Case Study of Particle Number Fluxes and Size Distributions during Nucleation Events in Southeastern Italy in the Summer

Atmosphere

Marianna Conte³  Antonio Donateo³  Adelaide Dinoi³  Franco Belosi¹  Daniele Contini³  Robert W. Talbot² 

[1] Istituto di Scienze dell’Atmosfera e del Clima, ISAC-CNR, 40129 Bologna, Italy; E-Mail:Istituto di Scienze dell’Atmosfera e del Clima, ISAC-CNR, 73100 Lecce, Italy;;Istituto di Scienze dell’Atmosfera e del Clima, ISAC-CNR, 73100 Lecce, Italy; E-Mails:

关键词: SMPS;    particle flux;    nucleation events;    CO₂/H₂O fluxes;    particle size distributions;   

DOI  :  10.3390/atmos6070942

来源: mdpi

【 摘 要 】

Concentrations, size distributions and particle number vertical turbulent fluxes were measured by the eddy-covariance method at an urban background site in southeastern Italy during the summer. CO₂/H₂O concentrations and fluxes were also determined together with meteorological parameters. Time series show that particles could be divided into two size classes with negatively-correlated temporal trends in diurnal hours: nanoparticles (diameter D_p < 50 nm) and larger particles (D_p > 50 nm). Larger particles include part of the Aitken mode and the accumulation mode. Nanoparticles peaked in diurnal hours due to the presence of several days with nucleation events when particles D_p > 50 nm were at minimum concentrations. Nucleation increased diurnal total particle concentration by a factor of 2.5, reducing mean and median diameters from D_mean = 62.3 ± 1.2 nm and D_median = 29.1 ± 1.3 nm on non-event days to D_mean = 35.4 ± 0.6 nm and D_median = 15.5 ± 0.3 nm on event days. During nucleation events, particle deposition increased markedly (i.e., downward fluxes), but no significant changes in CO₂ concentrations and fluxes were observed. This is compatible with new particle formation above the measurement height and a consequent net transport towards the surface. Correlation with meteorology shows that the formation of new particles is correlated with solar radiation and favored at high wind velocity.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.