the peak MDA8 ozone concentrations. Declining emissions have lowered the 4th highest MDA8 ozone concentration. Meteorology explains the higher than expected 4th-high, ozone levels observed in 2014–2018, indicating that meteorology was a stronger forcer than the continued reductions in emissions during that time period. The model was applied to estimate future ozone levels. Meteorology developed from climate modeling of the representative concentration pathway (RCP) scenarios, and two sets of emissions were used in the application. The modeling results indicated climate trends will push ozone levels slightly higher if no further emissions reductions are realized and that of two emissions trajectories modeled, the more stringent is required to reliably meet the federal ozone standard given annual meteorological variability.

Development of GRAPES-CUACE adjoint model version 2.0 and its application in sensitivity analysis of ozone pollution in north China

We presented the development of the gaseous chemistry adjoint module of the meteorological-chemical model system GRAPES-CUACE (Global/Regional Assimilation and PrEdiction System coupled with CMA Unified Atmospheric Chemistry Environmental Forecasting System) on the basis of the previously constructed aerosol adjoint module. The latest version of the GRAPES-CUACE adjoint model mainly includes the adjoint of the physical and chemical processes, the adjoint of the transport processes, and the adjoint of interface programs, of both gas and aerosol. The adjoint implementation was validated for the full model, and adjoint results showed good agreement with brute force sensitivities. We also applied the newly developed adjoint model to the sensitivity analysis of an ozone episode occurred in Beijing on July 2, 2017, as well as the design of emission-reduction strategies for this episode. The relationships between the ozone concentration and precursor emissions were well captured by the adjoint model. It is indicated that for a case used here, the Beijing peak ozone concentration was influenced mostly by local emissions (6.2–24.3%), as well as by surrounding emissions, including Hebei (4.4–16.8%), Tianjin (1.8–6.6%), Shandong (1.8–2.6%), and Shanxi (<1%). In addition, reduction of NOx, VOCs, and CO emissions in these regions would effectively decrease the Beijing peak ozone concentration. This study highlights the capability of GRAPES-CUACE adjoint model in quantifying “emission-concentration” relationship and in providing guidance for environmental control policy.

Characteristics and Control Strategies on Summertime Peak Ozone Concentration in Shanghai

With the continuous development of air pollution control measures, the concentration of PM2.5 in Shanghai has shown a conspicuous downward trend in recent years. However, frequent O3 pollution events have highlighted the urgent need to explore the occurrence patterns of O3 pollution and develop scientific strategies for reducing O3 peaks. This study examines data from July 2017, when the cumulative number of O3 pollution days in 17 cities in the Yangtze River Delta was 165 days, of which Shanghai was the most serious, with an exceedance rate of 64.5%. During this period, the average concentration of NO2 in Shanghai was 27.1 μg·m-3 and volatile organic copunds (VOCs) mixing ratio was 22.5×10-9. By analyzing ozone precursor concentrations and meteorological factors, we determined that these events mainly resulted from a combination of unfavorable meteorological conditions such as high temperature, low humidity, low wind speed, and high precursor emissions. WRF-CMAQ scenario simulations showed that a reduction in precursor emissions in Shanghai alone would have a limited controlling effect on regional O3 pollution. Thus, regional joint control is recommended when widespread pollution events occur. Our analysis shows that if VOCs in Shanghai and nine neighboring cities can be reduced by 30%, the maximum 8-h O3 concentration in Shanghai could be reduced by 7.2%. If the reduction number of these cities rises to 17, the maximum 8-h O3 concentration reduction rate in Shanghai will increase to 7.8%. It is also recommended that the VOCs:NOx reduction ratio should be strictly controlled at more than 3:1, or else the O3 concentration in some areas will increase.

