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Baghel et. al.,/IJES/ 11(2) 2022 ; 62-73
International Journal of Environmental Sciences 62
Full Length Research Paper
Evaluation of Air Quality in Taj City at Dayalbagh during the Covid-19
Period
Neelam Baghel, Sonal Kumari, Anita Lakhani, Aparna Satsangi and K. Maharaj Kumari
Department of Chemistry, Faculty of Science, Dayalbagh Educational Institute, Dayalbagh, Agra 282005, India.
ARTICLE INFORMATION ABSTRACT
Introduction
Wuhan city, capital of Hubei province of China, faced the first outbreak of this COVID-19 during December 2019 and
gradually this disease spread across the world (Raibhandari et.al., 2020; Wang et.al., 2020a, b). The spread of
Coronavirus disease (COVID-19) has affected almost all the countries in the world (Buono et.al., 2020). Due to its
spread around the world it was declared as pandemic by World Health Organisation (WHO-March 11, 2020)
(https://www.who.int/emergencies/diseases/novel-coronavirus-2019/events-as-they-happen). The transmission of
COVID-19 between people is mainly via respiratory droplets and contact routes (Burke et.al., 2020; Li et.al., 2020; Liu
et.al., 2020; WHO 2020). For breaking the chain of transmission of COVID-19, social isolation is the only way. Social
distancing is a prevention strategy to control and slow down the rate of spread of infection by restricting the contact
between infected and non-infected people, contaminated surfaces, and also among the general public. Many countries to
bring social distancing have imposed dramatic interventions like lockdown of the entire country, curtailing human
interaction, restriction on public gatherings, and public transportations (He et.al., 2020).
An advisory for travellers from China was issued by the Government of India during early January and screening was
also started on the travellers from China (https://www.mygov.in/covid-19/?cbps=1). In India, first case of COVID-19
was reported on January 30, 2020, while on March 12, 2020 first death due to COVID-19 was reported in Karnataka,
during that time India was on its second phase spread of Coronavirus disease (www.economictimes.indiatimes.com). In
response to the global COVID-19 pandemic, the honourable Prime Minister of India Mr. Narendra Damodardas Modi
Vol. 11. No.2. 2022
©Copyright by CRDEEP Journals. All Rights Reserved.
Contents available at:
http://www.crdeepjournal.org
International Journal of Environmental Sciences (ISSN: 2277-1948) (CIF: 3.654)
A Peer Reviewed Quarterly Journal
Corresponding Author:
Neelam Baghel
Article history:
Received: 26-04-2022
Revised: 01-05-2022
Accepted: 08-05-2022
Published: 11-05-2022
Key words:
Trace Gases; Lockdown
Effect; Tropospheric
Ozone; Diurnal Variation
The nationwide lockdown in India announced from March 25-May 31, 2020 in four phases to
prevent the rapid spread of pandemic COVID-19 has resulted in the reduction of
anthropogenic emission sources (vehicular and industries mainly) to a great extent. Present
study reports change in air quality during the lockdown period at Dayalbagh, Agra, a semi-
urban site in Northern India. The concentration of surface O3, NOx and CO were measured
through continuously operating O3 (Thermo Fischer Model 49i), NOx (Thermo Fischer Model
42i) and CO (Teledyne T300) analysers, respectively. The data showed a remarkable
reduction in the mean pollutant levels influenced by traffic emissions, that is, Nitric oxide
(NO) by 54.1%, Nitrogen Dioxide (NO2) by 86.7% (64.6% (NOx)) during lockdown over same
period in the previous year (2019). Comparatively, a lower reduction of Carbon monoxide
(CO) 8.6% is attributed to the dominance of natural atmospheric chemical regulation,
biogenic sources in addition to anthropogenic contributions and long-life span. An
enhancement of secondary pollutant viz. Ozone (O3) 5.1% was observed during lockdown
over same period in the previous year. O3 showed same diurnal pattern during lockdown
phase as in other phases, while the bi-modal peaks of NO, NO2 (NOx) were supressed due to
less vehicular emission and other anthropogenic activities, however CO showed prominent
bi-modal peaks during lockdown. The concentration of NO, NO2, NOx and CO reduced by
38.0%, 71.9%, 48.6% and 34.8% respectively during lockdown period in comparison to pre-
lockdown period (2020), on contrast O3 concentration increase by 24.5%. While,
concentration of NO, NO2, NOx and CO increased by 44.4%, 79.7%, 72.0% and 3.5%
respectively during unlock period in comparison to lockdown period, on contrast O3
concentration decreased by 16.2%.
