Ground-level Ozone Levels Research Articles

Ozone management in Colorado: Why aren’t we there yet?

ABSTRACT Since 2004, the state of Colorado in the United States of America has created multiple nonattainment State Implementation Plans (SIPs) that are supposed to comprise air pollution mitigation actions, that have so far been unsuccessful at ensuring Front Range Communities have reduced ozone levels to below the United States Environmental Protection Agency (EPA) standards. By interviewing eight stakeholders and decision-makers involved in ozone SIP rulemaking and drawing on secondary literature, this paper examines shortcomings in the SIP process in Colorado. We found that ozone precursor measurement and the modeling of attainment could be improved by better factoring in uncertainties in emissions inventories and conducting appropriate sensitivity analyses that would require more investment of state staff time and resources. Structural issues with the way the process is organized in Colorado limit optimum overlap between state: Air Pollution Control Division (APCD) and quasi-state: Regional Air Quality Council (RAQC) agencies during the SIP process. Specifically, although the RAQC is currently charged with developing and submitting SIPs to the State for approval, it does not have the power to implement control strategies for several key sources and therefore does not have the authority to propose key policies to be included in the SIP. In recent years, Colorado SIPs have largely focused on the bare minimum emissions controls to demonstrate attainment via modeling. Interviewees recommend that state political leaders take more of a leadership role to lower ground-level ozone levels and bring the Denver Metropolitan Area/North Front Range back into attainment with EPA standards. Implications We evaluate why the State Implementation Plan (SIP) process has failed to achieve the attainment of the ozone standards in the Denver Metropolitan and North Front Range Area. Specifically, through interviewing several experts we identified several problems, namely: 1) errors in emissions inventories and modeling of ozone levels that have resulted in incorrect determinations that the ozone standards would be met with proposed emissions controls, and 2) structural problems in the way the SIP process is organized in Colorado, and the lack of political leadership.

Ozone pollution contributes to the yield gap for beans in Uganda, East Africa, and is co-located with other agricultural stresses

Air quality negatively impacts agriculture, reducing the yield of staple food crops. While measured data on African ground-level ozone levels are scarce, experimental studies demonstrate the damaging impact of ozone on crops. Common beans (Phaseolus vulgaris), an ozone-sensitive crop, are widely grown in Uganda. Using modelled ozone flux, agricultural surveys, and a flux-effect relationship, this study estimates yield and production losses due to ozone for Ugandan beans in 2015. Analysis at this scale allows the use of localised data, and results can be presented at a sub-regional level. Soil nutrient stress, drought, flood risk, temperature and deprivation were also mapped to investigate where stresses may coincide. Average bean yield losses due to ozone were 17% and 14% (first and second growing season respectively), equating to 184 thousand tonnes production loss. However, for some sub-regions, losses were up to 27.5% and other crop stresses also coincided in these areas. This methodology could be applied widely, allowing estimates of ozone impact for countries lacking air quality and/or experimental data. As crop productivity is below its potential in many areas of the world, changing agricultural practices to mitigate against losses due to ozone could help to reduce the crop yield gap.

Measurement report: Observations of ground-level ozone concentration gradients perpendicular to the Lake Ontario shoreline