Modelling the effects of ozone concentration and pulse vaccination on seasonal influenza outbreaks in Gansu Province, China

&lt;p style='text-indent:20px;'&gt;Common air pollutants, such as ozone (&lt;inline-formula&gt;&lt;tex-math id="M1"&gt;\begin{document}$ \rm{O}_{3} $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;), sulfur dioxide (&lt;inline-formula&gt;&lt;tex-math id="M2"&gt;\begin{document}$ \rm{SO}_2 $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;) and nitrogen dioxide (&lt;inline-formula&gt;&lt;tex-math id="M3"&gt;\begin{document}$ \rm{NO}_2 $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;), can affect the spread of influenza. We propose a new non-autonomous impulsive differential equation model with the effects of ozone and vaccination in this paper. First, the basic reproduction number of the impulsive system is obtained, and the global asymptotic stability of the disease-free periodic solution is proved. Furthermore, the uniform persistence of the system is demonstrated. Second, the unknown parameters of the ozone dynamics model are obtained by fitting the ozone concentration data by the least square method and Bootstrap. The MCMC algorithm is used to fit influenza data in Gansu Province to identify the most suitable parameter values of the system. The basic reproduction number &lt;inline-formula&gt;&lt;tex-math id="M4"&gt;\begin{document}$ R_{0} $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; is estimated to be &lt;inline-formula&gt;&lt;tex-math id="M5"&gt;\begin{document}$ 1.2486 $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; (&lt;inline-formula&gt;&lt;tex-math id="M6"&gt;\begin{document}$ 95\%\rm{CI}:(1.2470, 1.2501) $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;). Then, a sensitivity analysis is performed on the system parameters. We find that the average annual incidence of seasonal influenza in Gansu Province is 31.3374 per 100,000 people. Influenza cases started to surge in 2016, rising by a factor of one and a half between 2014 and 2016, further increasing in 2019 (54.6909 per 100,000 population). The average incidence rate during the post-upsurge period (2017-2019) is one and a half times more than in the pre-upsurge period (2014-2016). In particular, we find that the peak ozone concentration appears 5–8 months in Gansu Province. A moderate negative correlation is seen between influenza cases and monthly ozone concentration (Pearson correlation coefficient: &lt;inline-formula&gt;&lt;tex-math id="M7"&gt;\begin{document}$ r $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; = -0.4427). Finally, our results show that increasing the vaccination rate and appropriately increasing the ozone concentration can effectively prevent and control the spread of influenza.&lt;/p&gt;

2005–2018 trends in ozone peak concentrations and spatial contributions in the Guadalquivir Valley, southern Spain

We assessed 2005─2018 data series of NO, NO2, and O3 surface measurements, meteorological data and remote sensing of tropospheric NO2 by OMI-NASA in the Guadalquivir Valley (GV, Andalucía). The GV is one of the Spanish atmospheric basins with the most exceedances of the EU's hourly O3 information threshold (180 μg O3 m−3). We aimed to deepen understanding of the phenomenology of O3 episodes in the GV, quantify local and regional contributions from long-range transported O3, and identify key episodes and atmospheric parameters to validate modeling tools for the assessment of O3 abatement policies with acceptable uncertainty levels.A significant proportion of acute O3 episodes (defined as episodes of 1–7 consecutive days, when very high hourly O3 concentrations are recorded) in the GV is caused by long-range transported contributions in addition to the regional accumulation of pollution which is, in most cases, driven by the vertical recirculation of air masses, as described in several basins of the Iberian Peninsula. In these episodes, high O3 arises from the fumigation of high reserve recirculated strata as the boundary layer grows, sea-breeze transport of O3 and precursors, local formation, and long-range transport. The most acute episodes are recorded close to Sevilla, probably because of the mix of precursors from the urban areas and the petrochemical industry of Huelva.We quantified the average O3 contributions to O3 concentrations in Sevilla during these episodes as 53% background levels before the episode (defined as the concentration measured at the coastal remote sites at the beginning of the pollution episode, when the Atlantic air masses transport background O3 from synoptic air mass transport), 22% accumulation throughout the episode, and 25% of daily local and regional contribution to the average 8h-daily maxima (157 μg O3 m−3). Thus, a maximum decreasing potential of 74 μg O3 m−3 (47%) of the average 8h-daily maxima can be expected when applying abatement measures to reduce O3 precursors in the day before the start of an episode and until the end of the episode. Our results demonstrate that it is crucial to meteorologically forecast the occurrence of such recirculation and accumulation processes in the GV basin.

