Characteristics of submicron particles coming from a big firecrackers burning event: Implications to atmospheric pollution

Firecrackers burning on different occasions all over the world is a short-term big source of fine particles and their precursors in the air. This study presents the real-time changes in concentrations, composition and characteristics of non-refractory particulate matter smaller than 1 mu m aerodynamic diameter (NR-PM1), and black carbon (BC) during the Diwali festival, when a huge amount of firecrackers are burnt in India. Online measurements (1 min integration time) of organics, SO42-, NO3-, NH4+ and Cl- were performed using high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), and that of BC with seven wavelength aethalometer over a big urban city (Ahmedabad, 23.0 degrees N, 72.6 degrees E) in western India. A sharp increase (3-23 times higher) in the concentrations of all the measured species was observed on the evening of the Diwali that persisted overnight due to a combination of primary emissions and secondary formation of aerosol. Organics were the dominant contributor (similar to 85%) followed by SO42- (similar to 13%), Cl- (similar to 4%), NO3-(similar to 4%) and NH4+ (similar to 2%) to NR-PM 1 on the Diwali night. Further, variations in H/C and O/C ratios before, during and after the Diwali suggest fresh emissions of primary organics on the Diwali night, and highly oxidized secondary organic formation on the next day. Aerosol neutralization ratio (ANR, defined as the molar ratio of NH4+ to sum of SO42-, NO3- and Cl-), an indicative of aerosol acidity, reduced to as low as 0.1 on the Diwali night, which has implications to short-term acute atmospheric air pollution.