KUWATA Mikinori and LEE, Wen-Chien
Organic matter (OM) occupies a significant portion of aerosol particles in the atmosphere. Water-soluble fraction of organic matter (WSOM) has been known to contribute to water uptake process by aerosol particles. The process is critical for evaluating climatic and environmental impacts of aerosol particles, including influences on cloud formation and atmospheric radiation.
Traditionally, WSOM has operationally been defined as water-extractable fraction of OM. However, recent advances in theoretical studies on water uptake processes of aerosol particles demonstrated that variabilities in water-solubility/polarity of WSOM needs to be quantitatively considered. The potential importance of water-solubility/polarity distribution on water uptake has never been experimentally proved due to the lack of experimental technique.
We developed a method to retrieve water-solubility/polarity distribution of WSOM using 1-octanol-water partitioning coefficient (KOW). KOW has widely been used in the areas of pharmaceutical/environmental chemistry as a metric to indicate polarity, yet it has scarcely been employed for atmospheric chemistry. KOW is known to correlate well with water-solubility, meaning that water-solubility distribution of WSOM can be obtained once KOW distribution is available. The developed method was applied for estimating KOW distribution of WSOM from mosquito coil burning, which serves as a surrogate of biomass burning particles (Figure). We also obtained KOW distributions of WSOM from primary and secondary sources, in addition to the data for water uptake by corresponding particles. The data is currently analyzed for connecting the gap between theoretical studies on aerosol particles and actual water uptake processes, contributing to quantify roles of aerosol particles in the atmospheric/climatic systems.
Reference
Lee W-C, Chen J, & Kuwata M (2020) An inversion method for polarity distribution of atmospheric water-soluble organic matter. Aerosol Sci. Technol. 54(12):1504-1514
