Spatio-temporal concentration of atmospheric particulate matter (PM2.5) during pandemic: A study on most polluted cities of indo-gangetic plain (original) (raw)
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Current Science
In this study, we investigate the impact of the COVID-19 pandemic on PM 2.5 levels in the national capital city Delhi, India. PM 2.5 and meteorological data from 35 ground-based monitoring stations over Delhi city are utilized for the present study. Geographic Information System-based spatial interpolation method was employed to analyse the spatial pattern of PM 2.5 from January to April 2020 and compared with that of preceding years (2018-19). The findings indicate that the PM 2.5 level has reduced significantly during the lockdown period. About 40% of reduction in PM 2.5 concentrations is observed when compared to the prelockdown phase. Exclusively between 25 March and 30 April, about 94.44% of days were within the NAAQS 24-h standard limit of 60 μg/m 3. The significant role of meteorology in the dispersal of PM 2.5 over Delhi is clear from the correlation analysis. A strong negative correlation (r =-0.546) between the Temp and PM 2.5 indicates the better dispersion of air pollutants during high-temperature conditions. A higher reduction in PM 2.5 has been observed in Central, Northern and Eastern parts of the megacity. The present study provides insights to policymakers to prepare and implement future policy measures for controlling air pollution levels in the megacity.
Air Quality, Atmosphere & Health
Lockdown in India begins from 25 March and continues until 31 May 2020 due to the COVID-19 pandemic situation. Due to such an extended period of lockdown for about more than 2 months resulted in 1.38 billion populations restricted themselves from mass activities that contribute to air pollution. Thus, through our quantitative approach and trend analysis, the study aims to evaluate the changes in the level of PM 2.5 as a major pollutant for the top ten polluted cities in India, with a special emphasis on finding what happened to its concentration after the lockdown ended. Thus, to better understand the nature of variation in PM 2.5 , we divide the entire 7 months into three periods for our analysis, i.e., before lockdown (1 January to 24 March), during lockdown (25 March to 31 May), and post-lockdown or unlock 1 and 2 (1 June to 31 July). Our investigation reveals that before lockdown, all the top polluted cities of India violating the national standard of PM 2.5 , as the lockdown begins interestingly, all cities show a momentous reduction in PM 2.5 concentration. Further, surprisingly we found that after the post-lockdown period, the concentration of PM 2.5 was reduced to minimal, as the average concentration of PM 2.5 for all the cities is below the National Ambient Air Quality Standard (NAAQS). The study reveals that the lockdown has a consequence in improving overall air quality for the top polluted cities in India and further lockdown in the future with proper planning should be considered an alternative approach to restrain excessive emissions.
Stochastic Environmental Research and Risk Assessment
The outbreak of COVID-19 pandemic has impacted all the aspects of environment. The numbers of COVID-19 cases and deaths are increasing across the globe. In many countries lockdown has been imposed at local, regional as well as national level to combat with this global pandemic that caused the improvement of air quality. In India also lockdown was imposed on 25th March, 2020 and it was further extended in different phases. The lockdown due to outbreak of COVID-19 pandemic has showed substantial reduction of PM 2.5 concentrations across the cities of India. The present study aims to assess concentration of PM 2.5 across 12 cities located in different spatial segments Indo-Gangetic Plain (IGP). The result showed that there was substantial decrease of PM 2.5 concentrations across the cities located in IGP after implementation of lockdown. Before 30 days of lockdown, average PM 2.5 across cities was 65.77 lg/m 3 that reached to 42.72 lg/m 3 during lockdown periods (decreased by 35%). Maximum decrease of PM 2.5 concentrations has been documented in Lower Gangetic Plain (LGP) cities (57%) followed by Middle Gangetic Plain (MGP) cities (34%) and Upper Gangetic Plain (UGP) cities (27%) respectively. Among all the cities of IGP, maximum decrease of PM 2.5 concentrations was recorded in Kolkata (64%) (LGP) followed by Muzaffarpur (53%) (MGP), Asansol (51%) (LGP), Patna (43%) (MGP) and Varanasi (33%) (MGP).Therefore, this study has an immense potentiality to understand the impact of lockdown on a physical region (Ganga River Basin) and it may be also helpful for planners and policy makers to implement effective measures at regional level to control air pollution.
