key: cord-0831645-xy1fmw0j
authors: Garg, Manish; Goyal, Sujata; Bansal, Onam
title: Effect of lockdown amid COVID-19 pandemic on air quality of most polluted cities of Punjab (India)
date: 2021-11-03
journal: J Earth Syst Sci
DOI: 10.1007/s12040-021-01713-z
sha: 1fba151ac14cf22b428bcf718acc9fba4b6fa59f
doc_id: 831645
cord_uid: xy1fmw0j

In the last month of 2019, the outbreak of a viral disease named COVID-19 started in Wuhan, China. The disease has spread in most of the countries of the world and it was declared as a global pandemic in March 2020 by the World Health Organization (WHO). Many countries implemented countrywide lockdown. COVID-19 has forced many countries to observe complete lockdown. This complete lockdown has improved the air quality significantly due to less human activities. In India, a complete lockdown of 21 days was implemented in phase I (March 25, 2020 to April 14, 2020) to avoid the spread of corona virus disease. Further, this lockdown was extended to phase II (April 15, 2020–May 3, 2020), phase III (May 4–17, 2020) and phase IV (May 18–31, 2020) with some relaxations in restrictions. In the present work, we have analyzed the data of major air pollutants PM(2.5), PM(10), SO(2), NO(2), CO and O(3) from the three most polluted cities of Punjab for March 03–24, 2020 (before lockdown) vs. March 25, 2020 to May 31, 2020 (during lockdown divided into four phases). Further, an extensive comparison of the mean concentration of major air pollutants has been made for the different phases of lockdown including before lockdown period with the same periods in 2019. It is observed that the concentration of PM(2.5), PM(10), NO(2) and SO(2) has reduced significantly ~50% after first phase of lockdown. As observed in this study, there is an urgent need for interventions across northern India to knockdown air pollutant levels by more than 40% or so by adopting cleaner fuel technology and avoiding poor combustion activities.

In the end of 2019, Brst case of corona virus was reported in Wuhan city of China Lu et al. 2020) . Then it reached Europe and rapidly spread across the whole world. A report coming from different regions of the world tells that Severe Acute Respiratory Syndrome Virus (SARS-COV-2) is named as COVID-19 by World Health Organization (WHO). On March 11, 2020, it was declared as a global pandemic by WHO (Shehzad et al. 2020) . It has aAected people across the nations worldwide. As per the directions from WHO, Indian government implemented countrywide Brst phase of lockdown on March 25, 2020. This lockdown was implemented for a duration of 21 days up to April 14, 2020. Further partial lockdown was implemented in different phases II, III and IV from April 15-May 3, 2020, May 4-17, 2020 and May 18-31, 2020, respectively. These lockdowns in India were the Brst event during the last few decades when almost 1.40 billion people were locked in their homes. During the Brst phase of lockdown, all modes of transport including buses, railways and airlines were banned. Industries, construction work, markets and restaurants were closed throughout India. Only essential services, e.g., hospitals, medical stores were open with some conditions. Whereas, some restrictions were relaxed during the subsequent phases of lockdown. The complete lockdown has significant eAect on the reduction of air pollution (Bao and Zhang 2020; Kotnala et al. 2020) . Few studies have reported positive impact of the lockdown on air and water pollution (Gautam and Hens 2020; Singh and Chauhan 2020; Srivastava et al. 2020) . Kumari and Toshniwal (2020) investigated the impact of lockdown on the air quality of three Indian cities, namely Delhi, Mumbai and Singrauli. It is shown that the concentration of PM 2.5 , PM 10 , NO 2 and SO 2 has reduced significantly for these three cities. Otmani et al. (2020) studied the variation of air quality parameters before and after the lockdown in Sale city of Morocco. They analyzed that concentration of PM 10 and NO 2 has decreased by 75% and 49%, respectively. Many studies have been conducted worldwide to analyze the impact of lockdown on air quality (Berman and Ebisu 2020; Gupta et al. 2020; Lian et al. 2020; Mor et al. 2020) . According to World quality report (2018-2019), six cities of Punjab (Mandi-Gobindgarh, Amritsar, Jalandhar, Ludhiana, Patiala and Khanna) were among the top 50 polluted cities in the world. Ludhiana, Mandi-Gobindgarh and Patiala were reported the most polluted cities in Punjab. In the present work, we have analyzed the variations in air quality parameters across the three major cities of Punjab (namely Ludhiana, Mandi-Gobindgarh and Patiala) for the different phases of lockdown and compared with before lockdown period. Further, we have compared the mean concentration of major air pollutants for different periods (before lockdown and after lockdown divide into four phases) with the same periods in 2019.