Baghel et. al.,/IJES/ 11(2) 2022 ; 62-73
International Journal of Environmental Sciences 63
announced Janata curfew on 22 March 2020 from 7 am until 9 pm (https://economictimes.indiatimes.com/news/politics-
and-nation/after-janata-curfew-india-gets-ready-for-long-haul/articleshow/74765039.cms). Further complete lockdown
was enforced in the country from March 25, 2020 for twenty-one days. The country was under complete lockdown for
total 68 days due to this pandemic in three phases first from March 25, 2020 to April 14, 2020 for 21 days, further
extended by government from April 15, 2020 to May 3, 2020 for 19 days, still further from May 4, 2020 to May 17, 2020
followed by fourth phase of lockdown from May 18, 2020 to May 31, 2020 to prevent the spread of COVID-19. The
lockdown resulted in complete shutdown of all activities markets, construction, hotels, restaurants, industries, transport
(land, air and water) etc. except for limited essentials services like medicines, milk, fruits, vegetables etc. Due to this
lockdown 60-70% decline in fuel consumption is reported in India which is mainly attributed to no industrial activity and
very limited transport except for police vehicles and ambulances. Due to shut down of industries 9.2% decrease in
electricity demand was also reported (decrease in burning of coal) (Jain and Sharma, 2020). However, an improvement in
the air quality is observed across the world due to lockdown (Bao and Zhang, 2020; Represa et.al., 2020; Saadat et al.,
2020; Viteri et.al., 2020; Wetchayont, 2020). In the city of São Paulo, Brazil during partial lockdown (February to April,
2020), a decline in concentration of NO, NO2 and CO by 77.3%, 54.3% and 64.8% respectively is reported compared to
average concentration of pollutant in last five years during same months (Nakada and Urban, 2020). Similar decline in
pollutants concentration was reported by researchers across the world (Tobías et al., 2020 in Barcelona, Spain, Dantas et
al., 2020 in Rio de Jenario, Brazil and Xu et al., 2020 in Hubei Province, central China). The same trend was observed in
India (Mahato et al., 2020 in Delhi and Jain et al., 2020 in Chennai, Kolkata, Mumbai, Bangalore and Delhi) similarly,
pollutants in air at Gaziabad-world’s most pullulated city and industrial hub of India showed reduction in O3, CO and
NO2 concentration by 6%, 41% and 59% respectively (Kumari et.al., 2020). In Delhi 51% and 28% decrease in NO2 and
CO concentration respectively was reported during the lockdown period in comparison to concentration before
lockdown.
As there was a decrease in levels of precursors of ozone (O3), decline in O3 levels was expected. However, an increase in
the O3 level was observed during lockdown period. In Brazil during partial lockdown, 30.3-48.5% and 16.8-53.8%
reduction in levels of CO and NO2 respectively were reported; by contrast 67% increase in O3 concentration was reported
during same period (Dantas et.al., 2020). Before the lockdown the air quality was poor in most of the cities in India, this
affected a portion of population including children, aged population and people with respiratory and cardiovascular
disorders (Kumar et al., 2013; Aggarwal and Jain, 2015; WHO, 2018). However due to lockdown a drastic improvement
in air quality was observed in most of the cities. It was observed that improvement in air quality is helpful in controlling
the severity of COVID-19 outcome (Ogen, 2020; Wu et.al., 2020). The total number of deaths due to air pollution
decreased during lockdown period in China with decrease in the pollutant concentration in air (Dutheil et.al., 2020).
However, in November 2020, the spread of Coronavirus disease was in third phase (community spread), the process of
unlock in India (i.e., to slowly restart the services which are stopped due to lockdown) had started and with that increase
in concentration of pollutants was reported, so air quality was getting back to its previous conditions with almost same
concentration like previous year during same time period.
With this thought, the present study reports the effect of lockdown on air pollutant concentration (O3, NO, NO2, NOx and
CO). The pollutant concentrations during the study period were compared with their concentration previous year (2019)
and also with their concentration in different phases during 2020.
Methodology
Site description
Monitoring was carried out on the roof of Faculty of Science, Dayalbagh Educational Institute, Dayalbagh, Agra (Fig 1.).
Agra is located in the north-central (27°10’ N, 78°05’E) part of India, which is about 200km southwest of Delhi and lies
in middle of Indo-Gangetic Plain. It is a semiarid zone characterized by loose, sandy, and calcareous soil prone to
erosion. Climatically, Agra is hot during summer season (March-June) with maximum and minimum temperature
normally 45°C and 25°C respectively.
Fig 1. Sampling Site Dayalbagh Educational Institute, Agra
Baghel et. al.,/IJES/ 11(2) 2022 ; 62-73
International Journal of Environmental Sciences 64
Sampling of trace gases
O3, NOx and CO measurement: The concentration of surface O3, NOx and CO were measured through continuously
operating O3 (Thermo Fischer Model 49i), NOx (Thermo Fischer Model 42i) and CO (Teledyne T300) analysers,
respectively. The detailed description of the measurements has been reported in Kumari et al. (2018) and Verma et al.
(2018).
Classification of study period
This study adopts an intra-comparative approach to analyse the impact of COVID-19 lockdown on air quality during
January–September 2020.