Short-term impacts of air pollutants in three megacities of India during COVID-19 lockdown
Environment, Development and Sustainability, 2021
Lockdown was imposed by the Indian government in the month of March 2020 as an early precaution to the COVID-19 pandemic which obstructed the socioeconomic growth globally. The main aim of this study was to analyse the impact of lockdown (imposed in March and continued in April 2020) on the existing air quality in three megacities of India (Delhi, Mumbai and Kolkata) by assessing the trends of PM 10 and NO 2 concentrations. A comparison of the percentage reduction in concentrations of lockdown period with respect to same period in year 2019 and pre-lockdown period (February 14-March 24) was made. It was observed from the study that an overall decrease of pollutant concentrations was in the ranges of 30-60% and 52-80% of PM 10 and NO 2 , respectively, in the three cities during lockdown in comparison with previous year and pre-lockdown period. The overall decrease in concentrations of pollutants at urban sites was greater than the background sites. Highest decline in concentrations of PM 10 were observed in Kolkata city, followed by Mumbai and Delhi, while decline in NO 2 was highest in Mumbai. Results also highlighted that capital city Delhi had the worst air quality amongst three cities, with particulate matter (PM 10) being the dominant pollutant. Although COVID-19 has significantly affected the human life considering the mortality and morbidity, lockdowns imposed to control the pandemic had significantly improved the air quality in the selected study locations, although for the short amount of period.
Applied Journal of Environmental Engineering Science, 2021
Particulate matter is the pollutant generally viewed as most unsafe to human wellbeing. Its minuscule size permits the particles to enter the circulation system by means of respiration, causing asthma and heart disease. COVID-19 has been declared as a Public Health Emergency of International Concern by WHO on 30th January 2020. The objectives of the present study include air quality (with respect to PM2.5 and PM10) monitoring at pre-selected locations during and post COVID- 19 phase, comparative assessment of air quality parameters PM2.5 and PM10 concentrations in Delhi during and post COVID-19. To conduct this study the station for air quality monitoring selected is near Hauz Khas metro station, Delhi. Total 4 locations are selected around CPCB Air pollution monitoring station, Hauz Khas. PM sampling has been done for 12 continuous days. The dataset of the time frame (March and April of 2020) of the lockdown phase is collected from CPCB and compared with the dataset of the same time frame (March and April 2021) using excel software. The pollution level drastically increases after the lockdown phase according to present observation and improvement in air quality could not last long after the reopening of industries and vehicular activities.
