Article

Isolating and identifying atmospheric ice-nucleating aerosols: a new technique

{ "0" : "Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523, USA" , "2" : "Continuous-flow diffusion chamber" , "3" : "Ice nuclei" , "4" : "Aerosol"}
Atmospheric Research DOI:10.1016/S0169-8095(97)00068-9 pp.263-278

ABSTRACT Laboratory studies examined two key aspects of the performance of a continuous-flow diffusion chamber (CFD) instrument that detects ice nuclei (IN) concentrations in air samples: separating IN from non-IN, and collecting IN aerosols to determine chemical composition. In the first study, submicron AgI IN particles were mixed in a sample stream with submicron non-IN salt particles, and the sample stream was processed in the CFD at −19°C and 23% supersaturation with respect to ice. Examination of the residual particles from crystals nucleated in the CFD confirmed that only AgI particles served as IN in the mixed stream. The second study applied this technique to separate and analyze IN and non-IN particles in a natural air sample. Energy-dispersive X-ray analyses (EDS) of the elemental composition of selected particles from the IN and non-IN fractions in ambient air showed chemical differences: Si and Ca were present in both, but S, Fe and K were also detected in the non-IN fraction.

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Keywords

23% supersaturation
 
AgI particles
 
air samples
 
ambient air
 
chemical differences
 
continuous-flow diffusion chamber
 
crystals nucleated
 
detects ice nuclei
 
Energy-dispersive X-ray analyses
 
Fe
 
key aspects
 
mixed stream
 
natural air sample
 
non-IN fraction
 
non-IN fractions
 
non-IN particles
 
residual particles
 
sample stream
 
second study
 
submicron non-IN salt particles