A transmission electron microscopy study of particulate concentrations in seven individual snowflakes

An electron microscope analysis of seven individual snowflakes, which were collected over a six-hour period and allowed to dry upon collodion support films, showed the particle concentration to increase with elapsed time of snowfall, reach a maximum at $\text{3}\text{4}$ of the duration, and to essentially stabilize thereafter. The size of the particles ranged from less than 0.01 μm to 4.5 μm in diameter, with average particle size first increasing then decreasing with elapsed time of snowfall. The particle concentration in individual snowflakes was observed to be roughly 5 times greater than that observed previously in individual raindrops in the same geographic area, and there was no evidence of asbestiform fibers.