The current National Ambient Air Quality Standards for particulate matter (PM) currently are under review by the Environmental Protection Agency and probably will result in additional and more stringent standards below 2.5 microns. The Department of Defense (DoD) needs to characterize both the particle size and the chemical composition of PM from several emissions sources that likely would be impacted, such as turbines, boilers, and vehicles. Characterization of the health risks of constituents at various size ranges would allow for the most effective design of pollution control devices.
The objectives of this project are to develop advanced methods for the measurement of the size distribution and composition of PM emitted from mobile and stationary sources and to provide the DoD with the tools needed to characterize and control PM emissions from DoD facilities.
Two innovative techniques for the rapid measurement of fine PM will be used in combination with a dilution sampler. The first is an aerosol time of flight mass spectrometer (ATOFMS) that measures the size and composition of individual particles. The second is a photoelectric aerosol sampler (PAS) which, in combination with a photoacoustic detector for carbon, provides rapid measurement of the polycyclic aromatic hydrocarbon (PAH)-laden carbonaceous particles that dominate emissions from combustion sources. The approach is to apply these devices in parallel with conventional measurement techniques to establish their validity for characterizing PM emissions from DoD sources. Multiorifice impactors combined with chemical analysis will be used to obtain sufficiently detailed chemical characterization information in order to close material balances on the emissions. Optical particle counters and differential mobility analyzers will be used to obtain detailed size distributions to calibrate the ATOFMS and PAS.
The value of the ATOFMS for providing diagnostic information involving diesel operations has been demonstrated. A model has been developed to assess the impact of dilution sampling on particle size distribution. The ATOFMS has provided important data on the different classes of compounds emitted by diesel and spark ignition engines as well as coal-fired facilities. Size distributions and chemical compositions have been obtained on diesel emissions. The PAS has shown potential for measuring engine emissions under operating conditions from off-runway measurements. The photoacoustic detector has been applied successfully to monitor the elemental carbon emission from aircraft ground equipment. PAH distribution between vapor and particles and downstream of a filter have been determined.
The project will provide the DoD with rapid measurement procedures for measuring organic and inorganic emissions at a greatly reduced cost on a per analysis basis as well as detailed chemical compositions of major source categories by size. Assessments of the relative cost of alternative measurement strategies, ease of use, potential for use for feedback control, reliability, and speed will be provided.