COMPARISON AND COMBINATION OF AEROSOL-SIZE DISTRIBUTIONS MEASURED WITH A LOW-PRESSURE IMPACTOR, DIFFERENTIAL MOBILITY PARTICLE SIZER, ELECTRICAL AEROSOL ANALYZER, AND AERODYNAMIC PARTICLE SIZER

Data from a different mobility particle sizer (DMPS) or an electrical aerosol analyzer (EAA) has been combined with data from an aerodynamic particle sizer (APS) and converted to obtain aerosol mass distributio n parameters on a near real-time basis. A low pressure impactor (LPI), a direct and independent measure of this mass distribution, provided information for comparison. The number distribution of particles withi n the electrical measurement range was obtained with the DMPS and EAA. Data from the APS for particles greater than that size were used to c omplete the number distribution. Two methods of obtaining mass distrib ution parameters from this number data were attempted. The first was t o convert the number data, channel by channel, to mass data and then f it a log-normal function to this new mass distribution. The second met hod was to fit a log-normal function to the combined number distributi on and then use the Hatch-Choate equations to obtain mass parameters. Both the DMPS/APS and the EAA/APS systems were shown to successfully m easure aerosol mass distribution as a function of aerodynamic diameter . Careful operation of the measurement equipment and proper data manip ulation are necessary to achieve reliable results. A channel-by-channe l conversion from number to mass distribution provided the best compar ison to the LPI measurement. The DMPS/APS combination furnishes higher -size resolution and accuracy than the EAA/APS system. A small gap was observed in the EAA/APS combined data; however, this did not seem to adversely affect the determination of mass distribution parameters.