Abstract. Ground-level ozone (O3) is a secondary air pollutant that has harmful effects on human and ecosystem health. Close to larger bodies of water, the well-known sea-breeze (or lake-breeze) phenomenon plays a role in regulating ground-level ozone levels. An observed lake-edge removal effect, where ozone concentration decreases within the first 500 m to 1 km perpendicular to the lake, is thought to be related to the lake-breeze circulation as well as several dilution and removal pathways. A field campaign was conducted in summer 2022 and winter 2023 in two locations on the north shore of Lake Ontario: the urban centre of Toronto and suburban Oshawa, some 50 km east, to assess how the local environment and season affect the lake-edge removal effect. Ozone, wind speed, and wind direction were measured on 6–7 different days in each season and city along transects perpendicular to Lake Ontario's shoreline. A consistent negative linear relationship between ozone concentration and distance from shore over the first 500 m (i.e. a lake-edge removal effect) was observed in both cities and both seasons. The ozone gradient changed in Oshawa from −23.5 ± 8.5 (1 standard deviation) ppb km−1 in summer to −8.1 ± 5.1 ppb km−1 in winter. The slope remained consistent in Toronto at −15.4 ± 6.7 ppb km−1 in summer and −16.7 ± 7.3 ppb km−1 in winter. The year-round observation of an ozone gradient and lake-edge removal effect suggests that there is an inherent “baseline” ozone concentration gradient at the lake edge, caused by the dilution effect of the rapid increase of the boundary layer there. This gradient is seen to be enhanced in the summer and dependent on local effects such as lake-breeze circulation and increased deposition to vegetation.

Estimating morning and evening commute period O3 concentration in Taiwan using a fine spatial-temporal resolution ensemble mixed spatial model with Geo-AI technology

Elevated levels of ground-level ozone (O3) can have harmful effects on health. While previous studies have focused mainly on daily averages and daytime patterns, it's crucial to consider the effects of air pollution during daily commutes, as this can significantly contribute to overall exposure. This study is also the first to employ an ensemble mixed spatial model (EMSM) that integrates multiple machine learning algorithms and predictor variables selected using Shapley Additive exExplanations (SHAP) values to predict spatial-temporal fluctuations in O3 concentrations across the entire island of Taiwan. We utilized geospatial-artificial intelligence (Geo-AI), incorporating kriging, land use regression (LUR), machine learning (random forest (RF), categorical boosting (CatBoost), gradient boosting (GBM), extreme gradient boosting (XGBoost), and light gradient boosting (LightGBM)), and ensemble learning techniques to develop ensemble mixed spatial models (EMSMs) for morning and evening commute periods. The EMSMs were used to estimate long-term spatiotemporal variations of O3 levels, accounting for in-situ measurements, meteorological factors, geospatial predictors, and social and seasonal influences over a 26-year period. Compared to conventional LUR-based approaches, the EMSMs improved performance by 58% for both commute periods, with high explanatory power and an adjusted R2 of 0.91. Internal and external validation procedures and verification of O3 concentrations at the upper percentile ranges (in 1%, 5%, 10%, 15%, 20%, and 25%) and other conditions (including rain, no rain, weekday, weekend, festival, and no festival) have demonstrated that the models are stable and free from overfitting issues. Estimation maps were generated to examine changes in O3 levels before and during the implementation of COVID-19 restrictions. These findings provide accurate variations of O3 levels in commute period with high spatiotemporal resolution of daily and 50m * 50m grid, which can support control pollution efforts and aid in epidemiological studies.

The relationship between ground-level ozone levels and some infectious diseases

The relationship between ground-level ozone levels and the manifestations of some infectious diseases in Tbilisi was studied. Feedback was found between stratospheric ozone levels and acute sinusitis, epiglottitis and croup. Among some diseases in Tbilisi in 2015, 2017 and 2018. The issue is urgent and is still being studied.

Analysing the Pollutants Dispersion in Erbil City-Kurdistan with Support of Statistical Analysis.

Analysing the Pollutants Dispersion in Erbil City-Kurdistan with Support of Statistical Analysis.

Comparative assessment of modeling deep learning networks for modeling ground-level ozone concentrations of pandemic lock-down period

Covid-19 pandemic lock-down has resulted significant differences in air quality levels all over the world. In contrary to decrease seen in primary pollutant species, many of the countries have experienced elevated ground-level ozone levels in this period. Air pollution forecast gains more importance to achieve air quality management and take measures against the risks under such extra-ordinary conditions. Statistical models are indispensable tools for predicting air pollution levels. Considering the complex photochemical reactions involved in tropospheric ozone formation, modeling this pollutant requires efficient non-linear approaches. In this study, deep learning methods were applied to forecast hourly ozone levels during pandemic lock-down for an industrialized region in Turkey. With this aim, different deep learning methods were tested and efficiencies of the models were compared considering the calculated RMSE, MAE, R2 and loss values.