Extending Ozone‐Precursor Relationships in China From Peak Concentration to Peak Time

AbstractHigh ozone concentrations have become the major summertime air quality problem in China. Extensive in situ observations are deployed for developing strategies to effectively control the emissions of ozone precursors, that is, nitrogen oxides (NOX = NO + NO2) and volatile organic compounds (VOCs). The modeling analysis of in situ observations often makes uses of the dependence of ozone peak concentration on NOX and VOC emissions, because ozone observations are among the most widely available air quality measurements. To extract more information from regulatory ozone observations, we extend the ozone‐precursor relationship to ozone peak time in this study. We find that the sensitivities of ozone peak time and concentration are complementary for regions with large anthropogenic emissions such as China. The ozone peak time is sensitive to both VOC and NOX emissions, and the sensitivity is nearly linear in the transition regime of ozone production compared to the changing ozone peak concentration sensitivity in this regime, making the diagnostics of ozone peak time particularly valuable. The extended ozone‐precursor relationships can be readily applied to understand the effects on ozone by emission changes of NOX and VOC and to assess potential biases of NOX and VOC emission inventories. These observation constraints based on regulatory ozone observations can complement the other measurement and modeling analysis methods nicely. Furthermore, we suggest that the ozone peak time sensitivity we discussed here to be used as a model evaluation measure before the empirical kinetic modeling approach (EKMA) diagram is applied to understand the effectiveness of emission control on ozone concentrations.

Characteristics of the vertical distribution of tropospheric ozone in late autumn at Yangjiang station in Pearl River Delta (PRD), China. PartⅠ: Observed event

Ozone has become the main factor affecting the air quality in the Pearl River Delta (PRD) in recent years, and a clear understanding source of ozone pollution is a top priority of ozone pollution prevention. However, the vertical distribution of tropospheric ozone in the PRD is poorly understood. Based on daily ozone sounding data obtained in Yangjiang (111°58'00" E, 21°50'00" N), Guangdong Province, from 18 November tjo 3 December 2013, the detailed vertical distribution of tropospheric ozone and its influencing factors were determined and compared with weekly autumn ozone profile data obtained at the Hong Kong Observatory (HKO) and corresponding tropospheric column ozone (TCO) datasets from the Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) onboard satellite AURA. Overall, the ozone profiles observed in Yangjiang are in accordance with those of the HKO in terms of the vertical structure. The TCO values are 34.2 ± 4.0 and 34.3 ± 4.6 DU, respectively, that are, 4 DU higher than those of satellite data, indicating that the OMI/MLS product underestimates the TCO level in the PRD region. The Yangjiang ozone profiles indicate significant variations in the ozone vertical structure and concentration during the observation period. A significant ozone peak permanently occurs in the lower troposphere at 1.1 ± 0.4 km above the surface. The vertical structural difference is mainly reflected in the presence of low-ozone strata (below 30 ppbv) near the tropopause and ozone peaks and high-ozone stratification in the middle and upper troposphere. The average ozone peak concentrations in the lower, middle, and upper troposphere are 65.2 ± 9.9, 57.8 ± 7.7, 71.8 ± 13.6 ppbv, respectively, which are higher than the average ground-level ozone concentration (48.9 ± 9.4 ppbv). Based on the analysis of the profile characteristics, weather conditions, and backward trajectories, it can be concluded that the low-ozone strata near the tropopause are caused by the regional transport of the tropical air mass from the tropical cyclone storm area. Potential vorticity analysis shows that stratosphere-troposphere exchange (STE) is the main reason for the formation of the ozone peaks and its varying concentrations in the middle and upper troposphere. Photochemical reactions represent the main factor affecting the ozone concentration in the lower troposphere. The STE is also an important factor affecting the ozone in the lower troposphere, leading to an increase in the surface ozone concentration by ~10.9 ppbv.