The study period is divided into different phases as follow:
1. Pre-lockdown (PL): January 1-March 24, 2020
2. Lockdown (L): March 25-May 31, 2020
Lockdown Phase 1 (L1): March 24-April 14, 2020
Lockdown Phase 2 (L3): April 15-May 3, 2020
Lockdown Phase 3 (L3): May 4-May 17, 2020
Lockdown Phase 4 (L4): May 18-May 31, 2020
3. Unlock (UL): June 1-September 30, 2020
Unlock Phase 1 (UL1): June 1-June 31, 2020
Unlock Phase 2 (UL2): July 1-July 31, 2020
Unlock Phase 3 (UL3): August 1-August 31, 2020
Unlock Phase 4 (UL4): September 1-September
Results and discussion
Concentration of pollutants level in different phases during 2019 and 2020
Concentrations of O3 during pre-lockdown, lockdown and unlock period were 25.1 ± 10.1, 38.4 ± 16.1 and 28.9 ± 4.5
ppb respectively (2019) and 24.5 ± 9.5, 40.4 ± 12.9 and 29.2 ± 5.8 ppb respectively (2020) the percentage change in
concentration of O3 in each phase over previous year during same time period is listed in Table 1.
Table 1. Concentrations of Pollutants (O3, NO, NO2, NOx and CO) during different phases of study period in 2019 and
2020.
*Same period in 2019.
Pollutant
Phase
Conc. (ppb) 2019*
Conc. (ppb) 2020
% change
O3
Pre-Lockdown (January 1-
March 24)
25.1 ± 10.1
24.5 ± 9.5
-1.2%
Lockdown
(March 25-May 31)
38.4 ± 16.1
40.4 ± 12.9
2.5%
Unlock
(June 1-September 30)
28.9 ± 4.5
29.2 ± 5.8
0.3%
NO
Pre-Lockdown (January 1-
March 24)
4.3 ± 0.4
4.4 ± 0.6
1.3%
Lockdown
(March 25-May 31)
4.3 ± 1.4
2.0 ± 0.3
-37.0%
Unlock
(June 1-September 30)
5.1 ± 1.3
5.1 ± 0.5
0.3%
NO2
Pre-Lockdown (January 1-
March 24)
1.5 ± 0.3
1.5 ± 0.03
1.3%
Lockdown
(March 25-May 31)
2.0 ± 0.6
0.3 ± 0.04
-76.5%
Unlock
(June 1-September 30)
2.1 ± 0.4
2.3 ± 0.02
5.0%
NOx
Pre-Lockdown (January 1-
March 24)
5.5 ± 1.0
5.8 ± 0.7
2.4%
Lockdown
(March 25-May 31)
5.7 ± 2.2
2.0 ± 0.4
-47.7%
Unlock
(June 1-September 30)
6.8 ± 1.5
7.2 ± 0.9
2.99%
CO
Pre-Lockdown (January 1-
March 24)
696.2 ± 215.7
810.7 ± 215.7
7.6%
Lockdown
(March 25-May 31)
428.7 ± 96.6
391.8 ± 64.4
-8.6%
Unlock
(June 1-September 30)
422.5 ± 70.2
420.3 ± 80.5
-0.3%
Baghel et. al.,/IJES/ 11(2) 2022 ; 62-73
International Journal of Environmental Sciences 65
The comparison of different phases during study period can be seen in Fig.2, it is observed that during lockdown the
concentration of NO, NO2 and NOx showed a gradual decrease which is attributed to decrease in its emission from
vehicles and other anthropogenic sources, the concentration of CO also decreased during lockdown period but in
comparison to NOx it showed less impact which can be attributed to long atmospheric life time of CO mediated by
natural chemical processing in atmosphere and long range transfer of CO. The concentrations of CO during pre-
lockdown (January and February) showed much higher concentration than lockdown and unlock which may be attributed
to biomass burning during pre-lockdown period, in winters.
Fig.2 showed that unlike its primary pollutants the concentration of O3 was high during lockdown period this may be due
to suppression of fresh NO in atmosphere during lockdown period that leads to the reduction in O3 titration that causes
accumulation of O3 therefore increases its concentration. Concentration of O3 during lockdown period was higher than
their concentration during pre-lockdown and unlock period (2019) which is attributed to meteorological parameter i.e.,
sunlight, temperature, humidity, wind speed and wind direction. These factors favoured O3 formation during lockdown
(summer season include April and May) unlike pre-lockdown period (winter season include January and February) and
unlock period (rainy season include July and August). The concentration of NO, NO2 and NOx during pre-lockdown,
lockdown and unlock (2019) did not have any significant change like CO and O3, as the main source of NOx are vehicles.
Fig.2 Comparison of concentration of pollutants (O3, NO, NO2, NOx and CO) different phases during study duration.
The percentage change in concentrations of O3 during pre-lockdown, lockdown and unlock phases in 2020 compared to
previous year are -1.2%, 2.5% and 0.3% respectively. Percentage change in concentrations of NO, NO2, NOx and CO
during pre-lockdown are 1.3%, 1.3%, 2.4% and 7.6% respectively, during lockdown -37%, -76.5%, -47.7% and -8.6%
respectively and during unlock 0.3%, 5%, 3% and -0.3% respectively compared to their concentration previous year
during same time period.
