Egor Demidov

Discrete element method model for restructuring of atmospheric soot aggregates

Egor V. Demidov, Gennady Gor, Alexei F. Khalizov

ACS MARM, Oral presentation, 2024


Soot is a major component of atmospheric aerosols and it affects climate primarily by scattering and absorbing the sunlight. Morphologically, soot particles are fractal aggregates made of elemental carbon. In the atmosphere, the aggregates acquire coatings by interacting with trace gas chemicals and water vapor, resulting in their significant compaction. The addition of coatings and morphological compaction lead to changes in light absorption and scattering, and hence in climate forcing by soot aerosol. The mechanism of soot restructuring is not yet fully understood. Hence, the fractal morphology of soot and its evolution are neglected in atmospheric models, leading to reduced prediction accuracy. To address this deficiency, we develop a discrete element method model to quantitatively simulate restructuring of fractal soot aggregates. In the model, the aggregate is represented as a collection of spheres joined by Van der Waals forces and by carbon necks. We combine models for the bonded contacts, non-bonded frictional contacts, and Van der Waals attraction in an open-source code. The developed model is parametrized based on atomic force microscopy (AFM) experiments, where the force-displacement curves are recorded for soot aggregates that are being unraveled by the AFM cantilever tip. Future work involves adding to the model capillary forces produced by atmospheric condensates and integrating the soot restructuring model into a large-scale atmospheric simulation to quantify the time scale and extent of restructuring occurring under natural conditions.


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