Understanding ozone pollution in the Yangtze River Delta of eastern China from the perspective of diurnal cycles

Ozone (O3) pollution has aroused increasing attention in China in past years, especially in the Yangtze River Delta (YRD), eastern China. Ozone and its precursors generally feature different diurnal patterns, which is closely related to atmospheric physical and chemical processes. This work aims to shed more light on the causes of ozone pollution from the perspective of the diurnal patterns. Hundreds of ozone pollution days (with maximum hourly O3 concentration over 100 ppb) during 2013–2017 were identified and then clustered into 4 typical types according to the diurnal variation patterns. We found that ozone pollution in Shanghai was particularly severe when anthropogenic pollutant mixed with biogenic volatile organic compounds (BVOCs) under the prevailing southwesterly wind in summer. The reason could be attributed to the spatial disparities of ozone sensitivity regime in YRD: VOC-limited regime around in the urban area and NOx-limited regime in the rural forest regions in the southern and southwest. The transition of sensitivity regimes along south/southwest wind tended to promote the photochemical production of ozone, making daily O3 pollution time exceeding 6 h of the day. In addition, ozone peak concentration in Shanghai was highly dependent on the evolution of sea-land breezes (SLBs). Earlier sea breeze associated with approaching typhoon in the West Pacific caused less cloud (−25%) and more solar radiation (11%) in YRD, which subsequently led to a rapid increase of O3 concentration in the morning and a deteriorated ozone pollution during noon and the afternoon. This study highlights the importance of observation-based processes understanding in air quality studies.

Characteristics of Surface Ozone and Impact Factors at Different Station Types During the Autumn in Guangzhou

Surface ozone (O3) has become the primary air pollutant in Guangzhou. Due to the influences of topography, meteorological conditions, and differences in precursor emissions, there are also large differences in the characteristics, formation mechanisms, and influencing factors of ozone in different areas of the same city. Based on the ground measurement data for October 2015 at four air quality monitoring stations that represent different types of regions in Guangzhou [urban area:Guangzhou Monitoring Center (GMC); upwind suburbs:Huadu Normal School (HNS); downwind suburbs:Panyu Middle School (PMS); Mountain area:Maofengshan (MFS)] and the WRF simulated meteorological data, the changing characteristics, influencing factors, and sensitivity of O3 were studied at each station. The results showed that the diurnal variation of O3 and NOx exhibit unimodal and bimodal characteristics (except for NOx at the MFS station). The peak ozone concentration appeared on Saturday at the GMC, HNS, and MFS stations, and on Thursday at the PMS station. The ozone concentration at the MFS station was the highest (98.61 μg·m-3), whereas that at the GMC station was the lowest (44.83 μg·m-3). The NOx inflection point intervals for O3 at different sites were:GMC:55-90 μg·m-3; PMS:30-60 μg·m-3; MFS:10-20 μg·m-3. The temperature inflection point intervals affecting the rate of O3 formation at different sites were:GMC:28-30℃; HNS:26-28℃; PMS:24-26℃; however, this was not obvious at the MFS station. The relative humidity inflection point intervals were:GMC:55%-65% ; HNS and PMS:60%-70% ; MFS:80%-85%. The wind speed(WS) of the light wind type was proportional to the O3 concentration. The O3 concentration at the PMS site was the highest in the northwest wind direction, and the O3 concentration at the MFS site was the highest in the other wind directions. By analyzing the multivariate linear fitting of impact factors on the O3 concentration, the main controlling factors at each site were:GMC:WS and T; PMS and HNS:T and RH; MFS:RH and WS. The ozone sensitivity at each site was as follows:GMC and HNS had a VOCs-limited regime, MFS had a NOx-limited regime, and PMS had a transition regime.