Collivignarelli et.al., 2020 reported decrease in NOx and CO concentration by -47% and -57.6% respectively and
increase in O3 concentration by 43.1% in Milan, Italy during their study period from January 1-April 10, 2020. Jain and
Sharma also reported decrease in NOx concentration at Delhi, Chennai, Bangalore and Kolkata by 48%, 43%, 56% and
66% respectively and CO by 41%, 23%, 15% and 16% respectively while increase in O3 concentration by 14%, 73%,
21% and 87% respectively during their study period March-April, 2020 compared to previous year concentration during
same duration.
Other study conducted during covid period in India and in World
The impact of lockdown on air quality has been studied around the world including India. In India the study was done in
different cities by measuring the level of pollutants. Delhi, Mumbai, Chennai, Kolkata and Bangalore are main cities
where the pollutant levels were measured during lockdown and compared from their previous year concentration and a
drastic improvement in air quality was observed in all the cities (Jain and Sharma, 2020). In the comparison of pollutant
levels with their previous year concentration, during same duration, maximum dip was observed in NO2 concentration, in
all the cities. In Mumbai around 75% decrease in NO2 concentration was observed during lockdown (Jain and Sharma,
2020).
In Delhi, a drastic decline in concentration of all pollutants was observed which caused an improvement in air quality in
Delhi after a long time. In Delhi decline of 41%, 52%, 50% and 29% in average concentration of PM2.5 (from 66 to 39
ppb), PM10 (from 153 to73 ppb), NO2 (from 39 to 19 ppb) and CO (from 0.9 to 0.65 ppb) respectively were recorded
Baghel et. al.,/IJES/ 11(2) 2022 ; 62-73
International Journal of Environmental Sciences 66
during lockdown compared to before lockdown period. However, 7% incline in O3 concentration was also recorded
during lockdown (Jain and Sharma, 2020). A similar observation of decrease in concentration of pollutants except for O3
was reported in three cities in Hubei Province, Wuhan, Jingmen and Enshi, in central China (Xu et al., 2020). In Wuhan
30% to 61% and 7% to 23% decline in concentration of NO2 and CO was recorded from January to March 2017-2019 as
compared to concentration in January to March 2020. Like Delhi in Wuhan also increase in O3 concentration from 9% to
27% was reported during their lockdown period.
In other cities in India (Chennai, Kolkata, Mumbai and Bangalore) a similar decline in pollutant as reported in Delhi was
observed (Table 3). In Chennai, decline in concentrations of NO2 and CO by 30% (from 10 to 7 ppb) and 25% (from 0.75
to 0.56 ppb) respectively and an increase in O3 concentration by 3% (from 43 to 44 ppb) were recorded during lockdown
in comparison to before lockdown. Similarly, NO2 and CO concentration decline by 60% and 29% in Kolkata, 70% and
38% in Bangalore and 75% and 46% in Mumbai respectively during lockdown in comparison to concentrations before
lockdown. In contrast the concentration of O3 showed incline in Kolkata and Mumbai except for a decline in Bangalore.
In Kolkata O3 increased by 17% (from 51 to 60 ppb) and 8% (from 33% to 36 ppb) in Mumbai and decreased by 11% in
Bangalore (Jain and Sharma, 2020).
The contrasting trend of O3 may be attributed to more favourable conditions for photochemical reactions determining O3
formation and destruction (Dang and Liao, 2019; Xu et al., 2020). In China same trend of increase in O3 concentration
during lockdown was reported by Xu et al., 2020. NO2 and NO produce contrasting impact on surface O3 accumulation.
NO2 promotes formation of O3 in presence of sunlight whereas NO depletes O3 by formulating NO2 after reaction (Jain et
al., 2020). During lockdown 70-80% passenger vehicles and 60-70% goods vehicles were off roads and other
combustion activities were reduced (main anthropogenic source of NOx emission) therefore NOx emission reduced in a
VOC-limited environment which may have led to increase in O3 concentration (Tobías et al., 2020).
Kumari et.al. (2020), compared pollutant levels from 24th March-31st May in 2020 with their levels during same time
period in 2019 to estimate the impact of lockdown on air pollutants levels in 39 different cities of India which includes
10 Indian cities considered among the world’s 20 most polluted cities. Air pollution decreased but with substantial
variation among pollutants during lockdown period. The reduction was observed for NO2 (3– 79%) and CO (2–61%),
while O3 showed a mixed trend with increased levels at some cities which may be attributed to lower titration of O3 by
NO. In Ghaziabad and Patiala all the pollutants showed significant reduction during lockdown period except O3. Diurnal
patterns of CO and NOx showed lower values during lockdown period in 2020 with supressed bimodal peaks as
compared to 2019.
Meteorological parameters were also found to play significant role in reduction of air pollution during the lockdown
(Sharma et al., 2020). As in Delhi 1-2 weeks prior to lockdown the meteorological parameters: absolute temperature
(range from 22-27°C), wind speed (<0.5 m/s) and relative humidity (58-78%) were recorded which were not favourable
condition for dispersion of pollutants therefore high concentration of pollutants were recorded (Jain and Sharma, 2020b).
