Chemical Characterisation of Total Organic Carbon in PM10 Aerosols during a Festive Firework Event Using 1H NMR in Mumbai, India
SHWETA SAKPAL, Avik Kumar Sam, Shreya Dubey, Harish C Phuleria, Indian Institute of Technology, Bombay
Abstract Number: 590
Working Group: Carbonaceous Aerosols
Abstract
Background:
Diwali, celebrated worldwide, can be considered significant among many episodic events involving the substantial burning of fireworks associated with decreased air quality.
Objectives:
The present study aims to chemically characterize the total organic carbon in PM10 during Diwali using proton Nuclear Magnetic Resonance (1H NMR).
Materials and Methods:
PM10 aerosols were collected throughout the day in four periods (each 6h): morning, afternoon, evening, and night at an urban background location for two days: a day before and on the day of Diwali, in October 2022. The filters were extracted in water and methanol, followed by ultrasonication. The methanol-extracted filters were freeze-dried and redissolved in 0.03% w/v DSS-CD3OD for 1H NMR, while the water-extracted were subjected to TOC Analyser for Water-Soluble Organic Carbon (WSOC).
Results and Discussion:
High PM10 was observed throughout the sampling (2593.7±137.3 µg/m3), with the maximum reported on Diwali night (2858.1 µg/m3), while the WSOC was 232.26% higher than the non-Diwali night. The NMR analysis indicates that aliphatic groups (6072.9±1126.4 µmol/m3) are the dominant groups, followed by unsaturated structures (2947.1±653.8 µmol/m3) and the oxygenated groups (2294.2±305.5 µmol/m3), while the aromatic structures contributed the lowest resonances (362.1±97.4 µmol/m3). Diurnally, there was a decrease in concentrations from morning to afternoon, followed by an increase during the evening. Traffic activities are higher in the background during the morning, while the evening witnessed significant burning of firecrackers. On Diwali night, there were 51.1%, 185.1% and 170.3% increases in aliphatics, unsaturated and oxygenated groups compared to the previous night, while the aromatic structures decreased by 49.7%. In contrast, the aliphatics and aromatics on Diwali evening increased by 439.6% and 654.5% to the previous day. Our study highlighted the significant contribution of firecrackers towards the poor air quality observed while further analysis is underway.