Evaluation of the SMPS-APS system as a continuous monitor for measuring PM2.5, PM10 and coarse (PM2.5-10) concentrations

Respirable particulate matter (PM) has been linked to mortality and morbidity by a variety of epidemiological studies. This research has led to the creation of a new PM standard for particles with diameters < 2.5 mum (PM2.5) - Since the conclusion of these studies, many leaps have been made in the realm of continuous particle measurement. Because the literature is still dominated by 24-hour averaged data, the US Environmental Protection Agency still uses this time average as the basis of its federal reference method, despite the fact that PM varies on much shorter time intervals. The purpose of this work is to compare the Scanning Mobility Particle Sizer and Aerodynamic Particle Sizer tandem (SMPS-APS) to other continuous PM measurement devices and to time-integrated mass samplers. The instruments used for comparison include the DataRAM nephelometer, Micro-Orifice Uniform Deposit Impactor (MOUDI), and Partisol Dichotomous Sampler. The data was collected over 4-5 months at various sites in the Los Angeles basin. The results show excellent agreement between the SMPS-APS and the mass based MOUDI and Partisol samplers for PM2.5. The DataRAM and SMPS-APS continuous monitors show robust correlation with each other when relative humidity <70%. The coarse fraction (PM2.5-10) measured by the Partisol, however, does not track well with the same size range measured by the APS. Several sources of sampling error are discussed to account for this. Finally, mass concentrations collected in individual size ranges of the MOUDI were compared with those determined by the SNIPS. While the size ranges from 0.32 to 10 mum agree between samplers, the size ranges < 0.32 mum are significantly different from MOUDI to SNIPS, probably due to the differences between the aerosol sizing principles underlying each technique. (C) 2002 Elsevier Science Ltd. All rights reserved.