The Intrinsic Link between Optical Properties and Toxicity of Extractable Organic Matter in Combustion Particles: Mediated by Polycyclic Aromatic Compounds.

Organic compounds are important contributors to the optical properties and health effects of combustion-derived particles. However, the connection between optical properties and toxicity of combustion particles remains a matter of little concern. In this study, combustion particles were collected from 11 primary sources, including biomass burning, coal combustion, and vehicle exhaust. The extractable organic matter (EOM) in bituminous coal combustion particles shows the highest light-absorption, fluorescence properties, and toxicity among samples. Parallel factor (PARAFAC) analysis combined excitation-emission matrix (EEM) spectroscopy resolved 4 types of basic chromophore components in EOM. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis further resolved ∼800 molecules, predominantly aromatics (84% ± 4.6%), which showed positive correlations with the light-absorption, fluorescence properties and toxicity of EOM (p < 0.05). Aromatics are inferred to be the intrinsic link between the optical properties and toxicity of EOM in combustion particles. Additionally, the benzene poly-(carboxylic acid)-s (BPCAs) method, which could identify and quantify fused benzene rings in EOM, further indicates the high condensation degree of aromatics is closely correlated with the light-absorption, fluorescence properties of EOM. However, the toxicity of EOM may depend on the bay or fjord region of aromatics. These findings provide valuable insights into the light-absorption, fluorescence properties and toxicity of EOM in combustion particles.