Chemical speciation of aerosols and air quality degradation during the festival of lights (Diwali)

Özet

Ambient PM2.5 (particulate matter less than 2.5 mm) samples, collected in a 8-week wintertime samplingprogram in two residential sites of Bhilai, India during the Indian Diwali festival in November 2012, werechemically characterized for 38 chemical species including eight speciated carbonaceous fractions (SCFs)of elemental (EC) and organic carbon (OC), twenty one metallic elements, and nine water soluble ionicspecies. Our objectives were to investigate: 1) relative abundances of SCFs contained in PM2.5during theDiwali festival period compared to normal days, and 2) enrichment pattern of potential inorganicmarkers of firework emission in ambient PM2.5during the festival days. Eight-fold increase inPM2.5massconcentrations were measured during the Diwali festival days compared to concentrations occurring innormal days. Bursting of firecrackers in the residential streets have shown significant contribution to theemission markers (K, Mg, Zn, S, EC and OC) along with crustal markers (Ca, Fe, Al) in ambientPM2.5aerosol samples. Concentrations of water soluble ionic species were found to be 10 times greaterthan those found in normal days. Further, the anion/cation ratios were found to reach a factor of 2;indicating the acidic character of emissions resulting from fireworks. The relative abundance of SCFs andhigher ratios of OC to EC during the Diwali episode suggested the significant formation of secondaryorganic carbon (SOC) aerosols. We estimate that aerosols emitted from firework bursting contribute up to32% of total ambient PM2.5 during the Diwali festival.