Environmental Science and Pollution Research
The impact of restrictions during various phases of COVID-19 lockdown on daily mean PM 2.5 concentration in five Indian megacities (New Delhi, Chennai, Kolkata, Mumbai, and Hyderabad) was studied. The impact was studied for pre-lockdown (1st Mar-24th Mar 2020), lockdown (25th Mar-31st May 2020), and unlocking (1st Jun-31st Aug 2020) phases. The lockdown period comprises 4 lockdown phases with distinct measures, whereas the unlocking period had 3 phases. PM 2.5 concentration reduced significantly in all megacities and met the national standards during the lockdown period. The maximum reduction in PM 2.5 level was observed in Kolkata (62%), followed by Mumbai (49%), Chennai (34%), and New Delhi (26%) during the lockdown period. Comparatively, Hyderabad exhibited a smaller reduction in PM 2.5 concentration, i.e., 10%. The average PM 2.5 levels during the lockdown in the peak hour (i.e., 07:00−11:00 h) in New Delhi, Chennai, Kolkata, Mumbai, and Hyderabad decreased by 21.3%, 48.5%, 63.4%, 56.4%, and 23.8%, respectively, compared to those before lockdown period. During the unlocking period, except for Chennai, all megacities showed a reduction in average PM 2.5 levels compared to concentrations in the lockdown period, but these reductions were mainly linked with monsoon rains in India. The current study provided an opportunity to study air pollution in the absence of major anthropogenic activities and during limited activities in monsoon season having an ecological design. The study reports a new baseline of PM 2.5 , except for monsoon, and explores this knowledge to plan future air pollution reduction strategies. The study also discusses how this new learning of knowledge could strengthen air pollution control policies for better air quality and sustainability. Keywords COVID-19. Coronavirus. Lockdown. Air quality. Megacities. PM 2.5 Highlights • Studied the impact of COVID-19 lockdown on PM 2.5 levels in five Indian megacities • An ecological study design in the absence of major anthropogenic activities • A fall of 10 to 62% was noticed in all five Indian megacities during lockdown. • Peak hours PM 2.5 levels during lockdown decreased by 21.3 to 63.4% compared to pre lockdown period. • The study identifies a new baseline level of PM 2.5 except observed during monsoon. • The study aims to support short-and long-term air pollution reduction strategies.
Environmental Science and Pollution Research, 2020
The present work aims to investigate seasonal variations in air pollution levels in Lucknow and assess the ambient air quality of the city together with highlighting the health impacts of major pollutants like PM 10 , PM 2.5 , SO 2 , NO 2 , Pb, Ni and aerosols from 2010 to 2019. The maximum and minimum values of PM 10 , PM 2.5 , SO 2 , NO 2 , Pb and Ni were found to be 270.75 and 122.45 μg/m 3 , 124.95 and 95.52 μg/m 3 , 25.60 and 8.05 μg/m 3 , 75.65 and 23.85 μg/m 3 , 0.66 and 0.03 μg/m 3 and 0.07 and 0.01 ng/m 3 , respectively. Health impact of particulate matter has also been assessed with AirQ+, and it was estimated that long-term exposure of PM 10 was attributed to between 37 and 48% for post-neonatal (age 1-12 months) mortality rate due to all causes, whereas longterm attributable proportions in mortality due to exposure of PM 2.5 were to about 19 to 28% from all causes. Further, an attempt has also been made to evaluate the impact of lockdown amid COVID-19 on the ambient air quality of Lucknow. During the lockdown, PM 2.5 levels reduced by 65% (at Gomti Nagar), 23% (at central school), 79% (at Lalbagh) and 35% (at Talkatora), due to which, air quality index of Gomti Nagar came down to 43, well below 50 which falls in the healthy range. NO 2 levels also came down. However, levels of SO 2 did not show significant reduction. Correlating the data between aerosol optical depth and Angstrom exponent by Pearson correlation analysis revealed a significant positive correlation (r = 0.65, P < 0.001). Keywords Air pollution. Aerosol. AirQ+. Lockdown. AQI. Health effect Highlights • Spatio-temporal assessment of various pollutants like PM 10 , PM 2.5 , SO 2 , NO 2 , Pb, Ni and atmospheric aerosols from 2010 to 2019 was performed. • AQI score for most of the studied locations was found in the poor category. • During the lockdown, AQI scores decreased to well below 50, in the healthy range. • High AE value was observed in October to November because of stubble burning during the harvest season in Northern India. • The health impact of air pollutants was estimated using AirQ+ software. • Long-term exposure to PM 2.5 to ambient air increased the risk of stroke by 20%.
