In this study, 24-h average concentration of major pollutants, including PM2.5, PM10, NO₂, SO₂, O₃ and CO in the period 1 January to 30 July 2016 to 2020 were investigated to show how partial lockdown affects the behavior of pollutants' concentrations in an urban region. For this purpose, three sites of Aghdasieh, Setad-e Bohran and Shahr-e-Rey, which are located in various parts of Tehran considered. Results showed that PM10 had maximum reduction especially for Aghdasieh and Setad-e Bohran stations (20–30%) compared to the 5-year monthly average. Furthermore, the highest reduction in the Shahr-e-Rey station was related to NO₂ (−17.99%). The trend of AQI decreased considerably in 2020 compared to its pre-lockdown values. The relative reduction of AQI in March compared to February was about −12.8%, −27.6%, and −2.27% for Shahr-e-Rey, Aghdasieh, and Setad-e Bohran, respectively. The concentration of pollutants was expected to fall after the lockdown, but it was noted that compared to their average during the 5-year period, the concentrations of all pollutants especially O₃ increased to some extent. A major reason for this trend is the removal of the traffic control plan and the increasing use of private vehicles in an effort to implement social distancing.

在这项研究中，调查了 2016 年 1 月 1 日至 7 月 30 日至 2020 年期间主要污染物的 24 小时平均浓度，包括 PM2.5、PM10、NO ₂、SO ₂、O ₃和 CO城市地区污染物浓度的行为。为此，考虑了位于德黑兰不同地区的 Aghdasieh、Setad-e Bohran 和 Shahr-e-Rey 三个地点。结果表明，与 5 年月平均值相比，PM10 的减少量最大，尤其是 Aghdasieh 和 Setad-e Bohran 站 (20–30%)。此外，Shahr-e-Rey 站的最高减排量与 NO _2有关(−17.99%)。与锁定前的值相比，2020 年 AQI 的趋势显着下降。与 2 月相比，Shahr-e-Rey、Aghdasieh 和 Setad-e Bohran 3 月的 AQI 相对下降分别约为 -12.8%、-27.6% 和 -2.27%。污染物浓度预计在封锁后会下降，但值得注意的是，与 5 年期间的平均值相比，所有污染物的浓度，特别是 O ₃的浓度都有一定程度的增加。造成这种趋势的一个主要原因是交通管制计划的取消和私家车的使用越来越多，以努力实现社会距离。