However, during lockdown the absolute temperature was in range of 27-32°C, wind speed in range of 0.7-1.2 m/s and
relative humidity from 50-64%, which is more favourable condition for dispersion of pollutant than before lockdown,
therefore low pollutant concentration during lockdown were observed. Sharma et.al., 2020b reported average
meteorological conditions in India on regional basis during lockdown, in north India the wind direction was
predominantly from south and southwest with average wind speed 1.5 m/s whereas in southern India the wind speed was
1.0 m/s which is less comparing to northern India, therefore dilution of air pollutant is more in north India compared to
south India which may be the reason for lower concentration of pollutants in northern city like Delhi as compared to
concentration of pollutant in southern cities like Chennai and Bangalore.
In Milan, Italy the concentration of NOx and CO were reported to decrease by 47% and 57.6% respectively while O3
concentration increased by 43.1% during their study period from January 1-April 16,2020 (Collivignarelli et.al., 2020).
The change in concentrations of pollutants in counties around the world during their lockdown period is listed in Table 2.
Table 2. Change in concentration of pollutants in different countries around world.
City/Country
Study Duration
% change
Reference
NOx
CO
O3
Tehran, Iran
February 20-April
21, 2020
-13%
-13%
3%
Broomandi et.al., 2020
Milan, Italy
January 1- April
16, 2020
-47%
-57.6%
43.1%
Collivignarelli et.al., 2020
Rio de Janeiro, Brazil
March 2-April 16,
2020
-16.8% to -
53.8%
-30.3% to -
48.5%
67%
Dantas et.al., 2020
Almaty, Kazakhstan
February 21-April
14,2020
-35%
-49%
15%
Kerimray et.al., 2020
Singapore
April 7-May 11,
2020
-54% to -58%
-6% to -26%
18%
Li et.al., 2020
Baghel et. al.,/IJES/ 11(2) 2022 ; 62-73
International Journal of Environmental Sciences 67
Klang Valley,
Malaysia
February 20- April
21, 2020
-
-47.5%
-
Moh. Nadzir et.al., 2020
São Paulo, Brazil
February-April,
2020
-54.3%
-64.8%
30%
Nakada and Urban, 2020
Buenos Aires,
Argentina
January 24-May
14, 2020
-30%
-
-
Represa et.al., 2020
Barcelona, Spain
February 16-
March 30, 2020
-47% to -
51.4%
-
-28.5% to -
57.7%
Tobias et.al., 2020
Wuhan, China
January-March,
2020
-30.3% to -
60.6%
-7.4% to -
23.8%
9.6 to 16.3%
Xu et.al., 2020
Jingmen, China
-38.5% to -
64.3%
-22.4% to -
31.9%
3.2% to 15.5%
Enshi, China
-38.1% to -
65.2%
-31.1% to -
37.6%
6.9% to 15.4%
Albacete, Spain
March-June, 2020
-41.4% to -
78.4%
-7.5% to -
47.7%
7.1% to 16.4
Viteri et.al., 2020
Madrid, Spain
-50.8% to -
74.2%
-18.5% to -
36.2%
4% to 19.8%
Puertallano, Spain
-51.9% to -
80.1%
-39.9% to -
75.8%
14.7% to
27.1%
S. Pablo, Spain
-28.3% to -
50.4%
-
8.1% to 16.5%
Greater Bangkok,
Thailand
January 1-July 20,
2020
-41.5%
-8.0%
7.1%
Wetchayont, 2020
Table 3. Change in concentration of pollutants in different cities of India.
Diurnal Variation of Trace gases during the study period
The study of diurnal patterns of pollutants (Fig. 3) showed that O3 shows its usual pattern as previous year i.e., lower
concentration during morning and evening hours while higher during afternoon hours. Although the overall concentration
of O3 was higher than previous year concentration but it showed suppressed rush hour peak which may be due to lower
vehicular activities during lockdown period. O3 showed higher concentration during afternoon while lower during
morning and evening hours than its concentration previous year. The daytime increase in its concentration is attributed to
the photo-oxidation of its precursors (CO, CH4, and NMHCs) in the presence of NOx, lower O3 concentration during the
night is attributed to inhibition of photochemistry, titration of O3 by surface emissions of NO, and loss due to surface
deposition. NO, NO2 and NOx do not show their usual diurnal pattern like previous year, the prominent bi-modal peaks
City
Study Duration
% change
Reference
NOx
CO
O3
Delhi
March-April, 2020
-48%
-41%
14%
Jain and Sharma, 2020
Chennai, Tamil Nadu
-43%
-23%
73%
Bangalore, Karnataka
-56%
-15%
21%
Kolkata, West Bengal
-66%
-16%
87%
Ghaziabad, Uttar
Pradesh
March 24-May 31,
2020
-59%
-41%
-6%
Kumari et.al., 2020
Patiala, Punjab
-79%
-61%
2%
Amritsar, Punjab
February 1-May 3,
2020
-38.8%
-5.3%
-
Navinya et.al., 2020
Jaipur, Rajasthan
-68.4%
-55.0%
-
Ahmedabad, Gujrat
-67.5%
-36.5%
-
Nagpur, Maharashtra
-49.9%
-63.0%
-
Hyderabad,
Telangana
-35.0%
-26.1%
-
Bhubaneswar, Odisha
March-June, 2020
-67%
-14%
3%
Panda et.al., 2020
Kannur, Kerala
March 1-May 17,
2020
-61% to -71%
-67%
22%
Resmi et.al., 2020
Ajmer, Rajasthan
March 10-May 17,
2020
-32.72%
-
1.35%
Sharma et.al., 2020a
Alwar, Rajasthan
-30.22%
-
10.19%
Bhiwadi, Rajasthan
-64.41%
-
45.05%
Jaipur, Rajasthan
-56.18%
-
-25.86%
Jodhpur, Rajasthan
-56.69%
-
1.14%
Kota, Rajasthan
-44.83%
-
22.93%
Udaipur, Rajasthan
-57.98%
-
-0.52%
Bhubaneswar, Odisha
March-May, 2020
-19% to -69%
-2% to -18%
13% to 93%
Sahu et.al., 2020
Baghel et. al.,/IJES/ 11(2) 2022 ; 62-73
International Journal of Environmental Sciences 68
of NOx were suppressed during lockdown which may be attributed to less vehicular movement. Unlike NOx during
lockdown CO showed prominent bi-modal peaks although the evening peak of CO was supressed. The very less change
in concentration and diurnal pattern of CO can be attributed to its long- life and long-range transport.
