Characterization of particulate emissions: Size fractionation and chemical speciation

This study developed and validated innovative techniques for characterizing the amount and composition of PM10, PM2.5, and smaller particles for four major classes of DoD emission sources: aircraft ground support vehicles, rocket motors, aircraft, and sandblasting operations. The techniques include the coupling of dilution samplers with advanced measurement techniques for composition and size that provide detailed analyses sufficient to complete a material balance. The size-classified analyses include measurement made with the cascade impactor and aerosol time-of-flight mass spectrometer (ATOFMS). A photoelectric aerosol sensor (PAS) was being evaluated for use in rapidly evaluating field emissions of particle-bound polycyclic aromatic hydrocarbons (PAH). In addition, a photoacoustic spectrometer was investigated for use in measuring soot particle concentrations. The objective was to calibrate and enhance these instruments for DOD use. To this end, the devices are being demonstrated at DoD facilities, and the methodologies developed will be transferred to personnel responsible for monitoring emissions at DoD facilities. The objectives of this project were to develop advanced methods for the measurement of the size distribution and composition of particulate matter (PM) emitted from mobile and stationary sources in order to provide the DoD with the tools needed to characterize and control the emissions from DoD facilities. This information is needed for compliance with the new ambient particulate standards and for the assessment of the risks associated with PM emissions at DoD facilities. Combustion sources are significant contributors to PM emissions at DoD facilities, and a comprehensive discussion of combustion particle formation, composition, and measurement can be found in (Lighty et al., 2000). The feasibility of using advanced analytical measurements to characterize the chemical composition and size of particulate emissions from a diverse range of sources operated by the DoD was determined. The data obtained during the evaluation of the instruments will provide a measure of the relative importance of different DoD sources and will be useful for guiding the strategies for controlling the emissions from DoD facilities. The cost effectiveness of different measurement methods was assessed and recommendations made for the best protocols for measurement of the fine particle emissions. Three innovative techniques for rapid measurement of fine particles were used in combination with a dilution sampler. The first is an aerosol time-of-flight mass spectrometer (ATOFMS), which measures the size and composition of individual particles. The second is the photoacoustic (PA) detector, which provides a method for rapidly measuring elemental carbon. The third is a photoelectric PAH detector (PAS), which provides rapid measurement of the PAH-laden carbonaceous particles that dominate the emissions from combustion sources. The approach was to apply these devices in parallel with more conventional measurement techniques to establish their validity for characterizing the particle emissions from DoD sources. Optical particle counters (OPC) and differential mobility analyzers (DMA) were used to obtain detailed size distributions in order to calibrate the ATOFMS.