Are cooking fats affecting clouds?

Are cooking fats affecting clouds?

Fats being released from cookers such as deep fat fryers form into surprisingly complex droplets that may affect the formation of clouds and how the planet regulates heat.

 


 



Research conducted at MAX-Lab led by teams from the University of Reading and the University of Bath showed that fatty acid molecules that are emitted during cooking can spontaneously assemble into a variety of complex 3D structures. Such highly ordered structures are likely to extend the lifetime of aerosols in the atmosphere containing pollutants as well as affecting how clouds form.

 

The study was carried out using Small Angle X-ray Scattering (SAXS) in acoustic levitated droplets at the I911-4 beamline of the old MAX-Lab machine. MAX IV will have brand new dedicated SAXS beamline, named CoSAXS, which will start commissioning activities in autumn 2018. Once available to the user community, CoSAXS will represent a major upgrade in the technical possibilities compared with the previous beamline, paving the way for a new generation of experiments and providing a continuation of excellent science as this work shows. The CoSAXS beamline project manager, Dr. Tomás Plivelic is an author of the study and said:

 

“It is always a pleasure to collaborate with our colleagues from the UK and Lund University. The creativity and the science developed by the leaders of the project has been a huge motivation for making available state of the art x-ray scattering instruments such as the CoSAXS beamline aims to be.”

 

Dr. Christan Pfrang, an Associate Professor of Physical and Atmospheric Chemistry at the University of Reading, said:

 

“It is known that fatty acid molecules coating the surface of aerosol particles in the atmosphere may affect the aerosol’s ability to seed cloud formation. However, this is the first time scientists have considered what these molecules do inside of the aerosol droplet, and we have shown that they may be assembling into a range of complex, ordered patterns and structures. This means they may last longer in the atmosphere.”

 

“The impact of the surprisingly complex molecular arrangements of these fatty acid molecules in the environment is hard to quantify at this stage since these structures have not previously been considered by the atmospheric science community: there is no estimate available yet how much organic material may show such complex self-assembly in the atmosphere and further research is urgently needed.” 

 

“However, it is likely that these structures have a significant effect on water uptake of droplets in the atmosphere, increase lifetimes of reactive molecules and generally slow down transport inside these droplets with yet unexplored consequences.”

 

Dr. Adam Squires, an Associate Professor from the University of Bath commented:

 

“We know that the complex structures we saw are formed by similar fatty acid molecules in, for example, soap-water mixtures, where they dramatically affect whether the mixture is cloudy or transparent, solid or liquid, and how much it absorbs water from the atmosphere in a lab. The idea that this may also be happening in the air above our heads raises exciting challenges in fully understanding what these cooking fats are doing to the world around us.”

 

The international team also included researchers from the University of Bristol, Lund University and Diamond Light Source. This emphasises the importance of an international collaboration between scientists at universities and in large scale facilities, a sentiment that is strongly espoused by the League of European Accelerator-based Photon Sources or LEAPS.

Reference

Complex three-dimensional self-assembly in proxies for atmospheric aerosols
C. Pfrang, K. Rastogi, E. R. Cabrera-Martinez, A. M. Seddon, C. Dicko, A. Labrador, T. S. Plivelic, N. Cowieson & A. M. Squires
Nature Communications 8, Article number: 1724 (2017)
doi:10.1038/s41467-017-01918-1

Metrics

Abstract

We observed that organic molecules found in the atmosphere self-assemble into surprisingly complex 3D nanostructures in levitated aqueous droplets in a controlled gas-phase environment. We demonstrate that these droplets contain lyotropic phases including hexagonal and cubic close-packed arrangements of spherical and cylindrical micelles, lamellar stacks of bilayers, and micellar solutions. These nanostructures undergo transformations in response to atmospherically relevant humidity changes and chemical reactions. Acoustically trapped droplets of oleic acid/sodium oleate mixtures in brine were simultaneously analyzed by synchrotron X-ray scattering (SAXS) and Raman spectroscopy. We used Raman to follow loss of water, and oxidation by exposure to ozone, while observing accompanying changes in self-assembly with SAXS. Since self-assembly strongly affects a range of physical properties including viscosity, diffusion and optical transparency, the existence of such nanostructures in the atmosphere may have dramatic implications for radiative forcing, atmospheric residence times and many other aerosol characteristics fundamental to atmospheric research.



Photo Credit: Dr Christian Pfrang, University of Reading, 2016