COVID-19 and Air Pollution in Indian Cities: World’s Most Polluted Cities
Aerosol and Air Quality Research
In the present study, pollutants levels from 24 th March-31 st May in 2020 were compared with the same time period in 2019 to estimate the impact of lockdown on air pollutants levels in 39 different cities of India (including 10 Indian cities considered among the world's 20 most polluted cities). Data for air pollutants was obtained from the Central Pollution Control Board (CPCB) which was statistically analyzed. Tropospheric NO2 column retrieved from Ozone Monitoring Instrument (OMI) were compared between 2019 and 2020 to compare the NO2 levels. Impact of lockdown measures on Ghaziabad which is the world's most polluted city and Patiala which showed maximum reduction during the lockdown period in the present study was studied in detail. After the implementation of lockdown measures, air pollution decreased but with substantial variation among pollutants. The most significant reduction was observed for nitrogen dioxide (NO2) (3-79%) and carbon monoxide (CO) (2-61%), pollutants which are mainly related to traffic emissions. Ozone (O3) showed a mixed trend with increasing levels at some cities which may be attributed to lower titration of O3 by NO. Maximum reduction observed in PM10 and PM2.5 was 58 and 57%, respectively during the lockdown period in 2020 as compared to the previous year. Air quality of the cities also improved in 2020. During the lockdown period in 2020, AQI of only 15% of cities was in the 'Unhealthy' category (151-200) while in 2019, 56% of cities were in the 'Unhealthy' category. In Ghaziabad and Patiala all the pollutants showed significant reduction after lockdown implementation except O3. Diurnal patterns of PM10, PM2.5, CO and NO2 showed lower values during lockdown period in 2020 with less distinct bimodal patterns as compared to 2019. The present study provides evidence that widespread implementation of air pollution measures can result in immediate air quality benefits.
Environmental Science and Pollution Research, 2021
The megacities experience poor air quality frequently due to stronger anthropogenic emissions. India had one of the longest lockdowns in 2020 to curb the spread of COVID-19, leading to reductions in the emissions from anthropogenic activities. In this article, the frequency distributions of different pollutants have been analysed over two densely populated megacities: Delhi (28.70° N; 77.10° E) and Kolkata (22.57° N; 88.36° E). In Delhi, the percentage of days with PM 2.5 levels exceeding the National Ambient Air Quality Standards (NAAQS) between 25 March and 17 June dropped from 98% in 2019 to 61% in 2020. The lockdown phase 1 brought down the PM 10 (particulate matter having an aerodynamic diameter ≤ 10 μm) levels below the daily NAAQS limit over Delhi and Kolkata. However, PM 10 exceeded the limit of 100 μgm −3 during phases 2-5 of lockdown over Delhi due to lower temperature, weaker winds, increased relative humidity and commencement of limited traffic movement. The PM 2.5 levels exhibit a regressive trend in the highest range from the year 2019 to 2020 in Delhi. The daily mean value for PM 2.5 concentrations dropped from 85-90 μgm −3 to 40-45 μgm −3 bin, whereas the PM 10 levels witnessed a reduction from 160-180 μgm −3 to 100-120 μgm −3 bin due to the lockdown. Kolkata also experienced a shift in the peak of PM 10 distribution from 80-100 μgm −3 in 2019 to 20-40 μgm −3 during the lockdown. The PM 2.5 levels in peak frequency distribution were recorded in the 35-40 μgm −3 bin in 2019 which dropped to 15-20 μgm −3 in 2020. In line with particulate matter, other primary gaseous pollutants (NO x , CO, SO 2 , NH 3) also showed decline. However, changes in O 3 showed mixed trends with enhancements in some of the phases and reductions in other phases. In contrast to daily mean O 3 , 8-h maximum O 3 showed a reduction over Delhi during lockdown phases except for phase 3. Interestingly, the time of daily maximum was observed to be delayed by ~ 2 h over Delhi (from 1300 to 1500 h) and ~ 1 h over Kolkata (from 1300 to 1400 h) almost coinciding with the time of maximum temperature, highlighting the role of meteorology versus precursors. Emission reductions weakened the chemical sink of O 3 leading to enhancement (120%; 11 ppbv) in night-time O 3 over Delhi during phases 1-3.