Temporal and spatial analysis of ozone concentrations in Europe based on timescale decomposition and a multi-clustering approach

Abstract. Air quality measures that were implemented in Europe in the 1990s resulted in reductions of ozone precursor concentrations. In this study, the effect of these reductions on ozone is investigated by analyzing surface measurements of this pollutant for the time period between 2000 and 2015. Using a nonparametric timescale decomposition methodology, the long-term, seasonal and short-term variation in ozone observations were extracted. A clustering algorithm was applied to the different timescale variations, leading to a classification of sites across Europe based on the temporal characteristics of ozone. The clustering based on the long-term variation resulted in a site-type classification, while a regional classification was obtained based on the seasonal and short-term variations. Long-term trends of deseasonalized mean and meteo-adjusted peak ozone concentrations were calculated across large parts of Europe for the time period 2000–2015. A multidimensional scheme was used for a detailed trend analysis, based on the identified clusters, which reflect precursor emissions and meteorological influence either on the inter-annual or the short-term timescale. Decreasing mean ozone concentrations at rural sites and increasing or stabilizing at urban sites were observed. At the same time, downward trends for peak ozone concentrations were detected for all site types. In addition, a reduction of the amplitude in the seasonal cycle of ozone and a shift in the occurrence of the seasonal maximum towards earlier time of the year were observed. Finally, a reduced sensitivity of ozone to temperature was identified. It was concluded that long-term trends of mean and peak ozone concentrations are mostly controlled by precursor emissions changes, while seasonal cycle trends and changes in the sensitivity of ozone to temperature are among other factors driven by regional climatic conditions.

Volatile organic compounds and ozone at four national parks in the southwestern United States

Abstract The National Park Service is tasked with protecting the lands it oversees, including from impacts from air pollutants. While ozone is regularly monitored in many parks across the United States, precursors to ozone formation are not routinely measured. In this work we characterize volatile organic compounds (VOCs) at four national parks in the southwestern United States: Carlsbad Caverns (CAVE), Great Basin (GRBA), Grand Canyon (GRCA), and Joshua Tree (JOTR). Whole air samples were collected for VOC analysis for five months (mid-April through mid-September) in 2017. Samples were collected from 3 p.m. to 5 p.m. local time, corresponding approximately to the time of expected peak ozone concentrations, and were analyzed using gas chromatography for a variety of compounds including alkanes, alkenes, aromatics, biogenics, and alkyl nitrates. Among the four parks, the total measured VOC mixing ratio was greatest at CAVE, mostly due to an abundance of light alkanes (on average 94% of all VOCs measured) from oil and gas sources. VOC concentrations at the other three parks were similar to each other and approximately 7–10 times lower than at CAVE. While VOC sources varied across sites, VOC-OH reactivity was dominated by biogenic compounds at all sites except CAVE, which had similar contributions from biogenics and from light alkanes. JOTR had the highest levels of ozone, and the highest concentrations of biogenic VOCs among the parks studied. Back trajectory analysis suggests that the high levels of ozone occurred when air flow came from the west, in the direction of the greater Los Angeles area. The two parks most removed from oil and gas and urban sources, GRBA and GRCA, had the lowest concentrations of total VOCs, and were likely influenced by long range transport of pollutants. To better characterize source influences at the park with the highest VOC concentrations, intensive measurements were conducted in and around CAVE for one week in September 2017. These measurements showed an oil and gas influence throughout the region and indicated that the whole air samples collected over the five-month study did not capture the full range of VOC mixing ratios present at other times of the day.