Creating the Healthiest Nation: Climate Change and Environmental Health Impacts in Nigeria: A Narrative Review

Climate change is a “threat multiplier and a prime cause of universal threat to health in the 21st century, including 4th industrial revolution. The health effects of climate change will increase dramatically over the next few years and pose a risk to human life and the well-being of billions of people. As we all know, the milieu is fundamental to our sustained earth survival and environmental changes (natural and artificial) affect it either to the benefit or detriment of humans. Climate change is one of such changes in the physical environment which has grave consequences for the existence of mankind. Climate change is interestingly, no longer a speculative subject. There is a good international scientific consensus existing to show that this phenomenon is real and if recent global warming movements continue, temperature rise, ocean levels and more frequently weather conditions that is extreme (storms, heat-waves, droughts, floods, cyclones, etc.) may perhaps cause severe food shortages, loss of shelter, water, livelihoods, extinction of flora and fauna species. In the recent past, the earth has witnessed devastating weather-related events in different portions of the globe including hurricanes (e.g., Katrina and Rita in USA), tsunamis, typhoons, flooding especially in the Asian Continent, wild fires especially in Australia, USA, etc. Currently, the on-going flood incident in Pakistan that has so far claimed about 1,600 lives and rendered another four million people homeless is a sad reminder of the ugly and devastating consequences of global warming on the environment. There is no gainsaying the fact that humankind is paying dearly for the massive alterations in the environment that have induced changes in climate. This is because of frequent incidence of changes in climate related disasters in the world today. There is hardly any month that passes without an incident occurring in one part of the globe or another since the advent of the 21st century. Changes in climate has significant and potentially devastating health consequences, whether through direct actions (e.g., deaths resulting from heat wave and weather disasters) or disruption of complex biological methods (e.g., changes in infectious diseases patterns, supplies in fresh water and production of food).The report of the fourth assessment of the United Nations Intergovernmental Panel on Climate Change (IPCC) have globally submitted that “it is estimated that the health of millions of people is affected, for instance, malnutrition increases; deaths increase, diseases and injury; burden of increase diarrheal diseases; frequency of increased cardio-respiratory diseases caused by high levels of ground-level ozone in cities due to climate change; besides altered spatial distribution of some communicable diseases”. The association amongst changes in climate, its drivers, systemic effects, health and socioeconomic growth, mitigation and adaptation has been specified.

Assessment of ground-level ozone pollution with monitoring and modelling approaches in Makkah, Saudi Arabia

Long-term exposure to the high levels of ground-level ozone (O3) adversely affects human health, vegetation, and building materials. Atmospheric concentrations of O3 are dependent on the levels of its precursors and meteorological parameters. In this paper, the data of several air pollutants as nitrogen dioxide (NO2), nitric oxide (NO), carbon monoxide (CO), and sulfur dioxide (SO2) and meteorological parameters such as temperature, relative humidity, wind speed and direction, and atmospheric pressure are used to model O3 at five (5) air quality monitoring stations in the Holy City of Makkah, the Kingdom of Saudi Arabia, for the year 2019. The performance of the multiple linear regression model (MLRM) and the generalized additive model (GAM) was compared for modelling the concentrations of O3. It was found that NO, NO2, and relative humidity had a negative association, whereas other covariates had a positive association with O3. To quantify the association between modelled and observed O3 concentrations, several metrics including correlation coefficients and root mean square error (RMSE) were calculated. GAM outperformed MLRM at all five sites and was found to successfully capture nonlinearity in the association between O3 and predictor variables. Correlation coefficients for the cross-validated model using hold-out testing dataset for GAM were 0.82, 0.78, 0.86, 0.79, and 0.76 and for MLRM were 0.69, 0.61, 0.79, 0.64, and 0.63 for Haram, Aziziah, Umrah, Atebiah, and Shawqiah sites, respectively. To conclude, GAM being an advanced nonlinear model performed better than MLRM and therefore is preferred for modelling O3 in Makkah and other similar arid regions.

