A receptor-oriented and a source-oriented approach are applied to assess the contribution of traffic emissions to PM10 concentration levels in Milan (Italy). Both the approaches are based on the comparison between weekend and weekdays data. The differences observed between Sundays' and weekdays' PM10 concentrations are analysed in terms of probability distributions of occurrence: as a consequence of the reduced circulating traffic flows, Sundays' concentration levels are on average about 20 % lower, but concentration increase is sometimes observed under unfavourable meteorological conditions. The effect of the reduced traffic on Sundays is assessed also in terms of particles' number. The results obtained by the analysis of weekly PM10 concentration data are compared to information derived by the emission inventory for traffic. From observed seasonal reduction of Sundays' traffic flow, the corresponding expected variation in PM10 traffic emissions is calculated accounting for both exhaust and non-exhaust contribution. PM10 emission reductions are assessed in terms of probability by implementing the COPERT III methodology in a Monte Carlo simulation: on Sundays' PM10 primary emissions are on average about 50 % less than on weekdays'. Expected emission reductions are consistent with those observed for concentration: only a fourth of these latter are attributable to lowered primary traffic emissions, the remaining to limited resuspension of crustal material and reduced secondary formation in the urban atmosphere, both influenced by the reduced traffic flows. This latter finding confirms that control policies for air quality improvement still have to focus on the precursors of PM secondary components.
The role of traffic emissions from weekend and weekdays PM10 data in Milan
2004
9 Seiten, 2 Bilder, 2 Tabellen, 8 Quellen
Conference paper
English
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