Measurement report: Atmospheric new particle formation at a peri-urban site in Lille, northern France

[摘要] Formation of ultrafine particles (UFPs) in the urban atmosphere is expectedto be less favored than in the rural atmosphere due to the high existingparticle surface area acting as a sink for newly formed particles. Despitelarge condensation sink (CS) values, previous comparative studies betweenrural and urban sites reported higher frequency of new particle formation(NPF) events over urban sites in comparison to background sites as well ashigher particle formation and growth rates attributed to the higherconcentration of condensable species. The present study aims at a betterunderstanding the environmental factors favoring, or disfavoring,atmospheric NPF over Lille, a large city in the north of France, and toanalyze their impact on particle number concentration using a 4-yearlong-term dataset. The results highlight a strong seasonal variation of NPF occurrences with amaximum frequency observed during spring (27 events) and summer (53 events). It was found that high temperature ( T >295  K), low relative humidity (RH  <45  %), and high solar radiation are ideal to observeNPF events over Lille. Relatively high CS values (i.e., ∼ 2 × 10 - 2  s −1 ) are reported during event days suggesting that high CS does not inhibit the occurrence of NPF over the ATmospheric Observations in LiLLE (ATOLL) station. Moreover, the particle growth rate was positively correlated with temperatures most probably due to higher emission of precursors. Finally, the nucleation strength factor (NSF) was calculated to highlight the impact of those NPF events on particle number concentrations. NSF reached a maximum of four in summer, evidencing a huge contribution of NPF events to particle number concentration at this time of the year.

[学科分类] 医学（综合）