Alexei Khalizov, Associate Professor, Chemistry and Environmental Science at New Jersey Institute of Technology, will visit Friday Oct 18, 2024 and give a special seminar entitled: An unaccounted pathway for rapid aging of atmospheric soot.

The seminar will start at 10:45 am and be held at CE-CERT Room 105.  A zoom link will be provided.

If you would like to meet with the speaker, we will have an informal lunch with graduate students following the seminar. 

Abstract: Soot comes from a variety of combustion sources, and once in the air, soot particles travel over long distances, undergoing significant processing, which alters their composition, properties, and impacts. Processing can increase the soot toxicity and it also significantly alters the soot climate warming potential, which is highly sensitive to particle morphology and composition. Although soot particles are fractal aggregates, in atmospheric aerosol models they are commonly represented as spheres. Using laboratory experiments, we show that owing to fractal morphology, soot particles can rapidly acquire small amounts of condensate upon exposure to the trace gas chemicals similar to those co-released during combustion or generated by photochemical oxidation. Many of these chemicals are water-soluble and their addition, even in minute amounts, is sufficient to drastically improve the wettability of soot, promoting capillary condensation of water vapor, as manifested by significant soot particle compaction upon exposure to even moderate relative humidities. We developed a kinetic model for capillary condensation of trace gas chemicals and water vapor on fractal soot aggregates and used it successfully to support our experimental observations. To assess the role of capillary condensation in the aging of soot in the atmosphere, we extended our model towards multi-component trace vapors. Then, we employed this new multi-component capillary condensation model (MCCCM) in conjunction with the particle-resolved PartMC-MOSAIC aerosol model to explore relevant atmospheric scenarios. The results suggest that in a non-polluted environment, capillary condensation alone can rapidly transform hydrophobic soot particles into cloud condensation nuclei. Furthermore, we observe significantly different responses between fractal and spherical soot particle implementations towards changes in atmospheric trace gas concentrations caused by variations in air temperature and photochemical activity. We conclude that capillary condensation represents an important mechanism of atmospheric soot aging and must be incorporated into atmospheric aerosol models to improve their predictive power.