The effect of Covid-19 lockdown on airborne particulate matter in Rome, Italy: A magnetic point of view

Abstract

Between 9 March and 18 May 2020, strict lockdown measures were adopted in Italy for containing the COVID-19 pandemic: in Rome, despite vehicular traffic on average was more than halved, it was not observed a evident decrease of the airborne particulate matter (PM) concentrations, as assessed by air quality data. In this study, daily PM 10 filters were collected from selected automated stations operated in Rome by the regional network of air quality monitoring: their magnetic properties – including magnetic susceptibility, hysteresis parameters and FORC (first order reversal curves) diagrams - were compared during and after the lockdown, for outlining the impact of the COVID-19 measures on airborne particulate matter. In urban traffic sites, the PM 10 concentrations did not significantly change after the end of the lockdown, when traffic promptly returned to its usual levels; conversely, the average magnetic susceptibility approximately doubled, and the linear correlation between volume magnetic susceptibility and PM 10 concentration became significant, pointing out the link between PM 10 concentrations and the increasing levels of traffic-related magnetic emissions. Magnetite-like minerals, attributed to non-exhaust brakes emissions, dominated the magnetic fraction of PM 10 near urban traffic sites, with natural magnetic components emerging in background sites and during exogenous dusts atmospheric events. Magnetic susceptibility constituted a fast and sensitive proxy of vehicular particulate emissions: the magnetic properties can play a relevant role in the source apportionment of PM 10 , especially when unsignificant variations in its concentration levels may mask important changes in the traffic-related magnetic fraction. As a further hint, increasing attention should be drawn to the reduction of brake wear emissions, that are overcoming by far fuel exhausts as the main pollutant in traffic contexts.

Biomagnetic Characterization of Air Pollution Particulates in Lahore, Pakistan

“…Our leaf and exhaust residue specimens lie within the PSD range on the Day plot (Table S18 in Supporting Information S1, Day et al, 1977), while the brake pad residue specimens lie between theoretical magnetite SP-SD and MD mixing lines (Dunlop, 2002). Previous biomagnetic studies on leaves (Sagnotti et al, 2009) and lichens and leaf specimens (Winkler et al, 2020(Winkler et al, , 2021 show that their specimens lie closer to brake dust specimens than exhaust specimens. The higher proportion of exhaust emissions shown in our leaf specimen data might be due to (a) the sampling site being located next to a road section where cars flow freely with minimal braking; (b) oxidation of metallic Fe derived from brake pad dust over time in our leaf specimens; (c) a different profile of vehicle use in Lahore, which has a higher proportion of small, light vehicles such as rickshaws, which may produce higher exhaust emissions relative to brake dust emissions.…”

“…On average, the leaf FORCs more closely resemble those of the exhaust-pipe than the brake-pad samples, although some leaves were observed with a more prominent high coercivity (HC) ridge and backfield remanent coercivity distributions that approach the high values of the brake-pad samples. However, FORCs of PM 10 filters in Rome and Milan, Italy (Winkler et al, 2020), and lichens in Rome, Italy (Winkler et al, 2021) suggested dominant contribution from non-exhaust (brake wear) sources. This observation is consistent with the Day plot data discussed above and the explanations are the same.…”

Impacts of the COVID-19 lockdown measures on coarse and fine atmospheric aerosol particles (PM) in the city of Rome (Italy): compositional data analysis approach

“…Gualtieri et al (2020) investigated the period 24/02/2020-30/04/2020, and they reported that in the city of Rome the levels of PM 10 showed a small decrease of about 12-13% in urban traffic and background stations, whereas PM 2.5 levels remained comparable to those measured in the same period of 2019. Winkler et al (2021) reported that, despite the lockdown (March-May 2020), PM 10 levels in the city of Rome remained similar to those measured in previous years and relating to the same period. In the city of Milan, Collivignarelli et al (2020) stated that, during the considered lockdown period (March-April 2020), the overall levels of PM 10 and PM 2.5 decreased substantially when compared to the levels of PM 10 and PM 2.5 recorded previously in 2 weeks of February 2020.…”

“…This site is in the south-east of the city of Rome and at about 9 km from its center. The Cipro site is in a residential neighbourhood, it is close to a road with a large parking lot nearby (Fusaro et al 2021;Matassoni et al 2011;Winkler et al 2021).…”

Biomonitoring of Exposure to Urban Pollutants and Oxidative Stress during the COVID-19 Lockdown in Rome Residents

“…The lockdown scenario was a unique condition, which rendered possible the direct measurement of the effects of reduced exposure to traffic pollution on the same group of subjects for a long period [ 11 ]. Therefore, this study is the first one that aims to investigate the reduction in exposure biomarkers related to traffic pollution in Rome, due to the restrictions imposed by the Government to contain the COVID-19 pandemic.…”