O3 Concentration Levels Research Articles

Health impact assessment by the implementation of Madrid City air-quality plan in 2020

ObjectivesAir pollutant concentrations in many urban areas are still above the legal and recommended limits that are set to protect the citizens’ health. Madrid is one of the cities where traffic causes high NO2 levels. In this context, Madrid City Council launched the Air Quality and Climate Change Plan for the city of Madrid (Plan A), a local strategy approved by the previous government in 2017. The aim of this study was to conduct a quantitative health impact assessment to evaluate the number of premature deaths that could potentially be prevented by the implementation of Plan A in Madrid in 2020, at both citywide and within-city level. The main purpose was to support decision-making processes in order to maximize the positive health impacts from the implementation of Plan A measures. MethodsThe Regional Statistical Office provided information on population and daily mortality in Madrid. For exposure assessment, we estimated PM2.5, NO2 and O3 concentration levels for Madrid city in 2012 (baseline air-quality scenario) and 2020 (projected air-quality scenario based on the implementation of Plan A), by means of an Eulerian chemical-transport model with a spatial resolution of 1 km × 1 km and 30 vertical levels. We used the concentration-response functions proposed by two relevant WHO projects to calculate the number of attributable annual deaths corresponding to all non-accidental causes (ICD-10: A00-R99) among all-ages and the adult population (>30 years old) for each district and for Madrid city overall. This health impact assessment was conducted dependant on health-data availability. ResultsIn 2020, the implementation of Plan A would imply a reduction in the Madrid citywide annual mean PM2.5 concentration of 0.6 μg/m3 and 4.0 μg/m3 for NO2. In contrast, an increase of 1 μg/m3 for O3 would be expected. The annual number of all-cause deaths from long-term exposure (95% CI) that could be postponed in the adult population by the expected air-pollutant concentration reduction was 88 (57–117) for PM2.5 and 519 (295–750) for NO2; short-term exposure accounted for 20 (7–32) for PM2.5 and 79 (47–111) for NO2 in the total population. According to the spatial distribution of air pollutants, the highest mortality change estimations were for the city centre – including Madrid Central and mainly within the M-30 ring road –, as compared to peripheral districts. The positive health impacts from the reductions in PM2.5 and NO2 far exceeded the adverse mortality effects expected from the increase in O3. ConclusionsEffective implementation of Plan A measures in Madrid city would bring about an appreciable decline in traffic-related air-pollutant concentrations and, in turn, would lead to significant health-related benefits.

Monitoring on-road air quality and measuring vehicle emissions with remote sensing in an urban area

Simultaneous day-time measurement (8 a.m.–5 p.m.) of on-road air quality and emissions (remote sensing) on an urban road with traffic volumes varying between approximately 400-800 vehicles per hour and an average speed of about 40 km/h has been used to compare multiple measurement techniques and assess on-road air quality. It was found that observed daytime concentration levels of CO, NOx, NO2, O3, PM10 and PM2.5 are below current WHO health based guideline values, varying from a few percent (CO) to above 60% (O3 and PM2.5) of the guideline values. NO2 to NOx ratios were about a factor of two higher than measured in a previous tunnel study, which indicates that about half of measured NO2 concentrations are due to urban background levels. Statistical analysis suggest that on-road NO2 and ozone concentrations are largely driven by atmospheric chemistry processes, and not significantly affected by variation in local traffic volume and fleet mix. A significant positive weighted correlation (r = 0.71–0.74) between remote sensing and air concentration monitoring is observed for CO in calm conditions. Speciated VOC measurements on the road show large discrepancies with current COPERT (Australia) vehicle emission factors, confirming the results from an earlier tunnel study. The weight of evidence suggests that the current (EU based) VOC speciation in COPERT Australia is likely not appropriate for the Australian on-road fleet.