To study the eAect of lockdown on air quality, data were collected from the three most polluted cities of Punjab (Ludhiana, Mandi-Gobindgarh and Patiala). The air quality data for the above-mentioned cities have been taken before lockdown (March 3-24, 2020) and after lockdown (March 25-May 31, 2020) from the central pollution control board (CPCB) online portal (https://app. cpcbccr.com). Respirable Suspended Particulate Matter (RSPM) analyzer MP101M (ENVEA, France) has been used to measure the concentration of PM 2.5 and PM 10 at all the three sites. This instrument is based on beta gauge measurement method for the continuous measurement of concentration of Bne dust in ambient air. The detector is situated at downstream of the Blter ribbon which is made up of glass Bbre. For the measurement of the concentration of NO x , analyzer AC32M (ENVEA, France) was used which is based on the chemiluminescence technology. To measure SO 2 and CO concentrations, analyzers AF22e and CO12e (ENVEA, France), respectively, have been used. For the measurement of O 3 , UV photometry technology-based Analyzer O342e from ENVEA, France has been used. The instruments at the three sites have been provided by Punjab Pollution Control Board (PPCB), India. All the instruments used for the measurement of ambient air quality have high accuracy (Manual, ENVEA France). We have collected data for the selected cities during the same period in 2019. These cities were listed in the world's most polluted cities of the year 2018. In order to study the eAect of long-range transport of major pollutants, a three-day airmass back trajectories over Ludhiana, Mandi-Gobindgarh and Patiala at 500 m above sea level were retrieved for the whole study period using HYSPLIT model (Stein et al. 2015) (http://ready.arl.noaa.gov/ HYSPLIT.php).

Punjab is the most fertile region in western Indo-Gangetic Plain and is called India's 'bread-basket'. Though Punjab is an essentially agrarian economy, small, medium and few large-scale industrial units have been set up in major cities and towns of Punjab such as Ludhiana, Amritsar, Mandi-Gobindgarh, Dera Bassi, and Rajpura. Ludhiana city of Punjab is known as Manchester of India. Many types of units including textile, auto parts, food products, cycle and steel industries are operationally existing in Ludhiana. As per the report of 2014-2015 (micro, small and medium enterprises; MSME), there are 38,552 registered micro and small units and 153 medium and large units in the district Ludhiana. Mandi-Gobindgarh is known as the steel city of Punjab due to large number of steel industries. There are around 600 industrial units and more than 500 medium to small-sized metal scrap recycling industries. These units are The open burning in the agricultural Belds (October-November and mid-April to mid-May) emits large amount of particulate matter and trace gases (CO 2 , CO, CH 4 , N 2 O, NO x , SO 2 and non-methane hydrocarbons) into the atmosphere which perturb the regional air quality and atmospheric chemistry (Sahai et al. 2007; Rastogi et al. 2014 ). Details about the location of the selected cities for study are given in table 1 and Bgure 1. The hourly concentration of key pollutants PM 2.5 , PM 10 , SO 2 , NO 2 , CO and O 3 have been used for the present study. 24-hr average of all the pollutants has been calculated to observe the change between the pre-lock and post-lockdown phases.

