Abstract New particle formation (NPF) events were studied in the urban background of Lecce (Italy) at the ECO Environmental-Climate Observatory, GAW/ACTRIS regional station. The objective of this study was to obtain long-term information on nucleation phenomenon in the Salentum peninsula, a coastal area of the central Mediterranean basin for which no extensive data exists. Particle number size distributions of the atmospheric aerosol were continuously collected by a Mobility Particle Size Spectrometer (MPSS) in the size range of 10–800 nm. For this investigation, data was analyzed for the period from January 2015 to July 2016 together with simultaneous measurements of gaseous pollutants (SO2, NO, NO2, and O3) and meteorological parameters. Throughout the observation period, nucleation events have been identified in approximately 21% of days. The classification of the events showed a seasonal trend with higher frequencies in warm seasons with a maximum in September (38%) while the highest non-event days fraction was observed in cold seasons, ∼90% in November and December. The fraction of undefined days peaked in August and September, 15 and 19% respectively. The analysis of reactive gas showed that NO, NO2, and O3 did not play an evident role in the formation process, as observed by the comparison between event and non-event monthly median concentrations. Nucleation phenomenon seemed instead to be very sensitive to SO2 that was present with higher (about 40%) monthly median concentrations during event days compared to non-event days. The condensation sink (CS), calculated for the complete observational period, showed similar values comparing event and non-event days. It is noteworthy that all the events occurred during the central hours of the day, high pressure, dry air (RH

中文翻译：

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意大利南部新粒子形成事件的研究

摘要 在莱切（意大利）的城市背景下，在 GAW/ACTRIS 区域站 ECO 环境气候观测站研究了新粒子形成 (NPF) 事件。本研究的目的是获得关于 Salentum 半岛成核现象的长期信息，Salentum 半岛是地中海中部盆地的一个沿海地区，没有大量数据存在。大气气溶胶的粒径分布由流动性粒径谱仪 (MPSS) 在 10-800 nm 的粒径范围内连续收集。在本次调查中，分析了 2015 年 1 月至 2016 年 7 月期间的数据，同时对气态污染物（SO2、NO、NO2 和 O3）和气象参数进行了测量。在整个观察期内，在大约 21% 的天数内确定了成核事件。事件的分类显示出季节性趋势，在暖季频率较高，9 月达到最大值（38%），而在冷季观察到的非事件天数比例最高，11 月和 12 月约为 90%。未定义天数的比例分别在 8 月和 9 月达到峰值，分别为 15% 和 19%。反应气体分析表明，NO、NO2和O3在形成过程中没有发挥明显的作用，通过比较事件和非事件的月中值浓度可以看出。相反，成核现象似乎对 SO2 非常敏感，与非事件日相比，事件日期间存在更高（约 40%）的月中值浓度。为整个观测期计算的冷凝汇 (CS) 显示了比较事件和非事件天数的相似值。