Soot morphology and surface chemical composition − main drivers for ice nucleation on soot particles?

With an industry traffic forecast showing that airlines are welcoming a year-over-year increase of passengers, the airline industry keeps contributing to the intensification of emissions of solid particles in the atmosphere. These particles are involved in many physical and chemical processes that can affect the atmospheric radiative forcing. [I] For instance, soot particles may act as nucleating agents and promote the formation of ice crystals. Hence, they may help in the formation of contrails that may persist and further evolve into “man-made” cirrus clouds in cold and humid air parcels, and ultimately affect the formation of clouds and their lifetime expectancy (precipitations). Our work focuses on laboratory soot particles produced by a mini Combustion Aerosol Standard (miniCAST) generator, whose surface chemistry and structure can be modified by varying the fuel and oxidation airflows to mimic some of the physico-chemical properties of soot particles emitted by aircraft engines during the incomplete combustion of kerosene fuel. [II] To interpret ice nucleation activities of various soot samples, detailed analyses of their structure and surface chemical composition are performed using micro-Raman spectroscopy and mass spectrometry techniques (two-step laser and secondary ion mass spectrometry). The ultimate goal is to establish a link between the physicochemical properties of soot particles and their ice nucleation activity.

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