(71e) PM2.5 bound Species Variation and Source Characterization in the Post-Lockdown Period of the Covid-19 Pandemic and Fireworks Period in National Capital of India

The rapid growth of industrialization and increase in energy demand has led to the significant deterioration of air quality. Long-term Exposure to high PM_2.5 levels can result in acute and chronic health effects in adults and children. Therefore, knowledge and identification of aerosol sources can be very helpful for making quality control strategies, aerosol health impacts and climate change effects. Delhi is one of the world's most polluted cities, with numerous severe air pollution episodes and haze events in recent years, this forces us to investigate the sources of air pollution to make effective mitigation technology. This work analyzes the PM_2.5 Highly bound time-resolved non-refractory and elemental compositions to observe the lag effects of the COVID-19 lockdown in the capital city of India. Here, a comparative scenario between lockdown and unlock periods along with previous years' work is presented. The following eight source profiles are identified from the source apportionment of elements such as power plant (35.6%), dust (25.7%), biomass burning (16.2%), vehicular emission (10%), secondary chloride (4%), waste incineration (3.6%), coal combustion (2.8%) and industrial emission (2.2%). The apportion sources of organic aerosol (OA) yielded two primary factors, primary organic aerosol (POA) and biomass burning organic aerosol (BBOA), and two secondary factors, oxygenated organic aerosols 1 and 2 (OOA-1 and OOA-2). The two oxygenated factors, OOA-1 and OOA-2 dominated the total OA mass concentration with 67.5% and 22% contribution, followed by POA and BBOA with 6.5% and 4%, respectively. In this work, the POA was found to be lower as compared to previous studies, and it was about 72% lower, as reported by Shukla et al. (2021). The significant reduction might be attributed to restrictions imposed by the government in the lockdown period. Also in order to study the short-term air quality degradation with very high-intensity episodic event , especially the worsening of air quality in the form of ambient particulate matter (PM) pollution, which has been observed to link as a result of the firework displays (FW) due to nationwide celebrations in different countries like the Diwali Festival in India, Independence Day in the United States, the Lantern and Spring Festivals in China, Guy Fawkes Night in the United Kingdom, and the New Year's Eve celebrations around the world. Fireworks activity is behind the substantial increase in particulate concentration during Diwali in Delhi and the concomitantly enhanced atmospheric metal concentration. Therefore, a comprehensive understanding of the impact of fireworks on the atmosphere is crucial to developing a mitigation strategy. Accordingly, this study focuses on the comparative analysis of fireworks events in Diwali across 2019, 2020, and 2021. The current analysis studies the impact of Diwali fireworks for three consecutive years on Delhi's composition, concentration, and ambient PM_2.5 sources. The measurement of elements in PM_2.5 is performed using automated ambient metals monitor with sufficient resolution to capture the time-variation during the fireworks event. Dispersion normalized PMF (DN-PMF) was also performed using the time-dependent ventilation coefficient to factor out the impact of meteorology across the three years. The average ventilation coefficient was 3672, 2874, and 2000 m² /s in 2019, 29 2020, and 2021, respectively. Nine different sources were identified for all three years. The study apportioned over 85% of elemental mass to the firecrackers during Diwali.