Fig. 3 Diurnal pattern of pollutants during March 24-May 31, 2019 and 2020 (lockdown Period).
Comparison of pollutants levels during pre-lockdown, lockdown and unlock period in 2020.
The concentrations of pollutant during pre-lockdown, lockdown and unlock in 2020 were also compared. Table 4(a) and
4(b) showed the change in pollutant concentrations during lockdown over pre-lockdown period and unlock over
lockdown period respectively.
Table 4(a). Comparison of pollutant concentration in pre-lockdown and lockdown phase (2020).
Pollutant
Conc. (ppb)
% Change
Pre-lockdown
Lockdown
O3
24.5 ± 9.5
40.4 ± 12.8
24.5%
NO
4.38 ± 0.6
2.0 ± 0.3
-37.9%
NO2
1.6 ± 0.03
0.3 ± 0.04
-71.9%
NOx
5.8 ± 0.7
2.0 ± 0.4
-48.6%
CO
810.7 ± 215.7
391.8 ± 64.4
-34.8%
Table 4(b). Comparison of pollutant concentration in lockdown and unlock phase (2020).
Pollutant
Conc. (ppb)
% change
Lockdown
Unlock
O3
40.4 ± 12.8
29.2 ± 5.8
-16.2%
NO
2.0 ± 0.3
5.1 ± 0.5
44.4%
NO2
0.3 ± 0.04
2.3 ± 0.02
79.7%
NOx
2.0 ± 0.4
7.2 ± 0.9
72.0%
CO
391.8 ± 64.4
420.3 ± 80.5
3.5%
The concentrations of NO, NO2, NOx and CO decreased by 37.9%, 71.9%, 48.6% and 34.8% respectively during
lockdown over pre-lockdown while increased by 44.4%, 79.7%, 72.0% and 3.5% respectively during unlock over
lockdown period in 2020. O3 increased by 24.5% during lockdown over pre-lockdown and decreased by 16.2% during
unlock over lockdown period. In other countries also similar change in pollutant concentrations were reported. at Rio de
Janeiro, Brazil during their lockdown (March 2- April 10, 2020) decline in NOx and CO by 30.3% and 48.5%
respectively and incline in O3 concentration by 67% were reported (Dantas et. al., 2020). At Barcelona, Spain during
their lockdown (February 16- March 30, 2020) decline in NOx by 4.7% - 51.4% and incline in concentration by 28.5% -
57.5% were reported (Tobías et. al., 2020). Similarly decline in NOx by 30.3% - 60.6%, 38.5% - 64.3% and 38.1% -
65.2% and 7.4%, - 23.8%, 22.4% - 31.9% and 31.1% - 37.6% in CO concentration at Wuhan, Jingmen and Enshi
respectively were reported during their lockdown period (January-March, 2020).
Baghel et. al.,/IJES/ 11(2) 2022 ; 62-73
International Journal of Environmental Sciences 69
Incline in O3 concentration by 9.6% - 16.3%, 3.2% - 15.5% and 6.9% - 15.4% respectively was also reported at same
sites (Xu et.al., 2020). The statistics of measured pollutant concentrations during study period are listed in Table 5.
Table 5. Statistics of measured O3, NOx (NO and NO2) and CO during January to September (PL, L1, L2, L3, L4, UL1,
UL2, UL3 and UL4) at Dayalbagh, Agra
O3 (ppb)
Phase
Phase Date
Min
Max
Mean
S.D.
