Characterization of Aerosol Properties in the Delhi Region During the Biomass Burning and Subsequent Hudhud Cyclone
摘要
The physicochemical and optical attributes of aerosols (PM10) in the Delhi, National Physical Laboratory (NPL) [28.70°N; 77.10°E] region were examined during Biomass Burning (BB) and Subsequent Hudhud Cyclone (HC) in October 2014. Advanced offline characterization techniques, including Scanning Electron Microscope coupled with Energy Dispersive X-ray spectroscopy (SEM–EDS) and Wavelength Dispersive X-ray Fluorescence Spectroscopy (WD-XRF), were employed to probe particle morphology and chemical composition. Vertical profile data was obtained utilizing a dual-polarized micro-pulse lidar (MPL) system stationed at NPL. SEM–EDS analysis revealed the prevalence of carbon-rich spherical/core–shell aerosol particles attributed to the long-range transportation from BB activities in Punjab and Haryana. Frequency distribution analysis of the Aspect Ratio (AR), indicative of particle non-sphericity, shows that the majority of particles (~ 65%) fell within the AR range of 1.0–1.2, confirming the predominance of spherical/smooth particles during BB. During the HC, these particles transformed into non-spherical shapes upon mingling with moisture-laden sea aerosol spray particles predominantly composed of sea salts, exhibiting frequency distributions with peaks at AR range > 1.2–1.4 and > 1.6–1.8, and demonstrating a higher LDR value of ~ 4.7% (relative to ~ 3.7% during BB). WD-XRF analysis corroborated these findings, revealing an increase in Na and Cl element concentrations (avg.) from 6.54 to 7.52% and 0.63 to 1.03%, respectively, during the HC. Aerosol backscatter coefficient (ABC) values at 1.5 km (relative to that of lower altitudes i.e., 1 and 0.5 km) altitude during the HC were observed to be increased i.e., 0.052 km−1sr−1 owing to the predominance of particles with sea origins.