New York University, Tandon School of Engineering, Department of Civil and Urban Engineering, 6 MetroTech Center, Brooklyn, NY, 11201, USA.
J Environ Manage. 2022 Jun 15;312:114902. doi: 10.1016/j.jenvman.2022.114902. Epub 2022 Mar 23.
We have quantified the emissions of Nitrogen dioxide (NO) in the Northeast megalopolis of the United States during the COVID-19 lockdown. The measurement of NO emission serves as the indicator for the emission of the group of nitrogen oxides (NO). Approximately 56% of NO emissions in the US are from mobile sources, and the remainder is from stationary sources. Since 2002, clean air regulations have resulted in approximately 5% compound annual reduction of NO emissions in the US (8.2% in the study area). Therefore, when studying the impact of sporadic events like an epidemic on emissions, it is necessary to account for the persistent reduction of emissions due to policy driven emission reduction measures. Using spaceborne sensors, ground monitors, National Emission Inventory data, and the US Motor Vehicle Emission Simulator, we quantified the reduction of total NO emissions, distinguishing stationary sources from on-road mobile sources (trucks and automobiles). When considering total NO emissions (stationary and mobile combined), we find that the pandemic restrictions resulted in 3.4% reduction of total NO emissions in the study area in 2020. This is compared to (and in addition to) the expected 8.2% policy driven reduction of NO emissions in 2020. This somewhat low reduction of emissions is because most stationary sources (factories, power plants, etc.) were operational during the pandemic. Truck traffic, a significant source of mobile emissions, also did not decline significantly (average 4.8% monthly truck traffic reduction in the study area between March and August 2020), as they were delivering goods during the lockdown. On the other hand, automobile traffic, responsible for 24% of total NO emissions, dropped significantly, 52% in April, returning to near normal after 5 months. While the reduction of automobile traffic was significant, especially in the early months of the pandemic, its effect on emissions was relatively insignificant.
我们量化了美国东北部大都市在 COVID-19 封锁期间二氧化氮（NO）的排放。NO 排放的测量是氮氧化物（NO）排放组的指标。美国约 56%的 NO 排放来自移动源，其余来自固定源。自 2002 年以来，清洁空气法规导致美国 NO 排放量每年减少约 5%（研究区域为 8.2%）。因此，在研究像流行病这样的偶发事件对排放的影响时，有必要考虑到政策驱动的减排措施导致的排放持续减少。使用星载传感器、地面监测器、国家排放清单数据和美国机动车排放模拟器，我们量化了总 NO 排放量的减少，区分了固定源和道路移动源（卡车和汽车）。当考虑总 NO 排放量（固定源和移动源之和）时，我们发现 2020 年疫情限制导致研究区域总 NO 排放量减少了 3.4%。这与 2020 年预期的 8.2%的政策驱动的 NO 减排量相比有所减少。这种排放量的减少幅度相对较低，是因为大多数固定源（工厂、发电厂等）在疫情期间仍在运营。卡车交通是移动排放的一个重要来源，其流量也没有显著下降（2020 年 3 月至 8 月期间研究区域每月卡车交通量平均减少 4.8%），因为它们在封锁期间仍在运送货物。另一方面，负责总 NO 排放量 24%的汽车交通量显著下降，4 月份下降了 52%，5 个月后恢复到接近正常水平。虽然汽车交通量的减少非常显著，尤其是在疫情早期，但对排放的影响相对较小。
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