Fingerprints of festive emissions on PM2.5 in an urban metropolis: Carbonaceous species, metals, and aerosol acidity

This study examines ambient PM_2.5 concentrations during major festivals in Kolkata, revealing levels that peaked at 246.9 μg m^-3, surpassing Indian and WHO air quality standards. High enrichments of particle-bound Copper (Cu) and Lead (Pb) indicated significant anthropogenic contributions, especially during festive periods. During festive days with extensive firecracker use, elemental carbon (EC) concentration was observed up to ∼111.5 μg m^-3, and secondary organic carbon (SOC) reached up to ∼45.9 μg m⁻³. During Diwali days, collected aerosol masses were consistently acidic (pH 4.4–4.8), apparently due to the presence of sulfate and nitrate from firecracker-emitted SO₂ and NOx, while higher pH values (5.82–6.4) were observed during the festive period without extensive fireworks.

The findings show that festival activities significantly raised ambient PM_2.5 levels, mainly due to fireworks during Diwali and combustion from rituals, commercial activities, and urban transport during Durga Puja. Future efforts should emphasise strict emission controls, eco-friendly celebrations, and long-term pollution monitoring.