Effect of black carbon particles on the efficiency of water droplet freezing

Black carbon particles emitted by natural and anthropogenic sources of combustion are potential nuclei of ice formation of cirri in troposphere. The freezing of the ensembles of water microdroplets containing black carbon particles of different origins, including those modified with organic substances, is studied. Ice-forming ability is shown to be predetermined by the density and sizes of black carbon agglomerates, as well as the chemistry and wettability of their surface. Ice formation is most efficient in dispersions of black carbon particles that are stable with respect to sedimentation and have a uniform distribution of particles over the droplet volume. In the presence of oxygen-containing groups on the particle surface, freezing temperature increases. The efficiency of the ice formation decreases in the presence of noticeable amounts of water-soluble substances on the particle surface. The maximum freezing ability is inherent in ensembles of water droplets containing hydrophilic particles. Characteristics ensuring a high ice forming ability of nuclei are determined.