Impacts of Simulated Contrail Processing and Organic Content Change on the Ice Nucleation of Soot Particles

Abstract

Soot particles may undergo cloud-processing during atmospheric transport after which the particle porosity and surface wettability can be modified. Soot particles therefore show varying ice nucleation (IN) abilities via the pore condensation and freezing (PCF) mechanism, leading to poorly constrained effects on cirrus formation and climate. This study simulates a typical cloud-processing condition (at 228 K) for size-selected (200 and 400 nm) aviation soot proxies with different organic contents. Based on the particle size, mass and morphology changes, as well as the findings from parallel studies on similar soot samples, we demonstrate that cloud-processing increases the particle compactness and water-interaction ability. However, the pore availability change resulting from above property changes dominates the IN ability of cloud-processed particles via PCF. Even originally organic-rich and hydrophobic soot particles can nucleate ice via PCF if suitable pores can be generated after organic removal and cloud-processing.