15 COVID-19 Pandemic: An Unprecedented Blessing for Nature
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and anthropogenic sources (fossil fuel combustion and biomass burning) [26]. When
present in high concentration, NO x acts as a notorious air pollutant involved in the
production and depletion of tropospheric and stratospheric ozone, and formation of
photochemical smog such as PAN. NO 2 is biochemically highly reactive and more
toxic than NO, and can be very harmful to human and plant health. The estimated
global emission of NO x by anthropogenic activities is approximately 53 million tons
per year [6]. It is known to affect the plant growth and photosynthesis process and to
cause respiratory ailments such as bronchial hyper responsiveness, cellular inflammation and respiratory problems in humans. As per various studies [27–30], the strict
quarantine measures showed a positive impact on the air quality status at least from
the perspective of reduced emission of oxides of nitrogen. The NASA and ESA data
on reduced NO 2 emission up to 20–30% is one of the first reports on the improved
air quality in Wuhan, China, Spain, France, Italy and USA. The two space agencies using satellites AURA and Sentinel-5P, respectively, collected and compared
the data for NO 2 emission in 2019 and 2020. A large number of studies from China
included reporting of reduced levels of different forms of nitrogen from places such
as Shanghai (NO x 75%) [31], 366 urban areas of mainland China (NO 2 54%) [25],
Yangtze River Delta (YRD) region (NO x 29–47%) [32], 44 cities of northern China,
Hubei province (NO 2 25%) [8] and Wuhan (NO 2 56%) [33]. Lian et al. [21] also
found similar NO 2 decreased percentage (53%) at Wuhan, and suggested the reduced
NO 2 concentration to be highly correlated with the reduction in traffic pollution at
Wuhan during the lockdown period. Studies by [20, 22, 23, 34, 35] have reported
the decreased NO 2 concentration ranging 13–84% in the different cities of India
such as Agra, Ahmedabad, Amritsar, Amravati, Ankleshwar, Bengaluru, Bhopal,
Bhuj, Brijrajnagar, Chennai, Delhi, Dewas, Faridabad, Gandhinagar, Gaya, Hyderabad, Jamnagar, Jaipur, Jodhpur, Jorapokhar, Kanpur, Kolkata, Lucknow, Mumbai,
Nagpur, Palanpur, Patna, Pune, Rajkot, Singrauli, Surat, Vadodra, Varanasi and Thiruvananthapuram. ESA also confirmed a drop in NO 2 levels by around 40–50% in cities
of India owing to its nationwide quarantine (Fig. 15.2). The agency also reported a
decrease in the NO 2 level in the maritime route across the Indian Ocean due to less
maritime traffic [36] (Fig. 15.2). Kanniah et al. [37] used the Aura satellite sensor
to monitor NO 2 fluctuation, and reported a decreased NO 2 concentration over other
South-Asian cities such as Manila (34%), Kuala Lumpur (27%), Singapore (30%),
Bangkok (22%), Jakarta (34%) and Phnom Penh (6%). However, the study found an
increased NO 2 concentration by 1% and 3% in Ho Chi Minh City (Vietnam), and
Yangon (Myanmar), respectively. This increased NO 2 levels were attributed to the
high biomass-burning activity over the South-east Asian region along with several
other influential factors such as meteorology [37]. A recent data released by ESA
suggested that continuous lockdown measures in Europe have further lowered the
levels of NO 2 by 45–50% in Barcelona, Madrid, Milan, Paris and Rome (Fig. 15.2).
Studies by [38, 39] concurred with the ESA observation for Milan, Madrid and
Barcelona as the NO 2 concentration ranged between 48 and 62%. Reduction in the
NO 2 levels by 35, 51, 54 and 96% was also reported for Kazakhstan [10], New York
(USA) [40], Sau Paulo (Brazil) [41] and Morocco [42], respectively.
355
and anthropogenic sources (fossil fuel combustion and biomass burning) [26]. When
present in high concentration, NO x acts as a notorious air pollutant involved in the
production and depletion of tropospheric and stratospheric ozone, and formation of
photochemical smog such as PAN. NO 2 is biochemically highly reactive and more
toxic than NO, and can be very harmful to human and plant health. The estimated
global emission of NO x by anthropogenic activities is approximately 53 million tons
per year [6]. It is known to affect the plant growth and photosynthesis process and to
cause respiratory ailments such as bronchial hyper responsiveness, cellular inflammation and respiratory problems in humans. As per various studies [27–30], the strict
quarantine measures showed a positive impact on the air quality status at least from
the perspective of reduced emission of oxides of nitrogen. The NASA and ESA data
on reduced NO 2 emission up to 20–30% is one of the first reports on the improved
air quality in Wuhan, China, Spain, France, Italy and USA. The two space agencies using satellites AURA and Sentinel-5P, respectively, collected and compared
the data for NO 2 emission in 2019 and 2020. A large number of studies from China
included reporting of reduced levels of different forms of nitrogen from places such
as Shanghai (NO x 75%) [31], 366 urban areas of mainland China (NO 2 54%) [25],
Yangtze River Delta (YRD) region (NO x 29–47%) [32], 44 cities of northern China,
Hubei province (NO 2 25%) [8] and Wuhan (NO 2 56%) [33]. Lian et al. [21] also
found similar NO 2 decreased percentage (53%) at Wuhan, and suggested the reduced
NO 2 concentration to be highly correlated with the reduction in traffic pollution at
Wuhan during the lockdown period. Studies by [20, 22, 23, 34, 35] have reported
the decreased NO 2 concentration ranging 13–84% in the different cities of India
such as Agra, Ahmedabad, Amritsar, Amravati, Ankleshwar, Bengaluru, Bhopal,
Bhuj, Brijrajnagar, Chennai, Delhi, Dewas, Faridabad, Gandhinagar, Gaya, Hyderabad, Jamnagar, Jaipur, Jodhpur, Jorapokhar, Kanpur, Kolkata, Lucknow, Mumbai,
Nagpur, Palanpur, Patna, Pune, Rajkot, Singrauli, Surat, Vadodra, Varanasi and Thiruvananthapuram. ESA also confirmed a drop in NO 2 levels by around 40–50% in cities
of India owing to its nationwide quarantine (Fig. 15.2). The agency also reported a
decrease in the NO 2 level in the maritime route across the Indian Ocean due to less
maritime traffic [36] (Fig. 15.2). Kanniah et al. [37] used the Aura satellite sensor
to monitor NO 2 fluctuation, and reported a decreased NO 2 concentration over other
South-Asian cities such as Manila (34%), Kuala Lumpur (27%), Singapore (30%),
Bangkok (22%), Jakarta (34%) and Phnom Penh (6%). However, the study found an
increased NO 2 concentration by 1% and 3% in Ho Chi Minh City (Vietnam), and
Yangon (Myanmar), respectively. This increased NO 2 levels were attributed to the
high biomass-burning activity over the South-east Asian region along with several
other influential factors such as meteorology [37]. A recent data released by ESA
suggested that continuous lockdown measures in Europe have further lowered the
levels of NO 2 by 45–50% in Barcelona, Madrid, Milan, Paris and Rome (Fig. 15.2).
Studies by [38, 39] concurred with the ESA observation for Milan, Madrid and
Barcelona as the NO 2 concentration ranged between 48 and 62%. Reduction in the
NO 2 levels by 35, 51, 54 and 96% was also reported for Kazakhstan [10], New York
(USA) [40], Sau Paulo (Brazil) [41] and Morocco [42], respectively.