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 PM₁₀ 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 PM₁₀ concentrations did not significantly change after the end of the lockdown, when vehicular traffic promptly returned to its usual levels; conversely, the average volume and mass magnetic susceptibilities approximately doubled, and the linear correlation between volume magnetic susceptibility and PM₁₀ concentration became significant, pointing out the link between PM₁₀ concentrations and the increasing levels of traffic-related magnetic emissions.

Magnetite-like minerals, attributed to non-exhaust brakes emissions, dominated the magnetic fraction of PM₁₀ 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 PM₁₀, 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 particulate pollutant in traffic contexts.

2020 年 3 月 9 日至 5 月 18 日期间，意大利采取了严格的封锁措施以遏制 COVID-19 大流行：在罗马，尽管车辆交通平均减少了一半以上，但并未观察到空气中颗粒物（PM ) 浓度，根据空气质量数据评估。

在这项研究中，每日 PM ₁₀过滤器是从区域空气质量监测网络在罗马运营的选定自动化站收集的：它们的磁性 - 包括磁化率、磁滞参数和 FORC（一阶反转曲线）图 - 在期间和期间进行了比较封锁后，概述 COVID-19 措施对空气中颗粒物的影响。

在城市交通站点，PM ₁₀浓度在锁定结束后没有明显变化，此时车辆交通迅速恢复到正常水平；相反，平均体积磁化率和质量磁化率大约翻了一番，体积磁化率与 PM ₁₀浓度之间的线性相关性变得显着，指出 PM ₁₀浓度与交通相关磁排放水平增加之间的联系。

归因于非排气制动排放的类磁铁矿矿物在城市交通站点附近的 PM ₁₀的磁性部分中占主导地位，天然磁性成分出现在背景站点和外源尘埃大气事件中。

磁化率构成了车辆颗粒物排放的快速而灵敏的代表：磁性可以在 PM ₁₀的源解析中发挥相关作用，尤其是当其浓度水平的不显着变化可能掩盖与交通相关的磁性分数的重要变化时。

作为进一步的暗示，应该越来越多地关注减少制动器磨损排放，到目前为止，燃料排放作为交通环境中的主要颗粒污染物正在被克服。