COVID-19 Changes Nitrogen Dioxide Pollution Levels in China

A decline of air pollution over northern China has coincided with its lockdown to prevent the spread of the coronavirus (COVID-19), says the European Space Agency. 

The agency has released a map showing the variation of nitrogen dioxide concentrations over China from December to March based on data obtained via the Copernicus Sentinel-5P satellite. 

As news of the coronavirus broke out in the Hubei province, China, in late December 2019, stricter measures were put in place. As a result, by late January, factories were closed and streets were cleared as Chinese authorities had ceased daily activities to stop the spread of the illness. This led to the dramatic reduction in nitrogen dioxide concentrations – those released by power plants, industrial facilities and vehicles – in all major Chinese cities between late-January and February. 

By combining satellite observations with computer models of the atmosphere, ESA studies indicated a reduction of around 20-30 percent in surface particulate matter over large parts of China.

This animation, using data from the Copernicus Sentinel-5P satellite, shows the nitrogen dioxide concentrations from 20 December 2019 until 16 March 2020 – using a 10-day moving average. The drop in concentrations in late-January is visible, coinciding with the nationwide quarantine, and from the beginning of March, the nitrogen dioxide levels have begun to increase as China eases restrictions and activity ramps up.

Josef Aschbacher, ESA’s Director of Earth Observation Programmes, says, “As nitrogen dioxide is primarily produced by traffic and factories, it is a first-level indicator of industrial activity worldwide. What is clearly visible is a significant reduction of nitrogen dioxide levels over China, caused by reduced activity due to COVID-19 restrictions, but also the Chinese New Year in January.”

The Copernicus Sentinel-5 Precursor mission, also known as Sentinel-5P, is dedicated to monitoring air pollution by measuring a multitude of trace gases as well as aerosols.