Impact of COVID-19 lockdown on air quality in Chandigarh, India: Understanding the emission sources during controlled anthropogenic activities

Abstract

The variation in ambient air quality during COVID-19 lockdown was studied in Chandigarh, located in the Indo-Gangetic plain of India. Total 14 air pollutants, including particulate matter (PM ₁₀, PM _2.5), trace gases (NO ₂, NO, NO _x, SO ₂, O ₃, NH ₃, CO) and VOC's (benzene, toluene, o-xylene, m,p-xylene, ethylbenzene) were examined along with meteorological parameters. The study duration was divided into four parts, i.e., a) 21 days of before lockdown b) 21 days of the first phase of lockdown c) 19 days of the second phase of lockdown d) 14 days of the third phase of lockdown. The results showed significant reductions during the first and second phases for all pollutants. However, concentrations increased during the third phase. The concentrations of SO ₂, O _3, and m,p-xylene kept on increasing throughout the study period, except for benzene, which continuously decreased. The percentage decrease in the concentrations during consecutive periods of lockdown were 28.8 %, 23.4 % and 1.1 % for PM _2.5 and 36.8 %, 22.8 % and 2.4 % for PM ₁₀ respectively. The Principal Component Analysis (PCA) and characteristic ratios identified vehicular pollution as a primary source during different phases of lockdown. During the lockdown, residential sources showed a significant adverse impact on the air quality of the city. Regional atmospheric transfer of pollutants from coal-burning and stubble burning were identified as secondary sources of air pollution. The findings of the study offer the potential to plan air pollution reduction strategies in the extreme pollution episodes such as during crop residue burning period over Indo-Gangetic plain.

Graphical abstract

Highlights

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  Studied impact of COVID-19 lockdown phases on 20 air quality parameters.

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  Reduction in pollutants linked with meteorology and emissions.

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  Increasing O ₃ was linked with atmospheric reactivity.

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  Key emission sources identified were vehicles, coal power plants.

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  VOCs variations shows association with regional emissions e.g. biomass burning.