Effect of Diwali Firecrackers on Air Quality and Aerosol Optical Properties over Mega City (Delhi) in India

摘要

In this paper, the variations of aerosol properties due to crackers burning during Diwali event (11th–18th 2012) over mega city Delhi were investigated. The sky radiometer POM-2 aerosol optical property data from Skynet-India along with ambient air pollution data were critically analyzed. The aerosol optical depth (AOD) at 500 nm was 1.60 on 13th November, the Diwali day, and its value a maximum of 1.84 on 16th November. Due to stable atmosphere over Delhi during post Diwali, aerosols accumulate and remain in the atmosphere for longer time, which leads to higher AOD on 16th November. A lower value of single-scattering albedo (SSA) was observed at a longer wavelength (1020 nm) during the entire period that clearly indicates the dominance of absorbing-type black carbon aerosol. SSA showed a steep decrease after 16th November. Asymmetry parameter decreased to a maximum of 0.79 for the shorter wavelength at 340 nm and 0.632 is reported at the higher wavelength 1020 nm. Asymmetry parameter showed a decrease in value just after Diwali on 14th November, this suggesting the dominance of fine-mode aerosol from anthropogenic activities. The lowest value of the refractive index (1.4527) on 14th and 15th November indicates the higher loading of absorbing-type aerosol which may be associated with firecracker burning of Diwali festival. The significant correlation with the value of r = 0.9 was observed between sky radiometer and MODIS AOD with a standard deviation of 0.31 and an RMSE of 0.17 during the event. Radiative forcing and heating rate were estimated using SBDART. The maximum average concentrations 2641 and 1876 μg/m3 of PM10 and PM2.5, respectively, were observed on the Diwali night. A highest of 109 ppb surface ozone was reported in the night at 23:00 IST, which can be attributed to burning of the firecrackers.