Chemical speciation of respirable suspended particulate matter during a major firework festival in India

Abstract

Ambient respirable particles (PM≤10μm, denoted by PM10) were characterized with respect to 20 elements, 16 polycyclic aromatic hydrocarbons (PAHs), elemental and organic carbon (EC and OC) during a major firework event—the “Diwali” festival in Delhi, India. The event recorded extremely high 24-h PM10 levels (317.2–616.8μgm−3, 6–12 times the WHO standard) and massive loadings of Ba (16.8μgm−3, mean value), K (46.8μgm−3), Mg (21.3μgm−3), Al (38.4μgm−3) and EC (40.5μgm−3). Elemental concentrations as high as these have not been reported previously for any firework episode. Concentrations of Ba, K, Sr, Mg, Na, S, Al, Cl, Mn, Ca and EC were higher by factors of 264, 18, 15, 5.8, 5, 4, 3.2, 3, 2.7, 1.6 and 4.3, respectively, on Diwali as compared to background values. It was estimated that firework aerosol contributed 23–33% to ambient PM10 on Diwali. OC levels peaked in the post-Diwali samples, perhaps owing to secondary transformation processes. Atmospheric PAHs were not sourced from fireworks; instead, they correlated well with changes in traffic patterns indicating their primary source in vehicular emissions. Overall, the pollutant cocktail generated by the Diwali fireworks could be best represented with Ba, K and Sr as tracers. It was also found that chronic exposure to Diwali pollution is likely to cause at least a 2% increase in non-carcinogenic hazard index (HI) associated with Al, Mn and Ba in the exposed population.