Impact on VIscosity, Reactivity and Atmospheric Lifetimes of Complex Aerosol SElf-assembly (VIRAL CASE)

The behaviour of clouds and aerosols presents large uncertainties when assessing the man-made contribution to climate change. To obtain new insights into the importance of self-assembled atmospheric droplets originating from meat-cooking and biodiesel emissions, we propose a suite of intimately linked studies with novel experimental and modelling approaches. Surfactant molecules such as fatty acids are known to self-assemble in contact with water into a rich variety of nanostructures known as lyotropic liquid crystalline phases. These include bilayers, and spherical or cylindrical micelles or inverse micelles (water nano-spheres or cylinders surrounded by a
surfactant monolayer) which themselves can be organised into periodic 1–D, 2–D or 3–D arrays. This self-assembly can vary dramatically depending on parameters such as surfactant charge, concentration, pH and temperature, and strongly affects physical properties including light scattering, diffusion, viscosity and water uptake. These physical properties are key in an atmospheric context, e.g. for cloud
formation, light transmission and thus radiative forcing as well as the chemical reactivity and atmospheric lifetimes of organic molecules.
We will investigate lyotropic phases formed by mixtures approximating realistic atmospheric conditions in terms of surfactant composition, acidity, temperature and humidity.

The samples will be investigated in different forms: “bulk” mixtures of surfactant & water; thin films mimicking layers on solid atmospheric particles; and acoustically levitated water-based droplets. We will probe the selfassembly using a technique that allows investigation of the particle structure on the nanoscale (smallangle X-ray scattering, SAXS), and the reactivity, viscosity and water uptake using complementary techniques including Raman microscopy. These techniques will allow investigation of the impact of self-assembly on transport within droplets and thus on atmospheric lifetimes of reactive aerosol components by exposing levitated droplets to ozone, O3, and the night-time atmospheric oxidant, NO3.


More details are available on the project description at http://www.met.reading.ac.uk/nercdtp/home/available/desc/entry2017/SC201730.pdf