Water Solubility Distribution of Organic Matter Accounts for the Discrepancy in Hygroscopicity among Sub- and Supersaturated Humidity Regimes

Abstract

Water uptake properties of organic matter (OM) are critical for aerosol direct and indirect effects. OM contains various chemical species that have a wide range of water solubility. However, the role of water solubility on water uptake by OM has poorly been investigated. We experimentally retrieved water solubility distributions of water-soluble OM (WSOM) from combustion of mosquito coil and tropical peat using the 1-octanol–water partitioning method. In addition, hygroscopic growth and cloud condensation nuclei (CCN) activity of solubility-segregated WSOM were measured. The dominant fraction of WSOM from mosquito coil smoldering was highly soluble (water solubility (S) > 10–2 g cm–3), while that from peat combustion contained ∼40% of less-soluble species (S < 10–3 g cm–3). The difference in water solubility distributions induced changes in the roles of less water-soluble fractions (S < 10–3 g cm–3) on CCN activity. Namely, the less water-soluble fraction from mosquito coil combustion fully dissolved at the point of critical supersaturation, while that for tropical peat smoldering was limited by water solubility. The present result suggests that water solubility distributions of OM, rather than its bulk chemical property, need to be quantified for understanding the water uptake process.

Accounting for Cloud Nucleation Activation Mechanism of Secondary Organic Matter from α-Pinene Oxidation Using Experimentally Retrieved Water Solubility Distributions

“…The corresponding calculation for A 0 also suggests that WSOM in α-pinene SOM does not completely dissolve at the point of s c (Figure S23). The incomplete dissolution of WSOM at the point of s c was also reported for biomass-burning particles …”

“…Results of the model simulation. (a) The Köhler curve of SOM from dark ozonolysis of α-pinene simulated using the solubility distribution model. , A dry particle diameter of 100 nm was considered for the simulation. The water-insoluble fraction of the α-pinene SOM was estimated to be 7% .…”

“…The incomplete dissolution of WSOM at the point of s c was also reported for biomassburning particles. 46 A previous study estimated the threshold for water solubility that can contribute to CCN activation of α-pinene SOM using the chemical composition predicted by the MCM-SIMPOL model. 43 The study suggested that the threshold value falls in the range of 10 −2 −10 −1 g cm −3 .…”

“…During the CCN activation process, the fractions of OM in both A 1 A 0 [0.06] and A 1 A 0 [1.78] The Koḧler curve of SOM from dark ozonolysis of α-pinene simulated using the solubility distribution model. 43,46 A dry particle diameter of 100 nm was considered for the simulation. The water-insoluble fraction of the α-pinene SOM was estimated to be 7%.…”

Existence of Crystalline Ammonium Sulfate Nuclei Affects Chemical Reactivity of Oleic Acid Particles Through Heterogeneous Nucleation

“…For instance, highly oxygenated OA particles may serve as cloud condensation nuclei (CCN), influencing cloud properties (W.‐C. Lee et al., 2022; Massoli et al., 2010). Oxidized OA may provide oxidative stress to human body (S. Wang et al., 2021).…”