Part of the book: Air Quality Monitoring, Assessment and Management
Although it is well known that rain plays an important role in capturing air pollutants, its quantitative evaluation has not been done enough. In this study, the pollutant scavenging effect by size of raindrops was investigated by clarifying the chemical nature of individual size-resolved raindrops and their residual particles. Raindrops as a function of their size were collected using the raindrop collector devised by ourselves during high atmospheric loading for PM2.5. The raindrop number concentration (m−2 h−1) tended to drastically decrease as the drop size goes up. Particle scavenging rate, Rsca.(%), based on the actual measurement values were 38.7, 69.5, and 80.8% for the particles with 0.3–0.5, 0.5–1.0, and 1.0–2.0 μm diameter, respectively. S, Ca, Si, and Al ranked relatively high concentration in raindrops, especially small ones. Most of the element showed a continuous decrease in concentration with increasing raindrop diameter. The source profile by factor analysis for the components of residual particles indicated that the rainfall plays a valuable role in scavenging natural as well as artificial particles from the dirty atmosphere.
Part of the book: Rainfall