Atmospheric aerosol chemistry and source apportionment of PM10 using stable carbon isotopes and PMF modelling during fireworks over Hyderabad, southern India.

This study examined the influence of fireworks on atmospheric aerosols over the Southern Indian city of Hyderabad during festival of Diwali using mass closure, stable carbon isotopes and the EPA-PMF model. Identification of chemical species in day and night time aerosol samples for 2019 and 2020 Diwali weeks showed increased concentrations of NH, NO, SO, K, organic carbon (OC), Ba, Pb and Li, which were considered as tracers for fireworks. PM source apportionment was done using inorganic (trace elements, major ions) and carbonaceous (organic and elemental carbon; OC & EC) constituents, along with stable isotopic compositions of TC and EC. K/Na ∼1 and K/OC > 0.5 indicated contribution from fireworks. High NO, NH, Na, Cl and SO suggested the presence of deliquescent salts NaCl, NHNO and (NH)SO TAE/TCE >1 suggested H exclusion, indicating possible presence of HSO and NHHSO in the aerosols. Ba, Pb, Sb, Sr and Fe increased by 305 (87), 12 (11), 12 (3), 3 (2) and 3 (4) times on Diwali nights, compared to pre-Diwali of 2019 (2020), and are considered as metallic tracers of fireworks. δC and δC in aerosols closely resembled that of diesel and C plant burning emissions, with meagre contribution from firecrackers during Diwali period. The δC was relatively depleted than δC and δC. For both years, δC (δC - δC) were positive, suggesting photochemical aging of aerosols during long-range transport, while for pre-Diwali 2019 and post-Diwali 2020, δC were negative with high OC/EC ratio, implying secondary organic aerosols formation. High toluene during Diwali week contributed to fresh SOA formation, which reacted with precursor C, leading to C depletions. Eight-factored EPA-PMF source apportionment indicated highest contribution from residue/waste burning, followed by marine/dust soil and fireworks, while least was contributed from solid fuel/coal combustion.