Diesel exhaust quantification by scanning electron microscope with special emphasis on particulate size distribution

The purpose of this study was to investigate the potentials of electron microscopy to quantify diesel exhaust emission from work environments, where the aerosol consists of both diesel fumes and dust particles from pollutant sources. The mass and particles concentrations as well as size distributions were investigated. The size distribution consists of two modes: a group of particles with Dmin < 0.7 and a group of particles with Dmin > 1.0 μm, respectively. The Dmin in the range 0.7–1.0 μm should be regarded as an interval where there is an overlapping. To distinguish between organic and non-organic components of the particulate, low-temperature plasma ashing was made. This is a very slow oxidizing process that does not affect or disturb non-oxidizable material. The diesel fumes in the samples constitute only a small share of the total mass, while diesel fumes dominate by numbers in those samples. A big difference is observed between the number of concentrations for non-ashed and ashed samples, respectively. However, no significant differences are observed between the volume diagram for non-ashed and ashed samples. One should therefore consider the number of concentrations of particles below 1 μm in diameter rather than the gravimetric concentrations when studying exposure level for diesel exhaust.