Hygroscopicity of Organic Compounds as a Function of Their Physicochemical Properties

The interaction of organic aerosols with water vapor plays a crucial role in cloud processes but is still challenging to fully elucidate due to its complexity. Recently, we developed a water uptake methodology for particles collected on Teflon filters, enabling the quantification of both chemical composition and hygroscopicity of the same sample. In this study, the hygroscopicity of organic compounds with varying functionalities collected on Teflon filters was quantified, including dicarboxylic acids (malonic, glutaric, succinic), multifunctional dicarboxylic acids (tartaric, citric), sugars (glucose, levoglucosan), and a polyol (meso-erythritol) at three relative humidities (RHs: ≈84%, 90%, and 97%). The hygroscopicity parameter (κ) was derived and compared to previous studies. A regression model was developed that predicts κ as a function of physicochemical properties (O/C ratio, number of carbons, and ring oxygen (O*)), which may facilitate the use of Fourier-transform infrared (FTIR) spectroscopy to predict hygroscopicity in ambient samples.