Evaluation and comparison of continuous PM2.5 monitors for measurement of ambient aerosol, fresh diesel aerosol, and fresh secondary organic aerosol

To provide a scientific basis for the selection and use of continuous monitors for exposure, and for health effects studies and for compliance and episode measurements at strategic locations in the State of New Jersey, the performance of seven continuous PM2.5 monitors were evaluated by this research. Included were analyses for interference, and accuracy, and evaluations for seasonal conditions and ambient aerosol. Then the important specific aerosols in fresh diesel exhaust, and fresh secondary organic aerosol, were evaluated for reliability in detection using each technique. These seven PM monitors included as part of this field and laboratory evaluation and intercomparison were two nephelometers (SidePak, TSI Inc. and Nephelometer 903, Radiance), two loaded oscillating monitors (TEOM 50C, R&P Inc. and TEOM FDMS, R&P Inc.), two beta-radiation attenuation monitors (BAM, Metone Inc. and C14 Beta, Thermo Inc.) and one aethalometer (MAAP, Thermo Inc.). Environmental conditions, and physical and chemical properties of particles, e.g., particle size and black carbon content, were examined for their affect on the performance of real-time monitors. Gravimetric samplers (Harvard Impactor and Federal Reference Sampler) were collocated with real-time instruments as reference methods for experiments conducted in a controlled environmental facility (CEF) and at an outdoor site in Ewing, NJ.;Overall, for the compliance studies, instrumentation that could substitute for the filter based FRM would be the TEOM (FDMS) monitor, followed by beta gauges. The TEOM (50C) monitor should be used with caution for measuring ambient aerosol during winter because when compared to the gravimetric method the instrument underestimates the ambient mass. For the measurements of fresh diesel aerosol and fresh secondary organic aerosol, the SidePak nephelometer displays strength of low interference and the TEOM (50C) monitor has advantage of stable calibration. This suggested that the two instruments should be used together to strengthen results in locations demonstrated by these two sources, however, the loss of material from the TEOM (50C) could still be a problem in non-controlled environments. Thus, a faster response TEOM (FDMS) should be a consideration for development and use in composition of source oriented applications.