Particulate matter size distribution and associated polycyclic aromatic hydrocarbon content from indirect and direct injection diesel engines

Abstract

Within the framework of atmospheric aerosol study, evaluation of the contribution of the particle source to global atmospheric pollution is a challenge that requires an improvement in the knowledge of particulate matter. As a part of this knowledge improvement, this study has been focused on particles emitted from diesel vehicles. Two light-duty diesel vehicles were studied for particulate matter size distribution and associated polycyclic aromatic hydrocarbon (PAH) content. A diffusional and inertial spectrometer was used, allowing particles from 7.5 nm to 15 μm to be collected and analysed. Teflon-coated glass fibre filters were employed as collector substrates, and weighed prior to and after sampling. Each of them was extracted with methylene chloride in an accelerated solvent extractor, cleaned on a silica gel micro-column and analysed for PAH by gas chromatography/mass spectrometry using internal standards for quantitation. Both analytical and sampling methods were validated. The highest particle mass was found to be emitted at 0.2 μm for the direct injection engine and 0.07 μm for the indirect injection engine. PAHs were found to be essentially distributed on particles in the accumulation mode, at about 0.2 μm, and high molecular weight PAH distributions were found to be bimodal or trimodal, depending on the engine injection.