Ammonium sulfate crystallization in Andersen cascade impactor samples

Meteorologists are accustomed to the atmospheric phase changes of water. It is observed that phase changes ending with crystallization and crystal growth of (NH4)2SO4 take place in Andersen Samplers used to collect size-stratified samples of airborne particles. It is not at this point clear whether preformed (NH4)2SO4 crystals of small size are involved, although this is likely, but the cascade impaction processes evidently play a role in generating large (NH4)2SO4 crystals on the last few stages of these samplers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22246/1/0000682.pd