Polycyclic aromatic hydrocarbons in diesel emission, diesel fuel and lubricant oil

Abstract

This study determined the priority PAHs concentrations in diesel fuel sold in Brazil and in lubricant oil sampleted in different usage times. The solid phase extraction (SPE) techinique using florisil (magnesium silicate) as solid phase was used to separate the fraction containing aromatic components present in the diesel fuel and lubricating oil samples. The measurements were performed by gas chromatography coupled to mass spectrometry. The PAH priority profile in lubricant oil was similar to the PAH profile in diesel where Naphthalene, Phenanthrene and Pyrene were dominant. The PAHs concentration in Brazilian diesel fuel sample were compared with the emission factors of their PAHs respective in exhaust of a vehicle fueled with the same Brazilian diesel fuel in order to estimate how much of the PAHs present in diesel remains unchanged during combustion. The ratio between the PAHs emission factors in exhaust (μgL−1 diesel) and their respective concentrations in diesel fuel (μgL−1) ranged from 0.01±0.02 to 0.05±0.029, depending on the PAH. These values indicate that at least 95–99% of the PAHs identified in diesel fuel were destroyed, converted into other compounds during the combustion, and/or retained in the lubricant oil reservoir. On the other hand, PAHs with higher concentrations in diesel also had higher exhaust emission factors, which suggests that the PAHs from diesel have a contribution to total PAH emissions. Therefore, reducing the PAHs content in diesel will probably contribute to curbing emissions of these compounds and help improve air quality.