Abstract
Nitrogen dioxide (NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) as one of the key pollutants in the atmosphere, is an important trace gas of traffic emissions or industrial activities. The coronavirus disease (COVID-19) epidemic preventions have significantly reduced the emissions of NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , which provided an opportunity to disentangling the contributions to global emissions in major epidemic regions. Here, we quantified the influences of lockdown measures on the NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> concentration at a global scale during the two waves of the COVID-19 epidemic, and disentangled the relative contributions of the major epidemic regions (i.e., China, Europe, and USA) on the global NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> densities due to the lockdown measures. Our results revealed that there was an evident decrease of global NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in 2020, especially in China, Europe, and USA. The global mean NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> densities decreased approximately 2.1 and 3.9 μmol/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in the first and second waves of the epidemic. While in the Northern Hemisphere, NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> densities decreased 6.6 μmol/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> on average during the first stage of the epidemic, and a slight increase (i.e., 1.7 μmol/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) in the second wave of the epidemic. The magnitudes and durations of the second wave were much smaller than the first wave of the coronavirus infections. The strict lockdown measures implemented in China significantly decreased the NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> concentration, which therefore the largest contributor in the first wave decreases of global average NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> densities. Intervention at an early stage would be beneficial to the preventions of epidemic situation. Our study could provide references for economic loss assessments and economic recovery strategies during the stages ofpost-pandemic.
Highlights
T HE pandemic of the novel coronavirus disease (COVID19) has dramatically influenced people’s daily lives and socioeconomic activities [1]–[3]
We investigated the temporal dynamics of the NO2 tropospheric vertical column density (TVCD) in these epidemic regions since the implementation of the lockdown measures
Remarkable dynamic changes can be observed from the spatial patterns of global NO2 dynamics around the first and the second waves of the COVID-19 epidemic periods
Summary
T HE pandemic of the novel coronavirus disease (COVID19) has dramatically influenced people’s daily lives and socioeconomic activities [1]–[3]. After a decreasing of detected cases of COVID-19 in June to August of 2020, a second wave of the disease exacerbated in winter across European and other regions of the world [4], [5]. The intervening measures, such as lockdown have been widely implemented to protect the human health, which has significantly slowed down the spread of the COVID-19 [6], [7], substantially influenced on air pollutants dynamics [8], [9]. The worldwide epidemic preventions can be viewed as a natural laboratory which gives us an opportunity to quantify the influences of the epidemic preventions on global NO2 changes, and to disentangle the relative contributions to the global NO2 dynamics
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