The current study examines the impact of the COVID-19 lockdown (25th March until May 17, 2020) period in particulate matter (PM) concentrations and air pollutants (NO_x, SO₂, CO, NH₃, and O₃) at 63 stations located at Delhi, Uttar Pradesh and Haryana states within the Delhi-NCR, India. Large average reductions are recorded between the stations in each state such as PM₁₀ (−46 to −58%), PM_2.5 (−49 to −55%), NO₂ (−27 to −58%), NO (−54% to −59%), CO (−4 to −44%), NH₃ (−2 to −38%), while a slight increase is observed for O₃ (+4 to +6%) during the lockdown period compared to same periods in previous years. Furthermore, PM and air pollutants are significantly reduced during lockdown compared to the respective period in previous years, while a significant increase in pollution levels is observed after the re-opening of economy. The meteorological changes were rather marginal between the examined periods in order to justify such large reductions in pollution levels, which are mostly attributed to traffic-related pollutants (NO_x, CO and road-dust PM). The WRF-CHIMERE model simulations reveal a remarkable reduction in PM_2.5, NO₂ and SO₂ levels over whole Indian subcontinent and mostly over urban areas, due to limitation in emissions from the traffic and industrial sectors. A PM_2.5 reduction of −48% was simulated in Delhi in great consistency with measurements, rendering the model as a powerful tool for simulations of lower pollution levels during lockdown period.

_{当前的研究检查了 COVID-19 锁定期（2020 年 3 月 25 日至 2020 年 5 月 17 日）对颗粒物 (PM) 浓度和空气污染物（NO x}、SO ₂、CO、NH ₃和 O ₃）在 63 时的影响位于印度德里-NCR 内的德里、北方邦和哈里亚纳邦的车站。每个州的站点之间记录了较大的平均减少量，例如 PM ₁₀（-46 至 -58%）、PM _2.5（-49 至 -55%）、NO ₂（-27 至 -58%）、NO（-54 % 至 -59%）、CO（-4 至 -44%）、NH ₃（-2​​ 至 -38%），而观察到 O _{3略有增加}（+4 至 +6%）在锁定期间与往年同期相比。此外，与往年同期相比，锁定期间的 PM 和空气污染物显着减少，而在经济重新开放后观察到污染水平显着增加。为了证明污染水平如此大幅降低是合理的，这些检查期间的气象变化相当小，这主要归因于与交通相关的污染物（NO _x、CO 和道路灰尘 PM）。_{WRF-CHIMERE 模型模拟显示 PM 2.5}、NO ₂和 SO ₂显着减少由于交通和工业部门的排放限制，整个印度次大陆和大部分城市地区的水平。在德里模拟的PM _2.5减少了 −48%，与测量结果非常一致，使该模型成为模拟锁定期间较低污染水平的强大工具。