Suchergebnisse

This paper examines the contribution of primary and secondary NO2 production in NOx concentrations and offers a comprehensive analysis of the long-term trends of NOx, NO2 and O-3 concentrations, as well as of the NO2/NOx ratio, in the Athens urban conurbation. Long-term pollutant concentration time series show that NO2 concentrations in Athens have decreased since 1987 but at a slower rate than those of NOx, resulting to an increasing NO2/NOx concentration ratio. However, this increasing trend is much smaller than those observed in urban areas of other European countries. The possible causes of this trend are examined and especially the interaction with ozone and the amount of direct NO2 traffic emissions. The results indicate that the increasing NO2/NOx ratio in the Athens area is mainly attributable to an increased secondary formation of NO2 through photochemical reactions in the atmosphere. More specifically, two different empirical methodologies were applied to examine the primary NO2 concentration fraction in Athens, using ambient monitoring data from a kerbside station. Both methods indicate that the primary NO2 concentration share has not altered significantly between 1998 and 2006. This is mainly attributed to the fact that in the Athens area diesel passenger cars are not allowed and after-treatment technologies such as particle filters and oxidation catalysts are not yet applied in Greece. A probable future penetration of diesel passenger cars in Athens should be combined with inventories of primary NO2 emissions and with the development of appropriate policies to reduce ambient NO2 concentrations below the EU limit values. (C) 2010 Elsevier Ltd. All rights reserved.

Several characteristics of the annual PM10 concentrations in the Athens conurbation, together with the expected health implications, are investigated using data from the Athens network of monitoring stations. Annual PM10 concentrations show a decreasing trend; however, concentration levels are still high, exceeding the current EU air quality standard at four monitoring stations and the Air Quality Guideline (AQG) suggested by WHO at all eight stations. PM10 concentrations correlate well with those of NOx and NO2, while the results suggest that approximately 54% of the PM10 fraction is attributable to road traffic. An analysis of the health implications of the observed PM10 levels, based on a dose-response relationship, is coupled with available health-related data from the Athens area. This analysis suggests that if PM10 concentrations were reduced to the levels of the AQGs, then a significant decrease in respiratory and cardiovascular hospital admissions and mortality would be observed. Copyright © 2010 Inderscience Enterprises Ltd.

Recent risk assessment studies have shown that high outdoor NO, levels observed in residential areas contribute to increased respiratory and cardiovascular diseases and mortality. Detailed information on present NO2 levels as well as predictions of NO2 concentrations corresponding to reduced NOx levels in urban areas are very useful to decision and policy makers in order to protect the public health. In the present paper, monitoring stations of the Athens network are initially classified into two main groups, traffic affected and urban background, using effectively a criterion based on the ratio of annual mean NO:NO2 concentrations. Two empirical methodologies are then considered and compared for assessing the effect of different NOx levels on the attainment of the annual NO2 air quality standard at urban-background locations in the Athens area. An interesting finding is that these two methodologies, one more general and one both year and site dependent, give similar results for the specific study area and can be applied alternatively based on the length of available concentration time series. The results show that in order to meet the EU annual mean NO2 objective at all the urban-background locations of the Athens area, annual NOx concentrations should be reduced to approximately 60 mu g m(-3), requiring NOx emission reductions of up to 30%. An analysis of the health implications of the currently observed NO, levels is conducted, based on a dose-response relationship, and is coupled with available health-related data for the Athens area. This analysis suggests that if NO2 concentrations were reduced to the levels of the annual EU air quality standard, then a decrease of hospital admissions of up to 2.6% would be observed, depending on the levels of NO2 measured at different monitoring sites of the Athens conurbation. (C) 2007 Elsevier Ltd. All rights reserved.

Goal, Scope and Background. This paper describes a statistical modelling approach, suggested as a policy tool in the Athens area for the assessment of the emissions reduction level required to meet the air quality standards for two criteria air pollutants, namely CO and NO2. Methods. More than ten years of hourly CO and NOx-NO2 concentration data measured by the monitoring network of the Hellenic Ministry for the Environment, Physical Planning and Public Works were analyzed and the original dataset has been reduced using a data evaluation procedure. Results and Discussion. Seasonal pollutant concentration trends suggested that the reduction of CO and NOx concentrations observed in the beginning of the '90s is almost entirely attributed to the increase of the catalyst-equipped cars during this period. The numerical parameters of an empirical model relating EU standard exceedances with mean annual concentrations were defined and the model was validated using datasets from years that were not used for the estimation of these parameters. This model was used in conjunction with a roll-back equation as a policy tool for the assessment of the effect of different CO and NOx emissions reduction scenarios on air quality standard compliance for CO and NO2. Results predicted with this empirical modelling approach were assessed with monitored data averaged over a 3-year period, giving satisfactory results. Conclusion. A methodology suggested for assessing the effects of different emissions reduction scenarios on air quality standard attainment was successfully applied for CO and NO2 in the Athens area. Recommendation and Perspective. The proposed methodology can provide a useful tool for the evaluation of policies already in progress as well as the development of future policies for emissions reduction in urban areas with similar characteristics, aiming at air quality standard compliance on a timely manner. Such a methodology could be applied in other urban areas of Greece characterized by dense traffic, therefore assisting the development of national policies in relation to air pollutants for which standard exceedances occur. © 2007 ecomed publishers (Verlagsgruppe Hüthig Jehle Rehm GmbH).