Localized pollutant emission increases in China due to COVID-19 lockdowns

Abstract

Previous studies reported significant decreases in pollutant emissions across industrialized countries during COVID-19 lockdowns in the spring of 2020. However, high-resolution inverse modeling of satellite observations of nitrogen dioxide (NO₂) by the TROPOMI instrument reveals significant increases in nitrogen oxide (NO_x = NO + NO₂) emissions in some locations despite widespread reductions in economic activity and mobility due to COVID-19 control measures. The NO_x emission increases are associated with supply routes to locked-down cities and urban-to-suburban emission shifts. For example, the total NO_x emissions over the Jiang-Han Plain region, where the supply routes to Wuhan were located, increased by 25% during the lockdown. After the lockdown measures were lifted, NO_x emissions showed uneven recoveries of economic activities. Significant increases in NO_x emissions were observed in the northern part of Jiangsu Province, which has a notable concentration of small-scale or home-based factories, indicating a more rapid resurgence of small enterprises. This research highlights the potential of satellite-based pollutant observations as a valuable tool for assessing socioeconomic activities during pivotal events, such as a pandemic lockdown.