Abstract
The COVID-19 pandemic created an extreme natural experiment in which sudden changes in human behavior and economic activity resulted in significant declines in nitrogen oxide (NOx) emissions, immediately after strict lockdowns were imposed. Here we examined the impact of multiple waves and response phases of the pandemic on nitrogen dioxide (NO2) dynamics and the role of meteorology in shaping relative contributions from different emission sectors to NO2 pollution in post-pandemic New York City. Long term (> 3.5 years), high frequency measurements from a network of ground-based Pandora spectrometers were combined with TROPOMI satellite retrievals, meteorological data, mobility trends, and atmospheric transport model simulations to quantify changes in NO2 across the New York metropolitan area. The stringent lockdown measures after the first pandemic wave resulted in a decline in top-down NOx emissions by approx. 30 % on top of long-term trends, in agreement with sector-specific changes in NOx emissions. Ground-based measurements showed a sudden drop in total column NO2 in spring 2020, by up to 36 % in Manhattan and 19–29 % in Queens, New Jersey and Connecticut, and a clear weakening (by 16 %) of the typical weekly NO2 cycle. Extending our analysis to more than a year after the initial lockdown captured a gradual recovery in NO2 across the NY/NJ/CT tri-state area in summer and fall 2020, as social restrictions eased, followed by a second decline in NO2 coincident with the second wave of the pandemic and resurgence of lockdown measures in winter 2021. Meteorology was not found to have a strong NO2 biasing effect in New York City after the first pandemic wave. Winds, however, were favorable for low NO2 conditions in Manhattan during the second wave of the pandemic, resulting in larger column NO2 declines than expected based on changes in transportation emissions alone. Meteorology played a key role in shaping the relative contributions from different emission sectors to NO2 pollution in the city, with low-speed (< 5 ms−1) SW-SE winds enhancing contributions from the high-emitting power-generation sector in NJ and Queens and driving particularly high NO2 pollution episodes in Manhattan, even during – and despite – the stringent early lockdowns. These results have important implications for air quality management in New York City, and highlight the value of high resolution NO2 measurements in assessing the effects of rapid meteorological changes on air quality conditions and the effectiveness of sector-specific NOx emission control strategies.
Highlights
The global outbreak of the Coronavirus Disease 2019 (COVID-19) profoundly changed the world
The New Jersey Department of Environmental Protection (NJDEP) Photochemical Assessment Monitoring Station (PAMS) in New Brunswick, NJ, includes a Pandora sensor located on the roof of the Rutgers (NJDEP) research shelter, which is dedicated to atmospheric research, on a university research farm in a suburban neighborhood and approximately 20 km from the coast
As Metropolitan Transport Authority (MTA) bridge and tunnel traffic plummeted by up to 80 % in April 2020 (Fig. S2), total column NO2 (TCNO2) over a 50 × 50 km area around Manhattan dropped by 32 % in March–May 2020 compared to the same period in 2018– 2019 (Fig. 2a, d)
Summary
The global outbreak of the Coronavirus Disease 2019 (COVID-19) profoundly changed the world. The impact of multiple pandemic waves over longer time periods, and the role of meteorology and sector-specific emissions as key drivers of high NOx pollution episodes that occurred in major cities such as New York – even during, and despite, the most stringent early lockdown periods – remain largely unknown, driving this study. 12 000 km, McCarthy, 2021) remained in lockdown with strict social distancing measures, including school and non-essential business closures, limited transit services, and suspension of public events and gatherings, for more than 2 months, from mid-March through June 2020. Social distancing measures became strict again, including school closures, as the city experienced a surge in COVID-19 cases in late fall 2020 that reached a maximum in mid-January 2021 with more cases reported to NYC Department of Health and Mental Hygiene than during the first wave of the pandemic (Fig. S1). Goldberg et al (2020) reported a 20 % drop in TROPOMI NO2 within a 22 km radius of New York City between 13 March and 30 April 2020
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