Urban air quality in larger conurbations in the European Union

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Abstract

The air quality in about 200 urban agglomerations within the European Union (EU) is calculated for a reference year (1995) and for the year 2010. Relatively simple, robust tools have been applied which allow for a generalisation of the results on the scale of the whole EU. The projected air quality gives information on the frequency and severity of exceedance of air quality objectives and on the fraction of EU urban population potentially exposed. The parameter calculated is the urban background concentration, which is representative for the concentration in most of the urban area, with the exception of places under direct influence of sources, such as streets. Pollutants considered are SO2, NO2, PM10, Pb, O3, CO, and benzene. In 2010 the urban background concentrations will decrease strongly in the set of 200 modelled cities. It is projected, however, that the agreed or proposed air quality standards will still be exceeded in the future. The most serious problems are exceedances of the short- and long-term objectives for PM10 and exceedance of the long-term objective for NO2.

Introduction

Europe is a highly urbanised continent. In 1990, >70% of the total population lived in urban agglomerations. The concentration of human activities in a relatively small area puts enormous pressure on the urban system and has led to numerous environmental problems (e.g. noise, waste, air pollution). On the basis of pan-European surveys of the state of the environment (EEA, 1995, EEA, 1997, EEA, 1998) urban air pollution was regarded by the European Environment Agency (EEA) as one of the most important environmental problems in Europe. Whereas in the past industry and energy production have been the dominant sources of urban air pollution, nowadays transport, in particular road traffic, is the most important source.

In order to assess the urban air quality on European scale, a combination of atmospheric dispersion models and air quality measurements should be used. The extent of observational data available on urban air pollution is not large enough to fully characterise urban air quality on an European scale (Larssen and Hagen, 1996). Atmospheric dispersion models on urban scale have been used, for example, in the Auto Oil programmes I and II, launched by the European Commission in 1992 and 1997. These programmes used detailed modelling to study cost-effective measures to reduce road transport emissions, and to provide a foundation for a transition towards longer term air quality studies covering all emission sources. In the Auto Oil programmes, computationally demanding dispersion models were used in up to ten European cities.

A simpler methodology, based on less demanding atmospheric dispersion and empirical modelling, has been proposed by the EEA's European Topic Centres on Air Quality (ETC/AQ) and on Air Emissions (ETC/AE) to complement the Auto Oil II programme (De Leeuw et al., 2000). In contrast to the detailed modelling of ten cities, this approach aimed at a more general assessment of urban air quality in the European Union (EU). More precisely, the goal of this “Generalised Exposure Assessment (GEA)” is to estimate the fraction of the urban population that is living in European cities that are not in compliance with air quality objectives in future years and to estimate additional emission reductions needed to reach compliance. In the GEA-approach, simple robust tools are used to calculate, in a consistent way, air quality in a relatively large number of cities. The consistency allows for a generalisation of the results on the scale of the whole EU. Pollutants considered are SO2, NO2, PM10, O3, CO, and benzene.

Section snippets

Methodology

The main intention of this study is to provide information on current and future non-attainment of air quality objectives related to the protection of human health for the urban population in the EU. A combination of measuring and modelling tools is applied. Measurement data is used wherever possible; it is complemented using the results of atmospheric dispersion models to obtain a full coverage of urban areas. Results of these complementary procedures are presented together and discussed.

The

Ozone

Simulations with the OFIS model were performed for summer 1995. Scatter plots of observations and modelled results show in general a satisfactory agreement although notable mismatches are found. Fig. 3 shows the cumulative distribution of the urban area maximum and urban area average number of days with exceedance of the running 8 h-average of 120 μg/m3 ozone versus the percentage of population subject to these exceedances. The distribution is shown separately for cities in Northern Europe

Results for base case 2010

The base case scenario consists, broadly speaking, of a projection over the period 1990–2020 of emissions of all sources at 5-year intervals. It incorporates the expected effects of the Auto-Oil-I and other adopted or anticipated legislation. For the road transport component detailed information collected at national levels has been used. The base case is essentially a ‘business-as-usual’ scenario. This does not mean that it is a prediction of what will actually happen but rather of what could

Discussion

An overview of the results obtained by the various models for the reference year 1995 and 2010 is presented in Table 3.

The results for the reference year were compared to measured air quality data. The comparison of modelled and measured air quality is hampered by a lack of reliable data. To improve the coverage of the monitoring data, data over the period 1992–1996 has been used. The air quality database AIRBASE has proved to be valuable tool but needs further input of air concentration dam

Conclusions

In 1995 a large fraction of the urban population is exposed to concentrations of one or more pollutants which are in excess of the air quality objectives set for the year 2010. The situation will be much improved in 2010 under the AOPII base case scenario but a till compliance with all objectives is not expected. Full compliance can only be realised by means of additional reductions for source categories other than road transport. However, especially for NO2, CO, and benzene there are clear

Acknowledgements

This study is developed from the contribution of the European Topic Centre on Air Quality to the Working Group I of the Auto Oil II programme under contract to the European Environment Agency. Valuable contributions have been given by Robert Enesund, Tinus Pulles, Antoon Visschedijk and various other colleagues from the European Topic Centres on Air Emissions and on Land Cover.

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