Reproducibility of Single Particle Chemical Composition during a Heavy Duty Diesel Truck Dynamometer Study

The chemical reproducibility of single particle mass spectrometry (SPMS) instruments is complicated by numerous factors, including uncertainties in the laser desorption/ionization process leading to shot-to-shot variability in single particle mass spectra, excessive fragmentation of carbonaceous species, as well as a relatively low duty cycle (1-10 Hz). With source apportionment being a major application for these instruments, proper source profiles must be determined from major aerosol sources. This brief communication illustrates, for the first time, the chemical reproducibility of an aerosol time-of-flight mass spectrometer (ATOFMS) sampling highly transient heavy duty diesel (HDD) truck exhaust emissions from a transportable heavy duty vehicle emissions testing laboratory, which includes a dilution tunnel as well as a residence chamber.In addition to examining the reproducibility of ATOFMS using a complex mixture of "real" aerosol particles, the chemical reproducibility of a dynamometer system at the single particle level is tested. The results presented indicate that for future studies, truck-to-truck and source-to-source variations can be attributed to chemical differences and not just to innate variations due to instrumental variability.