A new approach for characterization of single raindrops

To determine the characteristics of single raindrops as a function of their size, the collodion film method was newly applied to the sampling of singl e raindrops. Sampling of single raindrops was performed at a height of 20 m above ground level of the Kyoto University building located in Uji, Japan during rain events from September to November 1999. It was possible to get successfully replicas of raindrop by collodion film method. And we tried to analyze the elemental components of the nuclei and pollutants that were in corporated into the developing raindrop. To the analysis of single raindrop s, Particle Induced X-ray Emission (PIXE) was applied. Several elements inc luding S in single raindrops were detected by PIXE. The concentrations of e very element increased with decreasing drop diameter. Furthermore, to acqui re more detailed information such as inner-structure and mixing state in si ngle raindrops, micro-PIXE analysis was performed. The nucleation centers o f single raindrops were successfully analyzed by micro-PIXE. Ca, S and Fe w ere apparently detected by scanning beam of 1 similar to 2 mum diameter and about 70 pA beam current.