Investigation of gaseous pollutants in residential-industrial area: Ambient levels, temporal variation and health risk assessment

Introduction: The purpose of the current study was to investigate the ambient concentration levels of ground-level ozone (GLO), nitrogen dioxide, and sulfur dioxide with temporal variations and to determine the risk of exposure to their pollutant on public people living in this area. Materials and methods: In the present study, GLO, NOx and SO2 concentrations were monitored using an ambient analyzer during the period of April to September 2018. Results: The obtained results demonstrated that the average concentrations of SO2, NO2 and GLO in the INZ station was significantly greater than the two other evaluated stations (i.e. SHV and CMC). The corresponding values for the measured parameters in INZ station was almost 8.9, 7.2 and 11.9 times higher than those in SHV station, however, 4.8, 5.3 and 2.9 times greater than of ones in CMC station, respectively. The average values of SO2 and NO2 concentrations in the INZ varied from 97.2 to 128.1 μg/m3 in the evening hours and from 50.2 to 62.3 μg/m3 in the morning hours respectively. Also, the lowest concentration of NO2 was observed during afternoon hours when GLO showed a peak. The maximum pikes of GLO concentration were observed at 13:00 PM with 249.3 μg/m3. Results of human health risk assessment indicated acceptable risk (hazard quotient (HQ) values˂ 1) for non-carcinogenic adverse health effect. Conclusion: The findings in the present study can be useful in developing control-based strategies for primary pollutant emissions, and also GLO formation, improve air quality and reducing possible risks on human health. Policymakers should enforce the limits on the release of pollutants into the atmosphere in the study area by strengthening existing legislation.

TB and Tailpipes: Does Traffic-Related Air Pollution Affect Mortality during Tuberculosis Treatment?

Vol. 126, No. 2 Science SelectionOpen AccessTB and Tailpipes: Does Traffic-Related Air Pollution Affect Mortality during Tuberculosis Treatment?is accompanied byTraffic-Related Air Pollution and All-Cause Mortality during Tuberculosis Treatment in California Silke Schmidt Silke Schmidt Search for more papers by this author Published:28 February 2018CID: 024005https://doi.org/10.1289/EHP2948View Article in:中文版AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit Although the success rate for treating tuberculosis (TB) is high in the United States, there remains variation in mortality rates during treatment.1 Thus, identifying modifiable risk factors may lead to novel interventions to reduce mortality. Results from an epidemiologic study published in Environmental Health Perspectives suggest that air pollution from nearby traffic may be one such modifiable risk factor for mortality during TB treatment.2Robert Blount, the study’s first author and an assistant professor of pulmonary medicine at the University of California, San Francisco, notes that recent observational studies3,4 and basic science experiments5 support the previously observed association between cigarette smoking and the risk of both acquiring and dying from TB. “The similarity of the chemicals in cigarette smoke and ambient air pollution prompted us to study the association [between] traffic proximity and mortality,” he says.According to Blount, California is a good place for this kind of study because it has long accounted for a large proportion of TB cases in the United States.6 The largely vehicle-dependent state also has many cities with very high levels of ground-level ozone and particle pollution.7Working with the California Department of Public Health, the researchers enrolled more than 32,000 patients identified as having active TB between 2000 and 2012. More than two-thirds of the patients were foreign-born, originating mostly from countries in Asia and Latin America where TB is endemic. Many patients faced socioeconomic hardship: 53% were unemployed, and 6% were homeless.Measures of traffic volume and density were based on 24-hour vehicle counts around the patients’ residential addresses, as recorded by the California Department of Transportation. These measures served as proxies for ambient air pollution. The authors used buffer zones of 100, 200, 300, and 400 meters around each patient’s home to determine the effects of traffic at different distances from the residence. Traffic volumes in each buffer zone were then divided into quintiles of estimated exposure.The authors estimated that patients who lived at addresses where the nearest road had the highest traffic volume were 28% more likely to die during treatment than patients who lived where the nearest road had the lowest volume of traffic. Estimates were adjusted for several factors related to both traffic exposures and mortality, including homelessness, unemployment, HIV infection, recent immigration, and race/ethnicity. However, the authors did not have individual-level information on cigarette smoking or income.For David Dowdy, an associate professor of epidemiology at the Johns Hopkins University who was not involved in the study, the results add to the larger body of literature suggesting that traffic proximity may increase mortality overall, but they do not support a TB-specific effect. “The low- and high-traffic groups of patients did not have any differences in TB markers, such as days to culture conversion [i.e., evidence of recovery], and we do not know the events leading to their death,” he says. “I think it is more likely that this study population represents a high-risk group for which it is easier to detect a more general effect of air pollution on mortality.”The authors themselves caution against overinterpreting the findings and consider the study to be hypothesis-generating. Ideally, replication studies would be conducted in countries with high levels of air pollution and a greater incidence of TB than California, such as China, Vietnam, or India. “If replicated,” Blount says, “our study would have implications at the public policy and individual level. It would provide additional motivation for government officials to curb vehicle emissions and would also support the clinical counseling of patients to stay inside when air pollution indices are high.”Much more study is necessary before concluding that exposure to traffic-related pollution is a risk factor for dying during TB treatment. However, if this hypothesis is proven, it might lead to individual-level interventions to improve the success of treatment. It also could provide additional support for measures to reduce population-wide exposures to traffic-related pollution. Image: © Chones/Shutterstock.

