Abstract
To collect individual snow crystals a particular method for the snow crystal replication was newly applied using collodion (nitrocellulose) film. Samplings of snow crystals were carried out at the Kyoto University Uji Campus during snowfall events in January 2001. Individual snow crystals, which were unagglomerated and maintained their original shapes such as hexagonal and dendritic plates ranged from 120 pm to 2.5 mm, were replicated on thin collodion film (130±10μm). Particle induced X-ray emission (PIXE) and micro-PIXE analytical methods were uniqucly applied to the analysis of individual snow crystals to investigate their particle scavenging properties and chemical characteristics including chemical inner-structure and elemental mixing state. It was possible to resolve the elemental peaks corresponding to channel number of PIXE spectra without filter rupture or film blank concentrations. Several elements, most of which became incorporated into the snow crystals by impaction scavenging of soluble and insoluble aerosol particles, were successfully analyzed. These elemental masses showed the strong size dependence of snow crystal. Almost all of the components were distributed at the rim portion of snow crystals. Every component retained in and/or on individual snow crystals existed as a mixed state of soil and anthropogenic components including sulfur. These detailed results such as the crystal size dependence of elemental mass, chemical inner-structure, and mixed elemental state in individual snow crystals obtained from this study should be helpful to better understand the ice-nucleation and scavenging processes of pollutants by snow.
