Costagliola, Maria Antonietta (2010) Evaluation of organic micropollutants and fine particles in vehicle exhausts and in ambient air. [Tesi di dottorato] (Unpublished)

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The incredible increasing of the number of vehicles circulating in the Italian cities, occurred in the last fifteen years, is the main reason for still considering the traffic as the most important source of gaseous and particle pollutants in the urban atmosphere. The large volume of on road vehicles balances and deletes the positive effects in terms of exhaust emissions coming from the recent technological improvements regarding the engine combustion efficiency, the fuel quality and the after-treatment device performances. The urban air quality, in fact, is still greatly influenced by the elevated traffic volume, whose negative effects on the air pollution are made worse by the type of driving pattern enforced to the vehicle in a congested traffic situation. The most critical pollutant are represented by particulate matter and organic compounds, generally indicated as organic volatile compounds, which include carcinogenic species. Due to very dangerous effects of such pollutants for human health and environment, it is very important both to characterise the pollution source in terms of quantity and quality of emissions at the exhaust of the several in-use vehicle technologies and to establish the real contribution of road traffic to ambient air pollutant concentrations. This experimental work is aimed to carry out a comprehensive characterisation of volatile organic compounds and fine particles (in terms of mass, number and PAHs content) at the vehicle exhaust and in the ambient air, and to find a correlation between the exhaust pollution source and the air pollution in several traffic urban sites in Napoli. The methodology applied to realize this research plan involved two parallel experimental programmes: one aimed to measure exhaust emissions and the other to evaluate ambient air concentrations. Vehicle exhaust emission factors were evaluated by executing experimental tests on chassis dynamometer on a fleet including 20 in use vehicles, each characterised by a different engine technology and type approval stage. For the air quality monitoring, in situ sampling were realised in several sites of Napoli city: urban and sub-urban sites and road tunnels. Particulate and PAHs analyses were carried out both in vehicle exhaust and in ambient air, whereas BTEXs measurements were realized only in ambient air. One of the most relevant result was that, taking into account the traffic composition in the urban area of Napoli, the PTWs cover a not negligible role in the particulate urban air pollution. The road tunnels present the highest concentrations of BTEX and particulate, followed by the urban traffic sampling sites and the sub-urban ones. Due to many needed assumptions, a weak quantitative correlation was found between the air concentrations and exhaust emission rates produced by the real monitored traffic. More reliable correlations come from a qualitative analysis of pollutants measured in air and at the exhaust. A very good correlation was observed between the PAH ratios and BTEX ratios evaluated in both ambient air and exhaust emissions.

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