Comparison of real-time instruments used to monitor airborne particulate matter

Measurements collected using five real-time continuous airborne particle mo nitors were compared to measurements made using reference filter-based samp lers at Bakersfield, CA, between December 2, 1998, and January 31, 1999. Th e purpose of this analysis was to evaluate the suitability of each instrume nt for use in a real-time continuous monitoring network designed to measure the mass of airborne particles with an aerodynamic diam less than 2.5 mum (PM2.5) under wintertime conditions in the southern San Joaquin Valley. Mea surements of airborne particulate mass made with a beta attenuation monitor (BAM), an integrating nephelometer, and a continuous aerosol mass monitor (CAMM) were found to correlate well with reference measurements made with a filter-based sampler. A Dusttrak aerosol sampler overestimated airborne pa rticle concentrations by a factor of similar to3 throughout the study. Meas urements of airborne particulate matter made with a tapered element oscilla ting microbalance (TEOM) were found to be lower than the reference filter-b ased measurements by an amount approximately equal to the concentration of NH4NO3 observed to be present in the airborne particles. The performance of the Dusttrak sampler and the integrating nephelometer was affected by the size distribution of airborne particulate matter. The performance of the BA M, the integrating nephelometer, the CAMM, the Dusttrak sampler, and the TE OM was not strongly affected by temperature, relative humidity, wind speed, or wind direction within the range of conditions encountered in the curren t study. Based on instrument performance, the BAM, the integrating nephelom eter, and the CAMM appear to be suitable candidates for deployment in a rea l-time continuous PM2.5 monitoring network in central California for the ra nge of winter conditions and aerosol composition encountered during the stu dy.