Mechanisms of soot-aggregate restructuring and compaction

Soot aggregates form as open, fractal-like structures, but aged atmospheric particles are often observed to be restructured into more-compact shapes due internal mixing (“coating”). This compaction has a major effect on the radiative properties of aggregates, and may also influence their aerosol-cloud interactions, toxicity, deposition in human lungs. Recent laboratory studies have presented conflicting arguments whether this occurs during condensation or evaporation coatings. In three-part study, we combine theory experiments explain these results. First, review surface-science literature identify explicit mechanisms for condensation-compaction well evaporation-compaction. We mechanism avoiding condensation, based heterogeneous nucleation kinetic barriers capillary formation. Second, soot-restructuring find clear evidence both condensation- evaporation-compaction, with being norm. Third, present new experimental results where forces anthracene coatings were “switched on” off” by using solid liquid phases coating addition removal. Consequently, demonstrate condensation-compaction, no compaction, same soot source. Overall, our study indicates that will typically undergo when coatings, while avoided through coagulation gas-to-particle formation highly viscous coatings.Copyright © 2022 American Association Aerosol Research