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

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.

Air Quality in Six Northern Indian Cities During Diwali 2020: The Real Tragedy in Disguise

North Indian cities have been highly polluted, especially in winters, which coincide with the Diwali festival. This year, the government imposed ban on the burning of firecrackers. This study was undertaken from 4th-21st November, 2020 to monitor the air quality variation with respect to PM10 and PM2.5 for Delhi, Lucknow, Ghaziabad, Muzaffarnagar, Greater Noida and Bulandshahar cities during and post Diwali period, to know whether there was any impact of the warnings. The hourly variations in the AQI were very poor between 8:00 p.m.-10:00 p.m. on Diwali day. Significant short term variation in the AQI was observed during the night. A weak positive correlation was obtained between the temperature and AQI, whereas a negative relationship was established with humidity. As compared to last year’s AQI, higher values were obtained this year. The short-term variation in air quality may prove crucial in future in the wake of COVID-19 pandemic.

Source Contribution of Firecrackers Burst vs. Long-Range Transport of Biomass Burning Emissions Over an Urban Background

This study reports on the high-resolution data set of ground-level O3, surface-bound polycyclic aromatic hydrocarbons (SB-PAHs), and particle's number concentrations (range: 10 to 1,000 nm, referred to as condensation nucleus concentration: CNC) during a Diwali festival campaign (conducted from 08th to 16th Nov.2015) at Kanpur location. In this study, we have made an attempt to assess the change in atmospheric composition and chemistry (based on SB-PAHs, O3, and CNC) during Diwali festival (11th Nov.) and compared the results with pre-Diwali (08th−10th Nov.) and post-Diwali (12th−16th Nov.) scenarios. The wind pattern and cluster analysis have revealed a quite similar feature that from 10th to 16th of November the prevailed winds were north-westerly (NW). It is noteworthy that NW-winds during post-monsoon season (Oct–Nov) favors the long-range transport of biomass burning emissions (LRT-BB) from its source region in upwind Indo-Gangetic Plain (IGP). The influence of LRT-BB emissions at the receptor site during Diwali and post-Diwali period was reflected by the substantial increase in average concentrations of PM2.5, O3 and CNC (difference has been ascertained from a two-tailed t-test). The Lenshchow-type analysis revealed that the firecrackers (FC) burst and LRT-BB emissions have lead to increase the concentrations of CNC by 54% and 86%, respectively over the urban background level. On the other hand, the FC burst and LRT-BB increased the concentrations of O3 by 12% and 31% (over the urban background), respectively. Lenschow-type analysis revealed that FC burst and LRT-BB increased the daily PM2.5 concentration by 11% and 36%, respectively over its urban background level (286 μg m−3). However, the SB-PAHs concentrations were found to be decreased by 6% and 2%, respectively, during the FC burst activity and LRT-BB emissions. Based on the observations pertaining to the decrease in SB-PAHs concentrations from the Lenschow-type analysis and anti-correlation between SB-PAHs and O3 the heterogeneous-phase chemical reactivity and loss of SB-PAHs has been inferred in this study.