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arXiv · 2011.08140

Variation in chemical composition and sources of PM2.5 during the COVID-19 lockdown in Delhi

Chirag Manchanda·Mayank Kumar·Vikram Singh·Mohd Faisal·Naba Hazarika·Ashutosh Shukla·Vipul Lalchandani·Vikas Goel·Navaneeth Thamban·Dilip Ganguly·Sachchida Nand Tripathi
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Abstract

The Government of India (GOI) announced a nationwide lockdown starting 25th March 2020 to contain the spread of COVID-19, leading to an unprecedented decline in anthropogenic activities and in turn improvements in ambient air quality. This is the first study to focus on highly time-resolved chemical speciation and source apportionment of PM$_{2.5}$ to assess the impact of the lockdown and subsequent relaxations on the sources of ambient PM$_{2.5}$ in Delhi, India. The elemental, organic, and black carbon fractions of PM$_{2.5}$ were measured at the IIT Delhi campus from February 2020 to May 2020. We report source apportionment results using positive matrix factorization (PMF) of organic and elemental fractions of PM$_{2.5}$ during the different phases of the lockdown. The resolved sources such as vehicular emissions, domestic coal combustion, and semi-volatile oxygenated organic aerosol (SVOOA) were found to decrease by 96%, 95%, and 86%, respectively, during lockdown phase-1 as compared to pre-lockdown. An unforeseen rise in O$_3$ concentrations with declining NO$_x$ levels was observed, similar to other parts of the globe, leading to the low-volatility oxygenated organic aerosols (LVOOA) increasing to almost double the pre-lockdown concentrations during the last phase of the lockdown. The effect of the lockdown was found to be less pronounced on other resolved sources like secondary chloride, power plants, dust-related, hydrocarbon-like organic aerosols (HOA), and biomass burning related emissions, which were also swayed by the changing meteorological conditions during the four lockdown phases. The results presented in this study provide a basis for future emission control strategies, quantifying the extent to which constraining certain anthropogenic activities can ameliorate the ambient air.

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Chirag Manchanda, Mayank Kumar, Vikram Singh, Mohd Faisal, Naba Hazarika, Ashutosh Shukla, Vipul Lalchandani, Vikas Goel, Navaneeth Thamban, Dilip Ganguly, Sachchida Nand Tripathi. 2020-11-16. Variation in chemical composition and sources of PM2.5 during the COVID-19 lockdown in Delhi. https://doi.org/10.1016/j.envint.2021.106541

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