In this section, we present the air quality data analysis of three major polluted cities of Punjab before lockdown (March 3-24, 2020) and after lockdown period (March 25-May 31, 2020 divided into four phases). Figure 2 (a-f) represents the daily average concentration of PM 2.5 , PM 10 , SO 2 , NO 2 , CO and O 3 between March 3, 2020 and May 31, 2020 in Ludhiana, Mandi-Gobindgarh and Patiala. The 24 hrs average level of PM 2.5 (Bgure 2a) in Ludhiana varied from 28 to 98 lg/m 3 before lockdown and after lockdown period (phase I), it reduces to 14-41 lg/m 3 . The highest level of PM 2.5 Mandi-Gobindgarh and Patiala was recorded as 26 and 17 lg/m 3 , respectively. The range of NO 2 (Bgure 2c) in Ludhiana, before and after lockdown (phase I) was 20-83 and 19-25 lg/m 3 , respectively. In Mandi-Gobindgarh, average value of NO 2 shows a slight increase. This may be due to the emission of gases from large number of iron and steel industries and power plant in the region. In Patiala, NO 2 level decrease from 5-12 to Ozone chemistry depends on the concentration of Nitrogen oxides (NOx), volatile organic compounds (VOCs) as well as solar radiation (Seinfeld and Pandis 1998; Lee et al. 2002) . After implementation of lockdown, NOx as well as VOC concentrations decreased due to sudden full stop on anthropogenic activities, but solar radiation increased. Therefore, the concentration of ozone increased due to increase in solar radiation (Dang and Liao 2019; Li et al. 2019) . It is observed that the increase in the concentration of O 3 is relatively lower than 2019 due to decrease in concentration of its precursors except in phase 2 over Ludhiana and phase 4 over Mandi-Gobindgarh. This difference in the concentration of O 3 is not significant in the case of Patiala. Figure 3 shows the variation in mean concentrations of all the pollutants before and after lockdown (phase I) in Ludhiana, Mandi-Gobindgarh and Patiala. Due to less activity in transport sector and industrial activities, concentrations of the major air pollutants (PM 2.5 , PM 10 and NO 2 ) have significantly reduced after lockdown (phase I). The average value of PM 2.5 was 44.0 and 25.5 lg/m 3 for Patiala before and after lockdown (phase I), respectively. The average value of PM 2.5 was 80.9 lg/m 3 in Mandi-Gobindgarh before lockdown which reduces to 40.69 lg/m 3 after lockdown (phase I). The average value of PM 10 was found to be 93.6 lg/ m 3 in Mandi-Gobindgarh before lockdown and 45.2 lg/m 3 after lockdown (phase I). The maximum average value of NO 2 was reported in Ludhiana before lockdown. In case of Mandi-Gobindgarh, there was a slight increase in the level of NO 2 after lockdown (phase I). For SO 2 , the average value decreased from 20.3 to 7.7 lg/m 3 in Mandi-Gobindgarh after lockdown (phase I). The average value of CO in the Ludhiana reduced from 20.3 to 9.1 lg/m 3 after lockdown (phase I) with a maximum decrease of 64.5%. It is clear from Bgures 2 and 3 that during the days of lockdown (phase I), average value of all the key pollutants was lower than the National Ambient Air Quality Standards (NAAQS) table 2.

