{"title":"Air Quality Before and After COVID-19 Lockdown Phases Around New Delhi, India.","authors":"Sudesh Chaudhary, Sushil Kumar, Rimpi Antil, Sudesh Yadav","doi":"10.5696/2156-9614-11.30.210602","DOIUrl":null,"url":null,"abstract":"<p><strong>Background: </strong>The COVID-19 pandemic has had a deep global impact, not only from a social and economic perspective, but also with regard to human health and the environment. To restrict transmission of the virus, the Indian government enforced a complete nationwide lockdown except for essential services and supplies in phases from 25 March to 31 May 2020. Ambient air quality in and around New Delhi, one of the most polluted cities of world, was also impacted during this period.</p><p><strong>Objective: </strong>The aim of the present study was to assess and understand the impact of four different lockdown phases (LD1, LD2, LD3 and LD4) on five air pollutants (particulate matter (PM) PM<sub>2.5</sub>, PM<sub>10</sub>, nitrogen oxide (NO<sub>x</sub>), sulfur dioxide (SO<sub>2</sub>) and ozone (O<sub>3</sub>)) compared to before lockdown (BLD) at 13 air monitoring stations in and around New Delhi.</p><p><strong>Methods: </strong>Secondary data on five criteria pollutants for 13 monitoring stations in and around New Delhi for the period 1 March to 31 May 2020 was accessed from the Central Pollution Control Bard, New Delhi. Data were statistically analyzed across lockdown phases, meteorological variables, and prevailing air sources around the monitoring stations.</p><p><strong>Results: </strong>Pollutant concentrations decreased during LD1 compared to BLD except for O<sub>3</sub> at all stations. PM<sub>2.5</sub> and PM<sub>10</sub> remained either close to or higher than the National Ambient Air Quality Standards (NAAQS) due to prevailing high-speed winds. During lockdown phases, NO<sub>2</sub> decreased, whereas O<sub>3</sub> consistently increased at all stations. This was a paradoxical situation as O<sub>3</sub> is formed via photochemical reactions among NO<sub>x</sub> and volatile organic compounds. Principal component analysis (PCA) extracted two principal components (PC1 and PC2) which explained up to 80% of cumulative variance in data. PM<sub>2.5</sub>, PM<sub>10</sub> and NO<sub>2</sub> were associated with PC1, whereas PC2 had loadings of either O<sub>3</sub> only or O<sub>3</sub> and SO<sub>2</sub> depending upon monitoring station.</p><p><strong>Conclusions: </strong>The present study found that air pollutants decreased during lockdown phases, but these decreases were specific to the site(s) and pollutant(s). The decrease in pollutant concentrations during lockdown could not be attributed completely to lockdown conditions as the planetary boundary layer increased two-fold during lockdown compared to the BLD phase. Such restrictions could be applied in the future to control air pollution but should be approached with caution.</p><p><strong>Competing interests: </strong>The authors declare no competing financial interests.</p>","PeriodicalId":52138,"journal":{"name":"Journal of Health and Pollution","volume":"11 30","pages":"210602"},"PeriodicalIF":2.4000,"publicationDate":"2021-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8276728/pdf/","citationCount":"4","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Health and Pollution","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.5696/2156-9614-11.30.210602","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2021/6/1 0:00:00","PubModel":"eCollection","JCR":"Q1","JCRName":"Medicine","Score":null,"Total":0}
引用次数: 4
Abstract
Background: The COVID-19 pandemic has had a deep global impact, not only from a social and economic perspective, but also with regard to human health and the environment. To restrict transmission of the virus, the Indian government enforced a complete nationwide lockdown except for essential services and supplies in phases from 25 March to 31 May 2020. Ambient air quality in and around New Delhi, one of the most polluted cities of world, was also impacted during this period.
Objective: The aim of the present study was to assess and understand the impact of four different lockdown phases (LD1, LD2, LD3 and LD4) on five air pollutants (particulate matter (PM) PM2.5, PM10, nitrogen oxide (NOx), sulfur dioxide (SO2) and ozone (O3)) compared to before lockdown (BLD) at 13 air monitoring stations in and around New Delhi.
Methods: Secondary data on five criteria pollutants for 13 monitoring stations in and around New Delhi for the period 1 March to 31 May 2020 was accessed from the Central Pollution Control Bard, New Delhi. Data were statistically analyzed across lockdown phases, meteorological variables, and prevailing air sources around the monitoring stations.
Results: Pollutant concentrations decreased during LD1 compared to BLD except for O3 at all stations. PM2.5 and PM10 remained either close to or higher than the National Ambient Air Quality Standards (NAAQS) due to prevailing high-speed winds. During lockdown phases, NO2 decreased, whereas O3 consistently increased at all stations. This was a paradoxical situation as O3 is formed via photochemical reactions among NOx and volatile organic compounds. Principal component analysis (PCA) extracted two principal components (PC1 and PC2) which explained up to 80% of cumulative variance in data. PM2.5, PM10 and NO2 were associated with PC1, whereas PC2 had loadings of either O3 only or O3 and SO2 depending upon monitoring station.
Conclusions: The present study found that air pollutants decreased during lockdown phases, but these decreases were specific to the site(s) and pollutant(s). The decrease in pollutant concentrations during lockdown could not be attributed completely to lockdown conditions as the planetary boundary layer increased two-fold during lockdown compared to the BLD phase. Such restrictions could be applied in the future to control air pollution but should be approached with caution.
Competing interests: The authors declare no competing financial interests.
期刊介绍：
The Journal of Health and Pollution (JH&P) was initiated with funding from the European Union and World Bank and continues to be a Platinum Open Access Journal. There are no publication or viewing charges. That is, there are no charges to readers or authors. Upon peer-review and acceptance, all articles are made available online. The high-ranking editorial board is comprised of active members who participate in JH&P submissions and editorial policies. The Journal of Health and Pollution welcomes manuscripts based on original research as well as findings from re-interpretation and examination of existing data. JH&P focuses on point source pollution, related health impacts, environmental control and remediation technology. JH&P also has an interest in ambient and indoor pollution. Pollutants of particular interest include heavy metals, pesticides, radionuclides, dioxins, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), air particulates (PM10 and PM2.5), and other severe and persistent toxins. JH&P emphasizes work relating directly to low and middle-income countries, however relevant work relating to high-income countries will be considered on a case-by-case basis.
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