Chemical composition and source identification of fluorescent components in water-soluble organic carbon in the city of Karlsruhe, Germany

This study investigates the fluorescent properties of the water-soluble organic aerosol (WSOC) in PM_2.5 and PM₁₀ from the city of Karlsruhe, Germany. Major fluorescent components were identified by excitation–emission matrix spectroscopy with parallel factor analysis in this study. The lower humification index (HIX) value of PM_2.5 and PM₁₀ (0.72 ± 0.13, 0.77 ± 0.06), together with lower biological index (BIX) value of PM_2.5 and PM₁₀ (0.85 ± 0.07, 0.84 ± 0.06) and fluorescence index (FI) value of PM_2.5 and PM₁₀ (1.34 ± 0.16, 1.32 ± 0.06) showed that fluorescent source of WSOC influenced by the primary aerosol’s emissions (such as vehicles emission and heating) and natural dust (such as road and building contributions). The fluorescent components identified of the water-soluble organic aerosol show that Component 1 (Ex < 240/Ex = 323 nm, Em = 408 nm) and Component 2 (Ex = 248/362 nm, Em = 469 nm) can be identified as Highly oxygenated humic-like substance (HULIS) components. Component 3 (Ex <240 nm, Em = 363 nm) is associated with biomass burning with less-oxygenated HULIS component and Component 4 (Ex = 242/269 nm, Em = 311 nm) is substances from multiple sources of mixtures. Relative contribution of Highly oxygenated HULIS components (Component 1 & Component 2) in heating period (52.7%) is lower than in non-heating period (67.6%); Biomass burning with less-oxygenated HULIS component (Component 3) had the highest contribution (41%) in winter and the phenol- and naphthalene-like component (Component 4) had lower contributions and in different periods.