(235a) Aerosol Residual Water Content And The Effects On Ccn Activity And Hygroscopicity Of Simple And Complex Aerosol Particles

Significant research in the past two decades has focused on individual particulate constituents and their interactions with water. Previously, the interaction between water and the inorganic fraction of atmospheric aerosols has been well characterized, and the role of organics in aerosols is becoming more fully understood. It still remains to investigate the water interactions of particles containing numerous inorganic and organic constituents to develop a more realistic simulation of the complex nature of ambient particulates and to discover the best way to simplify natural aerosols for modeling studies.

In this work, we will present results of CCN studies along with scanning electron microscope (SEM) and atomic force microscope (AFM) imagery of complex aerosols. These results are compared to single-component aerosols of the complex aerosol constituent species obtained from the literature and also from our experiments. A novel method for determining residual water content of aerosol particles has been developed.

The results indicate that most chemically complex ambient aerosols would be expected to display similar CCN activity. This implies that even under low RH conditions, most ambient aerosols would be expected to contain water. This has been confirmed by SEM and AFM investigations. Chemically complex aerosol particles including multiple organic constituents have been shown to retain water below 2% RH and to demonstrate identical CCN activity compared to the same aerosols generated at over 25% RH.