Identification of PM2.5 sources contributing to both Brown carbon and reactive oxygen species generation in winter in Beijing, China

Abstract

Better understanding of fine particulate matter (PM2.5) composition and sources associated with brown carbon (BrC) and reactive oxygen species (ROS) are essential for developing effective air quality control strategies to mitigate climate warming and protect human health. To identify the common chemical composition and sources associated with BrC and ROS, BrC light absorption and hydroxyl radical (·OH), one of the most reactive ROS, were measured for the same batch of filter samples collected in Beijing, China during a winter sampling period covering days with different pollution levels, together with detailed chemical composition analysis, including major components and individual organic and inorganic source-specific tracers. The results showed that both light absorption of BrC and ·OH generation by per mass PM2.5 decreased with increase of PM2.5 mass concentrations, which could be primarily attributed to the predominant roles played by secondary inorganic aerosols in the increased PM2.5 mass, while both of them increased with the fractions of water-soluble organic carbon (WSOC) in PM2.5. WSOC and combustion-related sources were found to be the common and major contributors to both BrC and ·OH generation in Beijing winter. However, BrC exhibited better correlations with fossil source WSOC, while ·OH better correlated with biomass burning source related WSOC. During the study period, fossil sources especially coal combustion were more important sources for BrC, while biomass burning played a relatively stronger role in ·OH generation.