Nvironmental Monitoring of NOX, Total Oxidants and the Implications for Photochemistry of Air Pollution over Ilorin Shed, Nigeria

Environmental Monitoring of NOX, Total Oxidants and the Implications for Photochemistry of Air Pollution over Ilorin Shed, Nigeria Abdul Raheem A.M.O., Adekola F.A., Obioh I.B. Abstract The assessment of oxides of nitrogen (NOX) and total oxidants as ozone (O3) over the air shed of a typical average tropical equatorial city monitored with the aid of high volume sampler for three years is presented using three urban site classes and a control. The mean concentrations for all sites during wet season (May - October) were 3.31 ± 0.40 ppb for NOX, 21.86 ± 2.47 for O3 while the dry season (November - April) mean concentration values were 2.03 ± 0.23 ppb for NOx and 32.44 ± 5.13 for O3. Mean value at the control site was an order of magnitude lower than the urban sites during the two seasons except concentration of O3 higher during the dry season. Traffic density and trace gas concentrations showed good correlation of 0.98 (P<0.05). NOx was confirmed to be a strong precursor for O3 formation. The influence of Harmattan dust in impeding the photochemistry of O3 formation from November to January (NDJ) months was observed. The overall concentration levels of NOx and O3 for the air shed are 2.67 ± 0.32 and 27.15 ± 3.8 respectively, within the limit of United States Environmental Protection Agency (USEPA) guidelines for air quality standards. Full Text: PDF DOI: 10.15640/jcb.v7n1a1

A Predictive Model for Steady State Ozone Concentration at an Urban-Coastal Site.

Ground level ozone (O3) plays an important role in controlling the oxidation budget in the boundary layer and thus affects the environment and causes severe health disorders. Ozone gas, being one of the well-known greenhouse gases, although present in small quantities, contributes to global warming. In this study, we present a predictive model for the steady-state ozone concentrations during daytime (13:00–17:00) and nighttime (01:00–05:00) at an urban coastal site. The model is based on a modified approach of the null cycle of O3 and NOx and was evaluated against a one-year data-base of O3 and nitrogen oxides (NO and NO2) measured at an urban coastal site in Jeddah, on the west coast of Saudi Arabia. The model for daytime concentrations was found to be linearly dependent on the concentration ratio of NO2 to NO whereas that for the nighttime period was suggested to be inversely proportional to NO2 concentrations. Knowing that reactions involved in tropospheric O3 formation are very complex, this proposed model provides reasonable predictions for the daytime and nighttime concentrations. Since the current description of the model is solely based on the null cycle of O3 and NOx, other precursors could be considered in future development of this model. This study will serve as basis for future studies that might introduce informing strategies to control ground level O3 concentrations, as well as its precursors’ emissions.

The antiproliferative effects of cold atmospheric plasma-activated media on different cancer cell lines, the implication of ozone as a possible underlying mechanism.

Recent studies have proven several promising anticancer activities for cold atmospheric plasma (CAP) against a wide range of cancer cells in vitro. Recently, media treated with CAP have also found to effectively eradicate cancer cells similar to the CAP. Based on advantages, many researchers prefer to apply CAP-activated media (PAM) as an alternative to cap in the treatment of cancer. However, less has been achieved regarding the anticancer effects and anticancer mechanisms of PAM. Investigating the selective anticancerous activities of PAM, the viability of SKBR3, MCF7, ASPC-1, A-549, G-292, and SW742 cancer cell lines, as well as normal human skin fibroblasts (FMGB-1) and MCF10A cells in relation to the media activation time, and the length of exposure was studied. Also, we examined the concentration of ozone in media as a function to CAP activation time since recent studies have proposed ozone as a pivotal reactive species in the induction of cell death. Based on the result, both increasing the duration of media activation time and the length of exposure to PAM could significantly increase the anticancer activity. Nevertheless, the cytotoxicity on normal cells was either not affected or slightly increased. Among the six tested cancer cell lines, SW742 was the most resistant and SKBR3 the most susceptible cancer cell lines to PAM. Also, increasing duration of treatment with CAP resulted in a significant rise in O3 concentration levels in media. Overall, these results suggest PAM, as a promising tool in the treatment of different cancers and O 3 formation as a probable underlying mechanism.

