1-octanol-water partitioning as a classifier of water soluble organic matters: Implication for solubility distribution

<p>Water-soluble organic matters (WSOMs) play an important role in determining magnitudes of climatic and environmental impacts of organic aerosol particles because of their contributions to hygroscopic growth and cloud formation. These processes are dependent on water solubility as well as distribution of this property in a particle, yet no method has been available to quantify such characteristics. In this study, we developed a theoretical framework to classify WSOM by 1-octanol-water partitioning that has a strong correlation with water solubility. 1-octanol-water partitioning coefficient also has a strong correlation with a traditional solid phase extraction method, facilitating interpretation of data from the technique. The theoretical analysis demonstrated that the distributions of WSOM classified by 1-octanol-water partitioning depend on (1) the volume ratio of 1-octanol and aqueous phases, and (2) extraction steps. The method was tested by using organic aerosol particles generated by smoldering of a mosquito coil, which serves as a surrogate for biomass burning particles. The WSOM extracted from the mosquito coil burning particles was classified by 1-octanol-water partitioning at different volume ratios. These solutions, including both the 1-octanol and aqueous phases, were nebulized to generate particles for measurements using an online aerosol mass spectrometer. The mass spectra indicated that highly oxygenated species tend to be highly soluble, while high molecular weight compounds are less soluble. Linear combinations of these mass spectra allowed the estimation of the mass fractions of WSOM partitioned to 1-octanol and aqueous phases, thereby facilitating the evaluation of the mass fractions of cloud condensation nuclei (CCN) active materials.</p> <p>© 2017 American Association for Aerosol Research</p

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

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 –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

Time courses of relative expression levels of phosphorylated PKC-ε, TrkB, and NM23-H1 for <i>me_</i>SWH-treated MSCs in NIM (upper panel) and in NIM without SHH, bFGF and FGF-8 (lower panel).

<p>Time courses of relative expression levels of phosphorylated PKC-ε, TrkB, and NM23-H1 for <i>me_</i>SWH-treated MSCs in NIM (upper panel) and in NIM without SHH, bFGF and FGF-8 (lower panel).</p

Cell morphology of <i>me</i>_SWH-treated MSCs (A, B, C in upper panel) and intact MSCs (D, E, F in lower panel) before and after neuronal differentiation induction.

<p>A and D are cells before induction; B and E are cells inducted with NIM for 5 and 7 days, respectively. C and F are cells induced with ERK inhibitor-containing NIM for 5 and 7 days, respectively.</p

Schematic diagram showing the signaling pathways that support neuronal differentiation and survival.

<p>Schematic diagram showing the signaling pathways that support neuronal differentiation and survival.</p

Amount of BDNF secreted by MSCs and <i>me</i>_SWH-treated MSCs.

<p>The intact MSCs were treated with NIM (with or without ERK inhibitor) for 7 days and <i>me</i>_SWH-treated MSCs for 5 days.Bar heights with SD error bars represent the average value of 3–7 replicate samples.</p

Two-dimensional gel electrophoresis of <i>me_</i>SWH-treated MSCs before (a) and after induction for neuronal differentiation for 5 days (b).

<p>The spot images of nucleoside diphosphate kinase A (NM23-H1) in different gels from <i>me_</i>SWH-treated MSCs before (upper panel) and after induction (lower panel) are also shown.</p