**4. Conclusions**

Ambient particles are ultimately removed from the atmosphere by the natural processes generally referred to as wet precipitation and dry deposition. The former is the most important natural removal mechanism of ambient air pollutants including PM2.5. The clear landscapes after the rain is a good proof of this wet precipitation. In this study, the scavenging properties of ambient particles were investigated by collection of raindrops as a function of their size and clarifying their chemical nature. Particle scavenging rates based on both the actual measurement and the theoretically calculated values indicated that raindrops, especially small raindrops, played a great role to remove ambient particles including both naturally and artificially formed ones. On the other hand, through the PIXE analytical technique for the residuals in and/or on individual raindrops, it was obvious that several hazard components like Pb, Cr, and Mn had meaningful amount. Therefore, we must be thankful for the role of the rain, at the same time, we should avoid getting wet to protect our health from heavy metals. Further study on a comparison of the real measured data with the calculated result for the particle scavenging by raindrops is being planned in the near future.

*Rainfall - Extremes, Distribution and Properties*
