Abstract |
An experimental network of modified cascade impactors was set up, as part of the National Air Surveillance Network, to determine gravimetrically the particle size distribution of suspended particulate matter in the air in six urban areas. The modified cascade impactor, the analytical methodology, and the computer processing of data are described. Results of the first year's operation indicate that suspended particulate matter in urban air is predominantly submicron in size (expressed as equivalent spheres of unit density). Variations in the quarterly composites of mass median diameter, various size fractions less than or equal to 1 and 2 microns, and the degree of particle dispersion expressed by the geometric deviation generally followed seasonal patterns. Future expansion of the network is discussed. (Author) |