Characterization of ultrafine particles and the occurrence of new particle formation events in an urban and coastal site of the Mediterranean area

Abstract. In this work, new particle formation events (NPFs) occurring at two locations in southern Italy, the urban background site of Lecce (ECO station) and coastal Lamezia Terme (LMT station), are identified analyzed. The study aims to compare properties NPF sites, located 225 km away from each other characterized by marked differences terms emission sources local weather dynamics. Continuous measurements number size distributions, range 10 800 m, were performed both sites a mobility spectrometer (MPSS). occurrence events, observed throughout period that lasted 5 years, produced different results frequency occurrence: 25 % days ECO 9 LMT. showed seasonal patterns: higher during spring summer autumn–winter site. Some these happened simultaneously indicating nucleation process on large spatial scale. Cluster analysis 72 h back trajectories stations influenced similar air masses, most which originated north-western direction. Local meteorological conditions high pressure, with prevalence clear skies, low levels relative humidity (RH < 52 %), moderate winds (3–4 m s−1) dominated sites. Notable SO2 PM2.5 concentrations H2SO4 proxy levels, resulting ∼65 %, ∼80 50 lower LMT compared ECO, respectively. It is likely level recognized as one main gas precursors involved could be responsible for smaller (∼60 less than ECO)