Black Carbon, Aerosol Water, Mixing States and Cloud Condensation Nuclei

Black Carbon is complex and understanding the interaction of ubiquitous black carbon with atmospheric water and the role of black Carbon as cloud condensation nuclei is imperative. In this presentation we show data to describe the CCN activation of Black Carbon using electrical mobility and aerodynamic sizing instrumentation. Furthermore to characterize and modify mixing states, a flow tube apparatus was developed to control the extent of mixing of black carbon, organic and inorganic fractions under different environmental conditions. Data sets yielding multiple activation curves have been recreated by mixing multiple inorganic and organic compounds in the flow tube. Results show that aerosol water is a significant factor; under dry conditions, the aerosols remained externally mixed while humid conditions facilitated internal mixing. For example, ammonium sulfate (inorganic) and succinic acid (organic) when dry, maintained an external mixture and multiple activation curves were observed to be constant. Under humid conditions,external mixing was initially observed; however, the aerosol water promoted internal mixing and the activation curves were observed to converge onto a single curve. The data agree well with Kohler Theory and single parameter (kappa) theory thermodynamic predictions of droplet activation. The method of analysis and the effect of mixing states of multiple components on the supersaturated hygroscopic properties of aerosols are presented.