Spatial variability of fine particle number concentration in an urban area

A real-time condensation particle counter (CPC) was used for measuring number concentration of fine particles (FPs) from 20 to 1000 nm in the urban area of Naples, Italy. The monitoring campaign lasted from 4th April to 25th May 2018. Different sites (15 receptors) were selected as monitoring points and about 100 field data were collected. A large spatial variability inside the urban area was observed. Depending on site characteristics, the receptor points are classified into six different categories. The spatial variability is studied in dependence on the category of the receptor points: measures at inlet/exit of tunnels show the highest PN concentration while the lowest was observed at the background site. A clear dependence of FPs number concentration on the aspect ratio 0 <= H/W <= 5.5 is observed at road side receptors. Finally, using FPs number concentration data, PM2.5 mass concentrations were estimated in correspondence of all receptor points and effect of the background concentration was analysed.