Considerations on Ambient Levels of Ozone Concentrations and Relationship with NOx in an Urban Environment

The serious air pollution problem has determined public concerns, worldwide. One of the main challenges for countries all over the world is caused by the elevated levels of ground-level ozone (O3) concentrations and its anthropogenic precursors. Ploiesti city, as one of the major urban area of Romania, is facing the same situation. This research aims to investigate spatial and temporal distribution characteristics of O3 in relationship with nitrogen oxides (NOx) using statistical analysis methods. Hourly O3 and NOx measurements were collected during 2014 year in Ploiesti. The results obtained showed that the ozone spatial distribution was non-normal for each month in 2014. The diurnal cycle of ground-level ozone concentrations showed a mid-day peak, while NOx diurnal variations presented 2 daily peaks, one in the morning (7:00 a.m.) and one in the afternoon (between 5:00 and 7:00 p.m.). In addition, it was observed a distinct pattern of weekly variations for O3 and NOx. Like in many other urban areas, the results indicated the presence of the �ozone weekend effect� in Ploiesti during the 2014 year, ozone concentrations being slightly higher on weekends compared to weekdays. For the same monitoring site, the nitrogen oxides were less prevalent on Saturdays and Sundays, probably due to reducing of road traffic and other pollution-generating activities on weekends than during the week.

Photochemical model evaluation of the ground-level ozone impacts on ambient air quality and vegetation health in the Alberta oil sands region: Using present and future emission scenarios

