Qualitative Evaluation of Particulate Matter Inside Public Transit Buses Operated by Biodiesel

The Environmental scanning electron microscopy (ESEM) has been used in a preliminary study to determine the size and morphology of fine particulate matter (PM). This was done with several samples collected inside public tran- sit buses fueled with a 20 percent biodiesel blend of biodiesel and ultra-low sulfur diesel (B20). As the technique is non- destructive, particles of interest can be relocated for further analysis. The practical issue of instrumentation compatibility is addressed. In addition, results showing SEM chemical images from several PM of particle size less than 10 � m (PM10) samples are reported. Shape analysis suggested the possible sources. Particle size distribution suggested a median and mean diameter of particles counted was 0.24±0.02� m and 0.27±0.04� m, respectively. The conclusion is that SEM meth- odology is a valuable tool for studying the distribution of particulate pollutants.