Characterization of Organic Aerosols in the Ambient Air of Raipur, Central India: Distribution, Seasonal Variations, and Source Apportionment

Abstract

Due to their influence on climate and human health, organic aerosols, a substantial component of atmospheric particulate matter (PM), are a major area of scientific focus. This study investigates the distribution, seasonal variations, and sources of organic constituents —including n-alkanes, alkanol acids, alkanols, sugars, phthalate esters, lignin and resin products, sterols, and polycyclic aromatic hydrocarbons (PAHs)— in the coarse mode (PM₁₀) of ambient air samples collected in Raipur, India. The total concentration of the organic aerosols ranged from 5106 to 29,099 ng m^− 3, with a mean value of 16,701 ± 3355 ng m^− 3. Fatty acids, phthalates, and levoglucosan were the major components. Seasonal analysis revealed higher concentrations of n-alkanes, PAHs, and lignin products during the winter, while alcohols, fatty acids, sterols, and sugars exhibited elevated levels in both autumn and winter. Size segregation analysis showed that all organic species, except phthalates and PAHs, accumulated predominantly in the fine and ultrafine particle fractions. Source apportionment through factor analysis revealed a complex mixture of sources shaping aerosol composition, including vehicular emissions, various combustion activities (biomass burning and charbroiled cooking), natural background factors, and the combination of urban dust and biogenic materials. The findings highlight the significant climatic and health implications of organic aerosols in the study region, necessitating urgent mitigation measures to address air pollution.