Evaluating the Influence of Meteorological Parameters on Ozone Concentration Levels

Over the years, anthropogenic activities have led to the increase in air pollution concentration levels in the atmosphere, this persistent increase in pollution levels can be influenced by meteorological parameters. These parameters assist in the formation and transportation of air pollutants in the atmosphere. Hence, this study aims at evaluating the association between meteorological parameters and air pollutants. The analysis was carried out using Ozone (O3), Particulate matter (PM10), Nitrogen dioxide (NO2), temperature, humidity, wind speed, and wind direction data from 2006 to 2010, from two industrial air quality monitoring stations. Stepwise regression (SR) analysis was used to assess the influence of meteorological parameters in accounting for the variability of O3 concentration levels. The SR analysis showed that meteorological parameters accounted for more than 50 % of O3 variability. It can be concluded that different relationship between meteorological parameters and O3 can exist in different locations in the same region.

Exposure- and flux-based assessment of ozone risk to sugarcane plants

Ozone (O3) is a toxic oxidative air pollutant, with significant detrimental effects on crops. Sugarcane (Saccharum spp.) is an important crop with no O3 risk assessment performed so far. This study aimed to assess O3 risk to sugarcane plants by using exposure-based indices (AOT40 and W126) based on O3 concentrations in the air, and the flux-based index (PODy, where y is a threshold of uptake) that considers leaf O3 uptake and the influence of environmental conditions on stomatal conductance (gsto). Two sugarcane genotypes (IACSP94-2094 and IACSP95-5000) were subjected to a 90-day Free-Air Controlled Experiment (FACE) exposure at three levels of O3 concentrations: ambient (Amb); Amb x1.2; and Amb x1.4. Total above-ground biomass (AGB), stalk biomass (SB) and leaf biomass (LB) were evaluated and the potential biomass production in a clean air was estimated by assuming a theoretical clean atmosphere at 10 ppb as 24 h O3 average. The Jarvis-type multiplicative algorithm was used to parametrize gsto including environmental factors i.e. air temperature, light intensity, air vapor pressure deficit, and minimum night-time temperature. Ozone exposure caused a negative impact on AGB, SB and LB. The O3 sensitivity of sugarcane may be related to its high gsto (∼535 mmol H2O m−2 s−1). As sugarcane is adapted to hot climate conditions, gsto was restricted when the current minimum air temperature (Tmin) was below ∼14 °C and the minimum night-time air temperature of the previous day (Tnmin) was below ∼7.5 °C. The flux-based index (PODy) performed better than the exposure-based indices in estimating O3 effect on biomass losses. We recommend a y threshold of 2 nmol m−2 s−1 to incorporate O3 effects on both AGB and SB and 1 nmol m−2 s−1 on LB. In order not to exceed 4% reduction in the growth of these two sugarcane genotypes, we recommend the following critical levels: 1.09 and 1.04 mmol m−2 POD2 for AGB, 0.91 and 0.96 mmol m−2 POD2 for SB, and 3.00 and 2.36 mmol m−2 POD1 for LB of IACSP95-5000 and IACSP94-2094, respectively.

Forecasting ozone concentration levels using Box-Jenkins ARIMA modelling and artificial neural networks: A comparative study

An accurate forecasting of tropospheric ozone (O3) concentration is beneficial for strategic planning of air quality. In this study, various forecasting techniques are used to forecast the daily maximum O3 concentration levels at a monitoring station in the Klang Valley, Malaysia. The Box-Jenkins autoregressive integrated moving-average (ARIMA) approach and three types of neural network models, namely, back-propagation neural network, Elman recurrent neural network and radial basis function neural network are considered. The daily maximum data, spanning from 1 January 2011 to 7 August 2011, was obtained from the Department of Environment, Malaysia. The performance of the four methods in forecasting future values of ozone concentrations is evaluated based on three criteria, which are root mean square error (RMSE), mean absolute error (MAE) and mean absolute percentage error (MAPE). The findings show that the Box-Jenkins approach outperformed the artificial neural network methods.

