The COVID-19 pandemic, as a worldwide threat to public health, has led many governments to impose mobility restrictions and adopt partial or full lockdown strategies in many regions to control the disease outbreak. Although these lockdowns are imposed to save public health by reducing the transmission of the virus, rather significant improvements of the air quality in this period have been reported in different areas, mainly as a result of the reduction in vehicular trips. In this research, the city of Turin in the northern part of Italy has been considered as the study area, because of its special meteorology and geographic location in one of the most polluted regions in Europe, and also its high density of vehicular emissions. A Lagrangian approach is applied to illustrate and analyze the effect of imposing full lockdown restrictions on the reduction of traffic-induced air pollution in the city. To do this, the real-time traffic flow during the lockdown period is recorded, and by utilizing CALPUFF version 7, the dispersion of PM_2.5, Total Suspended Particulate (TSP), Benzo(a)pyrene (BaP), NO_x, and Black Carbon (BC) emitted from all circulating vehicles during and before the lockdown period are compared. Results indicate that the concentration of pollutants generated by road traffic sources (including passenger cars, busses, heavy-duty vehicles, light-duty vehicles, mopeds, and motorcycles) reduced at least 70% (for PM_2.5) up to 88.1% (for BaP) during the studied period. Concentration maps show that the concentration reduction varied in different areas of the town, mainly due to the characteristics and strength of the emission sources and the geophysical features of the area.

COVID-19 大流行作为全球公共卫生威胁，已导致许多政府实施行动限制，并在许多地区采取部分或全部封锁策略来控制疾病爆发。尽管实施这些封锁是为了通过减少病毒传播来保护公众健康，但据报道，不同地区的空气质量在此期间有了显着改善，这主要是由于车辆出行减少。在本次研究中，意大利北部的都灵市被认为是研究区，因为它在欧洲污染最严重的地区之一的特殊气象和地理位置，以及高密度的车辆排放。应用拉格朗日方法来说明和分析实施全面封锁限制对减少城市交通引起的空气污染的影响。为此，记录锁定期间的实时交通流量，并利用 CALPUFF 版本 7，PM 的分散_2.5比较封城期间和封城前所有流通车辆排放的总悬浮颗粒物（TSP）、苯并（a）芘（BaP）、氮氧化物_{和黑碳（BC）。}结果表明，道路交通源（包括客车、公共汽车、重型汽车、轻型汽车、轻便摩托车和摩托车）产生的污染物浓度至少降低了 70%（对于 PM _2.5）高达 88.1%（对于BaP) 在研究期间。浓度图显示，全镇不同区域的浓度降幅存在差异，这主要与排放源的特点和强度以及该区域的地球物理特征有关。