Particulate Oxidative Potential (OP) Associated with Fireworks Activity during Diwali at a site in the Indo-Gangetic Plain

Abstract

The potential of the atmospheric fine aerosols (PM2.5) to generate reactive oxygen species (ROS) during firework activity in Diwali festival was assessed by the dithiothreitol (DTT) assay at a site in the Indo-Gangetic Plain, India. The 12-h mean PM2.5 was found to be 262.9 ±150.7 µg m-3 during the study period which was 4.4 times exceeded the NAAQS limits. Firework activity was also characterized by increased levels of gaseous pollutants (NOx, SO2, CO and O3), and trace metal concentrations like Ba, Pb, Cu, Fe, Mg, K, Al and Mn. Elevated PM2.5-NOx slope for fireworks including traffic emissions suggested significant contribution of fireworks. The highest value of PM ROS activity, volume-based DTT value was 1.37 nmol min-1 m-3 and mass-based DTT value was 11.77 pmol min-1 μg-1, found in the next morning of Diwali, suggesting stronger PM associated ROS activity due to fireworks. A positive association was found between redox-active metals like Cd, Cr, Cu, Ni, and V and DTT activity that could be due to the ability of these metals to catalyze ROS generation in ambient air, while Ba, Be and Se in atmosphere as major constituents of firecrackers were also strongly associated with DTT activity. The ozone levels were strongly correlated (r2 = 0.87) with DTTv activity during daytime due to photochemical activities including chemical species associated with fireworks responsible for forming tropospheric O3. Comparison of the daily DTTv activity and hazard index (HI) suggests that the HI may be a poor metric to measure the health effects by which PM exposure can induce deterioration in human health.