Characterization of Surface Ozone Behavior at Different Regimes

Previous studies showed that the influence of meteorological variables and concentrations of other air pollutants on O3 concentrations changes at different O3 concentration levels. In this study, threshold models with artificial neural networks (ANNs) were applied to characterize the O3 behavior at an urban site (Porto, Portugal), describing the effect of environmental and meteorological variables on O3 concentrations. ANN characteristics, and the threshold variable and value, were defined by genetic algorithms (GAs). The considered predictors were hourly average concentrations of NO, NO2, and O3, and meteorological variables (temperature, relative humidity, and wind speed) measured from January 2012 to December 2013. Seven simulations were performed and the achieved models considered wind speed (at 4.9 m·s−1), temperature (at 17.5 °C) and NO2 (at 26.6 μg·m−3) as the variables that determine the change of O3 behavior. All the achieved models presented a similar fitting performance: R2 = 0.71–0.72, RMSE = 14.5–14.7 μg·m−3, and the index of agreement of the second order of 0.91. The combined effect of these variables on O3 concentration was also analyzed. This statistical model was shown to be a powerful tool for interpreting O3 behavior, which is useful for defining policy strategies for human health protection concerning this air pollutant.

Interaction between isoprene and ozone fluxes in a poplar plantation and its impact on air quality at the European level

The emission of isoprene and other biogenic volatile organic compounds from vegetation plays an important role in tropospheric ozone (O3) formation. The potentially large expansion of isoprene emitting species (e.g., poplars) for bioenergy production might, therefore, impact tropospheric O3 formation. Using the eddy covariance technique we have simultaneously measured fluxes isoprene, O3 and of CO2 from a poplar (Populus) plantation grown for bioenergy production. We used the chemistry transport model LOTOS-EUROS to scale-up the isoprene emissions associated with the existing poplar plantations in Europe, and we assessed the impact of isoprene fluxes on ground level O3 concentrations. Our findings suggest that isoprene emissions from existing poplar-for-bioenergy plantations do not significantly affect the ground level of O3 concentration. Indeed the overall land in Europe covered with poplar plantations has not significantly changed over the last two decades despite policy incentives to produce bioenergy crops. The current surface area of isoprene emitting poplars-for-bioenergy remains too limited to significantly enhance O3 concentrations and thus to be considered a potential threat for air quality and human health.

Variations of surface ozone at Ieodo Ocean Research Station in the East China Sea and the influence of Asian outflows

Abstract. Ieodo Ocean Research Station (IORS), a research tower (~ 40 m a.s.l.) for atmospheric and oceanographic observations, is located in the East China Sea (32.07° N, 125.10° E). The IORS is almost equidistant from South Korea, China, and Japan and, therefore, it is an ideal place to observe Asian outflows without local emission effects. The seasonal variation of ozone was distinct, with a minimum in August (37 ppbv) and two peaks in April and October (62 ppbv), and was largely affected by the seasonal wind pattern over east Asia. At IORS, six types of air masses were distinguished with different levels of O3 concentrations by the cluster analysis of backward trajectories. Marine air masses from the Pacific Ocean represent a relatively clean background air with a lowest ozone level of 32 ppbv, which was most frequently observed in summer (July–August). In spring (March–April) and winter (December–February), the influence of Chinese outflows was dominant with higher ozone concentrations of 62 and 49 ppbv, respectively. This study confirms that the influence of Chinese outflows was the main factor determining O3 levels at IORS and its extent was dependent on meteorological state, particularly at a long-term scale.

Physiological and visible injury responses in different growth stages of winter wheat to ozone stress and the protection of spermidine

The open top chamber (OTC) method was used in a farmland to study the influence of different levels of O3 concentrations (40 ppb, 80 ppb and 120 ppb) on the enzymatic activity and metabolite contents of the antioxidation system of the winter wheat leaves during the jointing, heading and milk stage. The protective effect of exogenous spermidine (Spd) against the antioxidation of winter wheat under the O3 stress was investigated. With the increasing O3 concentrations and fumigation time, the injuries of the winter wheat leaves were observed to be more serious. For instance, when the O3 concentration reached 120 ppb, the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and nitrate reductase (NR) in the jointing stage decreased by 50.3%, 64.9%, 75.5% and 92.9%, respectively; peroxidase (POD) and glutathione reductase (GR) increased by 45.1% and 80.5%, respectively; the contents of malondialdehyde (MDA), ascorbic acid (AsA) and reduced glutathione (GSH) increased by 314.3%, 8.4% and 31.7%, respectively; and the soluble protein (SP) content decreased by 47.5%. The O3 stress also had significant impact on the contents of proline (Pro), NO3––N and NH4+–N of the winter wheat leaves. During the heading stage, when the O3 concentration was 40 ppb and 80 ppb, the content of Pro was 163.9% and 173.2% higher than that in the control group, respectively. But under 120 ppb, it was decreased by 42.4%. Exogenous application of Spd increased the activities of SOD, POD, CAT, APX and GR, as well as the contents of GSH and SP, but decreased the contents of MDA and AsA. This indicates that Spd is an effective antioxidant to relieve the O3 stress on winter wheat leaves, thereby might be applicable to protect winter wheat from the harm of O3.

