Analyses of Sulfur Aerosol Size Distributions for a Forty-Day Period in Summer 1992 at Meadview, Arizona

Abstract

A DRUM (Davis Rotating-drum Universal-size-cut Monitoring) impactor was employed at Meadview, AZ, from July 12 to September 2, 1992, during the Project MOHAVE (Measurement of Haze and Visual Effects) summer intensive monitoring period. The DRUM impactor collects aerosol from 0.07- to 15-μm diameter in eight size ranges on the outside curved surface of eight drums rotating one revolution per month. Focused beam PIXE (Particle Induced X-ray Emission) analysis of the aerosol deposits results in a time history of size-resolved elemental composition with 6-hour resolution. Comparisons of the component composition of less than 2.5-μm diameter particles from the DRUM impactor with the composition of the PM2.5 from the collocated IMPROVE (Interagency Monitoring of Protected Visual Environments) filter sampler are used to assess the quality of DRUM data. Comparisons are also made of the sulfur concentrations in three size ranges below 2.5 μm as measured by the DRUM and MOUDI (Micro Orifice Uniform Deposit Impactor) samplers. From these analyses a 40-day period of DRUM sulfur data (155 6-hour time periods) is identified for subsequent use to generate and analyze sulfur size distributions. Techniques to display and summarize these sulfur size distribution histories are developed, including contoured plots of sulfur concentration by size and time, and cluster analysis. The results indicate that all periods can be well represented by several distinct size distributions. Relationships between these characteristic distributions and coincident meteorological, air quality, and optical parameters are determined and the consequences of these relationships discussed.