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Wintertime Chemistry of Ionic and Carbonaceous Species of Fine Aerosol Particles at an Arid Desert Region in North-Western India
SAYANTEE ROY, Rishabh Dev, Gazala Habib, Ramya Sunder Raman, Indian Institute of Technology Delhi
Abstract Number: 426
Working Group: Remote and Regional Atmospheric Aerosol
Abstract
The arid desert region to North-western India, also known as the Great Indian Thar desert is characterized by a unique topography, climatic conditions, and vegetation cover from the rest of India. However, due to the lack of measurement and characterization of aerosols at such locations, the factual information of the aerosol chemistry and properties are unknown. Moreover, owing to the number of sprawling towns in the region and the probable influx of transboundary pollutants, the question regarding source contribution which actually determines the aerosol chemistry, locally, is also unanswered. Therefore, herein, we report the wintertime chemistry, microphysical and optical properties of fine particulate matter investigated from mid-October 2020 to end of January 2021 in Bikaner, Rajasthan, India. Additionally, the contribution of firework displays during one of the major festivals in India i.e., Diwali has also been addressed. The site selection has been done following IMPROVE protocol to identify a regionally representative location. A 5-channel Speciation Air Sampling System (SASS) was used to collect PM2.5 particles (every alternate day for 24-hour duration) onto multiple filter substrates to identify the characteristics of the water-soluble inorganic ion (WSII) and carbonaceous species (CS) using ion chromatography and OC-EC analyzer. Real-time PM mass, Black Carbon (BC), and particle scattering were also measured using Quartz Crystal Microbalance, AE-33 aethalometer, and IN102 nephelometer. Despite being an area dominated by desert dust, the atmospheric chemistry is significantly governed by anthropogenic activities rather than dust sources agreeing with the fact of increased biomass burning and absence of dust events during the winter. The fine particle concentration (< 4.0 µm) was found to be dominant, most significantly during Diwali and winter haze periods. Probable source contribution and causality will be discussed along with the relationship between regional meteorology and aerosol species.