Further in this paper, the analysis has been extended to phase II, III and IV of lockdown. The major decrease in the concentration of all the air pollutants was observed in the Brst phase of lockdown in comparison to the other three phases. This could be due to the relaxation in the later phases of lockdown. It has been observed from Bgure 3 that there is an increase in the concentration of air pollutants during phases III and IV as compared to the other phases. Two major reasons for this increase are the burning of Rabi crop residue and dust storm in the month of May. Thus, dust events might have contributed for enhancement of PM 2.5 and PM 10 concentration during phase III and IV (Yadav et al. 2017; Sarkar et al. 2019) . It is observed that there is an increase in the concentration of O 3 March onwards, but when this trend was compared with the previous year, it has been noticed that a similar trend is there in 2019. Figure 4 represents the percentage change in all the pollutants for the selected cities of Punjab after lockdown (phase I). It is observed that most significant decline in Ludhiana for PM 2.5 , PM 10 , NO 2 and CO was 54.8%, 54.8%, 60.7% and 64.5%, respectively. The maximum reduction in the level of SO 2 in Mandi-Gobindgarh after lockdown (phase I) was 62.1%. But the concentration of O 3 increases by 46.6% in Ludhiana. From March onwards, meteorological parameters also change significantly with time. So one may also conclude that the decrease in the concentration of the major air pollutants is due to this change in meteorological parameters. Therefore, we have examined the variation in the concentration of major air pollutants for four phases of the lockdown in 2020 and compared with the corresponding periods in 2019. It has been observed from Bgure 5(a-q) that during 2019, there is no significant change in the mean concentration of almost all the air pollutants from March to May for the selected cities of Punjab. It is also investigated that in 2019, the concentration of some air pollutants has shown increasing trend from March to April. But on the other hand, in 2020 there is significant decrease in the concentration of all major air pollutants before and after lockdown (phase I). Thus, this decrease is attributed solely to the lockdown imposed in 2020 rather than the changes in meteorological parameters. It is observed from Bgure 5(d) that NO 2 in Ludhiana shows much higher concentration in 2020 with respect to 2019 during lockdown phase. The increase in NO 2 concentrations over Ludhiana may be due to large industries.

To study the inCuence of long-range transport of atmospheric pollutants, the air mass back trajectory analysis was performed at all the three sites. The average values of all the major pollutants showed a significant decrease after lockdown. It is observed that the air motion is mostly in northwest and west direction travelled from Afghanistan, Tajikistan and Pakistan via Rajasthan to Punjab (Bgure 6). The air quality for the three cities was significantly inCuenced by long-range transport. The seasonal pattern of air mass trajectories over Patiala site has been examined in a previous study (Bansal et al. 2019) .

COVID-19 has aAected adversely public health and the economy worldwide. On the other side, it has positive impact on nature as air pollution after lockdown has significantly reduced. In the present study, the eAect of various phases of lockdown on the air quality of three major polluted cities of Punjab has been investigated. It is observed that there is a significant decrease in the levels of PM 2.5 , PM 10 , NO 2 and SO 2 for the three cities after phase I lockdown. Furthermore, the two most polluted cities Ludhiana and Mandi-Gobindgarh showed the maximum decrease in key air pollutants after lockdown (phase I). It has been observed that during the month of May (phases III and IV), level of air pollution arises due to relaxations in lockdown as well burning of rabi crop residue. It is also observed that after lockdown the concentration of O 3 has increased for the three selected cities. The rise in concentration of O 3 could be due to increase in solar radiation. By comparing the data for the same periods in 2019, it is concluded that decrease in the concentration of air pollutants is mainly due to lockdown implemented. With the decrease in air pollution, many health issues like cardiovascular and respiratory diseases can be significantly reduced. As per the WHO report, around *7 million of the premature deaths globally are due to air pollution. So, with the decrease in air pollution due to lockdown can reduce mortality due to pollution. By taking lesson from this situation, state and central governments can formulate a strategy to reduce air pollution. The responsibility of the citizens is to avoid undue contribution to air pollution. People could be motivated to celebrate 'No Vehicle Day' once a month.

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Authors are thankful to reviewers for their valuable suggestions. Authors are also thankful to Central Pollution Control Board, New Delhi and Punjab Pollution Control Board, Patiala.

Manish Garg: Conceptualization, methodology, investigation, data curation, writing manuscript. Sujata Goyal: Supervision, conceptualization. Onam Bansal: Writingreviewing and editing.