Ultrafine particles in the urban environment

Ultrafine particles (UFP) are the smallest constituents of atmospheric particulate matter (PM). Until now, their potential adverse effects on human health are of great concern because of their specific properties and acting mechanisms. The work in this thesis focuses on the measurement of UFP and their effect and contribution to air quality in Leicester, UK and a set of cities in North West (NW) Europe. The thesis explores novel work around new particle formation (NPF) events and their association with Lung Deposited Surface Area (LDSA) in an urban environment. A final focus of this thesis was the identification sources are contribute to the PM10 across NW Europe region. Particle number size distribution were measured at two urban background locations (automatic urban and rural network (AURN), and Brookfield (BF)) in Leicester in order to quantify NPF events. Quantification of primary and secondary sources of UFP was undertaken using black carbon as a tracer for the primary UFP in urban areas. At the AURN site, which is influenced by fresh vehicle exhaust emissions, total number concentrations (TNC) was segregated into two components, TNC = N1 + N2. The component N1 represents components directly emitted as particles and compounds which nucleate immediately after emission. The component N2 represents the particles formed during the dilution and cooling of vehicle exhaust emissions and by in situ NPF. Furthermore, the composition of the PM10 was studied at five sites across NW Europe. The samples collected at four urban background, and one industrial sites were analysed for elements, water soluble ions, organic matter, and monosaccharides, and the principal component analysis (PCA) was applied to the data set. Overall, during the measurement period, the frequency of NPF events was 13.3%, and 22.2% at AURN and BF sites, respectively. The percentage of N2 (57%) was greater than the percentage of N1 (43%) for all days at the AURN site. The PCA yielded 5 factors which apportioned the main pollution sources to PM10 concentrations across NW Europe: (1) traffic emissions, (2) secondary inorganic aerosols, (3) organic matter, (4) industrial and sea salt, (5) biomass burning.