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 distribution 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 within the electrical measurement range was obtained with the DMPS and EAA. Data from the APS for particles greater than that size were used to complete the number distribution. Two methods of obtaining mass distribution parameters from this number data were attempted. The first was to convert the number data, channel by channel, to mass data and then fit a log-normal function to this new mass distribution. The second method was to fit a log-normal function to the combined number distribution and then use the Hatch-Choate equations to obtain mass parameters. Both the DMPS/APS and the EAA/APS systems were shown to successfully measure aerosol mass distribution as a function of aerodynamic diameter. Careful operation of the measurement equipment and proper data manipulation are necessary to achieve reliable results. A channel-by-channel conversion from number to mass distribution provided the best comparison 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.