Lee W-C, Chen J, & Kuwata M
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.
有机物是大气气溶胶中的重要成分。其中，水溶性有机物能透过吸湿增长等过程影响云的生成及大气辐射，进而影响气候及环境。传统的操作上仅将有机物分为水溶性及非水溶性，并未详细探讨其水溶解度/极性对吸湿增长过程的影响。然而近年的理论研究指出，水溶性有机物的水溶解度/极性需要被定量探讨，才能进一步了解有机气溶胶的吸湿增长过程。
本研究利用1-辛醇−水分配系数(1-octanol−water partitioning coefficient, KOW)及水溶解度的正相关，提出由KOW作为水溶性有机物水溶性/极性的指标，并由此推导大气气溶胶水溶性有机物的水溶解度/极性分布。此方法被应用于生物质燃烧产生的水溶性有机物中(图以蚊香燃烧生成的有机物为例)。此外，本方法亦被应用于其他原生性/衍生性气溶胶水溶性有机物中，探讨水溶性有机物水溶解度/极性及粒子吸湿特性的关联，以便定量理解气溶胶对大气及气候系统的影响。
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
