Long term assessment of firework emissions and air quality during Diwali festival and impact of 2020 fireworks ban on air quality over the states of Indo Gangetic Plains airshed in India

Abstract

The study assesses 13 air pollutants, including VOCs from fireworks during the Diwali festival from 2017 to 2020, in six Indo Gangetic Plains (IGP) states. Percentage increase in 8-h average nighttime concentrations on Diwali compared to the previous night and Pearson correlation analysis were used to assess the pollutants emitted from fireworks. Stubble burning (SB) season in IGP coincides with Diwali festival every year and its influence on ambient air during Diwali was also checked. Air quality on Diwali had an additional effect of SB emissions during all years and maximum was observed in 2018. Results showed that PM2.5 and SO2 are emitted as major fractions from fireworks. NH3, NO and ethyl-benzene were also prominent in firework emissions but in lesser proportions. The highest hourly PM2.5 concentration was found above 900 μg/m3 in 2017 in Delhi. Ozone rarely showed an increase and was negatively correlated with all pollutants during all years. Only PM2.5, among the major emissions from fireworks, showed significant Long-Range Transport (LRT) in IGP. NO, CO and PM2.5 in years which had more stubble burning, showed their regional transport to lower IGP due to their longer atmospheric lifetimes and meteorology. These same years had an excessive increase in NO and CO concentrations on Diwali. The combined effect of SB with firework emissions resulted in more elevated trends for the coming days. The years with maximum fireworks were 2019 in Punjab and Haryana, 2017 in Delhi and 2018 in Uttar Pradesh, Bihar and West Bengal. In 2020, least fireworks were observed among all states, showing the positive effects of a ban on burning fireworks in the whole airshed of IGP. The study fills the gap in evaluating the combined impact of Diwali fireworks and SB emissions on the air quality of IGP airshed, which was missing in the literature.