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Monitoring atmospheric pollution in urban areas frequently involves mapping tools that are assisting the researcher and/or the decision maker to describe and quantify the pollution at locations where no measurements are available. The preparation of these pollution maps is a complex task, which is only possible if a spatial correlation of the variable of interest is identified. Furthermore, the spatial correlation may not only change in time and space, but also according to the pollution levels. To illustrate this point, this paper investigates the fractal dimension of the spatial correlation of different levels of annual nitrogen dioxide (NO2) concentrations in the greater area of Milan in Italy for the years 1997-1999. It is shown that low levels (<20µg/m3) and high levels (>32µg/m3) of annual NO2 concentrations present less correlation in space than mid levels (20-32µg/m3) do. As a result, probability maps defining areas with high and low probability of exceeding a specific concentration threshold will have an uncertainty associated to the estimated probabilities that is related to the different NO2 annual levels. In the light of these results, the development of environmental policies related to the EC Directive is briefly discussed. Rather than trying to define an optimal NO2 sampling network, suggestions are made on how the information provided by the analysis of the spatial correlation could improve the existing network of NO2 monitoring sites.

Additional information

Authors: DUBOIS G, Department of Mineralogy and Petrography, University of Lausanne (CH);SAISANA M, European Commission, Joint Research Centre, Institute for the Protection and Security of the Citizen, Ispra (IT);CHALOULAKOU A, Department of Chemical Engineering, National Technical University of Athens (GR);SPYRELLIS N, Department of Chemical Engineering, National Technical University of Athens (GR)
Bibliographic Reference: An oral paper given at: iEMSs 2002 congress ( ) Organised by: International Environmental Modelling and Software Society Held at: Lugano (IT), 24-27 June 2002
Availability: The paper is published on pages 536-541 of the online proceedings of the congress at:
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