One of the potential environmental issues associated with oil sands development is increased ozone formation resulting from NOX and volatile organic compound emissions from bitumen extraction, processing and upgrading. To manage this issue in the Athabasca Oil Sands Region (AOSR) in northeast Alberta, a regional multi-stakeholder group, the Cumulative Environmental Management Association (CEMA), developed an Ozone Management Framework that includes a modelling based assessment component. In this paper, we describe how the Community Multi-scale Air Quality (CMAQ) model was applied to assess potential ground-level ozone formation and impacts on ambient air quality and vegetation health for three different ozone precursor cases in the AOSR. Statistical analysis methods were applied, and the CMAQ performance results met the U.S. EPA model performance goal at all sites. The modelled 4th highest daily maximum 8-h average ozone concentrations in the base and two future year scenarios did not exceed the Canada-wide standard of 65 ppb or the newer Canadian Ambient Air Quality Standards of 63 ppb in 2015 and 62 ppb in 2020. Modelled maximum 1-h ozone concentrations in the study were well below the Alberta Ambient Air Quality Objective of 82 ppb in all three cases. Several ozone vegetation exposure metrics were also evaluated to investigate the potential impact of ground-level ozone on vegetation. The chronic 3-months SUM60 exposure metric is within the CEMA baseline range (0–2000 ppb-hr) everywhere in the AOSR. The AOT40 ozone exposure metric predicted by CMAQ did not exceed the United Nations Economic Commission for Europe (UN/ECE) threshold of concern of 3000 ppb-hr in any of the cases but is just below the threshold in high-end future emissions scenario. In all three emission scenarios, the CMAQ predicted W126 ozone exposure metric is within the CEMA baseline threshold of 4000 ppb-hr. This study outlines the use of photochemical modelling of the impact of an industry (oil sands) on ground-level ozone levels as an air quality management tool in the AOSR. It allows an evaluation of the relationships between the pollutants emitted to the atmosphere and potential ground level ozone concentrations throughout the AOSR thereby extending the spatial coverage of the results beyond the monitoring network and also allowing an assessment of the potential impacts of possible future emission cases.

How effective is ‘greening’ of urban areas in reducing human exposure to ground-level ozone concentrations, UV exposure and the ‘urban heat island effect’? A protocol to update a systematic review

Abstract Background The impact of climate change on public health may occur through a number of main pathways including increased temperature, ground-level ozone levels and ultra-violet radiation, which have a range of consequences for human health. One strategy for adaptation to the predicted effects of climate change on health that has been proposed, is to ‘green’ urban areas, essentially by increasing the abundance and cover of vegetation. This protocol is for an update of a systematic review which aimed to address the question: How effective is ‘greening’ of urban areas in reducing human exposure to ground-level ozone concentrations, UV exposure and the ‘urban heat island effect’? Methods A sensitive search of multiple databases and relevant journals for relevant published articles will be conducted. A search for relevant unpublished articles will be undertaken through an internet search and of websites of relevant organisations. Inclusion criteria will be applied at title, abstract and full-text. Repeatability checks of this screening process will be undertaken. Articles included at full-text will be critically appraised using a standardised checklist. A repeatability check will be made of this process. Pre-defined data items will be extracted from included articles. If appropriate, quantitative synthesis will be undertaken through meta-analysis and/or a narrative synthesis will be undertaken.

Evaluation of the 'Clean Air Works' program on actual ozone concentrations: a case study in North Carolina

This study examines the effectiveness of the 'Clean Air Works' program in the state of North Carolina on ozone concentration levels. 'Clean Air Works' is a voluntary program which educates people about the negative effects of air pollution on health. The contribution of this study is that it examines three effects: The effectiveness of the 'Clean Air Works' program in the Charlotte Area of North Carolina State and whether ozone smog alerts are more effective under this program. Finally, the effects on ozone levels coming from the change in the warning threshold from 80 particles per billion (ppb) to 75 ppb, which took place in 2008, are established. In all cases, we find reduction in ground-level ozone levels and improvement of the air quality in the treatment group where the 'Clean Air Works' program is implemented.

Demystifying the air quality health index.

Demystifying the air quality health index.