The long-term trend and production sensitivity change in the US ozone pollution from observations and model simulations

Abstract. We investigated the ozone pollution trend and its sensitivity to key precursors from 1990 to 2015 in the United States using long-term EPA Air Quality System (AQS) observations and mesoscale simulations. The modeling system, a coupled regional climate–air quality model (CWRF-CMAQ; Climate-Weather Research Forecast and the Community Multiscale Air Quality), captured well the summer surface ozone pollution during the past decades, having a mean slope of linear regression with AQS observations of ∼0.75. While the AQS network has limited spatial coverage and measures only a few key chemical species, CWRF-CMAQ provides comprehensive simulations to enable a more rigorous study of the change in ozone pollution and chemical sensitivity. Analysis of seasonal variations and diurnal cycle of ozone observations showed that peak ozone concentrations in the summer afternoon decreased ubiquitously across the United States, up to 0.5 ppbv yr−1 in major non-attainment areas such as Los Angeles, while concentrations at certain hours such as the early morning and late afternoon increased slightly. Consistent with the AQS observations, CMAQ simulated a similar decreasing trend of peak ozone concentrations in the afternoon, up to 0.4 ppbv yr−1, and increasing ozone trends in the early morning and late afternoon. A monotonically decreasing trend (up to 0.5 ppbv yr−1) in the odd oxygen (Ox=O3+NO2) concentrations are simulated by CMAQ at all daytime hours. This result suggests that the increased ozone in the early morning and late afternoon was likely caused by reduced NO–O3 titration, driven by continuous anthropogenic NOx emission reductions in the past decades. Furthermore, the CMAQ simulations revealed a shift in chemical regimes of ozone photochemical production. From 1990 to 2015, surface ozone production in some metropolitan areas, such as Baltimore, has transited from a VOC-sensitive environment (&gt;50 % probability) to a NOx-sensitive regime. Our results demonstrated that the long-term CWRF-CMAQ simulations can provide detailed information of the ozone chemistry evolution under a changing climate and may partially explain the US ozone pollution responses to regional and national regulations.

Evaluation of Ozone Removal by Spent Coffee Grounds

Activated carbon is the most known material used to adsorb ozone. Activating carbonaceous materials by ozonation is commonly used to produce activated carbon, however, requiring sophisticated skills and professional equipment. This paper presents a reversed idea: to adsorb ozone using an unactivated carbonaceous material, coffee. Three powder adsorbents are presented: fresh coffee (unactivated), spent coffee grounds (unactivated), and activated carbon (commercially available). The test is conducted by measuring and comparing the ozone concentration in an ozone-supplied chamber with or without the ozone adsorbent. The results show that, at the specific conditions, the peak ozone concentration is lowered by 38% to 56% when the chamber has the activated carbon. At the same conditions, the peak ozone concentration is lowered by 25% to 43% when the chamber has the coffee powders (either fresh or spent). The elemental analysis demonstrates that the oxygen content after the ozone adsorption increases by 20%, 14.4%, and 34.5% for the fresh coffee, the spent coffee grounds, and the activated carbon, respectively. The characteristic analysis (the Fourier-transform infrared spectroscopy, the thermogravimetric, and the Brunauer-Emmett-Teller) suggests that the unactivated coffee is not porous, however, contains various organic compounds that could react with and consume ozone.

Peak concentrations of ground-level ozone during the summer heat waves of 2010 and 2016 in the background region of the Kirov region of the Russian Federation

The analysis of continuous monitoring data on surface ozone concentrations during summer heat waves in July and August 2010 and 2016 in a low-urbanized region of European Russia, Kirov region is presented. The values of the maximum short-term (peak) recorded values, obtained at 20-minute, 1-hour and 8-hour averaging, were analyzed. Under close temperature conditions, the amplitudes and durations of peak ozone concentrations in 2016 significantly exceeded the values observed in 2010. One of the possible reasons for this difference may be associated with an increase in the concentration of ozone precursors in the region’s atmosphere.