Reducing Air Pollution in the Lombardy Region: Sources for Fine
Particles and Ozone
Bo R. Larsen
European Commission – Joint Research Centre (JRC)
Milano, 5 novembre 2012
The air pollution in the Lombardy region with regard to particulate matter and ozone is amongst the highest in Europe. What are the sources?
From 2007 to 2009 JRC studied ambient particulate matter (PM) and ozone precursors at ten sites distributed over the Lombardy region spanning from urban to rural background pollution (Milan, Brescia, Bergamo, Saronno,
Mantova, Cantu’, Sondrio, Lodi and Pavia). A data-base was built up consisting of more than 60000 records of chemical compounds in ambient air and their associated uncertainty. The chemical composition of the ambient air samples were compared with chemical fingerprints of known pollution sources (e.g. traffic exhaust, residential heating, road dust, industry, and energy production). Sophisticated mathematical models were used to disentangle the mixture of chemical fingerprints in the ambient samples from the ten sites and special de-convolution processes, known as source apportionment, afforded the recognition of individual fingerprints from the pollution sources in the region and the estimation of the contribution from each source by chemical mass balance. A detailed overview will be given of the used methods and the obtained results:
 Road transport - via its primary and secondary emissions - is responsible for 50% of the air pollution in the Lombardy region with respect to particulate matter and ozone. The abatement of transport emissions by renewing the vehicle park (Euro 5 for light duty vehicles, Euro 6 for heavy duty vehicles) is essential, but may not be sufficient to reduce the particulate matter pollution below the limits for PM
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and PM
2.5
. With the exhaust after-treatment technology available today a reduction in particulate emissions involves a tradeoff for increased NOx emissions, which eventually imply soaring concentrations in the atmosphere of secondary particles.
Furthermore, renewing the vehicle park does not intervene on two significant features of road transport emissions, namely brake/tire wear and traffic related re-suspension of road dust. To meet air quality limits it is envisaged that a reduction of the vehicle park
(number of vehicles and/or the number of driven kilometres) is needed.
 Enforcement of the already existing ban in the Po valley on inefficient wood burning for residential heating may reduce the annual mean concentrations of particulate matter in the order of 10%. However, the implementation of a ban on biomass/wood burning in the
Valtelline valley would have a higher effect than in the Po valley and would also be a significant step in abating benzo(a)pyrene, which frequently exceeds the air quality limit of 1 ng/m 3 (per year).

 NOx emitted by industry, energy production, and natural gas combustion and road transport together with ammonia from agricultural emissions are the main sources for a high secondary PM pollution in Lombardy (33-47 % of the PM
10
mass during winter 2007 and 41-57 % of the PM
2.5
mass during winter 2009). This strong secondary component together with the meteorological coupling of the pollution throughout the entire Po Plain imply that only little can be gained from local and short term mitigation measures such as ad
hoc traffic-bans during pollution peaks or traffic restrictions in confined city-zones. Coordinated large-scale and long-term abatement strategies are called for that inevitably intervene on road transport and gaseous emissions of NOx from industry, energy production, and natural gas combustion.
A strong collaboration with other scientists in JRC, ARPA and universities of
Milan has been a key element for the successful outcome of the described project and is gratefully acknowledged.
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