Influence of elevated ozone concentration on methanotrophic bacterial communities in soil under field condition

The open top chamber (OTC) method was used in combination with real-time quantitative PCR and terminal restriction fragment length polymorphism (T-RFLP) techniques in the wheat field to study the influence of different levels of O3 concentrations (ambient air filtered by activated carbons, 40 ppb, 80 ppb and 120 ppb) on the quantity and community structure of methanotrophic bacteria. O3 stress can influence the potential methane oxidation rate (PMOR) and potential methane production rate (PMPR) in the farmland soil. O3 treatment of 40 ppb improved significantly the 16S rRNA gene copy number in the total methanotrophic bacteria pmoA, and type I and type II methanotrophic bacteria in the soil depth of 0–20 cm. When the O3 concentration reached 120 ppb, the 16S rRNA gene copy number in the total methanotrophic bacteria pmoA and type I methanotrophic bacteria decreased significantly as compared to the control treatment in 10–20 cm layer. The 16s rRNA gene copy number of total methanotrophic bacteria pmoA and type I and type II methanotrophic bacteria were influenced by different O3 concentration and soil depth. The T-RFLP analysis indicated that O3 stress influenced significantly the community structure of the methanotrophic bacteria in soil, causing potential threat to the diversity of methanotrophic bacteria. It seems to imply that the rise of O3 concentration could produce an impact on the carbon cycling and the methane emission of the wheat field soil by changing the community structure and diversity of methanotrophic bacteria, which then influences the global climate change.

Low Air Pollution and Cardiovascular Mortality: a Population Based Case-Crossover Study

Background: The aim was to study short-term associations of NO2, O3, PM10, SO2, and H2S concentrations and cardiovascular mortality in Reykjavik capital area. Methods: Data on daily mortality were obtained from the National Cause-of-Death Registry, Statistics Iceland, during 2003 to 2009. One hour measures of NO2, O3, PM10, SO2, and H2S were obtained from the Environment Agency of Iceland for the same time period. A time-stratified case-crossover design was used to estimate the possible effect of short-term exposure of air pollution and cardiovascular mortality. Results: The total number of deaths due to cardiovascular causes over the study period was 2,070 cases. The inter-quartile range (IQR) of the 24-hour concentration levels of NO2, O3, PM10, SO2, and H2S over the study period was 17 µg/m3, 20 µg/m3, 13 µg/m3, 2 µg/m3, 2 µg/m3, respectively. The association for IQR increases of the pollutants and cardiovascular mortality were not statistically significant (confidence interval: 95%) at any time lag, with odds ratios near unity. Conclusion: The pollution concentration levels in Reykjavik are generally low in an international perspective, but peaks of pollutants, such as PM10, may exceed peaks occurring in other European cities. Previous studies have implied that air pollution in Reykjavik could increase consumption of medicament against asthma and angina pectoris. However, there were no short-term associations between air pollution and cardiovascular mortality in the present study, contrary to what has been found elsewhere.

Outdoor Air Pollution and Emergency Department Visits for Respiratory Illness in Greater Tunis District, between 2007 and 2010

