Emerging Investigator Series: COVID-19 lockdown effects on aerosol particle size distributions in northern Italy
Jiali Shen, Alessandro Bigi, Angela Marinoni, Janne Lampilahti, Jenni Kontkanen, Giancarlo Ciarelli, Jean Philippe Putaud, Tuomo Nieminen, Markku Kulmala, Katrianne Lehtipalo, Federico Bianchi
Abstract
) showed no significant changes. The impact of lockdown measures on particle number size distributions were also quite limited. During the lockdown period, the number concentrations of 10-25 and 25-50 nm primary particles were reduced by 66% and 34%, respectively, at the regional background site (Ispra) but surprisingly there was no difference during and after lockdown at the urban background site (Modena). Conversely, the NPF frequency was exceptionally high, 70%, in Modena during the lockdown as compared to values (22-26%) observed for the same period in 2006 and 2009, while NPF frequency in Ispra only slightly increased compared to the same period in 2016-2019. The particle growth rates, however, were slightly lower during the lockdown at both sites compared to other periods. The study shows that a drastic decrease in traffic had little influence on particulate pollution levels in the Po Valley, suggesting that other sources and processes also have a prominent impact on particle number and particulate matter mass concentration in this region.