Polarity Dependent Chemical Characteristics of Water-Soluble Organic Matter from Laboratory-Generated Biomass Burning Revealed by 1-Octanol-Water Partitioning

Polarity distribution of water-soluble organic matter (WSOM) is an important factor in determining hygroscopic and cloud nucleation abilities of organic aerosol particles. We applied a novel framework to quantitatively classify WSOM based on 1-octanol-water partition coefficient (KOW), which often serves as a proxy of polarity. In this study, WSOM was generated by laboratory biomass burning experiment with smoldering of Indonesian peat and vegetation samples. The fractionated WSOM was analyzed using the UV-Visible spectrophotometer, spectrofluorometer, and time-of-flight aerosol chemical speciation monitor (ToF-ACSM). Several deconvolution methods, including positive matrix factorization, parallel factor analysis, and least-squares analysis, were applied to the measured spectra, resulting in three classes of WSOM. The highly-polar fraction of WSOM, which predominantly exists in the range of log KOW < 0, is highly oxygenated and exhibits similar optical properties to those of light-absorbing humic-like sub...