Background: Ambient air pollution contributes to the development and the exacerbation of respiratory illness. The aim of this work was to study the impact of the outdoor air pollution on the emergency department visits for asthma and chronic obstructive pulmonary disease (COPD) exacerbation. Methods: Morbidity data were collected from the emergency department register of the A Mami hospital, from January, 1st 2007 to December, 31th 2010. Information about age, sex and date of the emergency department visits were obtained for patients with the diagnosis of asthma or COPD. Concentration levels of NO2, SO2, O3, and particulate matter (PM10) were collected from the National Observatory of the air quality in Tunisia. The impact of the outdoor air pollution on the daily emergency department visits was studied by a simple Pearson correlation and by a binomial negative regression using generalized linear models. Results: We recorded 9814 visits to the emergency department for asthma (6499, 65.5%) or COPD exacerbation (3315, 34.5%) between 2007 and 2010. Overall mean age was 52±21 years; it was respectively 47±21 and 60±18 years for asthma and COPD. About 63% were male. Positive correlation was observed between number of visits for respiratory symptoms and NO2 ambient air concentration (Spearman correlation coefficient =0.204, p&lt;10-3), and O3 level (Spearman correlation coefficient=0.109, p&lt;10-3). Multivariate analysis showed significant positive association between the daily numbers of emergency department visits for asthma and COPD (Adjusted OR=1.011, 95% CI: 1.006-1.015, p&lt;10-3). Conclusions: Exacerbation of respiratory illness in the Greater Tunis was correlated to the NO2 outdoor air concentration level which can be related to the traffic density in the capital city of Tunisia and its provinces.

A Survey of Indoor Air Quality in Archives

Archives are the indoor spaces which have the special purpose of preservation of records. But the values of the Korean standard about air quality in archives are not realistic. Furthermore there are no measured data for analysis about indoor air quality level of archives. So, we measured indoor air quality of three archives on site for evaluation standard level. We carried comparative analyses of the Korean standard and ISO-11799 the international standard for review of the adequacy of standard. SO₂, O₃ and CO concentration levels in archives were much lower(about 10% level) than the Korean standard. PM10 and Formaldehyde concentrations were about 40% level of the Korean standard, and NOx was about 65% level. But, TVOCs concentration was exceed the standard value(400 μg/m³). Temperature and Relative humidity level were far off the standard range. SO₂, O₃ and CO standard values should be improved to the international standard levels for realistic regulation values. NOx and Formaldehyde regulation values in the Korean standard should be gradually improved to the international standard levels, and their concentration management methods should be researched at the same time. As TVOCs concentration levels were exceed the standard, it is necessary to control the indoor air quality more strictly. The thermo-hygrostat must be installed to control temperature and humidity in archives.

Scorched Earth: how will changes in the strength of the vegetation sink to ozone deposition affect human health and ecosystems?

Abstract. This study investigates the effect of ozone (O3) deposition on ground level O3 concentrations and subsequent human health and ecosystem risk under hot summer "heat wave" type meteorological events. Under such conditions, extended drought can effectively "turn off" the O3 vegetation sink leading to a substantial increase in ground level O3 concentrations. Two models that have been used for human health (the CMAQ chemical transport model) and ecosystem (the DO3SE O3 deposition model) risk assessment are combined to provide a powerful policy tool capable of novel integrated assessments of O3 risk using methods endorsed by the UNECE Convention on Long-Range Transboundary Air Pollution. This study investigates 2006, a particularly hot and dry year during which a heat wave occurred over the summer across much of the UK and Europe. To understand the influence of variable O3 dry deposition three different simulations were investigated during June and July: (i) actual conditions in 2006, (ii) conditions that assume a perfect vegetation sink for O3 deposition and (iii) conditions that assume an extended drought period that reduces the vegetation sink to a minimum. The risks of O3 to human health, assessed by estimating the number of days during which running 8 h mean O3 concentrations exceeded 100 μg m−3, show that on average across the UK, there is a difference of 16 days exceedance of the threshold between the perfect sink and drought conditions. These average results hide local variation with exceedances between these two scenarios reaching as high as 20 days in the East Midlands and eastern UK. Estimates of acute exposure effects show that O3 removed from the atmosphere through dry deposition during the June and July period would have been responsible for approximately 460 premature deaths. Conversely, reduced O3 dry deposition will decrease the amount of O3 taken up by vegetation and, according to flux-based assessments of vegetation damage, will lead to a reduction in the impact of O3 on vegetation across the UK. The new CMAQ-DO3SE model was evaluated by comparing observation vs. modelled estimates of various health related metrics with data from both urban and rural sites across the UK; although these comparisons showed reasonable agreement there were some biases in the model predictions with attributable deaths at urban sites being over predicted by a small margin, the converse was true for rural sites. The study emphasises the importance of accurate estimates of O3 deposition both for human health and ecosystem risk assessments. Extended periods of drought and heat wave type conditions are likely to occur with more frequency in coming decades, therefore understanding the importance of these effects will be crucial to inform the development of appropriate national and international policy to mitigate against the worst consequences of this air pollutant.

