Chaudhary Sudesh, Kumar Sushil, Antil Rimpi, Yadav Sudesh
Centre of Excellence for Energy and Environmental Studies, Deenbandhu Chhotu Ram University of Science and Technology, Murthal, India.
School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India.
J Health Pollut. 2021 May 28;11(30):210602. doi: 10.5696/2156-9614-11.30.210602. eCollection 2021 Jun.
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.
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, PM, nitrogen oxide (NO), sulfur dioxide (SO) and ozone (O)) compared to before lockdown (BLD) at 13 air monitoring stations in and around New Delhi.
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.
Pollutant concentrations decreased during LD1 compared to BLD except for O at all stations. PM and PM remained either close to or higher than the National Ambient Air Quality Standards (NAAQS) due to prevailing high-speed winds. During lockdown phases, NO decreased, whereas O consistently increased at all stations. This was a paradoxical situation as O is formed via photochemical reactions among NO 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, PM and NO were associated with PC1, whereas PC2 had loadings of either O only or O and SO depending upon monitoring station.
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.
The authors declare no competing financial interests.
新冠疫情对全球产生了深远影响，不仅在社会和经济层面，在人类健康和环境方面亦是如此。为限制病毒传播，印度政府于2020年3月25日至5月31日分阶段实施了全国范围的全面封锁，仅保留基本服务和物资供应。在此期间，世界上污染最严重的城市之一新德里及其周边地区的空气质量也受到了影响。
本研究旨在评估并了解新德里及其周边13个空气监测站在四个不同封锁阶段（LD1、LD2、LD3和LD4）与封锁前（BLD）相比，对五种空气污染物（颗粒物（PM）、PM、PM、氮氧化物（NO）、二氧化硫（SO）和臭氧（O））的影响。
从新德里中央污染控制委员会获取了2020年3月1日至5月31日期间新德里及其周边13个监测站的五种标准污染物的二级数据。对各封锁阶段、气象变量以及监测站周围主要空气来源的数据进行了统计分析。
与封锁前相比，除所有监测站的O外，LD1期间污染物浓度均有所下降。由于盛行高速风，PM和PM仍接近或高于国家环境空气质量标准（NAAQS）。在封锁阶段，NO下降，而所有监测站的O持续上升。这是一种自相矛盾的情况，因为O是通过NO与挥发性有机化合物之间的光化学反应形成的。主成分分析（PCA）提取了两个主成分（PC1和PC2），它们解释了数据中高达80%的累积方差。PM、PM和NO与PC1相关，而PC2的载荷根据监测站的不同，要么仅为O，要么为O和SO。
本研究发现，封锁阶段空气污染物浓度下降，但这些下降因地点和污染物而异。封锁期间污染物浓度的下降不能完全归因于封锁措施，因为与封锁前阶段相比，封锁期间行星边界层增加了两倍。未来可应用此类限制措施来控制空气污染，但应谨慎行事。
作者声明不存在相互竞争的财务利益。