Pre-lockdown (PL)
Jan 1-Mar 24
15.3
39.5
24.5
9.5
Lockdown-1 (L1)
Mar 25-Apr 14
16.5
50.0
34.0
12.4
Lockdown-2 (L2)
Apr 15-May 3
24.9
58.0
42.8
12.2
Lockdown-3 (L3)
May 4-May 17
29.4
65.0
48.6
13.0
Lockdown-4 (L4)
May 18-May 31
20.9
57.2
38.7
14.5
Unlock-1 (UL1)
Jun 1-Jun 30
24.5
44.5
35.0
7.2
Unlock-2 (UL-2)
Jul 1-Jul 31
19.4
43.1
31.2
8.8
Unlock-3 (UL-3)
Aug 1-Aug 31
19.6
26.8
22.7
2.3
Unlock-4 (UL-4)
Sep 1-Sep 30
17.7
33.8
26.2
6.0
NO (ppb)
Phase
Phase Date
Min
Max
Mean
S.D.
Pre-lockdown (PL)
Jan 1-Mar 24
0.8
1.6
1.1
0.3
Lockdown-1 (L1)
Mar 25-Apr 14
0.7
2.8
1.1
0.5
Lockdown-2 (L2)
Apr 15-May 3
1.4
2.3
1.7
0.2
Lockdown-3 (L3)
May 4-May 17
1.3
2.2
1.7
0.2
Lockdown-4 (L4)
May 18-May 31
0.7
1.8
1.0
0.3
Unlock-1 (UL1)
Jun 1-Jun 30
4.8
7.2
5.5
0.6
Unlock-2 (UL-2)
Jul 1-Jul 31
3.7
6.2
4.1
0.5
Unlock-3 (UL-3)
Aug 1-Aug 31
0.4
10.6
4.1
2.2
Unlock-4 (UL-4)
Sep 1-Sep 30
0.6
7.3
5.1
0.6
NO2 (ppb)
Phase
Phase Date
Min
Max
Mean
S.D.
Pre-lockdown (PL)
Jan 1-Mar 24
1.5
1.6
1.6
0.03
Lockdown-1 (L1)
Mar 25-Apr 14
0.2
0.3
0.3
0.02
Lockdown-2 (L2)
Apr 15-May 3
0.2
0.3
0.3
0.02
Lockdown-3 (L3)
May 4-May 17
0.2
0.3
0.2
0.01
Lockdown-4 (L4)
May 18-May 31
0.2
0.4
0.3
0.1
Unlock-1 (UL1)
Jun 1-Jun 30
0.7
1.5
1.0
0.2
Unlock-2 (UL-2)
Jul 1-Jul 31
3.3
3.4
3.3
0.02
Unlock-3 (UL-3)
Aug 1-Aug 31
2.4
2.6
2.5
0.1
Unlock-4 (UL-4)
Sep 1-Sep 30
0.1
7.2
2.4
1.3
NOx (ppb)
Phase
Phase Date
Min
Max
Mean
S.D.
Pre-lockdown (PL)
Jan 1-Mar 24
2.0
2.5
2.2
0.1
Lockdown-1 (L1)
Mar 25-Apr 14
0.8
1.9
1.1
0.3
Lockdown-2 (L2)
Apr 15-May 3
1.5
2.5
1.8
0.3
Lockdown-3 (L3)
May 4-May 17
1.4
2.2
1.7
0.2
Lockdown-4 (L4)
May 18-May 31
0.7
2.2
1.5
0.5
Unlock-1 (UL1)
Jun 1-Jun 30
5.4
7.5
6.0
0.6
Unlock-2 (UL-2)
Jul 1-Jul 31
4.5
7.7
5.3
0.7
Unlock-3 (UL-3)
Aug 1-Aug 31
0.8
9.2
5.6
2.2
Unlock-4 (UL-4)
Sep 1-Sep 30
0.2
10.0
5.9
3.2
CO (ppb)
Phase
Phase Date
Min
Max
Mean
S.D.
Pre-lockdown (PL)
Jan 1-Mar 24
874.9
1640.1
1210.7
215.7
Lockdown-1 (L1)
Mar 25-Apr 14
408.7
676.5
494.2
67.3
Lockdown-2 (L2)
Apr 15-May 3
254.8
489.0
347.8
65.6
Lockdown-3 (L3)
May 4-May 17
300.6
584.4
401.8
74.7
Lockdown-4 (L4)
May 18-May 31
218.3
562.8
338.5
90.2
Unlock-1 (UL1)
Jun 1-Jun 30
389.3
824.8
480.5
107.8
Unlock-2 (UL-2)
Jul 1-Jul 31
262.9
747.5
438.9
125.7
Unlock-3 (UL-3)
Aug 1-Aug 31
210.8
613.3
394.7
104.5
Baghel et. al.,/IJES/ 11(2) 2022 ; 62-73
International Journal of Environmental Sciences 70
Unlock-4 (UL-4)
Sep 1-Sep 30
210.4
710.4
510.3
97.9
The concentration of O3 was higher during lockdown compared to its concentration during pre-lockdown and unlock
period which can be attributed to meteorological conditions (intense sunlight, high temperature, less humidity, slow wind
speed) in favour of O3 formation (April- May summer seasons) while pre-lockdown (January and February-winter
season) and unlock period (July and August-rainy season) had meteorological conditions less in favour of O3 formation
than lockdown period (Singla et.al., 2011; Verma et.al., 2018).
