Global fine-scale changes in ambient NO2 during COVID-19 lockdowns

Abstract

Nitrogen dioxide (NO2) is an important contributor to air pollution and can adversely affect human health1–9. A decrease in NO2 concentrations has been reported as a result of lockdown measures to reduce the spread of COVID-1910–20. Questions remain, however, regarding the relationship of satellite-derived atmospheric column NO2 data with health-relevant ambient ground-level concentrations, and the representativeness of limited ground-based monitoring data for global assessment. Here we derive spatially resolved, global ground-level NO2 concentrations from NO2 column densities observed by the TROPOMI satellite instrument at sufficiently fine resolution (approximately one kilometre) to allow assessment of individual cities during COVID-19 lockdowns in 2020 compared to 2019. We apply these estimates to quantify NO2 changes in more than 200 cities, including 65 cities without available ground monitoring, largely in lower-income regions. Mean country-level population-weighted NO2 concentrations are 29% ± 3% lower in countries with strict lockdown conditions than in those without. Relative to long-term trends, NO2 decreases during COVID-19 lockdowns exceed recent Ozone Monitoring Instrument (OMI)-derived year-to-year decreases from emission controls, comparable to 15 ± 4 years of reductions globally. Our case studies indicate that the sensitivity of NO2 to lockdowns varies by country and emissions sector, demonstrating the critical need for spatially resolved observational information provided by these satellite-derived surface concentration estimates.

Ground-Level NO2 Surveillance from Space Across China for High Resolution Using Interpretable Spatiotemporally Weighted Artificial Intelligence

“… 53 , 54 Previous studies based on ground-based measurements and satellite estimates have also reported this phenomenon. 51 , 55 The lockdown had a strong and sustained impact on surface NO 2 concentrations (relative changes > 30%) until the 48th day after the Lunar New Year (P3). After P3, the impact gradually decreased in most areas (P4) due to increasing anthropogenic emissions as the epidemic was gradually controlled and cities lifted bans.…”

Inferring and evaluating satellite-based constraints on NOx emissions estimates in air quality simulations

“…(Jaegle et al, 2018;Salmon et al, 2018). In India, bottom-up emissions inventories report sustained growth of NOx emissions (Kurokawa and Ohara, 2020;McDuffie et al, 2020) and NO2 levels observed by OMI have been increasing since 2005 (Goldberg et al, 2021;Cooper et al, 2022). The decrease in anthropogenic NOx emissions inferred by TROPOMI observations contrasts with these trends in bottom-up estimates and OMI observations.…”

Diesel passenger vehicle shares influenced COVID-19 changes in urban nitrogen dioxide pollution

“…While non-uniform changes in NO 2 within cities are interesting and have been the subject of other studies (e.g. [48]), the primary goal of our study is to reconcile differences among cities' ∆NO 2 in light of their different diesel shares.…”