Development and Application of Artificial Neural Network Modeling in Forecasting PM10 Levels in a Mediterranean City

The study of atmospheric concentration levels at a local scale is one of the most important topics in environmental sciences. Multivariate analysis, fuzzy logic, and neural networks have been introduced in forecasting procedures in order to elaborate operational techniques for level characterization of specific atmospheric pollutants at different spatial and temporal scales. Particularly, approaches based on artificial neural networks (ANNs) have been proposed and successfully applied for forecasting concentration levels of PM10, NO2, SO2, CO, and O3. The present study explores the development and application of ANN models for forecasting, 24 h ahead, not only the daily concentration levels of PM10 but also the number of hours exceeding the PM10 concentration threshold during the day in five different regions within the greater Athens area (GAA). The ANN modeling was based on measurements and estimates of the mean daily PM10 concentration, the maximum hourly NO2 concentration, air temperature, relative humidity, wind speed, and the mode daily value of wind direction from five different monitoring stations for the period 2001–2005. The evaluation of the model performance showed the risk of daily PM10 concentration levels exceeding certain thresholds as well as the duration of the exceedances can be successfully predicted. Despite the limitations of the model, the results indicate that ANNs, when adequately trained, have considerable potential to be used for 1 day ahead PM10 concentration forecasting and the duration within the GAA.

Issues related to aircraft take-off plumes in a mesoscale photochemical model

The physical and chemical characteristics of aircraft plumes at the take-off phase are simulated with the mesoscale CAMx model using the individual plume segment approach, in a highly resolved domain, covering the Athens International Airport. Emission indices during take-off measured at the Athens International Airport are incorporated. Model predictions are compared with in situ point and path-averaged observations (NO, NO2) downwind of the runway at the ground. The influence of modeling process, dispersion properties and background air composition on the chemical evolution of the aircraft plumes is examined. It is proven that the mixing properties mainly determine the plume dispersion. The initial plume properties become significant for the selection of the appropriate vertical resolution. Besides these factors, the background NOx and O3 concentration levels control NOx distribution and their conversion to nitrogen reservoir species.

Diurnal/nocturnal concentrations and sources of particulate-bound PAHs, OPAHs and NPAHs at traffic and suburban sites in the region of Paris (France)

Particulate concentrations of polycyclic aromatic compounds (PACs) including, 17 polycyclic aromatic hydrocarbons (PAHs), 9 oxygenated PAHs (OPAHs) and 18 nitrated PAHs (NPAHs) were determined at traffic and suburban sites located in the region of Paris. A 12h sampling basis time resolution was applied in order to study their diurnal and nocturnal variations. Observed concentrations were about 10 times higher at the traffic site for all compounds and were higher during the night-time for both sites (except for NPAHs at the traffic site). No significant differences in PAH and OPAH profiles were observed at both sites whereas, for NPAHs, 1-nitropyrene (diesel source) was the most abundant at the traffic site and 2+3-nitrofluoranthene (secondary formed by gas-phase reaction) was predominant at the suburban site. The study of the specific ratio 2-nitrofluoranthene/1-nitropyrene (2-NFlt/1-NP) showed a local formation of NPAHs in gaseous phase at the suburban site. A detailed analysis showed that atmospheric humidity and rainfalls modified differently PAH and NPAH profiles, in comparison to OPAH. A difference of the scale variability of water solubility between, light (MW≤228gmol−1) and heavy compounds (MW≥273gmol−1), could explain these observations. The specific study of the relationships between PACs and other measured pollutants highlighted that particle resuspension could constitute a significant source of PM on the traffic site. Even if NPAH formation seemed clearly evident at the suburban site during periods characterised by high O3 and NO2 concentration levels, results showed also that the primary and/or secondary origins of OPAHs and NPAHs were strongly dependent on the sampling site and on sampling conditions. Finally, we conclude that higher time sampling resolutions would be helpful in investigating the atmospheric chemistry and behaviours of PACs in correlation with the local meteorological variations and the daily cycle of human activities.