AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Phase Behavior and Surface Tension of Sea Spray Aerosol Droplets using Microfluidics
SHIHAO LIU, Lucy Nandy, Cari Dutcher, University of Minnesota
Abstract Number: 164 Working Group: Aerosol Physics
Abstract Sea spray aerosol (SSA) is one of the largest contributors of atmospheric aerosol particles worldwide. As chemically complex aqueous systems that include mixtures of biological, organic, and salt constituents, it is a challenge to predict the phase of sea spray aerosol as they age in the atmosphere, which impacts species uptake, equilibrium partitioning and optical properties. In addition, various components in SSA are surface active, leading to an impact on surface tension and cloud condensation nuclei (CCN) activity. In this work, microfluidics is used to study droplet phase and surface tension of aqueous systems containing sea spray aerosol samples and chemical mimics. For some systems, 3-methylglutaric acid is added, to further study the impact of organics on the aerosol properties. For the phase behavior study, the aqueous droplets are generated in microfluidic channels and stored in passive traps until dehydration. Different phase states of collected sea surface microlayer (SSML) samples, including two LLPS and two crystallization, are observed. The main sea-salts in the samples are separated to study the contribution of each salt, the effect of solute concentration, and solute molar ratios on the observed phase and internal heterogeneities. For the surface tension study, a high-throughput multi-layer microfluidic tensiometer is used. Bubbles are generated and deformed in the microfluidic channel, where the deformation is controlled by the elongational effect from the viscous fluid (deforming force) and surface tension (restoring force). Image analysis is applied to capture the edge of the bubbles and extract flow field information for surface tension calculation. By investigating phase transitions and surface properties of aged aerosols, this study informs the properties and fate of SSA in the atmosphere.