Photochemical aging process on PM2.5 bound PAHs emission from solid fuel combustion in traditional and improved stoves

Abstract Solid fuels are widely used as energy sources in the developing countries across the world. In this study, emissions of primary and secondary (i.e., photochemically aged) parent polycyclic aromatic hydrocarbons (p-PAHs) and their derivate from a variety of solid fuel burning were determined through a potential aerosol mass-oxidation flow reactor (PAM-OFR). The improved technology stoves showed reductions of 61.2–66.8% to the primary and secondary EFs of the total quantified PAHs (tPAHs) in comparison to the traditional stoves. In addition, the primary and secondary EFs of the tPAHs for the anthracite coal and maize straw charcoal were 80.9–88.7% and 19.4–51.6%, respectively, lower than those of the raw bituminous coal and maize straw briquette. Results demonstrated that the total p-PAHs and alkylated PAHs decreased for ~20% and ~ 50% after the 2- and 7- equivalent aged days, respectively, whereas the total oxygenated- and nitro-PAHs (i.e., o-PAHs and n-PAHs) had increases of ~30% and ~ 80%, respectively. Significant formations of carbonyl functional group in the aged samples were confirmed by the Fourier transform infrared spectroscopy, well consistent to the increases of EFs of the oxygenated species (e.g., o-PAHs). Unique diagnostic ratios for the o-PAHs and n-PAHs including 3 N-FLA/(3 N-FLA + 1 N-PYR) (> 0.2 for coal, 0.5 for coal;