The concentration of NO, NO2 and NOx showed significant decrease in its concentration during lockdown period
comparing to pre-lockdown and unlock period in 2020 which is contributed to less vehicular emissions during lockdown
period, while their concentrations during pre-lockdown and unlock period in 2020 do not have any significant change
which is attributed to their emission from vehicles and other anthropogenic sources.
The concentrations of CO do not show any significant change during lockdown period compared to unlock period in
2020 however its concentration during pre-lockdown period were higher than its concentration during lockdown and
unlock period as pre-lockdown period which is attributed to biomass burning during pre-lockdown period as it includes
January and February which are months of winter season in India. Fig. 4 shows comparison of pollutants during pre-
lockdown, lockdown and unlock phase in 2020.
Fig. 4 Comparison of pollutants during Pre-lockdown (PL), Lockdown (L) and Unlock (UL) phase in 2020.
The diurnal variation of pollutants is shown in Fig. 5, the concentration of O3 during all four phases of lockdown period
are higher than pre-lockdown phase while mixed variation in its concentration was observed during all four phases
during UL1 and UL2 the O3 concentrations are higher than its concentration during pre-lockdown while lower during
UL3 and UL4 than its concentration during pre-lockdown period.
Fig. 5 Diurnal variation of O3, NO, NO2, NOx and CO during pre-lockdown, lockdown1, lockdown2, lockdown3,
lockdown4, unlock1, unlock2, unlock3 and unlock4 at Dayalbagh Educational Institute, Agra
The increase in O3 concentration may be attributed to favourable meteorological conditions for photochemical reactions
which are attributed to increase in solar radiation and decrease in NO2 that leads to change in photochemical reaction
which determines formation and destruction of O3 (Sharma et.al., 2016; Dang and Liao 2019). The chemistry between
anthropogenic emission (like NOx) in a VOC-limited region along with meteorological parameters govern the
Baghel et. al.,/IJES/ 11(2) 2022 ; 62-73
International Journal of Environmental Sciences 71
accumulation of O3 in atmosphere (Gorai et.al., 2015; Saini et.al., 2017). The increase in O3 concentration during
lockdown period can be better explained by the following equations which represent the chemistry between NOx and O3:
NO2 + hν NO + O• (Eq.1)
O2 + O• O3 (Eq.2)
O3 + NO NO2 + O2 (Eq.3)
NO2 and NO show inverse effect on governing O3 accumulation in atmosphere. NO2 promotes O3 formation in presence
of sunlight while NO depletes O3 formation by forming NO2 after reaction with O3.
More than 30-50% NOx is emitted by vehicles, diesel vehicles emit more NOx than petrol vehicles (Aggarwal and Jain
2015; Jain et.al., 2016). This lockdown leads to 70-80% decrease in passenger vehicles while 60-70% good vehicles and
other reduced anthropogenic sources result in reduced NOx in VOC-limited environment which cause increase in O3
concentration (Kim et.al., 2018; Tobías et.al., 2020). Therefore, increased O3 concentration during lockdown period can
be attributed to decreased NOx emissions.
Conclusions
The extent of change in air quality was studied over Dayalbagh, Agra, during a nationwide lockdown scenario.
A significant reduction of primary pollutants, NOx (NO and NO2) by 64.6% (53.9% and 86.6%) and CO (8.6%)
respectively during lockdown period (2020) in comparison to the same period of the previous year (2019) was
observed. This reveals that reduced traffic pollution and essential anthropogenic activities led to better air
quality during lockdown period this year compared to same period previous year.
However, there was an incline in O3 concentration by 5.0% during lockdown period compared to previous year
concentration. The overall increase in O3 was attributed to high VOC/NOx ratio as NOx reduced during
lockdown while due to increase in use of disinfectant and sanitizers VOCs concentration did not change leading
to high VOC/NOx ratio which eventually lead to higher O3 concentration as additional meteorological
conditions like solar radiation intensity, temperature and low wind speed (March-May summer season) support
O3 formation as same duration previous year.
Among CO and NOx, CO was the least impacted from the lockdown due to lower contribution of fossil fuels to
CO sources and a much longer atmospheric lifetime mediated by natural chemical processing in the atmosphere.
The concentration of NOx (NO, NO2) and CO reduced by 48.6% (38.0%, 71.9%) and 34.8% during lockdown
compared to pre-lockdown period in 2020. The concentration of CO during pre-lockdown was higher than
during lockdown which is attributed to long-life of CO.
O3 and CO showed their usual diurnal pattern during lockdown with suppressed rush hour peaks while NO, NO2
and NOx does not show bi-modal peaks in their diurnal pattern which is attributed to their less emission from
vehicles and other anthropogenic sources.
In contrast the concentration of O3 increase by 24.5% during lockdown compared to pre-lockdown period.
Acknowledgements
The authors are thankful to Director, Dayalbagh Educational Institute, Agra and the Head, Department of Chemistry for
necessary help. The authors gratefully acknowledge the financial support by ISRO GBP under AT-CTM Project.
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