Direct Evaluation of primary pollutant trends and dynamics during the COVID 19 Imposed Quarantine on the NYC Metropolitan Area

Abstract:

Based on human mortality levels due to COVID19, the New York City Metropolitan area was by far the most lethal epicenter in the United States. At the height of the COVID19 trend in early April, more than 10,000 cases were being reported daily and mortality rates > 800 were peaking in those periods with the majority occurring in the NYC area. Due to such dangerous numbers and unknown transmission potential, NYC and the State imposed a dramatic lockdown of all nonessential businesses and travel on March 22 (just 8 days after the first confirmed death) although unofficial reduction of travel and other economic impacts were felt much earlier. While the lions share of attention into COVID19 research was on exploring potential environmental factors, a significant side effect of the strong quarantine was the expected dramatic reduction in urban air quality with particular sensitivity to NOx emissions and potential primary / secondary Fine Particulate Matter (PM25).

In this presentation, we first note that surface Urban NO2 concentrations in the critical March 15-March 31 period dropped dramatically from 2019-2020 but that the level of reduction was strongly time dependent with the largest decreases being observed during morning rush hour. The same trends were observed for CO and to a lesser extent on PM25. However, the differences during April, May were less significant well before the Phase 1 reopening. To better understand this picture, the monthly mean averaged spatial imagery of the TROPOMI NO2 was calculated and while the large decreases were seen in the primary March period, the pollution levels in the heavily urban center recovered more quickly in comparison to 2019 than the suburban regions which can indicate mass population exodus as well as being due to the late afternoon observation times for TROPOMI. To help better understand some of these observations, supplemental meteorological measurements will be discussed as well as the pollution effects on downwind O3.