Evaluation of Ozone Smog Alerts on Actual Ozone Concentrations: A Case Study in North Carolina

Ground-level ozone is an important pollutant regulated under the Clean Air Acts that affects respiratory morbidity, decreases lung function, and negatively affects those with existing respiratory conditions like asthma. This study examines the “Clean Air Works” program on ozone concentration levels, which is operating in Charlotte area of North Carolina State. “Clean Air Works” is a voluntary program which educates people about the negative effects of air pollution on health. Moreover, this program encourages people to reduce air pollution by using voluntarily alternative transportation modes, such as carpooling and public transit, especially when a smog ozone alert is issued. The contribution of this study is that it examines three effects: The effectiveness of the “Clean Air Works” program and whether ozone smog alerts are more effective under this program. Finally, the effects on ozone levels coming from the change in the warning threshold from 80 particles per billion (ppb) to 75 ppb, which took place in 2008, are established. For this purpose a quadruple Differences (DDDD) estimator is applied. In both cases, we find reduction in ground-level ozone levels and improvement of the air quality in the treatment group where the “Clean Air Works” program is implemented. In addition, the air quality is improved when smog alerts are associated with the program. Finally, taken additionally into consideration the change of the threshold at 75 ppb the air quality is improved by 1.5 ppb in the treatment group relatively to the control group. This study suggests that the ozone warning system associated with voluntary programs can help to clean the air and improve the public health.

Identifying controlling factors of ground-level ozone levels over southwestern Taiwan using a decision tree

Kaohsiung City and the suburban region of southwestern Taiwan have suffered from severe air pollution since becoming the largest center of heavy industry in Taiwan. The complex process of ozone (O3) formation and its precursor compounds (the volatile organic compounds (VOCs) and nitrogen oxide (NOx) emissions), accompanied by meteorological conditions, make controlling ozone difficult. Using a decision tree is especially appropriate for analyzing time series data that contain ozone levels and meteorological and explanatory variables for ozone formation. Results show that dominant variables such as temperature, wind speed, VOCs, and NOx can play vital roles in describing ozone variations among observations. That temperature and wind speed are highly correlated with ozone levels indicates that these meteorological conditions largely affect ozone variability. The results also demonstrate that spatial heterogeneity of ozone patterns are in coastal and inland areas caused by sea-land breeze and pollutant sources during high ozone episodes over southwestern Taiwan. This study used a decision tree to obtain quantitative insight into spatial distributions of precursor compound emissions and effects of meteorological conditions on ozone levels that are useful for refining monitoring plans and developing management strategies.

The Beat

The Beat

Simulation and Evaluation of Control Strategies for Ozone Reduction in a Complex Terrain in Southwestern Spain

During the central months of the year, southwestern Spain is under strong insolation and weak synoptic forcing, promoting the development of sea breezes and mountain-induced winds and creating recirculations of pollutants. The complex topography of the Southwestern Iberia Peninsula induces the formation of vertical layers, into which the pollutants are injected and subjected to long-distance transport and compensatory subsidence. The characteristics of these highly complex flows have important effects on the pollutant dispersion. Air pollution studies in very complex terrains require high-resolution modelling for resolving the flow dynamics. This paper shows the results obtained from using the MM5-CAMx multiscale-nested air quality model to relate the sensitivity regimes for ozone, nitrogen oxides and volatile organic compounds in an area of high geographical complexity. The article assesses the impact on the hourly and eight-hourly maximum daily ozone concentrations of four reduction strategies during two ozone pollution episodes. This analysis of the ozone response has led to a preliminary evaluation of the effectiveness of the most common control strategies: traffic, industry, mixed traffic and industry, and closure of some of the largest industries (oil and petrochemical refineries). Photochemical indicators show that ozone chemistry in southwestern Spain is strongly sensitive to NOx. However, volatile organic compound-sensitive points are found in areas with anthropogenic influence (highways, cities and industrial parks). Our results indicate that reductions in road traffic lead to ozone reductions over large areas, whereas reductions in industrial emissions, despite sometimes showing greater decreases in the maximum hourly and eight-hourly ground-level ozone levels, lead to ozone reductions in a local area only. In the control study case, with the oil refinery and the petrochemical plants closed, decreases in ozone hourly concentrations are up to 40% higher than in the other emission control scenarios studied. This analysis provides an assessment of the effectiveness of different policies for controlling precursor emissions by comparing the modelled results for different scenarios.