Fireworks: A Major source of elemental aerosols during Diwali in Delhi-NCR

Fireworks activities worldwide seem to play a significant role in air quality degradation, especially during different events that lead to worsening air quality in the form of ambient particulate matter (PM) pollution. The fireworks activity in Delhi is one of the primary cause for the considerable increase in the particulate concentration during Diwali in Delhi. The substantial increase due to extensive firework activity results in enhanced metal concentration in the atmosphere. Therefore a comprehensive understanding of fireworks induced into the atmosphere is crucial to develop an enhanced mitigation strategy. Thus this study focuses on the comparative analysis of fireworks used in Diwali for the years 2019, 2020 and 2021. The current analysis studies the impact of Diwali for three consecutive years on the concentration, composition, and sources of ambient PM2.5. The measurement of elements in PM2.5 was performed with half-hourly time resolution using the Xact 625 Ambient Metals Monitor. The 12-hour average concentration of metals during Diwali night for 2019, 2020 and 2021 are 181 ug/m3, 117 ug/m3, and 151 ug/m3, respectively. Concentration levels of species like K, Al, Sr, Ba, and S displayed distinct peaks during the firework event and were identified as tracers for the same. We conducted source apportionment by positive matrix factorization (PMF) of the elemental mass measurable by the Xact. The source apportionment study indicated that more than 85% of elemental mass had been apportioned to firecrackers during Diwali. The reported enhancement in the mass concentration of elemental metals like Al, Ba, Cl, Pb, and Mn poses a severe threat to the health of the exposed population as the average mass concentration of these species exceeded the standard EPA risk-based levels by orders of magnitude during the Diwali phase. Moreover, possible carcinogens like As also exceeded the risk-based concentration significantly.