It is expected by now that COVID-19 and the lockdowns have drastically decreased pollution levels in countries imposing them. The relationship between human activities and decreased primary pollution has been established.
However, a notable study by Huang et. al (2021) seemed to have differing views. The study raised questions and challenged this relationship after noting that despite generally decreasing levels of primary pollution, there were still several periods of heavy haze pollution in the Eastern part of China.
It was then revealed that the haze was caused by secondary sources of pollution.
Notably, a relationship was derived that due to the large decrease in nitrogen oxides from reduced transportation emissions, the ozone and nighttime nitrogen oxide radically formed. To simply the science, this increase in atmospheric oxidising capacity actually facilitated the formation of secondary particulate matter, contributing to further air pollution.
Essentially, the secondary particulate formation offsets the reduction in primary pollution caused from reduced human activity. This would completely negate the initial sentiments the the lockdown was a blessing in disguise.
In China, haze and ozone pollution are two of the main air quality challenges that the country faces. It affects dozens of millions of lives and their health and livelihood.
Indeed, while it seems that COVID-19 was a step towards cleaner air; it could in fact turn out to be a double whammy.