NEW ATTEMPTS TO THE STUDY OF INDIVIDUAL
RAINDROPS

Ma, Chang Jin; Choi, Kum Chan; Park, Jeong Ho

Environmental Engineering Research 2001;6(2): 81-89.

NEW ATTEMPTS TO THE STUDY OF INDIVIDUAL RAINDROPS

Chang Jin Ma¹^†, Kum Chan Choi², and Jeong Ho Park³

¹Energy and Environment, Graduate School of Energy Science, Kyoto University, Kyoto 611-0011, Japan
²Division of Earth & Environmental Engineering, Dong-A University, Pusan 604-714, Korea
³Department of Environmental Engineering, Chinju National University, Chinju 660-758, Korea

Corresponding Author: Chang Jin Ma ,Tel: +81-774-38-4413, Fax: +81-774-38-4411, Email: ma@uji.energy.kyoto-u.ac.jp

Received: October 7, 2000; Accepted: April 7, 2001.

ABSTRACT

In order to determine the characteristics of individual and size-segregated raindrops, raindrop sampling and analysis methods were newly proposed in this study. Thin Collodion film was newly prepared and applied to the sampling of individual raindrops. Moreover the freezing method described by Ma⁴⁾ was simultaneously applied. Samplings were performed at a Kyoto University building located in Kyoto, Japan from June to July 2000. Replicas of individual raindrops (drop radius, D_r≤ 1.05 mm) were formed successfully on the thin Collodion film. We tried to analyze the elemental components of the nuclei and pollutants that were incorporated into the developing raindrop. For the analysis of individual raindrops, Particle Induced X-ray Emission (PIXE) analytical method was applied. Several elements including sulfur in and/or on single raindrop replicas were successfully detected by PIXE. Furthermore micro-PIXE analysis was applied to acquire more detailed information such as inner-structure and mixing state of single raindrop. The concentrations of every element increased with decreasing drop diameter. The masses of every element fell right down to the lowest point at subsequent rain event. If the small circle in the center of raindrop replica is the nucleation center of raindrop, we can assume that CCN was mainly initiated from soil components in our sampling periods. Ca, S and Fe were apparently detected at a portion of frozen raindrop by 2.5 MeV H⁺ micro beam accelerated by 3 MV single-end accelerator.