Polycyclic aromatic compounds (PAC) in diesel fuels and exhaust emissions : aspects of sampling techniques, chemical determination, multivariate data interpretation and PAC emissions reduction

Abstract: The rapid growth in the number of motor vehicles has raised serious environmental health hazard problems in urban areas associated with vehicle exhaust emissions. Exhaust emissions from heavy duty diesel vehicles are very complex mixtures containing thousands of chemical components distributed between the particulate, semivolatile and gaseous phases. So far only those regulated pollutant are legislated, and it is important to be aware of the contribution of unregulated pollutants, as potential health effects can be linked to these pollutants. Polycyclic aromatic compounds (PAC) are an important group of unregulated compounds that exist in diesel exhaust emissions. Some PAC represent some of the most important chemical carcinogens known to humans today.This thesis addresses PAC in diesel fuels and exhaust emissions from heavy duty diesel vehicles. Sampling techniques associated with the particulate and semivolatile phases are discussed. For the particulate phase, Teflon coated glass fibre filters gave a good recovery of PAC; for the semivolatile phase, polyurethane foam (PUF) plugs gave the highest recovery of PAC. Chemical determination of PAC by capillary gas chromatography-mass spectrometry (GC-MS) was carried out. For Nitro-PAH determination, high performance liquid chromatography with chemiluminescence detection (HPLC-CL) technique was developed, high sensitivity is demonstrated. Nitro-PAH analysis using both HPLC with fluorescence detection (HPLC-FL) and HPLC-CL techniques were performed on the diesel exhaust emission sample matrix.Multivariate analysis methods such as principal component analysis (PCA) and partial least squares projection on latent structures (PLS) have been used to investigate and interpret the correlation of PAC in fuels with PAC in emissions, and the correlation of chemical data with biological (Ames test) data.The ability of diesel emission extracts fractions and subtractions concerning their PAC content, to compete with 2,3,7,8-tetrachloro[l,6-^H]dibenzo-p-dioxin (TCDD) for the dioxin (Ah) receptor was determined and interpreted.Particulate traps and catalytic converters used on heavy-duty diesel vehicles are powerful ways to reduce exhaust emissions. The pollutants emitted in the regeneration mode of a particulate trap are negligible. By an appropriate selection of fuel, the PAC emissions can be reduced from today's level by a factor up to 10. By using a particulate trap and catalytic converter the PAC emissions can also be reduced by a factor of 5-10. It is possible to further reduce PAC emissions by combining diesel fuel selection with the use of particulate traps and catalytic converters.